[llvm-commits] [llvm] r52303 - /llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Chris Lattner
sabre at nondot.org
Sun Jun 15 23:30:22 PDT 2008
Author: lattner
Date: Mon Jun 16 01:30:22 2008
New Revision: 52303
URL: http://llvm.org/viewvc/llvm-project?rev=52303&view=rev
Log:
move a bunch of predicates up into their own section
in this file, no other changes.
Modified:
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=52303&r1=52302&r2=52303&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Mon Jun 16 01:30:22 2008
@@ -32,6 +32,173 @@
#include <algorithm>
using namespace llvm;
+//===----------------------------------------------------------------------===//
+// Useful predicates
+//===----------------------------------------------------------------------===//
+
+// Determine if an AllocationInst instruction escapes from the function it is
+// contained in. If it does not escape, there is no way for another function to
+// mod/ref it. We do this by looking at its uses and determining if the uses
+// can escape (recursively).
+static bool AddressMightEscape(const Value *V) {
+ for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end();
+ UI != E; ++UI) {
+ const Instruction *I = cast<Instruction>(*UI);
+ switch (I->getOpcode()) {
+ case Instruction::Load:
+ break; //next use.
+ case Instruction::Store:
+ if (I->getOperand(0) == V)
+ return true; // Escapes if the pointer is stored.
+ break; // next use.
+ case Instruction::GetElementPtr:
+ if (AddressMightEscape(I))
+ return true;
+ break; // next use.
+ case Instruction::BitCast:
+ if (AddressMightEscape(I))
+ return true;
+ break; // next use
+ case Instruction::Ret:
+ // If returned, the address will escape to calling functions, but no
+ // callees could modify it.
+ break; // next use
+ case Instruction::Call:
+ // If the call is to a few known safe intrinsics, we know that it does
+ // not escape
+ if (!isa<MemIntrinsic>(I))
+ return true;
+ break; // next use
+ default:
+ return true;
+ }
+ }
+ return false;
+}
+
+/// getUnderlyingObject - This traverses the use chain to figure out what object
+/// the specified value points to. If the value points to, or is derived from,
+/// a unique object or an argument, return it. This returns:
+/// Arguments, GlobalVariables, Functions, Allocas, Mallocs.
+static const Value *getUnderlyingObject(const Value *V) {
+ if (!isa<PointerType>(V->getType())) return V;
+
+ // If we are at some type of object, return it. GlobalValues and Allocations
+ // have unique addresses.
+ if (isa<GlobalValue>(V) || isa<AllocationInst>(V) || isa<Argument>(V))
+ return V;
+
+ // Traverse through different addressing mechanisms...
+ if (const Instruction *I = dyn_cast<Instruction>(V)) {
+ if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I))
+ return getUnderlyingObject(I->getOperand(0));
+ } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+ if (CE->getOpcode() == Instruction::BitCast ||
+ CE->getOpcode() == Instruction::GetElementPtr)
+ return getUnderlyingObject(CE->getOperand(0));
+ }
+ return V;
+}
+
+static const User *isGEP(const Value *V) {
+ if (isa<GetElementPtrInst>(V) ||
+ (isa<ConstantExpr>(V) &&
+ cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
+ return cast<User>(V);
+ return 0;
+}
+
+static const Value *GetGEPOperands(const Value *V,
+ SmallVector<Value*, 16> &GEPOps){
+ assert(GEPOps.empty() && "Expect empty list to populate!");
+ GEPOps.insert(GEPOps.end(), cast<User>(V)->op_begin()+1,
+ cast<User>(V)->op_end());
+
+ // Accumulate all of the chained indexes into the operand array
+ V = cast<User>(V)->getOperand(0);
+
+ while (const User *G = isGEP(V)) {
+ if (!isa<Constant>(GEPOps[0]) || isa<GlobalValue>(GEPOps[0]) ||
+ !cast<Constant>(GEPOps[0])->isNullValue())
+ break; // Don't handle folding arbitrary pointer offsets yet...
