[llvm-commits] [llvm] r45670 - in /llvm/trunk: include/llvm/CodeGen/LinkAllCodegenComponents.h include/llvm/LinkAllPasses.h include/llvm/Transforms/Scalar.h lib/CodeGen/ShadowStackCollector.cpp lib/Transforms/Scalar/LowerGC.cpp runtime/GC/SemiSpace/semispace.c test/CodeGen/Generic/GC/redundant_init.ll
Gordon Henriksen
gordonhenriksen at mac.com
Sun Jan 6 17:30:53 PST 2008
Author: gordon
Date: Sun Jan 6 19:30:53 2008
New Revision: 45670
URL: http://llvm.org/viewvc/llvm-project?rev=45670&view=rev
Log:
With this patch, the LowerGC transformation becomes the
ShadowStackCollector, which additionally has reduced overhead with
no sacrifice in portability.
Considering a function @fun with 8 loop-local roots,
ShadowStackCollector introduces the following overhead
(x86):
; shadowstack prologue
movl L_llvm_gc_root_chain$non_lazy_ptr, %eax
movl (%eax), %ecx
movl $___gc_fun, 20(%esp)
movl $0, 24(%esp)
movl $0, 28(%esp)
movl $0, 32(%esp)
movl $0, 36(%esp)
movl $0, 40(%esp)
movl $0, 44(%esp)
movl $0, 48(%esp)
movl $0, 52(%esp)
movl %ecx, 16(%esp)
leal 16(%esp), %ecx
movl %ecx, (%eax)
; shadowstack loop overhead
(none)
; shadowstack epilogue
movl 48(%esp), %edx
movl %edx, (%ecx)
; shadowstack metadata
.align 3
___gc_fun: # __gc_fun
.long 8
.space 4
In comparison to LowerGC:
; lowergc prologue
movl L_llvm_gc_root_chain$non_lazy_ptr, %eax
movl (%eax), %ecx
movl %ecx, 48(%esp)
movl $8, 52(%esp)
movl $0, 60(%esp)
movl $0, 56(%esp)
movl $0, 68(%esp)
movl $0, 64(%esp)
movl $0, 76(%esp)
movl $0, 72(%esp)
movl $0, 84(%esp)
movl $0, 80(%esp)
movl $0, 92(%esp)
movl $0, 88(%esp)
movl $0, 100(%esp)
movl $0, 96(%esp)
movl $0, 108(%esp)
movl $0, 104(%esp)
movl $0, 116(%esp)
movl $0, 112(%esp)
; lowergc loop overhead
leal 44(%esp), %eax
movl %eax, 56(%esp)
leal 40(%esp), %eax
movl %eax, 64(%esp)
leal 36(%esp), %eax
movl %eax, 72(%esp)
leal 32(%esp), %eax
movl %eax, 80(%esp)
leal 28(%esp), %eax
movl %eax, 88(%esp)
leal 24(%esp), %eax
movl %eax, 96(%esp)
leal 20(%esp), %eax
movl %eax, 104(%esp)
leal 16(%esp), %eax
movl %eax, 112(%esp)
; lowergc epilogue
movl 48(%esp), %edx
movl %edx, (%ecx)
; lowergc metadata
(none)
Added:
llvm/trunk/lib/CodeGen/ShadowStackCollector.cpp
llvm/trunk/test/CodeGen/Generic/GC/redundant_init.ll
Modified:
llvm/trunk/include/llvm/CodeGen/LinkAllCodegenComponents.h
llvm/trunk/include/llvm/LinkAllPasses.h
llvm/trunk/include/llvm/Transforms/Scalar.h
llvm/trunk/lib/Transforms/Scalar/LowerGC.cpp
llvm/trunk/runtime/GC/SemiSpace/semispace.c
Modified: llvm/trunk/include/llvm/CodeGen/LinkAllCodegenComponents.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/LinkAllCodegenComponents.h?rev=45670&r1=45669&r2=45670&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/LinkAllCodegenComponents.h (original)
+++ llvm/trunk/include/llvm/CodeGen/LinkAllCodegenComponents.h Sun Jan 6 19:30:53 2008
@@ -17,6 +17,7 @@
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/CodeGen/Collectors.h"
namespace {
struct ForceCodegenLinking {
@@ -35,6 +36,8 @@
(void) llvm::createSimpleRegisterCoalescer();
+ (void) llvm::createShadowStackCollector();
+
(void) llvm::createBURRListDAGScheduler(NULL, NULL, NULL);
(void) llvm::createTDRRListDAGScheduler(NULL, NULL, NULL);
(void) llvm::createTDListDAGScheduler(NULL, NULL, NULL);
Modified: llvm/trunk/include/llvm/LinkAllPasses.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/LinkAllPasses.h?rev=45670&r1=45669&r2=45670&view=diff
==============================================================================
--- llvm/trunk/include/llvm/LinkAllPasses.h (original)
+++ llvm/trunk/include/llvm/LinkAllPasses.h Sun Jan 6 19:30:53 2008
@@ -84,7 +84,6 @@
(void) llvm::createLoopRotatePass();
(void) llvm::createLoopIndexSplitPass();
(void) llvm::createLowerAllocationsPass();
- (void) llvm::createLowerGCPass();
(void) llvm::createLowerInvokePass();
(void) llvm::createLowerPackedPass();
(void) llvm::createLowerSelectPass();
Modified: llvm/trunk/include/llvm/Transforms/Scalar.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar.h?rev=45670&r1=45669&r2=45670&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Scalar.h (original)
+++ llvm/trunk/include/llvm/Transforms/Scalar.h Sun Jan 6 19:30:53 2008
@@ -296,13 +296,6 @@
//===----------------------------------------------------------------------===//
//
-// LowerGCPass - This function returns an instance of the "lowergc" pass, which
-// lowers garbage collection intrinsics to normal LLVM code.
