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authorDan Gohman <gohman@apple.com>2009-07-17 22:25:10 +0000
committerDan Gohman <gohman@apple.com>2009-07-17 22:25:10 +0000
commit3a7a68c10880c2a28387617b42d14d774e218727 (patch)
tree19703b7ade7ad668d0c54a0d0f97d2f0bce51d82
parent8f080f0233ce28044182e3c81f3ebc12d43e081e (diff)
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Make BasicAliasAnalysis and Value::getUnderlyingObject use
GEPOperator's hasNoPointer0verflow(), and make a few places in instcombine that create GEPs that may overflow clear the NoOverflow value. Among other things, this partially addresses PR2831. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76252 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--lib/Analysis/BasicAliasAnalysis.cpp10
-rw-r--r--lib/Transforms/Scalar/InstructionCombining.cpp20
-rw-r--r--lib/VMCore/Value.cpp14
3 files changed, 28 insertions, 16 deletions
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index c10c6f3..dcb5903 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -23,6 +23,7 @@
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
+#include "llvm/Operator.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallVector.h"
@@ -38,10 +39,11 @@ using namespace llvm;
//===----------------------------------------------------------------------===//
static const User *isGEP(const Value *V) {
- if (isa<GetElementPtrInst>(V) ||
- (isa<ConstantExpr>(V) &&
- cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
- return cast<User>(V);
+ if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V))
+ // For the purposes of BasicAliasAnalysis, if the GEP has overflow it
+ // could do crazy things.
+ if (GEP->hasNoPointerOverflow())
+ return GEP;
return 0;
}
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 9ddd0e0..dbdf449 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2310,7 +2310,10 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
cast<PointerType>(CI->getOperand(0)->getType())->getAddressSpace();
Value *I2 = InsertBitCastBefore(CI->getOperand(0),
Context->getPointerType(Type::Int8Ty, AS), I);
- I2 = InsertNewInstBefore(GetElementPtrInst::Create(I2, Other, "ctg2"), I);
+ GetElementPtrInst *GEP = GetElementPtrInst::Create(I2, Other, "ctg2");
+ // A GEP formed from an arbitrary add may overflow.
+ cast<GEPOperator>(GEP)->setHasNoPointerOverflow(false);
+ I2 = InsertNewInstBefore(GEP, I);
return new PtrToIntInst(I2, CI->getType());
}
}
@@ -8942,7 +8945,12 @@ Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
// If Offset is evenly divisible by Size, we can do this xform.
if (Size && !APIntOps::srem(Offset, APInt(Offset.getBitWidth(), Size))){
Offset = APIntOps::sdiv(Offset, APInt(Offset.getBitWidth(), Size));
- return GetElementPtrInst::Create(X, Context->getConstantInt(Offset));
+ GetElementPtrInst *GEP =
+ GetElementPtrInst::Create(X, Context->getConstantInt(Offset));
+ // A gep synthesized from inttoptr+add+ptrtoint must be assumed to
+ // potentially overflow, in the absense of further analysis.
+ cast<GEPOperator>(GEP)->setHasNoPointerOverflow(false);
+ return GEP;
}
}
// TODO: Could handle other cases, e.g. where add is indexing into field of
@@ -8966,8 +8974,12 @@ Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
Instruction *P = InsertNewInstBefore(new IntToPtrInst(X, CI.getType(),
"tmp"), CI);
- return GetElementPtrInst::Create(P,
- Context->getConstantInt(Offset), "tmp");
+ GetElementPtrInst *GEP =
+ GetElementPtrInst::Create(P, Context->getConstantInt(Offset), "tmp");
+ // A gep synthesized from inttoptr+add+ptrtoint must be assumed to
+ // potentially overflow, in the absense of further analysis.
+ cast<GEPOperator>(GEP)->setHasNoPointerOverflow(false);
+ return GEP;
}
}
return 0;
diff --git a/lib/VMCore/Value.cpp b/lib/VMCore/Value.cpp
index b35ad50..3322c68 100644
--- a/lib/VMCore/Value.cpp
+++ b/lib/VMCore/Value.cpp
@@ -16,6 +16,7 @@
#include "llvm/DerivedTypes.h"
#include "llvm/InstrTypes.h"
#include "llvm/Instructions.h"
+#include "llvm/Operator.h"
#include "llvm/Module.h"
#include "llvm/ValueSymbolTable.h"
#include "llvm/Support/Debug.h"
@@ -372,15 +373,12 @@ Value *Value::getUnderlyingObject() {
Value *V = this;
unsigned MaxLookup = 6;
do {
- if (Instruction *I = dyn_cast<Instruction>(V)) {
- if (!isa<BitCastInst>(I) && !isa<GetElementPtrInst>(I))
+ if (Operator *O = dyn_cast<Operator>(V)) {
+ if (O->getOpcode() != Instruction::BitCast &&
+ (O->getOpcode() != Instruction::GetElementPtr ||
+ !cast<GEPOperator>(V)->hasNoPointerOverflow()))
return V;
- V = I->getOperand(0);
- } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() != Instruction::BitCast &&
- CE->getOpcode() != Instruction::GetElementPtr)
- return V;
- V = CE->getOperand(0);
+ V = O->getOperand(0);
} else {
return V;
}