[llvm] r173760 - Extracted ObjCARCContract from ObjCARCOpts into its own file.
Michael Gottesman
mgottesman at apple.com
Mon Jan 28 19:03:03 PST 2013
Author: mgottesman
Date: Mon Jan 28 21:03:03 2013
New Revision: 173760
URL: http://llvm.org/viewvc/llvm-project?rev=173760&view=rev
Log:
Extracted ObjCARCContract from ObjCARCOpts into its own file.
This also required adding 2x headers Dependency Analysis.h/Provenance Analysis.h
and a .cpp file DependencyAnalysis.cpp to unentangle the dependencies inbetween
ObjCARCContract and ObjCARCOpts.
Added:
llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.cpp
llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.h
llvm/trunk/lib/Transforms/ObjCARC/ObjCARCContract.cpp
llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp
llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.h
Modified:
llvm/trunk/lib/Transforms/ObjCARC/CMakeLists.txt
llvm/trunk/lib/Transforms/ObjCARC/ObjCARC.h
llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
llvm/trunk/lib/Transforms/ObjCARC/ObjCARCUtil.cpp
Modified: llvm/trunk/lib/Transforms/ObjCARC/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/CMakeLists.txt?rev=173760&r1=173759&r2=173760&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/CMakeLists.txt (original)
+++ llvm/trunk/lib/Transforms/ObjCARC/CMakeLists.txt Mon Jan 28 21:03:03 2013
@@ -5,6 +5,9 @@ add_llvm_library(LLVMObjCARCOpts
ObjCARCAPElim.cpp
ObjCARCAliasAnalysis.cpp
ObjCARCUtil.cpp
+ ObjCARCContract.cpp
+ DependencyAnalysis.cpp
+ ProvenanceAnalysis.cpp
)
add_dependencies(LLVMObjCARCOpts intrinsics_gen)
Added: llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.cpp?rev=173760&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.cpp (added)
+++ llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.cpp Mon Jan 28 21:03:03 2013
@@ -0,0 +1,262 @@
+//===- DependencyAnalysis.cpp - ObjC ARC Optimization ---------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file defines special dependency analysis routines used in Objective C
+/// ARC Optimizations.
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "objc-arc-dependency"
+#include "ObjCARC.h"
+#include "ProvenanceAnalysis.h"
+#include "DependencyAnalysis.h"
+
+#include "llvm/Support/CFG.h"
+
+using namespace llvm;
+using namespace llvm::objcarc;
+
+/// Test whether the given instruction can result in a reference count
+/// modification (positive or negative) for the pointer's object.
+bool
+llvm::objcarc::CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
+ ProvenanceAnalysis &PA,
+ InstructionClass Class) {
+ switch (Class) {
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_User:
+ // These operations never directly modify a reference count.
+ return false;
+ default: break;
+ }
+
+ ImmutableCallSite CS = static_cast<const Value *>(Inst);
+ assert(CS && "Only calls can alter reference counts!");
+
+ // See if AliasAnalysis can help us with the call.
+ AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
+ if (AliasAnalysis::onlyReadsMemory(MRB))
+ return false;
+ if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
+ for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+ I != E; ++I) {
+ const Value *Op = *I;
+ if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+ }
+
+ // Assume the worst.
+ return true;
+}
+
+/// Test whether the given instruction can "use" the given pointer's object in a
+/// way that requires the reference count to be positive.
+bool
+llvm::objcarc::CanUse(const Instruction *Inst, const Value *Ptr,
+ ProvenanceAnalysis &PA, InstructionClass Class) {
+ // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
+ if (Class == IC_Call)
+ return false;
+
+ // Consider various instructions which may have pointer arguments which are
+ // not "uses".
+ if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
+ // Comparing a pointer with null, or any other constant, isn't really a use,
+ // because we don't care what the pointer points to, or about the values
+ // of any other dynamic reference-counted pointers.
+ if (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
+ return false;
+ } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
+ // For calls, just check the arguments (and not the callee operand).
+ for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
+ OE = CS.arg_end(); OI != OE; ++OI) {
+ const Value *Op = *OI;
+ if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+ } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // Special-case stores, because we don't care about the stored value, just
+ // the store address.
+ const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
+ // If we can't tell what the underlying object was, assume there is a
+ // dependence.
+ return IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Op, Ptr);
+ }
+
+ // Check each operand for a match.
+ for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
+ OI != OE; ++OI) {
+ const Value *Op = *OI;
+ if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+}
+
+/// Test if there can be dependencies on Inst through Arg. This function only
+/// tests dependencies relevant for removing pairs of calls.
+bool
+llvm::objcarc::Depends(DependenceKind Flavor, Instruction *Inst,
+ const Value *Arg, ProvenanceAnalysis &PA) {
+ // If we've reached the definition of Arg, stop.
+ if (Inst == Arg)
+ return true;
+
+ switch (Flavor) {
+ case NeedsPositiveRetainCount: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ return false;
+ default:
+ return CanUse(Inst, Arg, PA, Class);
+ }
+ }
+
+ case AutoreleasePoolBoundary: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ // These mark the end and begin of an autorelease pool scope.
+ return true;
+ default:
+ // Nothing else does this.
+ return false;
+ }
+ }
+
+ case CanChangeRetainCount: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ // Conservatively assume this can decrement any count.
+ return true;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ return false;
+ default:
+ return CanAlterRefCount(Inst, Arg, PA, Class);
+ }
+ }
+
+ case RetainAutoreleaseDep:
+ switch (GetBasicInstructionClass(Inst)) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ // Don't merge an objc_autorelease with an objc_retain inside a different
+ // autoreleasepool scope.
+ return true;
+ case IC_Retain:
+ case IC_RetainRV:
+ // Check for a retain of the same pointer for merging.
+ return GetObjCArg(Inst) == Arg;
+ default:
+ // Nothing else matters for objc_retainAutorelease formation.
+ return false;
+ }
+
+ case RetainAutoreleaseRVDep: {
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ switch (Class) {
+ case IC_Retain:
+ case IC_RetainRV:
+ // Check for a retain of the same pointer for merging.
+ return GetObjCArg(Inst) == Arg;
+ default:
+ // Anything that can autorelease interrupts
+ // retainAutoreleaseReturnValue formation.
+ return CanInterruptRV(Class);
+ }
+ }
+
+ case RetainRVDep:
+ return CanInterruptRV(GetBasicInstructionClass(Inst));
+ }
+
+ llvm_unreachable("Invalid dependence flavor");
+}
+
+/// Walk up the CFG from StartPos (which is in StartBB) and find local and
+/// non-local dependencies on Arg.
+///
+/// TODO: Cache results?
+void
+llvm::objcarc::FindDependencies(DependenceKind Flavor,
+ const Value *Arg,
+ BasicBlock *StartBB, Instruction *StartInst,
+ SmallPtrSet<Instruction *, 4> &DependingInsts,
+ SmallPtrSet<const BasicBlock *, 4> &Visited,
+ ProvenanceAnalysis &PA) {
+ BasicBlock::iterator StartPos = StartInst;
+
+ SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
+ Worklist.push_back(std::make_pair(StartBB, StartPos));
+ do {
+ std::pair<BasicBlock *, BasicBlock::iterator> Pair =
+ Worklist.pop_back_val();
+ BasicBlock *LocalStartBB = Pair.first;
+ BasicBlock::iterator LocalStartPos = Pair.second;
+ BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
+ for (;;) {
+ if (LocalStartPos == StartBBBegin) {
+ pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
+ if (PI == PE)
+ // If we've reached the function entry, produce a null dependence.
+ DependingInsts.insert(0);
+ else
+ // Add the predecessors to the worklist.
+ do {
+ BasicBlock *PredBB = *PI;
+ if (Visited.insert(PredBB))
+ Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
+ } while (++PI != PE);
+ break;
+ }
+
+ Instruction *Inst = --LocalStartPos;
+ if (Depends(Flavor, Inst, Arg, PA)) {
+ DependingInsts.insert(Inst);
+ break;
+ }
+ }
+ } while (!Worklist.empty());
+
+ // Determine whether the original StartBB post-dominates all of the blocks we
+ // visited. If not, insert a sentinal indicating that most optimizations are
+ // not safe.
+ for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
+ E = Visited.end(); I != E; ++I) {
+ const BasicBlock *BB = *I;
+ if (BB == StartBB)
+ continue;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
+ const BasicBlock *Succ = *SI;
+ if (Succ != StartBB && !Visited.count(Succ)) {
+ DependingInsts.insert(reinterpret_cast<Instruction *>(-1));
+ return;
+ }
+ }
+ }
+}
Added: llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.h?rev=173760&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.h (added)
+++ llvm/trunk/lib/Transforms/ObjCARC/DependencyAnalysis.h Mon Jan 28 21:03:03 2013
@@ -0,0 +1,79 @@
+//===- DependencyAnalysis.h - ObjC ARC Optimization ---*- mode: c++ -*-----===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file declares special dependency analysis routines used in Objective C
+/// ARC Optimizations.
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_OBJCARC_DEPEDENCYANALYSIS_H
+#define LLVM_TRANSFORMS_OBJCARC_DEPEDENCYANALYSIS_H
+
+#include "llvm/ADT/SmallPtrSet.h"
+
+namespace llvm {
+ class BasicBlock;
+ class Instruction;
+ class Value;
+}
+
+namespace llvm {
+namespace objcarc {
+
+class ProvenanceAnalysis;
+
+/// \enum DependenceKind
+/// \brief Defines different dependence kinds among various ARC constructs.
+///
+/// There are several kinds of dependence-like concepts in use here.
+///
+enum DependenceKind {
+ NeedsPositiveRetainCount,
+ AutoreleasePoolBoundary,
+ CanChangeRetainCount,
+ RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
+ RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
+ RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
+};
+
+void FindDependencies(DependenceKind Flavor,
+ const Value *Arg,
+ BasicBlock *StartBB, Instruction *StartInst,
+ SmallPtrSet<Instruction *, 4> &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4> &Visited,
+ ProvenanceAnalysis &PA);
+
+bool
+Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
+ ProvenanceAnalysis &PA);
+
+/// Test whether the given instruction can "use" the given pointer's object in a
+/// way that requires the reference count to be positive.