-//
-FunctionPass *createLowerGCPass();
-
-//===----------------------------------------------------------------------===//
-//
// BlockPlacement - This pass reorders basic blocks in order to increase the
// number of fall-through conditional branches.
//
Added: llvm/trunk/lib/CodeGen/ShadowStackCollector.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/ShadowStackCollector.cpp?rev=45670&view=auto
==============================================================================
--- llvm/trunk/lib/CodeGen/ShadowStackCollector.cpp (added)
+++ llvm/trunk/lib/CodeGen/ShadowStackCollector.cpp Sun Jan 6 19:30:53 2008
@@ -0,0 +1,441 @@
+//===-- ShadowStackCollector.cpp - GC support for uncooperative targets ---===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements lowering for the llvm.gc* intrinsics for targets that do
+// not natively support them (which includes the C backend). Note that the code
+// generated is not quite as efficient as collectors which generate stack maps
+// to identify roots.
+//
+// This pass implements the code transformation described in this paper:
+// "Accurate Garbage Collection in an Uncooperative Environment"
+// Fergus Henderson, ISMM, 2002
+//
+// In runtime/GC/SemiSpace.cpp is a prototype runtime which is compatible with
+// this collector.
+//
+// In order to support this particular transformation, all stack roots are
+// coallocated in the stack. This allows a fully target-independent stack map
+// while introducing only minor runtime overhead.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "shadowstackgc"
+#include "llvm/CodeGen/Collectors.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/CodeGen/Collector.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/LLVMBuilder.h"
+#include "llvm/Analysis/Verifier.h"
+#include <cstdlib>
+
+using namespace llvm;
+
+namespace {
+
+ class VISIBILITY_HIDDEN ShadowStackCollector : public Collector {
+ /// RootChain - This is the global linked-list that contains the chain of GC
+ /// roots.
+ GlobalVariable *Head;
+
+ /// StackEntryTy - Abstract type of a link in the shadow stack.
+ ///
+ const StructType *StackEntryTy;
+
+ /// Roots - GC roots in the current function. Each is a pair of the
+ /// intrinsic call and its corresponding alloca.
+ std::vector<std::pair<CallInst*,AllocaInst*> > Roots;
+
+ public:
+ ShadowStackCollector();
+
+ bool initializeCustomLowering(Module &M);
+ bool performCustomLowering(Function &F);
+
+ private:
+ bool IsNullValue(Value *V);
+ Constant *GetFrameMap(Function &F);
+ const Type* GetConcreteStackEntryType(Function &F);
+ void CollectRoots(Function &F);
+ static GetElementPtrInst *CreateGEP(LLVMBuilder &B, Value *BasePtr,
+ int Idx1, const char *Name);
+ static GetElementPtrInst *CreateGEP(LLVMBuilder &B, Value *BasePtr,
+ int Idx1, int Idx2, const char *Name);
+ };
+
+ CollectorRegistry::Add<ShadowStackCollector>
+ Y("shadow-stack",
+ "Very portable collector for uncooperative code generators");
+
+ /// EscapeEnumerator - This is a little algorithm to find all escape points
+ /// from a function so that "finally"-style code can be inserted. In addition
+ /// to finding the existing return and unwind instructions, it also (if
+ /// necessary) transforms any call instructions into invokes and sends them to
+ /// a landing pad.
+ ///
+ /// It's wrapped up in a state machine using the same transform C# uses for
+ /// 'yield return' enumerators, This transform allows it to be non-allocating.
+ class VISIBILITY_HIDDEN EscapeEnumerator {
+ Function &F;
+ const char *CleanupBBName;
+
+ // State.
+ int State;
+ Function::iterator StateBB, StateE;
+ LLVMBuilder Builder;
+
+ public:
+ EscapeEnumerator(Function &F, const char *N = "cleanup")
+ : F(F), CleanupBBName(N), State(0) {}
+
+ LLVMBuilder *Next() {
+ switch (State) {
+ default:
+ return 0;
+
+ case 0:
+ StateBB = F.begin();
+ StateE = F.end();
+ State = 1;
+
+ case 1:
+ // Find all 'return' and 'unwind' instructions.
+ while (StateBB != StateE) {
+ BasicBlock *CurBB = StateBB++;
+
+ // Branches and invokes do not escape, only unwind and return do.
+ TerminatorInst *TI = CurBB->getTerminator();
+ if (!isa<UnwindInst>(TI) && !isa<ReturnInst>(TI))
+ continue;
+
+ Builder.SetInsertPoint(TI->getParent(), TI);
+ return &Builder;
+ }
+
+ State = 2;
+
+ // Find all 'call' instructions.
+ SmallVector<Instruction*,16> Calls;
+ for (Function::iterator BB = F.begin(),
+ E = F.end(); BB != E; ++BB)
+ for (BasicBlock::iterator II = BB->begin(),
+ EE = BB->end(); II != EE; ++II)
+ if (CallInst *CI = dyn_cast<CallInst>(II))
+ if (!CI->getCalledFunction() ||
+ !CI->getCalledFunction()->getIntrinsicID())
+ Calls.push_back(CI);
+
+ if (Calls.empty())
+ return 0;
+
+ // Create a cleanup block.