+ GEPOps.erase(GEPOps.begin()); // Drop the zero index
+ GEPOps.insert(GEPOps.begin(), G->op_begin()+1, G->op_end());
+ V = G->getOperand(0);
+ }
+ return V;
+}
+
+/// isIdentifiedObject - Return true if this pointer refers to a distinct and
+/// identifiable object. This returns true for:
+/// Global Variables and Functions
+/// Allocas and Mallocs
+/// ByVal and NoAlias Arguments
+///
+static bool isIdentifiedObject(const Value *V) {
+ if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
+ return true;
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->hasNoAliasAttr() || A->hasByValAttr();
+ return false;
+}
+
+/// isKnownNonNull - Return true if we know that the specified value is never
+/// null.
+static bool isKnownNonNull(const Value *V) {
+ // Alloca never returns null, malloc might.
+ if (isa<AllocaInst>(V)) return true;
+
+ // A byval argument is never null.
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->hasByValAttr();
+
+ // Global values are not null unless extern weak.
+ if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
+ return !GV->hasExternalWeakLinkage();
+ return false;
+}
+
+/// isNonEscapingLocalObject - Return true if the pointer is to a function-local
+/// object that never escapes from the function.
+static bool isNonEscapingLocalObject(const Value *V) {
+ // If this is a local allocation, check to see if it escapes.
+ if (isa<AllocationInst>(V))
+ return !AddressMightEscape(V);
+
+ // If this is an argument that corresponds to a byval or noalias argument,
+ // it can't escape either.
+ if (const Argument *A = dyn_cast<Argument>(V))
+ if (A->hasByValAttr() || A->hasNoAliasAttr())
+ return !AddressMightEscape(V);
+ return false;
+}
+
+
+/// isObjectSmallerThan - Return true if we can prove that the object specified
+/// by V is smaller than Size.
+static bool isObjectSmallerThan(const Value *V, unsigned Size,
+ const TargetData &TD) {
+ const Type *AccessTy = 0;
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+ AccessTy = GV->getType()->getElementType();
+
+ if (const AllocationInst *AI = dyn_cast<AllocationInst>(V))
+ if (!AI->isArrayAllocation())
+ AccessTy = AI->getType()->getElementType();
+
+ if (const Argument *A = dyn_cast<Argument>(V))
+ if (A->hasByValAttr())
+ AccessTy = cast<PointerType>(A->getType())->getElementType();
+
+ if (AccessTy && AccessTy->isSized())
+ return TD.getABITypeSize(AccessTy) < Size;
+ return false;
+}
+
+//===----------------------------------------------------------------------===//
+// NoAA Pass
+//===----------------------------------------------------------------------===//
+
namespace {
/// NoAA - This class implements the -no-aa pass, which always returns "I
/// don't know" for alias queries. NoAA is unlike other alias analysis
@@ -91,6 +258,10 @@
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
+//===----------------------------------------------------------------------===//
+// BasicAA Pass
+//===----------------------------------------------------------------------===//
+
namespace {
/// BasicAliasAnalysis - This is the default alias analysis implementation.
/// Because it doesn't chain to a previous alias analysis (like -no-aa), it
@@ -138,57 +309,6 @@
return new BasicAliasAnalysis();
}
-/// getUnderlyingObject - This traverses the use chain to figure out what object
-/// the specified value points to. If the value points to, or is derived from,
-/// a unique object or an argument, return it. This returns:
-/// Arguments, GlobalVariables, Functions, Allocas, Mallocs.
-static const Value *getUnderlyingObject(const Value *V) {
- if (!isa<PointerType>(V->getType())) return V;
-
- // If we are at some type of object, return it. GlobalValues and Allocations
- // have unique addresses.
- if (isa<GlobalValue>(V) || isa<AllocationInst>(V) || isa<Argument>(V))
- return V;
-
- // Traverse through different addressing mechanisms...
- if (const Instruction *I = dyn_cast<Instruction>(V)) {
- if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I))
- return getUnderlyingObject(I->getOperand(0));
- } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() == Instruction::BitCast ||
- CE->getOpcode() == Instruction::GetElementPtr)
- return getUnderlyingObject(CE->getOperand(0));
- }
- return V;
-}
-
-static const User *isGEP(const Value *V) {
- if (isa<GetElementPtrInst>(V) ||
- (isa<ConstantExpr>(V) &&
- cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
- return cast<User>(V);
- return 0;
-}
-
-static const Value *GetGEPOperands(const Value *V,
- SmallVector<Value*, 16> &GEPOps){
- assert(GEPOps.empty() && "Expect empty list to populate!");
- GEPOps.insert(GEPOps.end(), cast<User>(V)->op_begin()+1,
- cast<User>(V)->op_end());
-
- // Accumulate all of the chained indexes into the operand array
- V = cast<User>(V)->getOperand(0);
-
- while (const User *G = isGEP(V)) {
- if (!isa<Constant>(GEPOps[0]) || isa<GlobalValue>(GEPOps[0]) ||
- !cast<Constant>(GEPOps[0])->isNullValue())
- break; // Don't handle folding arbitrary pointer offsets yet...