+bool
+CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
+ InstructionClass Class);
+
+/// Test whether the given instruction can result in a reference count
+/// modification (positive or negative) for the pointer's object.
+bool
+CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
+ ProvenanceAnalysis &PA, InstructionClass Class);
+
+} // namespace objcarc
+} // namespace llvm
+
+#endif // LLVM_TRANSFORMS_OBJCARC_DEPEDENCYANALYSIS_H
Modified: llvm/trunk/lib/Transforms/ObjCARC/ObjCARC.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ObjCARC.h?rev=173760&r1=173759&r2=173760&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ObjCARC.h (original)
+++ llvm/trunk/lib/Transforms/ObjCARC/ObjCARC.h Mon Jan 28 21:03:03 2013
@@ -29,10 +29,12 @@
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
+#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/ObjCARC.h"
+#include "llvm/Transforms/Utils/Local.h"
namespace llvm {
namespace objcarc {
@@ -163,6 +165,24 @@ static inline bool IsNoThrow(Instruction
Class == IC_AutoreleasepoolPop;
}
+/// Test whether the given instruction can autorelease any pointer or cause an
+/// autoreleasepool pop.
+static inline bool
+CanInterruptRV(InstructionClass Class) {
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_CallOrUser:
+ case IC_Call:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ return true;
+ default:
+ return false;
+ }
+}
+
/// \brief Determine if F is one of the special known Functions. If it isn't,
/// return IC_CallOrUser.
InstructionClass GetFunctionClass(const Function *F);
@@ -184,6 +204,8 @@ static inline InstructionClass GetBasicI
return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
}
+/// \brief Determine what kind of construct V is.
+InstructionClass GetInstructionClass(const Value *V);
/// \brief This is a wrapper around getUnderlyingObject which also knows how to
/// look through objc_retain and objc_autorelease calls, which we know to return
@@ -225,6 +247,137 @@ static inline Value *StripPointerCastsAn
return V;
}
+/// \brief Assuming the given instruction is one of the special calls such as
+/// objc_retain or objc_release, return the argument value, stripped of no-op
+/// casts and forwarding calls.
+static inline Value *GetObjCArg(Value *Inst) {
+ return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
+}
+
+static inline bool isNullOrUndef(const Value *V) {
+ return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
+}
+
+static inline bool isNoopInstruction(const Instruction *I) {
+ return isa<BitCastInst>(I) ||
+ (isa<GetElementPtrInst>(I) &&
+ cast<GetElementPtrInst>(I)->hasAllZeroIndices());
+}
+
+
+/// \brief Erase the given instruction.
+///
+/// Many ObjC calls return their argument verbatim,
+/// so if it's such a call and the return value has users, replace them with the
+/// argument value.
+///
+static inline void EraseInstruction(Instruction *CI) {
+ Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
+
+ bool Unused = CI->use_empty();
+
+ if (!Unused) {
+ // Replace the return value with the argument.
+ assert(IsForwarding(GetBasicInstructionClass(CI)) &&
+ "Can't delete non-forwarding instruction with users!");
+ CI->replaceAllUsesWith(OldArg);
+ }
+
+ CI->eraseFromParent();
+
+ if (Unused)
+ RecursivelyDeleteTriviallyDeadInstructions(OldArg);
+}
+
+/// \brief Test whether the given value is possible a retainable object pointer.
+static inline bool IsPotentialRetainableObjPtr(const Value *Op) {
+ // Pointers to static or stack storage are not valid retainable object pointers.
+ if (isa<Constant>(Op) || isa<AllocaInst>(Op))
+ return false;
+ // Special arguments can not be a valid retainable object pointer.
+ if (const Argument *Arg = dyn_cast<Argument>(Op))
+ if (Arg->hasByValAttr() ||
+ Arg->hasNestAttr() ||
+ Arg->hasStructRetAttr())
+ return false;
+ // Only consider values with pointer types.
+ //
+ // It seemes intuitive to exclude function pointer types as well, since
+ // functions are never retainable object pointers, however clang occasionally
+ // bitcasts retainable object pointers to function-pointer type temporarily.
+ PointerType *Ty = dyn_cast<PointerType>(Op->getType());
+ if (!Ty)
+ return false;
+ // Conservatively assume anything else is a potential retainable object pointer.
+ return true;
+}
+
+static inline bool IsPotentialRetainableObjPtr(const Value *Op,
+ AliasAnalysis &AA) {
+ // First make the rudimentary check.
+ if (!IsPotentialRetainableObjPtr(Op))
+ return false;
+
+ // Objects in constant memory are not reference-counted.
+ if (AA.pointsToConstantMemory(Op))
+ return false;
+
+ // Pointers in constant memory are not pointing to reference-counted objects.
+ if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
+ if (AA.pointsToConstantMemory(LI->getPointerOperand()))
+ return false;
+
+ // Otherwise assume the worst.
+ return true;
+}
+
+/// \brief Helper for GetInstructionClass. Determines what kind of construct CS
+/// is.
+static inline InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
+ for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+ I != E; ++I)
+ if (IsPotentialRetainableObjPtr(*I))
+ return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
+
+ return CS.onlyReadsMemory() ? IC_None : IC_Call;
+}
+
+/// \brief Return true if this value refers to a distinct and identifiable
+/// object.
+///
+/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
+/// special knowledge of ObjC conventions.
+static inline bool IsObjCIdentifiedObject(const Value *V) {
+ // Assume that call results and arguments have their own "provenance".
+ // Constants (including GlobalVariables) and Allocas are never
+ // reference-counted.
+ if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
+ isa<Argument>(V) || isa<Constant>(V) ||
+ isa<AllocaInst>(V))
+ return true;
+
+ if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
+ const Value *Pointer =
+ StripPointerCastsAndObjCCalls(LI->getPointerOperand());
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
+ // A constant pointer can't be pointing to an object on the heap. It may
+ // be reference-counted, but it won't be deleted.
+ if (GV->isConstant())
+ return true;
+ StringRef Name = GV->getName();
+ // These special variables are known to hold values which are not
+ // reference-counted pointers.
+ if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
+ Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
+ Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
+ Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
+ Name.startswith("\01l_objc_msgSend_fixup_"))
+ return true;
+ }
+ }
+
+ return false;
+}
} // end namespace objcarc
} // end namespace llvm
Added: llvm/trunk/lib/Transforms/ObjCARC/ObjCARCContract.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ObjCARCContract.cpp?rev=173760&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ObjCARCContract.cpp (added)
+++ llvm/trunk/lib/Transforms/ObjCARC/ObjCARCContract.cpp Mon Jan 28 21:03:03 2013
@@ -0,0 +1,537 @@
+//===- ObjCARCOpts.cpp - ObjC ARC Optimization ----------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This file defines late ObjC ARC optimizations. ARC stands for Automatic
+/// Reference Counting and is a system for managing reference counts for objects
+/// in Objective C.
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+// TODO: ObjCARCContract could insert PHI nodes when uses aren't
+// dominated by single calls.
+
+#define DEBUG_TYPE "objc-arc-contract"
+#include "ObjCARC.h"
+#include "ProvenanceAnalysis.h"
+#include "DependencyAnalysis.h"
+
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/IR/InlineAsm.h"
+#include "llvm/IR/Operator.h"
+
+using namespace llvm;
+using namespace llvm::objcarc;
+
+STATISTIC(NumPeeps, "Number of calls peephole-optimized");
+STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
+
+namespace {
+ /// \brief Late ARC optimizations
+ ///
+ /// These change the IR in a way that makes it difficult to be analyzed by
+ /// ObjCARCOpt, so it's run late.
+ class ObjCARCContract : public FunctionPass {
+ bool Changed;
+ AliasAnalysis *AA;
+ DominatorTree *DT;
+ ProvenanceAnalysis PA;
+
+ /// A flag indicating whether this optimization pass should run.
+ bool Run;
+
+ /// Declarations for ObjC runtime functions, for use in creating calls to
+ /// them. These are initialized lazily to avoid cluttering up the Module
+ /// with unused declarations.
+
+ /// Declaration for objc_storeStrong().
+ Constant *StoreStrongCallee;
+ /// Declaration for objc_retainAutorelease().
+ Constant *RetainAutoreleaseCallee;
+ /// Declaration for objc_retainAutoreleaseReturnValue().
+ Constant *RetainAutoreleaseRVCallee;
+
+ /// The inline asm string to insert between calls and RetainRV calls to make
+ /// the optimization work on targets which need it.
+ const MDString *RetainRVMarker;
+
+ /// The set of inserted objc_storeStrong calls. If at the end of walking the
+ /// function we have found no alloca instructions, these calls can be marked
+ /// "tail".
+ SmallPtrSet<CallInst *, 8> StoreStrongCalls;
+
+ Constant *getStoreStrongCallee(Module *M);
+ Constant *getRetainAutoreleaseCallee(Module *M);
+ Constant *getRetainAutoreleaseRVCallee(Module *M);
+
+ bool ContractAutorelease(Function &F, Instruction *Autorelease,
+ InstructionClass Class,
+ SmallPtrSet<Instruction *, 4>
+ &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4>
+ &Visited);
+
+ void ContractRelease(Instruction *Release,
+ inst_iterator &Iter);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool doInitialization(Module &M);
+ virtual bool runOnFunction(Function &F);
+
+ public:
+ static char ID;
+ ObjCARCContract() : FunctionPass(ID) {
+ initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCContract::ID = 0;
+INITIALIZE_PASS_BEGIN(ObjCARCContract,
+ "objc-arc-contract", "ObjC ARC contraction", false, false)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_END(ObjCARCContract,
+ "objc-arc-contract", "ObjC ARC contraction", false, false)
+
+Pass *llvm::createObjCARCContractPass() {
+ return new ObjCARCContract();
+}
+
+void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<AliasAnalysis>();
+ AU.addRequired<DominatorTree>();
+ AU.setPreservesCFG();
+}
+
+Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
+ if (!StoreStrongCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *I8XX = PointerType::getUnqual(I8X);
+ Type *Params[] = { I8XX, I8X };
+
+ AttributeSet Attr = AttributeSet()
+ .addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind)
+ .addAttribute(M->getContext(), 1, Attribute::NoCapture);
+
+ StoreStrongCallee =
+ M->getOrInsertFunction(
+ "objc_storeStrong",
+ FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
+ Attr);
+ }
+ return StoreStrongCallee;
+}
+
+Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
+ if (!RetainAutoreleaseCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainAutoreleaseCallee =
+ M->getOrInsertFunction("objc_retainAutorelease", FTy, Attribute);
+ }
+ return RetainAutoreleaseCallee;
+}
+
+Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
+ if (!RetainAutoreleaseRVCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainAutoreleaseRVCallee =
+ M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
+ Attribute);
+ }
+ return RetainAutoreleaseRVCallee;
+}
+
+/// Merge an autorelease with a retain into a fused call.