+ BasicBlock *CleanupBB = new BasicBlock(CleanupBBName, &F);
+ UnwindInst *UI = new UnwindInst(CleanupBB);
+
+ // Transform the 'call' instructions into 'invoke's branching to the
+ // cleanup block. Go in reverse order to make prettier BB names.
+ SmallVector<Value*,16> Args;
+ for (unsigned I = Calls.size(); I != 0; ) {
+ CallInst *CI = cast<CallInst>(Calls[--I]);
+
+ // Split the basic block containing the function call.
+ BasicBlock *CallBB = CI->getParent();
+ BasicBlock *NewBB =
+ CallBB->splitBasicBlock(CI, CallBB->getName() + ".cont");
+
+ // Remove the unconditional branch inserted at the end of CallBB.
+ CallBB->getInstList().pop_back();
+ NewBB->getInstList().remove(CI);
+
+ // Create a new invoke instruction.
+ Args.clear();
+ Args.append(CI->op_begin() + 1, CI->op_end());
+
+ InvokeInst *II = new InvokeInst(CI->getOperand(0),
+ NewBB, CleanupBB,
+ Args.begin(), Args.end(),
+ CI->getName(), CallBB);
+ II->setCallingConv(CI->getCallingConv());
+ II->setParamAttrs(CI->getParamAttrs());
+ CI->replaceAllUsesWith(II);
+ delete CI;
+ }
+
+ Builder.SetInsertPoint(UI->getParent(), UI);
+ return &Builder;
+ }
+ }
+ };
+
+}
+
+// -----------------------------------------------------------------------------
+
+Collector *llvm::createShadowStackCollector() {
+ return new ShadowStackCollector();
+}
+
+ShadowStackCollector::ShadowStackCollector() : Head(0), StackEntryTy(0) {
+ InitRoots = true;
+ CustomRoots = true;
+}
+
+Constant *ShadowStackCollector::GetFrameMap(Function &F) {
+ // doInitialization creates the abstract type of this value.
+
+ Type *VoidPtr = PointerType::getUnqual(Type::Int8Ty);
+
+ // Truncate the ShadowStackDescriptor if some metadata is null.
+ unsigned NumMeta = 0;
+ SmallVector<Constant*,16> Metadata;
+ for (unsigned I = 0; I != Roots.size(); ++I) {
+ Constant *C = cast<Constant>(Roots[I].first->getOperand(2));
+ if (!C->isNullValue())
+ NumMeta = I + 1;
+ Metadata.push_back(ConstantExpr::getBitCast(C, VoidPtr));
+ }
+
+ Constant *BaseElts[] = {
+ ConstantInt::get(Type::Int32Ty, Roots.size(), false),
+ ConstantInt::get(Type::Int32Ty, NumMeta, false),
+ };
+
+ Constant *DescriptorElts[] = {
+ ConstantStruct::get(BaseElts, 2),
+ ConstantArray::get(ArrayType::get(VoidPtr, NumMeta),
+ Metadata.begin(), NumMeta)
+ };
+
+ Constant *FrameMap = ConstantStruct::get(DescriptorElts, 2);
+
+ std::string TypeName("gc_map.");
+ TypeName += utostr(NumMeta);
+ F.getParent()->addTypeName(TypeName, FrameMap->getType());
+
+ // FIXME: Is this actually dangerous as WritingAnLLVMPass.html claims? Seems
+ // that, short of multithreaded LLVM, it should be safe; all that is
+ // necessary is that a simple Module::iterator loop not be invalidated.
+ // Appending to the GlobalVariable list is safe in that sense.
+ //
+ // All of the output passes emit globals last. The ExecutionEngine
+ // explicitly supports adding globals to the module after
+ // initialization.
+ //
+ // Still, if it isn't deemed acceptable, then this transformation needs
+ // to be a ModulePass (which means it cannot be in the 'llc' pipeline
+ // (which uses a FunctionPassManager (which segfaults (not asserts) if
+ // provided a ModulePass))).
+ Constant *GV = new GlobalVariable(FrameMap->getType(), true,
+ GlobalVariable::InternalLinkage,
+ FrameMap, "__gc_" + F.getName(),
+ F.getParent());
+
+ Constant *GEPIndices[2] = { ConstantInt::get(Type::Int32Ty, 0),
+ ConstantInt::get(Type::Int32Ty, 0) };
+ return ConstantExpr::getGetElementPtr(GV, GEPIndices, 2);
+}
+
+const Type* ShadowStackCollector::GetConcreteStackEntryType(Function &F) {
+ // doInitialization creates the generic version of this type.
+ std::vector<const Type*> EltTys;
+ EltTys.push_back(StackEntryTy);
+ for (size_t I = 0; I != Roots.size(); I++)
+ EltTys.push_back(Roots[I].second->getAllocatedType());
+ Type *Ty = StructType::get(EltTys);
+
+ std::string TypeName("gc_stackentry.");
+ TypeName += F.getName();
+ F.getParent()->addTypeName(TypeName, Ty);
+
+ return Ty;
+}
+
+/// doInitialization - If this module uses the GC intrinsics, find them now. If
+/// not, exit fast.