- GEPOps.erase(GEPOps.begin()); // Drop the zero index
- GEPOps.insert(GEPOps.begin(), G->op_begin()+1, G->op_end());
- V = G->getOperand(0);
- }
- return V;
-}
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
@@ -199,46 +319,6 @@
return false;
}
-// Determine if an AllocationInst instruction escapes from the function it is
-// contained in. If it does not escape, there is no way for another function to
-// mod/ref it. We do this by looking at its uses and determining if the uses
-// can escape (recursively).
-static bool AddressMightEscape(const Value *V) {
- for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end();
- UI != E; ++UI) {
- const Instruction *I = cast<Instruction>(*UI);
- switch (I->getOpcode()) {
- case Instruction::Load:
- break; //next use.
- case Instruction::Store:
- if (I->getOperand(0) == V)
- return true; // Escapes if the pointer is stored.
- break; // next use.
- case Instruction::GetElementPtr:
- if (AddressMightEscape(I))
- return true;
- break; // next use.
- case Instruction::BitCast:
- if (AddressMightEscape(I))
- return true;
- break; // next use
- case Instruction::Ret:
- // If returned, the address will escape to calling functions, but no
- // callees could modify it.
- break; // next use
- case Instruction::Call:
- // If the call is to a few known safe intrinsics, we know that it does
- // not escape
- if (!isa<MemIntrinsic>(I))
- return true;
- break; // next use
- default:
- return true;
- }
- }
- return false;
-}
-
// getModRefInfo - Check to see if the specified callsite can clobber the
// specified memory object. Since we only look at local properties of this
// function, we really can't say much about this query. We do, however, use
@@ -287,72 +367,6 @@
return AliasAnalysis::getModRefInfo(CS, P, Size);
}
-/// isIdentifiedObject - Return true if this pointer refers to a distinct and
-/// identifiable object. This returns true for:
-/// Global Variables and Functions
-/// Allocas and Mallocs
-/// ByVal and NoAlias Arguments
-///
-static bool isIdentifiedObject(const Value *V) {
- if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
- return true;
- if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasNoAliasAttr() || A->hasByValAttr();
- return false;
-}
-
-/// isKnownNonNull - Return true if we know that the specified value is never
-/// null.
-static bool isKnownNonNull(const Value *V) {
- // Alloca never returns null, malloc might.
- if (isa<AllocaInst>(V)) return true;
-
- // A byval argument is never null.
- if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasByValAttr();
-
- // Global values are not null unless extern weak.
- if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
- return !GV->hasExternalWeakLinkage();
- return false;
-}
-
-/// isNonEscapingLocalObject - Return true if the pointer is to a function-local
-/// object that never escapes from the function.
-static bool isNonEscapingLocalObject(const Value *V) {
- // If this is a local allocation, check to see if it escapes.
- if (isa<AllocationInst>(V))
- return !AddressMightEscape(V);
-
- // If this is an argument that corresponds to a byval or noalias argument,
- // it can't escape either.
- if (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr() || A->hasNoAliasAttr())
- return !AddressMightEscape(V);
- return false;
-}
-
-
-/// isObjectSmallerThan - Return true if we can prove that the object specified
-/// by V is smaller than Size.
-static bool isObjectSmallerThan(const Value *V, unsigned Size,
- const TargetData &TD) {
- const Type *AccessTy = 0;
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
- AccessTy = GV->getType()->getElementType();
-
- if (const AllocationInst *AI = dyn_cast<AllocationInst>(V))
- if (!AI->isArrayAllocation())
- AccessTy = AI->getType()->getElementType();
-
- if (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr())
- AccessTy = cast<PointerType>(A->getType())->getElementType();
-
- if (AccessTy && AccessTy->isSized())
- return TD.getABITypeSize(AccessTy) < Size;
- return false;
-}
// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
// as array references. Note that this function is heavily tail recursive.
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