+bool
+ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
+ InstructionClass Class,
+ SmallPtrSet<Instruction *, 4>
+ &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4>
+ &Visited) {
+ const Value *Arg = GetObjCArg(Autorelease);
+
+ // Check that there are no instructions between the retain and the autorelease
+ // (such as an autorelease_pop) which may change the count.
+ CallInst *Retain = 0;
+ if (Class == IC_AutoreleaseRV)
+ FindDependencies(RetainAutoreleaseRVDep, Arg,
+ Autorelease->getParent(), Autorelease,
+ DependingInstructions, Visited, PA);
+ else
+ FindDependencies(RetainAutoreleaseDep, Arg,
+ Autorelease->getParent(), Autorelease,
+ DependingInstructions, Visited, PA);
+
+ Visited.clear();
+ if (DependingInstructions.size() != 1) {
+ DependingInstructions.clear();
+ return false;
+ }
+
+ Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+ DependingInstructions.clear();
+
+ if (!Retain ||
+ GetBasicInstructionClass(Retain) != IC_Retain ||
+ GetObjCArg(Retain) != Arg)
+ return false;
+
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "ObjCARCContract::ContractAutorelease: Fusing "
+ "retain/autorelease. Erasing: " << *Autorelease << "\n"
+ " Old Retain: "
+ << *Retain << "\n");
+
+ if (Class == IC_AutoreleaseRV)
+ Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
+ else
+ Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
+
+ DEBUG(dbgs() << " New Retain: "
+ << *Retain << "\n");
+
+ EraseInstruction(Autorelease);
+ return true;
+}
+
+/// Attempt to merge an objc_release with a store, load, and objc_retain to form
+/// an objc_storeStrong. This can be a little tricky because the instructions
+/// don't always appear in order, and there may be unrelated intervening
+/// instructions.
+void ObjCARCContract::ContractRelease(Instruction *Release,
+ inst_iterator &Iter) {
+ LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
+ if (!Load || !Load->isSimple()) return;
+
+ // For now, require everything to be in one basic block.
+ BasicBlock *BB = Release->getParent();
+ if (Load->getParent() != BB) return;
+
+ // Walk down to find the store and the release, which may be in either order.
+ BasicBlock::iterator I = Load, End = BB->end();
+ ++I;
+ AliasAnalysis::Location Loc = AA->getLocation(Load);
+ StoreInst *Store = 0;
+ bool SawRelease = false;
+ for (; !Store || !SawRelease; ++I) {
+ if (I == End)
+ return;
+
+ Instruction *Inst = I;
+ if (Inst == Release) {
+ SawRelease = true;
+ continue;
+ }
+
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+
+ // Unrelated retains are harmless.
+ if (IsRetain(Class))
+ continue;
+
+ if (Store) {
+ // The store is the point where we're going to put the objc_storeStrong,
+ // so make sure there are no uses after it.
+ if (CanUse(Inst, Load, PA, Class))
+ return;
+ } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
+ // We are moving the load down to the store, so check for anything
+ // else which writes to the memory between the load and the store.
+ Store = dyn_cast<StoreInst>(Inst);
+ if (!Store || !Store->isSimple()) return;
+ if (Store->getPointerOperand() != Loc.Ptr) return;
+ }
+ }
+
+ Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
+
+ // Walk up to find the retain.
+ I = Store;
+ BasicBlock::iterator Begin = BB->begin();
+ while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
+ --I;
+ Instruction *Retain = I;
+ if (GetBasicInstructionClass(Retain) != IC_Retain) return;
+ if (GetObjCArg(Retain) != New) return;
+
+ Changed = true;
+ ++NumStoreStrongs;
+
+ LLVMContext &C = Release->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *I8XX = PointerType::getUnqual(I8X);
+
+ Value *Args[] = { Load->getPointerOperand(), New };
+ if (Args[0]->getType() != I8XX)
+ Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
+ if (Args[1]->getType() != I8X)
+ Args[1] = new BitCastInst(Args[1], I8X, "", Store);
+ CallInst *StoreStrong =
+ CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
+ Args, "", Store);
+ StoreStrong->setDoesNotThrow();
+ StoreStrong->setDebugLoc(Store->getDebugLoc());
+
+ // We can't set the tail flag yet, because we haven't yet determined
+ // whether there are any escaping allocas. Remember this call, so that
+ // we can set the tail flag once we know it's safe.
+ StoreStrongCalls.insert(StoreStrong);
+
+ if (&*Iter == Store) ++Iter;
+ Store->eraseFromParent();
+ Release->eraseFromParent();
+ EraseInstruction(Retain);
+ if (Load->use_empty())
+ Load->eraseFromParent();
+}
+
+bool ObjCARCContract::doInitialization(Module &M) {
+ // If nothing in the Module uses ARC, don't do anything.
+ Run = ModuleHasARC(M);
+ if (!Run)
+ return false;
+
+ // These are initialized lazily.
+ StoreStrongCallee = 0;
+ RetainAutoreleaseCallee = 0;
+ RetainAutoreleaseRVCallee = 0;
+
+ // Initialize RetainRVMarker.
+ RetainRVMarker = 0;
+ if (NamedMDNode *NMD =
+ M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
+ if (NMD->getNumOperands() == 1) {
+ const MDNode *N = NMD->getOperand(0);
+ if (N->getNumOperands() == 1)
+ if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
+ RetainRVMarker = S;
+ }
+
+ return false;
+}
+
+bool ObjCARCContract::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ // If nothing in the Module uses ARC, don't do anything.
+ if (!Run)
+ return false;
+
+ Changed = false;
+ AA = &getAnalysis<AliasAnalysis>();
+ DT = &getAnalysis<DominatorTree>();
+
+ PA.setAA(&getAnalysis<AliasAnalysis>());
+
+ // Track whether it's ok to mark objc_storeStrong calls with the "tail"
+ // keyword. Be conservative if the function has variadic arguments.
+ // It seems that functions which "return twice" are also unsafe for the
+ // "tail" argument, because they are setjmp, which could need to
+ // return to an earlier stack state.
+ bool TailOkForStoreStrongs = !F.isVarArg() &&
+ !F.callsFunctionThatReturnsTwice();
+
+ // For ObjC library calls which return their argument, replace uses of the
+ // argument with uses of the call return value, if it dominates the use. This
+ // reduces register pressure.
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+
+ DEBUG(dbgs() << "ObjCARCContract: Visiting: " << *Inst << "\n");
+
+ // Only these library routines return their argument. In particular,
+ // objc_retainBlock does not necessarily return its argument.
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ switch (Class) {
+ case IC_Retain:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ break;
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
+ continue;
+ break;
+ case IC_RetainRV: {
+ // If we're compiling for a target which needs a special inline-asm
+ // marker to do the retainAutoreleasedReturnValue optimization,
+ // insert it now.
+ if (!RetainRVMarker)
+ break;
+ BasicBlock::iterator BBI = Inst;
+ BasicBlock *InstParent = Inst->getParent();
+
+ // Step up to see if the call immediately precedes the RetainRV call.
+ // If it's an invoke, we have to cross a block boundary. And we have
+ // to carefully dodge no-op instructions.
+ do {
+ if (&*BBI == InstParent->begin()) {
+ BasicBlock *Pred = InstParent->getSinglePredecessor();
+ if (!Pred)
+ goto decline_rv_optimization;
+ BBI = Pred->getTerminator();
+ break;
+ }
+ --BBI;
+ } while (isNoopInstruction(BBI));
+
+ if (&*BBI == GetObjCArg(Inst)) {
+ DEBUG(dbgs() << "ObjCARCContract: Adding inline asm marker for "
+ "retainAutoreleasedReturnValue optimization.\n");
+ Changed = true;
+ InlineAsm *IA =
+ InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
+ /*isVarArg=*/false),
+ RetainRVMarker->getString(),
+ /*Constraints=*/"", /*hasSideEffects=*/true);
+ CallInst::Create(IA, "", Inst);
+ }
+ decline_rv_optimization:
+ break;
+ }
+ case IC_InitWeak: {
+ // objc_initWeak(p, null) => *p = null
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(1))) {
+ Value *Null =
+ ConstantPointerNull::get(cast<PointerType>(CI->getType()));
+ Changed = true;
+ new StoreInst(Null, CI->getArgOperand(0), CI);
+
+ DEBUG(dbgs() << "OBJCARCContract: Old = " << *CI << "\n"
+ << " New = " << *Null << "\n");
+
+ CI->replaceAllUsesWith(Null);
+ CI->eraseFromParent();
+ }
+ continue;
+ }
+ case IC_Release:
+ ContractRelease(Inst, I);
+ continue;
+ case IC_User:
+ // Be conservative if the function has any alloca instructions.
+ // Technically we only care about escaping alloca instructions,
+ // but this is sufficient to handle some interesting cases.
+ if (isa<AllocaInst>(Inst))
+ TailOkForStoreStrongs = false;
+ continue;
+ default:
+ continue;
+ }
+
+ DEBUG(dbgs() << "ObjCARCContract: Finished List.\n\n");
+
+ // Don't use GetObjCArg because we don't want to look through bitcasts
+ // and such; to do the replacement, the argument must have type i8*.
+ const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
+ for (;;) {
+ // If we're compiling bugpointed code, don't get in trouble.
+ if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
+ break;
+ // Look through the uses of the pointer.
+ for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
+ UI != UE; ) {
+ Use &U = UI.getUse();
+ unsigned OperandNo = UI.getOperandNo();
+ ++UI; // Increment UI now, because we may unlink its element.