+bool ShadowStackCollector::initializeCustomLowering(Module &M) {
+ // struct FrameMap {
+ // int32_t NumRoots; // Number of roots in stack frame.
+ // int32_t NumMeta; // Number of metadata descriptors. May be < NumRoots.
+ // void *Meta[]; // May be absent for roots without metadata.
+ // };
+ std::vector<const Type*> EltTys;
+ EltTys.push_back(Type::Int32Ty); // 32 bits is ok up to a 32GB stack frame. :)
+ EltTys.push_back(Type::Int32Ty); // Specifies length of variable length array.
+ StructType *FrameMapTy = StructType::get(EltTys);
+ M.addTypeName("gc_map", FrameMapTy);
+ PointerType *FrameMapPtrTy = PointerType::getUnqual(FrameMapTy);
+
+ // struct StackEntry {
+ // ShadowStackEntry *Next; // Caller's stack entry.
+ // FrameMap *Map; // Pointer to constant FrameMap.
+ // void *Roots[]; // Stack roots (in-place array, so we pretend).
+ // };
+ OpaqueType *RecursiveTy = OpaqueType::get();
+
+ EltTys.clear();
+ EltTys.push_back(PointerType::getUnqual(RecursiveTy));
+ EltTys.push_back(FrameMapPtrTy);
+ PATypeHolder LinkTyH = StructType::get(EltTys);
+
+ RecursiveTy->refineAbstractTypeTo(LinkTyH.get());
+ StackEntryTy = cast<StructType>(LinkTyH.get());
+ const PointerType *StackEntryPtrTy = PointerType::getUnqual(StackEntryTy);
+ M.addTypeName("gc_stackentry", LinkTyH.get()); // FIXME: Is this safe from
+ // a FunctionPass?
+
+ // Get the root chain if it already exists.
+ Head = M.getGlobalVariable("llvm_gc_root_chain");
+ if (!Head) {
+ // If the root chain does not exist, insert a new one with linkonce
+ // linkage!
+ Head = new GlobalVariable(StackEntryPtrTy, false,
+ GlobalValue::LinkOnceLinkage,
+ Constant::getNullValue(StackEntryPtrTy),
+ "llvm_gc_root_chain", &M);
+ } else if (Head->hasExternalLinkage() && Head->isDeclaration()) {
+ Head->setInitializer(Constant::getNullValue(StackEntryPtrTy));
+ Head->setLinkage(GlobalValue::LinkOnceLinkage);
+ }
+
+ return true;
+}
+
+bool ShadowStackCollector::IsNullValue(Value *V) {
+ if (Constant *C = dyn_cast<Constant>(V))
+ return C->isNullValue();
+ return false;
+}
+
+void ShadowStackCollector::CollectRoots(Function &F) {
+ // FIXME: Account for original alignment. Could fragment the root array.
+ // Approach 1: Null initialize empty slots at runtime. Yuck.
+ // Approach 2: Emit a map of the array instead of just a count.
+
+ assert(Roots.empty() && "Not cleaned up?");
+
+ SmallVector<std::pair<CallInst*,AllocaInst*>,16> MetaRoots;
+
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
+ if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
+ if (Function *F = CI->getCalledFunction())
+ if (F->getIntrinsicID() == Intrinsic::gcroot) {
+ std::pair<CallInst*,AllocaInst*> Pair = std::make_pair(
+ CI, cast<AllocaInst>(
+ IntrinsicInst::StripPointerCasts(CI->getOperand(1))));
+ if (IsNullValue(CI->getOperand(2)))
+ Roots.push_back(Pair);
+ else
+ MetaRoots.push_back(Pair);
+ }
+
+ // Number roots with metadata (usually empty) at the beginning, so that the
+ // FrameMap::Meta array can be elided.
+ Roots.insert(Roots.begin(), MetaRoots.begin(), MetaRoots.end());
+}
+
+GetElementPtrInst *
+ShadowStackCollector::CreateGEP(LLVMBuilder &B, Value *BasePtr,
+ int Idx, int Idx2, const char *Name) {
+ Value *Indices[] = { ConstantInt::get(Type::Int32Ty, 0),
+ ConstantInt::get(Type::Int32Ty, Idx),
+ ConstantInt::get(Type::Int32Ty, Idx2) };
+ return B.CreateGEP(BasePtr, Indices, Indices + 3, Name);
+}
+
+GetElementPtrInst *
+ShadowStackCollector::CreateGEP(LLVMBuilder &B, Value *BasePtr,
+ int Idx, const char *Name) {
+ Value *Indices[] = { ConstantInt::get(Type::Int32Ty, 0),
+ ConstantInt::get(Type::Int32Ty, Idx) };
+ return B.CreateGEP(BasePtr, Indices, Indices + 2, Name);
+}
+
+/// runOnFunction - Insert code to maintain the shadow stack.
+bool ShadowStackCollector::performCustomLowering(Function &F) {
+ // Find calls to llvm.gcroot.
+ CollectRoots(F);
+
+ // If there are no roots in this function, then there is no need to add a
+ // stack map entry for it.
+ if (Roots.empty())
+ return false;
+
+ // Build the constant map and figure the type of the shadow stack entry.
+ Value *FrameMap = GetFrameMap(F);
+ const Type *ConcreteStackEntryTy = GetConcreteStackEntryType(F);
+
+ // Build the shadow stack entry at the very start of the function.
+ BasicBlock::iterator IP = F.getEntryBlock().begin();
+ LLVMBuilder AtEntry(IP->getParent(), IP);
+
+ Instruction *StackEntry = AtEntry.CreateAlloca(ConcreteStackEntryTy, 0,
+ "gc_frame");
+
+ while (isa<AllocaInst>(IP)) ++IP;
+ AtEntry.SetInsertPoint(IP->getParent(), IP);
+
+ // Initialize the map pointer and load the current head of the shadow stack.
+ Instruction *CurrentHead = AtEntry.CreateLoad(Head, "gc_currhead");
+ Instruction *EntryMapPtr = CreateGEP(AtEntry, StackEntry,0,1,"gc_frame.map");
+ AtEntry.CreateStore(FrameMap, EntryMapPtr);
+
+ // After all the allocas...
+ for (unsigned I = 0, E = Roots.size(); I != E; ++I) {
+ // For each root, find the corresponding slot in the aggregate...
+ Value *SlotPtr = CreateGEP(AtEntry, StackEntry, 1 + I, "gc_root");
+
+ // And use it in lieu of the alloca.
+ AllocaInst *OriginalAlloca = Roots[I].second;
+ SlotPtr->takeName(OriginalAlloca);
+ OriginalAlloca->replaceAllUsesWith(SlotPtr);
+ }
+
+ // Move past the original stores inserted by Collector::InitRoots. This isn't
+ // really necessary (the collector would never see the intermediate state),
+ // but it's nicer not to push the half-initialized entry onto the stack.
+ while (isa<StoreInst>(IP)) ++IP;
+ AtEntry.SetInsertPoint(IP->getParent(), IP);
+
+ // Push the entry onto the shadow stack.
+ Instruction *EntryNextPtr = CreateGEP(AtEntry,StackEntry,0,0,"gc_frame.next");
+ Instruction *NewHeadVal = CreateGEP(AtEntry,StackEntry, 0, "gc_newhead");
+ AtEntry.CreateStore(CurrentHead, EntryNextPtr);
+ AtEntry.CreateStore(NewHeadVal, Head);
+
+ // For each instruction that escapes...
+ EscapeEnumerator EE(F, "gc_cleanup");
+ while (LLVMBuilder *AtExit = EE.Next()) {
+ // Pop the entry from the shadow stack. Don't reuse CurrentHead from
+ // AtEntry, since that would make the value live for the entire function.
+ Instruction *EntryNextPtr2 = CreateGEP(*AtExit, StackEntry, 0, 0,
+ "gc_frame.next");
+ Value *SavedHead = AtExit->CreateLoad(EntryNextPtr2, "gc_savedhead");
+ AtExit->CreateStore(SavedHead, Head);
+ }
+
+ // Delete the original allocas (which are no longer used) and the intrinsic
+ // calls (which are no longer valid). Doing this last avoids invalidating
+ // iterators.
+ for (unsigned I = 0, E = Roots.size(); I != E; ++I) {
+ Roots[I].first->eraseFromParent();
+ Roots[I].second->eraseFromParent();
+ }
+
+ F.dump();
+
+ Roots.clear();
+ return true;
+}
Modified: llvm/trunk/lib/Transforms/Scalar/LowerGC.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LowerGC.cpp?rev=45670&r1=45669&r2=45670&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LowerGC.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LowerGC.cpp Sun Jan 6 19:30:53 2008
@@ -1,350 +0,0 @@
-//===-- LowerGC.cpp - Provide GC support for targets that don't -----------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements lowering for the llvm.gc* intrinsics for targets that do
-// not natively support them (which includes the C backend). Note that the code
-// generated is not as efficient as it would be for targets that natively
-// support the GC intrinsics, but it is useful for getting new targets
-// up-and-running quickly.
-//
-// This pass implements the code transformation described in this paper:
-// "Accurate Garbage Collection in an Uncooperative Environment"
-// Fergus Henderson, ISMM, 2002
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "lowergc"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Instructions.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/ADT/SmallVector.h"
-using namespace llvm;
-
-namespace {
- class VISIBILITY_HIDDEN LowerGC : public FunctionPass {
- /// GCRootInt, GCReadInt, GCWriteInt - The function prototypes for the
- /// llvm.gcread/llvm.gcwrite/llvm.gcroot intrinsics.
- Function *GCRootInt, *GCReadInt, *GCWriteInt;
-
- /// GCRead/GCWrite - These are the functions provided by the garbage
- /// collector for read/write barriers.
- Constant *GCRead, *GCWrite;
-
- /// RootChain - This is the global linked-list that contains the chain of GC
- /// roots.
- GlobalVariable *RootChain;
-
- /// MainRootRecordType - This is the type for a function root entry if it
- /// had zero roots.
- const Type *MainRootRecordType;
- public:
- static char ID; // Pass identification, replacement for typeid
- LowerGC() : FunctionPass((intptr_t)&ID),
- GCRootInt(0), GCReadInt(0), GCWriteInt(0),
- GCRead(0), GCWrite(0), RootChain(0), MainRootRecordType(0) {}
- virtual bool doInitialization(Module &M);
- virtual bool runOnFunction(Function &F);
-
- private:
- const StructType *getRootRecordType(unsigned NumRoots);
- };
-
- char LowerGC::ID = 0;
- RegisterPass<LowerGC>
- X("lowergc", "Lower GC intrinsics, for GCless code generators");
-}
-
-/// createLowerGCPass - This function returns an instance of the "lowergc"
-/// pass, which lowers garbage collection intrinsics to normal LLVM code.