+
+ // If the call's return value dominates a use of the call's argument
+ // value, rewrite the use to use the return value. We check for
+ // reachability here because an unreachable call is considered to
+ // trivially dominate itself, which would lead us to rewriting its
+ // argument in terms of its return value, which would lead to
+ // infinite loops in GetObjCArg.
+ if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
+ Changed = true;
+ Instruction *Replacement = Inst;
+ Type *UseTy = U.get()->getType();
+ if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
+ // For PHI nodes, insert the bitcast in the predecessor block.
+ unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
+ BasicBlock *BB = PHI->getIncomingBlock(ValNo);
+ if (Replacement->getType() != UseTy)
+ Replacement = new BitCastInst(Replacement, UseTy, "",
+ &BB->back());
+ // While we're here, rewrite all edges for this PHI, rather
+ // than just one use at a time, to minimize the number of
+ // bitcasts we emit.
+ for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
+ if (PHI->getIncomingBlock(i) == BB) {
+ // Keep the UI iterator valid.
+ if (&PHI->getOperandUse(
+ PHINode::getOperandNumForIncomingValue(i)) ==
+ &UI.getUse())
+ ++UI;
+ PHI->setIncomingValue(i, Replacement);
+ }
+ } else {
+ if (Replacement->getType() != UseTy)
+ Replacement = new BitCastInst(Replacement, UseTy, "",
+ cast<Instruction>(U.getUser()));
+ U.set(Replacement);
+ }
+ }
+ }
+
+ // If Arg is a no-op casted pointer, strip one level of casts and iterate.
+ if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
+ Arg = BI->getOperand(0);
+ else if (isa<GEPOperator>(Arg) &&
+ cast<GEPOperator>(Arg)->hasAllZeroIndices())
+ Arg = cast<GEPOperator>(Arg)->getPointerOperand();
+ else if (isa<GlobalAlias>(Arg) &&
+ !cast<GlobalAlias>(Arg)->mayBeOverridden())
+ Arg = cast<GlobalAlias>(Arg)->getAliasee();
+ else
+ break;
+ }
+ }
+
+ // If this function has no escaping allocas or suspicious vararg usage,
+ // objc_storeStrong calls can be marked with the "tail" keyword.
+ if (TailOkForStoreStrongs)
+ for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
+ E = StoreStrongCalls.end(); I != E; ++I)
+ (*I)->setTailCall();
+ StoreStrongCalls.clear();
+
+ return Changed;
+}
+
+/// @}
+///
Modified: llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp?rev=173760&r1=173759&r2=173760&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp (original)
+++ llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp Mon Jan 28 21:03:03 2013
@@ -31,10 +31,13 @@
#define DEBUG_TYPE "objc-arc-opts"
#include "ObjCARC.h"
#include "ObjCARCAliasAnalysis.h"
+#include "ProvenanceAnalysis.h"
+#include "DependencyAnalysis.h"
#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/CFG.h"
using namespace llvm;
using namespace llvm::objcarc;
@@ -132,202 +135,6 @@ namespace {
/// \defgroup ARCUtilities Utility declarations/definitions specific to ARC.
/// @{
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Transforms/Utils/Local.h"
-
-/// \brief Test whether the given value is possible a retainable object pointer.
-static bool IsPotentialRetainableObjPtr(const Value *Op) {
- // Pointers to static or stack storage are not valid retainable object pointers.
- if (isa<Constant>(Op) || isa<AllocaInst>(Op))
- return false;
- // Special arguments can not be a valid retainable object pointer.
- if (const Argument *Arg = dyn_cast<Argument>(Op))
- if (Arg->hasByValAttr() ||
- Arg->hasNestAttr() ||
- Arg->hasStructRetAttr())
- return false;
- // Only consider values with pointer types.
- //
- // It seemes intuitive to exclude function pointer types as well, since
- // functions are never retainable object pointers, however clang occasionally
- // bitcasts retainable object pointers to function-pointer type temporarily.
- PointerType *Ty = dyn_cast<PointerType>(Op->getType());
- if (!Ty)
- return false;
- // Conservatively assume anything else is a potential retainable object pointer.
- return true;
-}
-
-/// \brief Helper for GetInstructionClass. Determines what kind of construct CS
-/// is.
-static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
- for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
- I != E; ++I)
- if (IsPotentialRetainableObjPtr(*I))
- return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
-
- return CS.onlyReadsMemory() ? IC_None : IC_Call;
-}
-
-/// \brief Determine what kind of construct V is.
-static InstructionClass GetInstructionClass(const Value *V) {
- if (const Instruction *I = dyn_cast<Instruction>(V)) {
- // Any instruction other than bitcast and gep with a pointer operand have a
- // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
- // to a subsequent use, rather than using it themselves, in this sense.
- // As a short cut, several other opcodes are known to have no pointer
- // operands of interest. And ret is never followed by a release, so it's
- // not interesting to examine.
- switch (I->getOpcode()) {
- case Instruction::Call: {
- const CallInst *CI = cast<CallInst>(I);
- // Check for calls to special functions.
- if (const Function *F = CI->getCalledFunction()) {
- InstructionClass Class = GetFunctionClass(F);
- if (Class != IC_CallOrUser)
- return Class;
-
- // None of the intrinsic functions do objc_release. For intrinsics, the
- // only question is whether or not they may be users.
- switch (F->getIntrinsicID()) {
- case Intrinsic::returnaddress: case Intrinsic::frameaddress:
- case Intrinsic::stacksave: case Intrinsic::stackrestore:
- case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
- case Intrinsic::objectsize: case Intrinsic::prefetch:
- case Intrinsic::stackprotector:
- case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
- case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
- case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
- case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
- case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
- case Intrinsic::invariant_start: case Intrinsic::invariant_end:
- // Don't let dbg info affect our results.
- case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
- // Short cut: Some intrinsics obviously don't use ObjC pointers.
- return IC_None;
- default:
- break;
- }
- }
- return GetCallSiteClass(CI);
- }
- case Instruction::Invoke:
- return GetCallSiteClass(cast<InvokeInst>(I));
- case Instruction::BitCast:
- case Instruction::GetElementPtr:
- case Instruction::Select: case Instruction::PHI:
- case Instruction::Ret: case Instruction::Br:
- case Instruction::Switch: case Instruction::IndirectBr:
- case Instruction::Alloca: case Instruction::VAArg:
- case Instruction::Add: case Instruction::FAdd:
- case Instruction::Sub: case Instruction::FSub:
- case Instruction::Mul: case Instruction::FMul:
- case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
- case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
- case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
- case Instruction::And: case Instruction::Or: case Instruction::Xor:
- case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
- case Instruction::IntToPtr: case Instruction::FCmp:
- case Instruction::FPTrunc: case Instruction::FPExt:
- case Instruction::FPToUI: case Instruction::FPToSI:
- case Instruction::UIToFP: case Instruction::SIToFP:
- case Instruction::InsertElement: case Instruction::ExtractElement:
- case Instruction::ShuffleVector:
- case Instruction::ExtractValue:
- break;
- case Instruction::ICmp:
- // Comparing a pointer with null, or any other constant, isn't an
- // interesting use, because we don't care what the pointer points to, or
- // about the values of any other dynamic reference-counted pointers.
- if (IsPotentialRetainableObjPtr(I->getOperand(1)))
- return IC_User;
- break;
- default:
- // For anything else, check all the operands.
- // Note that this includes both operands of a Store: while the first
- // operand isn't actually being dereferenced, it is being stored to
- // memory where we can no longer track who might read it and dereference
- // it, so we have to consider it potentially used.
- for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
- OI != OE; ++OI)
- if (IsPotentialRetainableObjPtr(*OI))
- return IC_User;
- }
- }
-
- // Otherwise, it's totally inert for ARC purposes.
- return IC_None;
-}
-
-/// \brief Erase the given instruction.
-///
-/// Many ObjC calls return their argument verbatim,
-/// so if it's such a call and the return value has users, replace them with the
-/// argument value.
-///
-static void EraseInstruction(Instruction *CI) {
- Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
-
- bool Unused = CI->use_empty();
-
- if (!Unused) {
- // Replace the return value with the argument.
- assert(IsForwarding(GetBasicInstructionClass(CI)) &&
- "Can't delete non-forwarding instruction with users!");
- CI->replaceAllUsesWith(OldArg);
- }
-
- CI->eraseFromParent();
-
- if (Unused)
- RecursivelyDeleteTriviallyDeadInstructions(OldArg);
-}
-
-/// \brief Assuming the given instruction is one of the special calls such as
-/// objc_retain or objc_release, return the argument value, stripped of no-op
-/// casts and forwarding calls.
-static Value *GetObjCArg(Value *Inst) {
- return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
-}
-
-/// \brief Return true if this value refers to a distinct and identifiable
-/// object.
-///
-/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
-/// special knowledge of ObjC conventions.
-static bool IsObjCIdentifiedObject(const Value *V) {
- // Assume that call results and arguments have their own "provenance".
- // Constants (including GlobalVariables) and Allocas are never
- // reference-counted.
- if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
- isa<Argument>(V) || isa<Constant>(V) ||
- isa<AllocaInst>(V))
- return true;
-
- if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
- const Value *Pointer =
- StripPointerCastsAndObjCCalls(LI->getPointerOperand());
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
- // A constant pointer can't be pointing to an object on the heap. It may
- // be reference-counted, but it won't be deleted.
- if (GV->isConstant())
- return true;
- StringRef Name = GV->getName();
- // These special variables are known to hold values which are not
- // reference-counted pointers.
- if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
- Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
- Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
- Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
- Name.startswith("\01l_objc_msgSend_fixup_"))
- return true;
- }
- }
-
- return false;
-}
-
/// \brief This is similar to StripPointerCastsAndObjCCalls but it stops as soon
/// as it finds a value with multiple uses.
static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
@@ -487,7 +294,6 @@ static bool DoesObjCBlockEscape(const Va
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/LLVMContext.h"
-#include "llvm/Support/CFG.h"
STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
@@ -498,187 +304,6 @@ STATISTIC(NumRRs, "Number of ret
STATISTIC(NumPeeps, "Number of calls peephole-optimized");
namespace {
- /// \brief This is similar to BasicAliasAnalysis, and it uses many of the same
- /// techniques, except it uses special ObjC-specific reasoning about pointer
- /// relationships.