-FunctionPass *llvm::createLowerGCPass() {
- return new LowerGC();
-}
-
-/// getRootRecordType - This function creates and returns the type for a root
-/// record containing 'NumRoots' roots.
-const StructType *LowerGC::getRootRecordType(unsigned NumRoots) {
- // Build a struct that is a type used for meta-data/root pairs.
- std::vector<const Type *> ST;
- ST.push_back(GCRootInt->getFunctionType()->getParamType(0));
- ST.push_back(GCRootInt->getFunctionType()->getParamType(1));
- StructType *PairTy = StructType::get(ST);
-
- // Build the array of pairs.
- ArrayType *PairArrTy = ArrayType::get(PairTy, NumRoots);
-
- // Now build the recursive list type.
- PATypeHolder RootListH =
- MainRootRecordType ? (Type*)MainRootRecordType : (Type*)OpaqueType::get();
- ST.clear();
- ST.push_back(PointerType::getUnqual(RootListH)); // Prev pointer
- ST.push_back(Type::Int32Ty); // NumElements in array
- ST.push_back(PairArrTy); // The pairs
- StructType *RootList = StructType::get(ST);
- if (MainRootRecordType)
- return RootList;
-
- assert(NumRoots == 0 && "The main struct type should have zero entries!");
- cast<OpaqueType>((Type*)RootListH.get())->refineAbstractTypeTo(RootList);
- MainRootRecordType = RootListH;
- return cast<StructType>(RootListH.get());
-}
-
-/// doInitialization - If this module uses the GC intrinsics, find them now. If
-/// not, this pass does not do anything.
-bool LowerGC::doInitialization(Module &M) {
- GCRootInt = M.getFunction("llvm.gcroot");
- GCReadInt = M.getFunction("llvm.gcread");
- GCWriteInt = M.getFunction("llvm.gcwrite");
- if (!GCRootInt && !GCReadInt && !GCWriteInt) return false;
-
- PointerType *VoidPtr = PointerType::getUnqual(Type::Int8Ty);
- PointerType *VoidPtrPtr = PointerType::getUnqual(VoidPtr);
-
- // If the program is using read/write barriers, find the implementations of
- // them from the GC runtime library.
- if (GCReadInt) // Make: sbyte* %llvm_gc_read(sbyte**)
- GCRead = M.getOrInsertFunction("llvm_gc_read", VoidPtr, VoidPtr, VoidPtrPtr,
- (Type *)0);
- if (GCWriteInt) // Make: void %llvm_gc_write(sbyte*, sbyte**)
- GCWrite = M.getOrInsertFunction("llvm_gc_write", Type::VoidTy,
- VoidPtr, VoidPtr, VoidPtrPtr, (Type *)0);
-
- // If the program has GC roots, get or create the global root list.
- if (GCRootInt) {
- const StructType *RootListTy = getRootRecordType(0);
- const Type *PRLTy = PointerType::getUnqual(RootListTy);
- M.addTypeName("llvm_gc_root_ty", RootListTy);
-
- // Get the root chain if it already exists.
- RootChain = M.getGlobalVariable("llvm_gc_root_chain", PRLTy);
- if (RootChain == 0) {
- // If the root chain does not exist, insert a new one with linkonce
- // linkage!
- RootChain = new GlobalVariable(PRLTy, false,
- GlobalValue::LinkOnceLinkage,
- Constant::getNullValue(PRLTy),
- "llvm_gc_root_chain", &M);
- } else if (RootChain->hasExternalLinkage() && RootChain->isDeclaration()) {
- RootChain->setInitializer(Constant::getNullValue(PRLTy));
- RootChain->setLinkage(GlobalValue::LinkOnceLinkage);
- }
- }
- return true;
-}
-
-/// Coerce - If the specified operand number of the specified instruction does
-/// not have the specified type, insert a cast. Note that this only uses BitCast
-/// because the types involved are all pointers.
-static void Coerce(Instruction *I, unsigned OpNum, Type *Ty) {
- if (I->getOperand(OpNum)->getType() != Ty) {
- if (Constant *C = dyn_cast<Constant>(I->getOperand(OpNum)))
- I->setOperand(OpNum, ConstantExpr::getBitCast(C, Ty));
- else {
- CastInst *CI = new BitCastInst(I->getOperand(OpNum), Ty, "", I);
- I->setOperand(OpNum, CI);
- }
- }
-}
-
-/// runOnFunction - If the program is using GC intrinsics, replace any
-/// read/write intrinsics with the appropriate read/write barrier calls, then
-/// inline them. Finally, build the data structures for
-bool LowerGC::runOnFunction(Function &F) {
- // Quick exit for programs that are not using GC mechanisms.
- if (!GCRootInt && !GCReadInt && !GCWriteInt) return false;
-
- PointerType *VoidPtr = PointerType::getUnqual(Type::Int8Ty);
- PointerType *VoidPtrPtr = PointerType::getUnqual(VoidPtr);
-
- // If there are read/write barriers in the program, perform a quick pass over
- // the function eliminating them. While we are at it, remember where we see
- // calls to llvm.gcroot.
- std::vector<CallInst*> GCRoots;
- std::vector<CallInst*> NormalCalls;
-
- bool MadeChange = false;
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
- for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
- if (CallInst *CI = dyn_cast<CallInst>(II++)) {
- if (!CI->getCalledFunction() ||
- !CI->getCalledFunction()->isIntrinsic())
- NormalCalls.push_back(CI); // Remember all normal function calls.
-
- if (Function *F = CI->getCalledFunction())
- if (F == GCRootInt)
- GCRoots.push_back(CI);
- else if (F == GCReadInt || F == GCWriteInt) {
- if (F == GCWriteInt) {
- // Change a llvm.gcwrite call to call llvm_gc_write instead.
- CI->setOperand(0, GCWrite);
- // Insert casts of the operands as needed.
- Coerce(CI, 1, VoidPtr);
- Coerce(CI, 2, VoidPtr);
- Coerce(CI, 3, VoidPtrPtr);
- } else {
- Coerce(CI, 1, VoidPtr);
- Coerce(CI, 2, VoidPtrPtr);
- if (CI->getType() == VoidPtr) {
- CI->setOperand(0, GCRead);
- } else {
- // Create a whole new call to replace the old one.
-
- // It sure would be nice to pass op_begin()+1,
- // op_begin()+2 but it runs into trouble with
- // CallInst::init's &*iterator, which requires a
- // conversion from Use* to Value*. The conversion
- // from Use to Value * is not useful because the
- // memory for Value * won't be contiguous.
- Value* Args[] = {
- CI->getOperand(1),
- CI->getOperand(2)
- };
- CallInst *NC = new CallInst(GCRead, Args, Args + 2,
- CI->getName(), CI);
- // These functions only deal with ptr type results so BitCast
- // is the correct kind of cast (no-op cast).
- Value *NV = new BitCastInst(NC, CI->getType(), "", CI);
- CI->replaceAllUsesWith(NV);
- BB->getInstList().erase(CI);
- CI = NC;
- }
- }
-
- MadeChange = true;
- }
- }
-
- // If there are no GC roots in this function, then there is no need to create
- // a GC list record for it.
- if (GCRoots.empty()) return MadeChange;
-
- // Okay, there are GC roots in this function. On entry to the function, add a
- // record to the llvm_gc_root_chain, and remove it on exit.
-
- // Create the alloca, and zero it out.
- const StructType *RootListTy = getRootRecordType(GCRoots.size());
- AllocaInst *AI = new AllocaInst(RootListTy, 0, "gcroots", F.begin()->begin());
-
- // Insert the memset call after all of the allocas in the function.
- BasicBlock::iterator IP = AI;
- while (isa<AllocaInst>(IP)) ++IP;
-
- Constant *Zero = ConstantInt::get(Type::Int32Ty, 0);
- Constant *One = ConstantInt::get(Type::Int32Ty, 1);
-
- Value *Idx[2] = { Zero, Zero };
-
- // Get a pointer to the prev pointer.
- Value *PrevPtrPtr = new GetElementPtrInst(AI, Idx, Idx + 2,
- "prevptrptr", IP);
-
- // Load the previous pointer.
- Value *PrevPtr = new LoadInst(RootChain, "prevptr", IP);
- // Store the previous pointer into the prevptrptr
- new StoreInst(PrevPtr, PrevPtrPtr, IP);
-
- // Set the number of elements in this record.
- Idx[1] = One;
- Value *NumEltsPtr = new GetElementPtrInst(AI, Idx, Idx + 2,
- "numeltsptr", IP);
- new StoreInst(ConstantInt::get(Type::Int32Ty, GCRoots.size()), NumEltsPtr,IP);
-
- Value* Par[4];
- Par[0] = Zero;
- Par[1] = ConstantInt::get(Type::Int32Ty, 2);
-
- const PointerType *PtrLocTy =
- cast<PointerType>(GCRootInt->getFunctionType()->getParamType(0));
- Constant *Null = ConstantPointerNull::get(PtrLocTy);
-
- // Initialize all of the gcroot records now.
- for (unsigned i = 0, e = GCRoots.size(); i != e; ++i) {
- // Initialize the meta-data pointer.
- Par[2] = ConstantInt::get(Type::Int32Ty, i);
- Par[3] = One;
- Value *MetaDataPtr = new GetElementPtrInst(AI, Par, Par + 4,
- "MetaDataPtr", IP);
- assert(isa<Constant>(GCRoots[i]->getOperand(2)) && "Must be a constant");
- new StoreInst(GCRoots[i]->getOperand(2), MetaDataPtr, IP);
-
- // Initialize the root pointer to null on entry to the function.
- Par[3] = Zero;
- Value *RootPtrPtr = new GetElementPtrInst(AI, Par, Par + 4,
- "RootEntPtr", IP);
- new StoreInst(Null, RootPtrPtr, IP);
-
- // Each occurrance of the llvm.gcroot intrinsic now turns into an
- // initialization of the slot with the address.
- new StoreInst(GCRoots[i]->getOperand(1), RootPtrPtr, GCRoots[i]);
- }
-
- // Now that the record is all initialized, store the pointer into the global
- // pointer.
- Value *C = new BitCastInst(AI, PointerType::getUnqual(MainRootRecordType), "", IP);
- new StoreInst(C, RootChain, IP);
-
- // Eliminate all the gcroot records now.