- ///
- /// In this context ``Provenance'' is defined as the history of an object's
- /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
- /// an ``independent provenance source'' of a pointer to determine whether or
- /// not two pointers have the same provenance source and thus could
- /// potentially be related.
- class ProvenanceAnalysis {
- AliasAnalysis *AA;
-
- typedef std::pair<const Value *, const Value *> ValuePairTy;
- typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
- CachedResultsTy CachedResults;
-
- bool relatedCheck(const Value *A, const Value *B);
- bool relatedSelect(const SelectInst *A, const Value *B);
- bool relatedPHI(const PHINode *A, const Value *B);
-
- void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
- ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
-
- public:
- ProvenanceAnalysis() {}
-
- void setAA(AliasAnalysis *aa) { AA = aa; }
-
- AliasAnalysis *getAA() const { return AA; }
-
- bool related(const Value *A, const Value *B);
-
- void clear() {
- CachedResults.clear();
- }
- };
-}
-
-bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
- // If the values are Selects with the same condition, we can do a more precise
- // check: just check for relations between the values on corresponding arms.
- if (const SelectInst *SB = dyn_cast<SelectInst>(B))
- if (A->getCondition() == SB->getCondition())
- return related(A->getTrueValue(), SB->getTrueValue()) ||
- related(A->getFalseValue(), SB->getFalseValue());
-
- // Check both arms of the Select node individually.
- return related(A->getTrueValue(), B) ||
- related(A->getFalseValue(), B);
-}
-
-bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
- // If the values are PHIs in the same block, we can do a more precise as well
- // as efficient check: just check for relations between the values on
- // corresponding edges.
- if (const PHINode *PNB = dyn_cast<PHINode>(B))
- if (PNB->getParent() == A->getParent()) {
- for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
- if (related(A->getIncomingValue(i),
- PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
- return true;
- return false;
- }
-
- // Check each unique source of the PHI node against B.
- SmallPtrSet<const Value *, 4> UniqueSrc;
- for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
- const Value *PV1 = A->getIncomingValue(i);
- if (UniqueSrc.insert(PV1) && related(PV1, B))
- return true;
- }
-
- // All of the arms checked out.
- return false;
-}
-
-/// Test if the value of P, or any value covered by its provenance, is ever
-/// stored within the function (not counting callees).
-static bool isStoredObjCPointer(const Value *P) {
- SmallPtrSet<const Value *, 8> Visited;
- SmallVector<const Value *, 8> Worklist;
- Worklist.push_back(P);
- Visited.insert(P);
- do {
- P = Worklist.pop_back_val();
- for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
- UI != UE; ++UI) {
- const User *Ur = *UI;
- if (isa<StoreInst>(Ur)) {
- if (UI.getOperandNo() == 0)
- // The pointer is stored.
- return true;
- // The pointed is stored through.
- continue;
- }
- if (isa<CallInst>(Ur))
- // The pointer is passed as an argument, ignore this.
- continue;
- if (isa<PtrToIntInst>(P))
- // Assume the worst.
- return true;
- if (Visited.insert(Ur))
- Worklist.push_back(Ur);
- }
- } while (!Worklist.empty());
-
- // Everything checked out.
- return false;
-}
-
-bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
- // Skip past provenance pass-throughs.
- A = GetUnderlyingObjCPtr(A);
- B = GetUnderlyingObjCPtr(B);
-
- // Quick check.
- if (A == B)
- return true;
-
- // Ask regular AliasAnalysis, for a first approximation.
- switch (AA->alias(A, B)) {
- case AliasAnalysis::NoAlias:
- return false;
- case AliasAnalysis::MustAlias:
- case AliasAnalysis::PartialAlias:
- return true;
- case AliasAnalysis::MayAlias:
- break;
- }
-
- bool AIsIdentified = IsObjCIdentifiedObject(A);
- bool BIsIdentified = IsObjCIdentifiedObject(B);
-
- // An ObjC-Identified object can't alias a load if it is never locally stored.
- if (AIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(B))
- return isStoredObjCPointer(A);
- if (BIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(A))
- return isStoredObjCPointer(B);
- // Both pointers are identified and escapes aren't an evident problem.
- return false;
- }
- } else if (BIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(A))
- return isStoredObjCPointer(B);
- }
-
- // Special handling for PHI and Select.
- if (const PHINode *PN = dyn_cast<PHINode>(A))
- return relatedPHI(PN, B);
- if (const PHINode *PN = dyn_cast<PHINode>(B))
- return relatedPHI(PN, A);
- if (const SelectInst *S = dyn_cast<SelectInst>(A))
- return relatedSelect(S, B);
- if (const SelectInst *S = dyn_cast<SelectInst>(B))
- return relatedSelect(S, A);
-
- // Conservative.
- return true;
-}
-
-bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
- // Begin by inserting a conservative value into the map. If the insertion
- // fails, we have the answer already. If it succeeds, leave it there until we
- // compute the real answer to guard against recursive queries.
- if (A > B) std::swap(A, B);
- std::pair<CachedResultsTy::iterator, bool> Pair =
- CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
- if (!Pair.second)
- return Pair.first->second;
-
- bool Result = relatedCheck(A, B);
- CachedResults[ValuePairTy(A, B)] = Result;
- return Result;
-}
-
-namespace {
/// \enum Sequence
///
/// \brief A sequence of states that a pointer may go through in which an
@@ -1300,300 +925,6 @@ Constant *ObjCARCOpt::getAutoreleaseCall
return AutoreleaseCallee;
}
-/// Test whether the given value is possible a reference-counted pointer,
-/// including tests which utilize AliasAnalysis.
-static bool IsPotentialRetainableObjPtr(const Value *Op, AliasAnalysis &AA) {
- // First make the rudimentary check.
- if (!IsPotentialRetainableObjPtr(Op))
- return false;
-
- // Objects in constant memory are not reference-counted.
- if (AA.pointsToConstantMemory(Op))
- return false;
-
- // Pointers in constant memory are not pointing to reference-counted objects.
- if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
- if (AA.pointsToConstantMemory(LI->getPointerOperand()))
- return false;
-
- // Otherwise assume the worst.
- return true;
-}
-
-/// Test whether the given instruction can result in a reference count
-/// modification (positive or negative) for the pointer's object.
-static bool
-CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
- ProvenanceAnalysis &PA, InstructionClass Class) {
- switch (Class) {
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- case IC_User:
- // These operations never directly modify a reference count.
- return false;
- default: break;
- }
-
- ImmutableCallSite CS = static_cast<const Value *>(Inst);
- assert(CS && "Only calls can alter reference counts!");
-
- // See if AliasAnalysis can help us with the call.
- AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
- if (AliasAnalysis::onlyReadsMemory(MRB))
- return false;
- if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
- for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
- I != E; ++I) {
- const Value *Op = *I;
- if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
- }
-
- // Assume the worst.
- return true;
-}
-
-/// Test whether the given instruction can "use" the given pointer's object in a
-/// way that requires the reference count to be positive.
-static bool
-CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
- InstructionClass Class) {
- // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
- if (Class == IC_Call)
- return false;
-
- // Consider various instructions which may have pointer arguments which are
- // not "uses".
- if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
- // Comparing a pointer with null, or any other constant, isn't really a use,
- // because we don't care what the pointer points to, or about the values
- // of any other dynamic reference-counted pointers.
- if (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
- return false;
- } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
- // For calls, just check the arguments (and not the callee operand).
- for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
- OE = CS.arg_end(); OI != OE; ++OI) {
- const Value *Op = *OI;
- if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
- } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- // Special-case stores, because we don't care about the stored value, just
- // the store address.
- const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
- // If we can't tell what the underlying object was, assume there is a
- // dependence.
- return IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Op, Ptr);
- }
-
- // Check each operand for a match.
- for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
- OI != OE; ++OI) {
- const Value *Op = *OI;
- if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
-}
-
-/// Test whether the given instruction can autorelease any pointer or cause an
-/// autoreleasepool pop.
-static bool
-CanInterruptRV(InstructionClass Class) {
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_CallOrUser:
- case IC_Call:
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- case IC_FusedRetainAutorelease:
- case IC_FusedRetainAutoreleaseRV:
- return true;
- default:
- return false;
- }
-}
-
-namespace {
- /// \enum DependenceKind
- /// \brief Defines different dependence kinds among various ARC constructs.
- ///
- /// There are several kinds of dependence-like concepts in use here.
- ///
- enum DependenceKind {
- NeedsPositiveRetainCount,
- AutoreleasePoolBoundary,
- CanChangeRetainCount,
- RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
- RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
- RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
- };
-}
-
-/// Test if there can be dependencies on Inst through Arg. This function only
-/// tests dependencies relevant for removing pairs of calls.
-static bool
-Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
- ProvenanceAnalysis &PA) {
- // If we've reached the definition of Arg, stop.
- if (Inst == Arg)
- return true;
-
- switch (Flavor) {
- case NeedsPositiveRetainCount: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- case IC_None:
- return false;
- default:
- return CanUse(Inst, Arg, PA, Class);
- }
- }
-
- case AutoreleasePoolBoundary: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- // These mark the end and begin of an autorelease pool scope.
- return true;
- default:
- // Nothing else does this.
- return false;
- }
- }
-
- case CanChangeRetainCount: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- // Conservatively assume this can decrement any count.
- return true;
- case IC_AutoreleasepoolPush:
- case IC_None:
- return false;
- default:
- return CanAlterRefCount(Inst, Arg, PA, Class);
- }
- }
-
- case RetainAutoreleaseDep:
- switch (GetBasicInstructionClass(Inst)) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- // Don't merge an objc_autorelease with an objc_retain inside a different
- // autoreleasepool scope.
- return true;
- case IC_Retain:
- case IC_RetainRV:
- // Check for a retain of the same pointer for merging.
- return GetObjCArg(Inst) == Arg;
- default:
- // Nothing else matters for objc_retainAutorelease formation.