- for (unsigned i = 0, e = GCRoots.size(); i != e; ++i)
- GCRoots[i]->getParent()->getInstList().erase(GCRoots[i]);
-
- // On exit from the function we have to remove the entry from the GC root
- // chain. Doing this is straight-forward for return and unwind instructions:
- // just insert the appropriate copy.
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
- if (isa<UnwindInst>(BB->getTerminator()) ||
- isa<ReturnInst>(BB->getTerminator())) {
- // We could reuse the PrevPtr loaded on entry to the function, but this
- // would make the value live for the whole function, which is probably a
- // bad idea. Just reload the value out of our stack entry.
- PrevPtr = new LoadInst(PrevPtrPtr, "prevptr", BB->getTerminator());
- new StoreInst(PrevPtr, RootChain, BB->getTerminator());
- }
-
- // If an exception is thrown from a callee we have to make sure to
- // unconditionally take the record off the stack. For this reason, we turn
- // all call instructions into invoke whose cleanup pops the entry off the
- // stack. We only insert one cleanup block, which is shared by all invokes.
- if (!NormalCalls.empty()) {
- // Create the shared cleanup block.
- BasicBlock *Cleanup = new BasicBlock("gc_cleanup", &F);
- UnwindInst *UI = new UnwindInst(Cleanup);
- PrevPtr = new LoadInst(PrevPtrPtr, "prevptr", UI);
- new StoreInst(PrevPtr, RootChain, UI);
-
- // Loop over all of the function calls, turning them into invokes.
- while (!NormalCalls.empty()) {
- CallInst *CI = NormalCalls.back();
- BasicBlock *CBB = CI->getParent();
- NormalCalls.pop_back();
-
- // Split the basic block containing the function call.
- BasicBlock *NewBB = CBB->splitBasicBlock(CI, CBB->getName()+".cont");
-
- // Remove the unconditional branch inserted at the end of the CBB.
- CBB->getInstList().pop_back();
- NewBB->getInstList().remove(CI);
-
- // Create a new invoke instruction.
- std::vector<Value*> Args(CI->op_begin()+1, CI->op_end());
-
- Value *II = new InvokeInst(CI->getCalledValue(), NewBB, Cleanup,
- Args.begin(), Args.end(), CI->getName(), CBB);
- cast<InvokeInst>(II)->setCallingConv(CI->getCallingConv());
- cast<InvokeInst>(II)->setParamAttrs(CI->getParamAttrs());
- CI->replaceAllUsesWith(II);
- delete CI;
- }
- }
-
- return true;
-}
Modified: llvm/trunk/runtime/GC/SemiSpace/semispace.c
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/runtime/GC/SemiSpace/semispace.c?rev=45670&r1=45669&r2=45670&view=diff
==============================================================================
--- llvm/trunk/runtime/GC/SemiSpace/semispace.c (original)
+++ llvm/trunk/runtime/GC/SemiSpace/semispace.c Sun Jan 6 19:30:53 2008
@@ -97,24 +97,26 @@
* FIXME: This should be in a code-generator specific library, but for now this
* will work for all code generators.
*/
-typedef struct GCRoot {
- void **RootPtr;
- void *Meta;
-} GCRoot;
+struct FrameMap {
+ int32_t NumRoots; // Number of roots in stack frame.
+ int32_t NumMeta; // Number of metadata descriptors. May be < NumRoots.
+ void *Meta[]; // May be absent for roots without metadata.
+};
-typedef struct GCRoots {
- struct GCRoots *Next;
- unsigned NumRoots;
- GCRoot RootRecords[];
-} GCRoots;
-GCRoots *llvm_gc_root_chain;
+struct StackEntry {
+ ShadowStackEntry *Next; // Caller's stack entry.
+ const FrameMap *Map; // Pointer to constant FrameMap.
+ void *Roots[]; // Stack roots (in-place array).
+};
+StackEntry *llvm_gc_root_chain;
void llvm_cg_walk_gcroots(void (*FP)(void **Root, void *Meta)) {
- GCRoots *R = llvm_gc_root_chain;
- for (; R; R = R->Next) {
+ for (StackEntry *R; R; R = R->Next) {
unsigned i, e;
- for (i = 0, e = R->NumRoots; i != e; ++i)
- FP(R->RootRecords[i].RootPtr, R->RootRecords[i].Meta);
+ for (i = 0, e = R->NumMeta; i != e; ++i)
+ FP(&R->Roots[i], R->Map->Meta[i]);
+ for (e = R->NumRoots; i != e; ++i)
+ FP(&R->Roots[i], NULL);
}
}
/* END FIXME! */
Added: llvm/trunk/test/CodeGen/Generic/GC/redundant_init.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Generic/GC/redundant_init.ll?rev=45670&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/Generic/GC/redundant_init.ll (added)
+++ llvm/trunk/test/CodeGen/Generic/GC/redundant_init.ll Sun Jan 6 19:30:53 2008
@@ -0,0 +1,17 @@
+; RUN: llvm-as < %s | llc -march=x86 | \
+; RUN: ignore grep {movl..0} | count 0
+
+%struct.obj = type { i8*, %struct.obj* }
+
+declare void @g() gc "shadow-stack"
+
+define void @f(i8* %o) gc "shadow-stack" {
+entry:
+ %root = alloca i8*
+ call void @llvm.gcroot(i8** %root, i8* null)
+ store i8* %o, i8** %root
+ call void @g()
+ ret void
+}
+
+declare void @llvm.gcroot(i8**, i8*)
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