- return false;
- }
-
- case RetainAutoreleaseRVDep: {
- InstructionClass Class = GetBasicInstructionClass(Inst);
- switch (Class) {
- case IC_Retain:
- case IC_RetainRV:
- // Check for a retain of the same pointer for merging.
- return GetObjCArg(Inst) == Arg;
- default:
- // Anything that can autorelease interrupts
- // retainAutoreleaseReturnValue formation.
- return CanInterruptRV(Class);
- }
- }
-
- case RetainRVDep:
- return CanInterruptRV(GetBasicInstructionClass(Inst));
- }
-
- llvm_unreachable("Invalid dependence flavor");
-}
-
-/// Walk up the CFG from StartPos (which is in StartBB) and find local and
-/// non-local dependencies on Arg.
-///
-/// TODO: Cache results?
-static void
-FindDependencies(DependenceKind Flavor,
- const Value *Arg,
- BasicBlock *StartBB, Instruction *StartInst,
- SmallPtrSet<Instruction *, 4> &DependingInstructions,
- SmallPtrSet<const BasicBlock *, 4> &Visited,
- ProvenanceAnalysis &PA) {
- BasicBlock::iterator StartPos = StartInst;
-
- SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
- Worklist.push_back(std::make_pair(StartBB, StartPos));
- do {
- std::pair<BasicBlock *, BasicBlock::iterator> Pair =
- Worklist.pop_back_val();
- BasicBlock *LocalStartBB = Pair.first;
- BasicBlock::iterator LocalStartPos = Pair.second;
- BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
- for (;;) {
- if (LocalStartPos == StartBBBegin) {
- pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
- if (PI == PE)
- // If we've reached the function entry, produce a null dependence.
- DependingInstructions.insert(0);
- else
- // Add the predecessors to the worklist.
- do {
- BasicBlock *PredBB = *PI;
- if (Visited.insert(PredBB))
- Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
- } while (++PI != PE);
- break;
- }
-
- Instruction *Inst = --LocalStartPos;
- if (Depends(Flavor, Inst, Arg, PA)) {
- DependingInstructions.insert(Inst);
- break;
- }
- }
- } while (!Worklist.empty());
-
- // Determine whether the original StartBB post-dominates all of the blocks we
- // visited. If not, insert a sentinal indicating that most optimizations are
- // not safe.
- for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
- E = Visited.end(); I != E; ++I) {
- const BasicBlock *BB = *I;
- if (BB == StartBB)
- continue;
- const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
- for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
- const BasicBlock *Succ = *SI;
- if (Succ != StartBB && !Visited.count(Succ)) {
- DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
- return;
- }
- }
- }
-}
-
-static bool isNullOrUndef(const Value *V) {
- return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
-}
-
-static bool isNoopInstruction(const Instruction *I) {
- return isa<BitCastInst>(I) ||
- (isa<GetElementPtrInst>(I) &&
- cast<GetElementPtrInst>(I)->hasAllZeroIndices());
-}
-
/// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
/// return value.
void
@@ -3337,511 +2668,3 @@ void ObjCARCOpt::releaseMemory() {
/// @}
///
-/// \defgroup ARCContract ARC Contraction.
-/// @{
-
-// TODO: ObjCARCContract could insert PHI nodes when uses aren't
-// dominated by single calls.
-
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/IR/InlineAsm.h"
-#include "llvm/IR/Operator.h"
-
-STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
-
-namespace {
- /// \brief Late ARC optimizations
- ///
- /// These change the IR in a way that makes it difficult to be analyzed by
- /// ObjCARCOpt, so it's run late.
- class ObjCARCContract : public FunctionPass {
- bool Changed;
- AliasAnalysis *AA;
- DominatorTree *DT;
- ProvenanceAnalysis PA;
-
- /// A flag indicating whether this optimization pass should run.
- bool Run;
-
- /// Declarations for ObjC runtime functions, for use in creating calls to
- /// them. These are initialized lazily to avoid cluttering up the Module
- /// with unused declarations.
-
- /// Declaration for objc_storeStrong().
- Constant *StoreStrongCallee;
- /// Declaration for objc_retainAutorelease().
- Constant *RetainAutoreleaseCallee;
- /// Declaration for objc_retainAutoreleaseReturnValue().
- Constant *RetainAutoreleaseRVCallee;
-
- /// The inline asm string to insert between calls and RetainRV calls to make
- /// the optimization work on targets which need it.
- const MDString *RetainRVMarker;
-
- /// The set of inserted objc_storeStrong calls. If at the end of walking the
- /// function we have found no alloca instructions, these calls can be marked
- /// "tail".
- SmallPtrSet<CallInst *, 8> StoreStrongCalls;
-
- Constant *getStoreStrongCallee(Module *M);
- Constant *getRetainAutoreleaseCallee(Module *M);
- Constant *getRetainAutoreleaseRVCallee(Module *M);
-
- bool ContractAutorelease(Function &F, Instruction *Autorelease,
- InstructionClass Class,
- SmallPtrSet<Instruction *, 4>
- &DependingInstructions,
- SmallPtrSet<const BasicBlock *, 4>
- &Visited);
-
- void ContractRelease(Instruction *Release,
- inst_iterator &Iter);
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool doInitialization(Module &M);
- virtual bool runOnFunction(Function &F);
-
- public:
- static char ID;
- ObjCARCContract() : FunctionPass(ID) {
- initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
- }
- };
-}
-
-char ObjCARCContract::ID = 0;
-INITIALIZE_PASS_BEGIN(ObjCARCContract,
- "objc-arc-contract", "ObjC ARC contraction", false, false)
-INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
-INITIALIZE_PASS_DEPENDENCY(DominatorTree)
-INITIALIZE_PASS_END(ObjCARCContract,
- "objc-arc-contract", "ObjC ARC contraction", false, false)
-
-Pass *llvm::createObjCARCContractPass() {
- return new ObjCARCContract();
-}
-
-void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<AliasAnalysis>();
- AU.addRequired<DominatorTree>();
- AU.setPreservesCFG();
-}
-
-Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
- if (!StoreStrongCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *I8XX = PointerType::getUnqual(I8X);
- Type *Params[] = { I8XX, I8X };
-
- AttributeSet Attr = AttributeSet()
- .addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind)
- .addAttribute(M->getContext(), 1, Attribute::NoCapture);
-
- StoreStrongCallee =
- M->getOrInsertFunction(
- "objc_storeStrong",
- FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
- Attr);
- }
- return StoreStrongCallee;
-}
-
-Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
- if (!RetainAutoreleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainAutoreleaseCallee =
- M->getOrInsertFunction("objc_retainAutorelease", FTy, Attribute);
- }
- return RetainAutoreleaseCallee;
-}
-
-Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
- if (!RetainAutoreleaseRVCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainAutoreleaseRVCallee =
- M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
- Attribute);
- }
- return RetainAutoreleaseRVCallee;
-}
-
-/// Merge an autorelease with a retain into a fused call.
-bool
-ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
- InstructionClass Class,
- SmallPtrSet<Instruction *, 4>
- &DependingInstructions,
- SmallPtrSet<const BasicBlock *, 4>
- &Visited) {
- const Value *Arg = GetObjCArg(Autorelease);
-
- // Check that there are no instructions between the retain and the autorelease
- // (such as an autorelease_pop) which may change the count.
- CallInst *Retain = 0;
- if (Class == IC_AutoreleaseRV)
- FindDependencies(RetainAutoreleaseRVDep, Arg,
- Autorelease->getParent(), Autorelease,
- DependingInstructions, Visited, PA);
- else
- FindDependencies(RetainAutoreleaseDep, Arg,
- Autorelease->getParent(), Autorelease,
- DependingInstructions, Visited, PA);
-
- Visited.clear();
- if (DependingInstructions.size() != 1) {
- DependingInstructions.clear();
- return false;
- }
-
- Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
- DependingInstructions.clear();
-
- if (!Retain ||
- GetBasicInstructionClass(Retain) != IC_Retain ||
- GetObjCArg(Retain) != Arg)
- return false;
-
- Changed = true;
- ++NumPeeps;
-
- DEBUG(dbgs() << "ObjCARCContract::ContractAutorelease: Fusing "
- "retain/autorelease. Erasing: " << *Autorelease << "\n"
- " Old Retain: "
- << *Retain << "\n");
-
- if (Class == IC_AutoreleaseRV)
- Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
- else
- Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
-
- DEBUG(dbgs() << " New Retain: "
- << *Retain << "\n");
-
- EraseInstruction(Autorelease);
- return true;
-}
-
-/// Attempt to merge an objc_release with a store, load, and objc_retain to form
-/// an objc_storeStrong. This can be a little tricky because the instructions
-/// don't always appear in order, and there may be unrelated intervening
-/// instructions.
-void ObjCARCContract::ContractRelease(Instruction *Release,
- inst_iterator &Iter) {
- LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
- if (!Load || !Load->isSimple()) return;
-
- // For now, require everything to be in one basic block.
- BasicBlock *BB = Release->getParent();
- if (Load->getParent() != BB) return;
-
- // Walk down to find the store and the release, which may be in either order.
- BasicBlock::iterator I = Load, End = BB->end();
- ++I;
- AliasAnalysis::Location Loc = AA->getLocation(Load);
- StoreInst *Store = 0;
- bool SawRelease = false;
- for (; !Store || !SawRelease; ++I) {
- if (I == End)
- return;
-
- Instruction *Inst = I;
- if (Inst == Release) {
- SawRelease = true;
- continue;
- }
-
- InstructionClass Class = GetBasicInstructionClass(Inst);
-
- // Unrelated retains are harmless.
- if (IsRetain(Class))
- continue;
-
- if (Store) {
- // The store is the point where we're going to put the objc_storeStrong,
- // so make sure there are no uses after it.
- if (CanUse(Inst, Load, PA, Class))
- return;
- } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
- // We are moving the load down to the store, so check for anything
- // else which writes to the memory between the load and the store.
- Store = dyn_cast<StoreInst>(Inst);
- if (!Store || !Store->isSimple()) return;
- if (Store->getPointerOperand() != Loc.Ptr) return;
- }
- }
-
- Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
-
- // Walk up to find the retain.
- I = Store;
- BasicBlock::iterator Begin = BB->begin();
- while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
- --I;
- Instruction *Retain = I;
- if (GetBasicInstructionClass(Retain) != IC_Retain) return;
- if (GetObjCArg(Retain) != New) return;
-
- Changed = true;
- ++NumStoreStrongs;
-
- LLVMContext &C = Release->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *I8XX = PointerType::getUnqual(I8X);
-
- Value *Args[] = { Load->getPointerOperand(), New };
- if (Args[0]->getType() != I8XX)
- Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
- if (Args[1]->getType() != I8X)
- Args[1] = new BitCastInst(Args[1], I8X, "", Store);
- CallInst *StoreStrong =
- CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
- Args, "", Store);
- StoreStrong->setDoesNotThrow();
- StoreStrong->setDebugLoc(Store->getDebugLoc());
-
- // We can't set the tail flag yet, because we haven't yet determined
- // whether there are any escaping allocas. Remember this call, so that
- // we can set the tail flag once we know it's safe.
- StoreStrongCalls.insert(StoreStrong);
-
- if (&*Iter == Store) ++Iter;
- Store->eraseFromParent();
- Release->eraseFromParent();
- EraseInstruction(Retain);
- if (Load->use_empty())
- Load->eraseFromParent();
-}
-
-bool ObjCARCContract::doInitialization(Module &M) {
- // If nothing in the Module uses ARC, don't do anything.
- Run = ModuleHasARC(M);
- if (!Run)
- return false;
-
- // These are initialized lazily.
- StoreStrongCallee = 0;
- RetainAutoreleaseCallee = 0;
- RetainAutoreleaseRVCallee = 0;
-
- // Initialize RetainRVMarker.
- RetainRVMarker = 0;
- if (NamedMDNode *NMD =
- M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
- if (NMD->getNumOperands() == 1) {
- const MDNode *N = NMD->getOperand(0);
- if (N->getNumOperands() == 1)
- if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
- RetainRVMarker = S;
- }
-
- return false;
-}
-
-bool ObjCARCContract::runOnFunction(Function &F) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!Run)
- return false;
-
- Changed = false;
- AA = &getAnalysis<AliasAnalysis>();
- DT = &getAnalysis<DominatorTree>();
-
- PA.setAA(&getAnalysis<AliasAnalysis>());
-
- // Track whether it's ok to mark objc_storeStrong calls with the "tail"
- // keyword. Be conservative if the function has variadic arguments.
- // It seems that functions which "return twice" are also unsafe for the
- // "tail" argument, because they are setjmp, which could need to
- // return to an earlier stack state.
- bool TailOkForStoreStrongs = !F.isVarArg() &&
- !F.callsFunctionThatReturnsTwice();
-
- // For ObjC library calls which return their argument, replace uses of the
- // argument with uses of the call return value, if it dominates the use. This
- // reduces register pressure.
- SmallPtrSet<Instruction *, 4> DependingInstructions;
- SmallPtrSet<const BasicBlock *, 4> Visited;
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
- Instruction *Inst = &*I++;
-
- DEBUG(dbgs() << "ObjCARCContract: Visiting: " << *Inst << "\n");
-
- // Only these library routines return their argument. In particular,
- // objc_retainBlock does not necessarily return its argument.
- InstructionClass Class = GetBasicInstructionClass(Inst);
- switch (Class) {
- case IC_Retain:
- case IC_FusedRetainAutorelease:
- case IC_FusedRetainAutoreleaseRV:
- break;
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
- continue;
- break;
- case IC_RetainRV: {
- // If we're compiling for a target which needs a special inline-asm
- // marker to do the retainAutoreleasedReturnValue optimization,
- // insert it now.
- if (!RetainRVMarker)
- break;
- BasicBlock::iterator BBI = Inst;
- BasicBlock *InstParent = Inst->getParent();
-
- // Step up to see if the call immediately precedes the RetainRV call.
- // If it's an invoke, we have to cross a block boundary. And we have
- // to carefully dodge no-op instructions.
- do {
- if (&*BBI == InstParent->begin()) {
- BasicBlock *Pred = InstParent->getSinglePredecessor();
- if (!Pred)
- goto decline_rv_optimization;
- BBI = Pred->getTerminator();
- break;
- }
- --BBI;
- } while (isNoopInstruction(BBI));
-
- if (&*BBI == GetObjCArg(Inst)) {
- DEBUG(dbgs() << "ObjCARCContract: Adding inline asm marker for "
- "retainAutoreleasedReturnValue optimization.\n");
- Changed = true;
- InlineAsm *IA =
- InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
- /*isVarArg=*/false),
- RetainRVMarker->getString(),
- /*Constraints=*/"", /*hasSideEffects=*/true);
- CallInst::Create(IA, "", Inst);
- }
- decline_rv_optimization:
- break;
- }
- case IC_InitWeak: {
- // objc_initWeak(p, null) => *p = null
- CallInst *CI = cast<CallInst>(Inst);
- if (isNullOrUndef(CI->getArgOperand(1))) {
- Value *Null =
- ConstantPointerNull::get(cast<PointerType>(CI->getType()));
- Changed = true;
- new StoreInst(Null, CI->getArgOperand(0), CI);
-
- DEBUG(dbgs() << "OBJCARCContract: Old = " << *CI << "\n"
- << " New = " << *Null << "\n");
-
- CI->replaceAllUsesWith(Null);
- CI->eraseFromParent();
- }
- continue;
- }
- case IC_Release:
- ContractRelease(Inst, I);
- continue;
- case IC_User:
- // Be conservative if the function has any alloca instructions.
- // Technically we only care about escaping alloca instructions,
- // but this is sufficient to handle some interesting cases.
- if (isa<AllocaInst>(Inst))
- TailOkForStoreStrongs = false;
- continue;
- default:
- continue;
- }
-
- DEBUG(dbgs() << "ObjCARCContract: Finished List.\n\n");
-
- // Don't use GetObjCArg because we don't want to look through bitcasts
- // and such; to do the replacement, the argument must have type i8*.
- const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
- for (;;) {
- // If we're compiling bugpointed code, don't get in trouble.
- if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
- break;
- // Look through the uses of the pointer.
- for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
- UI != UE; ) {
- Use &U = UI.getUse();
- unsigned OperandNo = UI.getOperandNo();
- ++UI; // Increment UI now, because we may unlink its element.
-
- // If the call's return value dominates a use of the call's argument
- // value, rewrite the use to use the return value. We check for
- // reachability here because an unreachable call is considered to
- // trivially dominate itself, which would lead us to rewriting its
- // argument in terms of its return value, which would lead to
- // infinite loops in GetObjCArg.
- if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
- Changed = true;
- Instruction *Replacement = Inst;
- Type *UseTy = U.get()->getType();
- if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
- // For PHI nodes, insert the bitcast in the predecessor block.
- unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
- BasicBlock *BB = PHI->getIncomingBlock(ValNo);
- if (Replacement->getType() != UseTy)
- Replacement = new BitCastInst(Replacement, UseTy, "",
- &BB->back());
- // While we're here, rewrite all edges for this PHI, rather
- // than just one use at a time, to minimize the number of
- // bitcasts we emit.
- for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
- if (PHI->getIncomingBlock(i) == BB) {
- // Keep the UI iterator valid.
- if (&PHI->getOperandUse(
- PHINode::getOperandNumForIncomingValue(i)) ==
- &UI.getUse())
- ++UI;
- PHI->setIncomingValue(i, Replacement);
- }
- } else {
- if (Replacement->getType() != UseTy)
- Replacement = new BitCastInst(Replacement, UseTy, "",
- cast<Instruction>(U.getUser()));
- U.set(Replacement);
- }
- }
- }
-
- // If Arg is a no-op casted pointer, strip one level of casts and iterate.
- if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
- Arg = BI->getOperand(0);
- else if (isa<GEPOperator>(Arg) &&
- cast<GEPOperator>(Arg)->hasAllZeroIndices())
- Arg = cast<GEPOperator>(Arg)->getPointerOperand();
- else if (isa<GlobalAlias>(Arg) &&
- !cast<GlobalAlias>(Arg)->mayBeOverridden())
- Arg = cast<GlobalAlias>(Arg)->getAliasee();
- else
- break;
- }
- }
-
- // If this function has no escaping allocas or suspicious vararg usage,
- // objc_storeStrong calls can be marked with the "tail" keyword.
- if (TailOkForStoreStrongs)
- for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
- E = StoreStrongCalls.end(); I != E; ++I)
- (*I)->setTailCall();
- StoreStrongCalls.clear();
-
- return Changed;
-}
-
-/// @}
-///
Modified: llvm/trunk/lib/Transforms/ObjCARC/ObjCARCUtil.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ObjCARCUtil.cpp?rev=173760&r1=173759&r2=173760&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ObjCARCUtil.cpp (original)
+++ llvm/trunk/lib/Transforms/ObjCARC/ObjCARCUtil.cpp Mon Jan 28 21:03:03 2013
@@ -21,6 +21,8 @@
#include "ObjCARC.h"
+#include "llvm/IR/Intrinsics.h"
+
using namespace llvm;
using namespace llvm::objcarc;
@@ -147,3 +149,94 @@ InstructionClass llvm::objcarc::GetFunct
// Anything else.
return IC_CallOrUser;
}
+
+/// \brief Determine what kind of construct V is.
+InstructionClass
+llvm::objcarc::GetInstructionClass(const Value *V) {
+ if (const Instruction *I = dyn_cast<Instruction>(V)) {
+ // Any instruction other than bitcast and gep with a pointer operand have a
+ // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
+ // to a subsequent use, rather than using it themselves, in this sense.
+ // As a short cut, several other opcodes are known to have no pointer
+ // operands of interest. And ret is never followed by a release, so it's
+ // not interesting to examine.
+ switch (I->getOpcode()) {
+ case Instruction::Call: {
+ const CallInst *CI = cast<CallInst>(I);
+ // Check for calls to special functions.
+ if (const Function *F = CI->getCalledFunction()) {
+ InstructionClass Class = GetFunctionClass(F);
+ if (Class != IC_CallOrUser)
+ return Class;
+
+ // None of the intrinsic functions do objc_release. For intrinsics, the
+ // only question is whether or not they may be users.
+ switch (F->getIntrinsicID()) {
+ case Intrinsic::returnaddress: case Intrinsic::frameaddress:
+ case Intrinsic::stacksave: case Intrinsic::stackrestore:
+ case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
+ case Intrinsic::objectsize: case Intrinsic::prefetch:
+ case Intrinsic::stackprotector:
+ case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
+ case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
+ case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
+ case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
+ case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
+ case Intrinsic::invariant_start: case Intrinsic::invariant_end:
+ // Don't let dbg info affect our results.
+ case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
+ // Short cut: Some intrinsics obviously don't use ObjC pointers.
+ return IC_None;
+ default:
+ break;
+ }
+ }
+ return GetCallSiteClass(CI);
+ }
+ case Instruction::Invoke:
+ return GetCallSiteClass(cast<InvokeInst>(I));
+ case Instruction::BitCast:
+ case Instruction::GetElementPtr:
+ case Instruction::Select: case Instruction::PHI:
+ case Instruction::Ret: case Instruction::Br:
+ case Instruction::Switch: case Instruction::IndirectBr:
+ case Instruction::Alloca: case Instruction::VAArg:
+ case Instruction::Add: case Instruction::FAdd:
+ case Instruction::Sub: case Instruction::FSub:
+ case Instruction::Mul: case Instruction::FMul:
+ case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
+ case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
+ case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
+ case Instruction::And: case Instruction::Or: case Instruction::Xor:
+ case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
+ case Instruction::IntToPtr: case Instruction::FCmp:
+ case Instruction::FPTrunc: case Instruction::FPExt:
+ case Instruction::FPToUI: case Instruction::FPToSI:
+ case Instruction::UIToFP: case Instruction::SIToFP:
+ case Instruction::InsertElement: case Instruction::ExtractElement:
+ case Instruction::ShuffleVector:
+ case Instruction::ExtractValue:
+ break;
+ case Instruction::ICmp:
+ // Comparing a pointer with null, or any other constant, isn't an
+ // interesting use, because we don't care what the pointer points to, or
+ // about the values of any other dynamic reference-counted pointers.
+ if (IsPotentialRetainableObjPtr(I->getOperand(1)))
+ return IC_User;
+ break;
+ default:
+ // For anything else, check all the operands.
+ // Note that this includes both operands of a Store: while the first
+ // operand isn't actually being dereferenced, it is being stored to
+ // memory where we can no longer track who might read it and dereference
+ // it, so we have to consider it potentially used.
+ for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
+ OI != OE; ++OI)
+ if (IsPotentialRetainableObjPtr(*OI))
+ return IC_User;
+ }
+ }
+
+ // Otherwise, it's totally inert for ARC purposes.
+ return IC_None;
+}
Added: llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp?rev=173760&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp (added)
+++ llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp Mon Jan 28 21:03:03 2013
@@ -0,0 +1,177 @@
+//===- ProvenanceAnalysis.cpp - ObjC ARC Optimization ---------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file defines a special form of Alias Analysis called ``Provenance
+/// Analysis''. The word ``provenance'' refers to the history of the ownership
+/// of an object. Thus ``Provenance Analysis'' is an analysis which attempts to
+/// use various techniques to determine if locally
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#include "ObjCARC.h"
+#include "ProvenanceAnalysis.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/STLExtras.h"
+
+using namespace llvm;
+using namespace llvm::objcarc;
+
+bool ProvenanceAnalysis::relatedSelect(const SelectInst *A,
+ const Value *B) {
+ // If the values are Selects with the same condition, we can do a more precise
+ // check: just check for relations between the values on corresponding arms.
+ if (const SelectInst *SB = dyn_cast<SelectInst>(B))
+ if (A->getCondition() == SB->getCondition())
+ return related(A->getTrueValue(), SB->getTrueValue()) ||
+ related(A->getFalseValue(), SB->getFalseValue());
+
+ // Check both arms of the Select node individually.
+ return related(A->getTrueValue(), B) ||
+ related(A->getFalseValue(), B);
+}
+
+bool ProvenanceAnalysis::relatedPHI(const PHINode *A,
+ const Value *B) {
+ // If the values are PHIs in the same block, we can do a more precise as well
+ // as efficient check: just check for relations between the values on
+ // corresponding edges.
+ if (const PHINode *PNB = dyn_cast<PHINode>(B))
+ if (PNB->getParent() == A->getParent()) {
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
+ if (related(A->getIncomingValue(i),
+ PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
+ return true;
+ return false;
+ }
+
+ // Check each unique source of the PHI node against B.
+ SmallPtrSet<const Value *, 4> UniqueSrc;
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
+ const Value *PV1 = A->getIncomingValue(i);
+ if (UniqueSrc.insert(PV1) && related(PV1, B))
+ return true;
+ }
+
+ // All of the arms checked out.
+ return false;
+}
+
+/// Test if the value of P, or any value covered by its provenance, is ever
+/// stored within the function (not counting callees).
+static bool isStoredObjCPointer(const Value *P) {
+ SmallPtrSet<const Value *, 8> Visited;
+ SmallVector<const Value *, 8> Worklist;
+ Worklist.push_back(P);
+ Visited.insert(P);
+ do {
+ P = Worklist.pop_back_val();
+ for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
+ UI != UE; ++UI) {
+ const User *Ur = *UI;
+ if (isa<StoreInst>(Ur)) {
+ if (UI.getOperandNo() == 0)
+ // The pointer is stored.
+ return true;
+ // The pointed is stored through.
+ continue;
+ }
+ if (isa<CallInst>(Ur))
+ // The pointer is passed as an argument, ignore this.
+ continue;
+ if (isa<PtrToIntInst>(P))
+ // Assume the worst.
+ return true;
+ if (Visited.insert(Ur))
+ Worklist.push_back(Ur);
+ }
+ } while (!Worklist.empty());
+
+ // Everything checked out.
+ return false;
+}
+
+bool ProvenanceAnalysis::relatedCheck(const Value *A,
+ const Value *B) {
+ // Skip past provenance pass-throughs.
+ A = GetUnderlyingObjCPtr(A);
+ B = GetUnderlyingObjCPtr(B);
+
+ // Quick check.
+ if (A == B)
+ return true;
+
+ // Ask regular AliasAnalysis, for a first approximation.
+ switch (AA->alias(A, B)) {
+ case AliasAnalysis::NoAlias:
+ return false;
+ case AliasAnalysis::MustAlias:
+ case AliasAnalysis::PartialAlias:
+ return true;
+ case AliasAnalysis::MayAlias:
+ break;
+ }
+
+ bool AIsIdentified = IsObjCIdentifiedObject(A);
+ bool BIsIdentified = IsObjCIdentifiedObject(B);
+
+ // An ObjC-Identified object can't alias a load if it is never locally stored.
+ if (AIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(B))
+ return isStoredObjCPointer(A);
+ if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ // Both pointers are identified and escapes aren't an evident problem.
+ return false;
+ }
+ } else if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ }
+
+ // Special handling for PHI and Select.
+ if (const PHINode *PN = dyn_cast<PHINode>(A))
+ return relatedPHI(PN, B);
+ if (const PHINode *PN = dyn_cast<PHINode>(B))
+ return relatedPHI(PN, A);
+ if (const SelectInst *S = dyn_cast<SelectInst>(A))
+ return relatedSelect(S, B);
+ if (const SelectInst *S = dyn_cast<SelectInst>(B))
+ return relatedSelect(S, A);
+
+ // Conservative.
+ return true;
+}
+
+bool ProvenanceAnalysis::related(const Value *A,
+ const Value *B) {
+ // Begin by inserting a conservative value into the map. If the insertion
+ // fails, we have the answer already. If it succeeds, leave it there until we
+ // compute the real answer to guard against recursive queries.
+ if (A > B) std::swap(A, B);
+ std::pair<CachedResultsTy::iterator, bool> Pair =
+ CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
+ if (!Pair.second)
+ return Pair.first->second;
+
+ bool Result = relatedCheck(A, B);
+ CachedResults[ValuePairTy(A, B)] = Result;
+ return Result;
+}
Added: llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.h?rev=173760&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.h (added)
+++ llvm/trunk/lib/Transforms/ObjCARC/ProvenanceAnalysis.h Mon Jan 28 21:03:03 2013
@@ -0,0 +1,79 @@
+//===- ProvenanceAnalysis.h - ObjC ARC Optimization ---*- mode: c++ -*-----===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file declares a special form of Alias Analysis called ``Provenance
+/// Analysis''. The word ``provenance'' refers to the history of the ownership
+/// of an object. Thus ``Provenance Analysis'' is an analysis which attempts to
+/// use various techniques to determine if locally
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H
+#define LLVM_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H
+
+#include "llvm/ADT/DenseMap.h"
+
+namespace llvm {
+ class Value;
+ class AliasAnalysis;
+ class PHINode;
+ class SelectInst;
+}
+
+namespace llvm {
+namespace objcarc {
+/// \brief This is similar to BasicAliasAnalysis, and it uses many of the same
+/// techniques, except it uses special ObjC-specific reasoning about pointer
+/// relationships.
+///
+/// In this context ``Provenance'' is defined as the history of an object's
+/// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
+/// an ``independent provenance source'' of a pointer to determine whether or
+/// not two pointers have the same provenance source and thus could
+/// potentially be related.
+class ProvenanceAnalysis {
+ AliasAnalysis *AA;
+
+ typedef std::pair<const Value *, const Value *> ValuePairTy;
+ typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
+ CachedResultsTy CachedResults;
+
+ bool relatedCheck(const Value *A, const Value *B);
+ bool relatedSelect(const SelectInst *A, const Value *B);
+ bool relatedPHI(const PHINode *A, const Value *B);
+
+ void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
+ ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
+
+public:
+ ProvenanceAnalysis() {}
+
+ void setAA(AliasAnalysis *aa) { AA = aa; }
+
+ AliasAnalysis *getAA() const { return AA; }
+
+ bool related(const Value *A, const Value *B);
+
+ void clear() {
+ CachedResults.clear();
+ }
+};
+
+} // end namespace objcarc
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H
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