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Refactor canonicalizing array indices to a helper function

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llvm-svn: 210438
This commit is contained in:
Jingyue Wu 2014-06-08 20:15:45 +00:00
parent 9018bd90e6
commit c4c2a9ced2
1 changed files with 51 additions and 32 deletions
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83
lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
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@ -236,6 +236,15 @@ class SeparateConstOffsetFromGEP : public FunctionPass {
AU.addRequired<DataLayoutPass>();
AU.addRequired<TargetTransformInfo>();
}
bool doInitialization(Module &M) override {
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
if (DLP == nullptr)
report_fatal_error("data layout missing");
DL = &DLP->getDataLayout();
return false;
}
bool runOnFunction(Function &F) override;
private:
@ -246,8 +255,23 @@ class SeparateConstOffsetFromGEP : public FunctionPass {
/// function only inspects the GEP without changing it. The output
/// NeedsExtraction indicates whether we can extract a non-zero constant
/// offset from any index.
int64_t accumulateByteOffset(GetElementPtrInst *GEP, const DataLayout *DL,
bool &NeedsExtraction);
int64_t accumulateByteOffset(GetElementPtrInst *GEP, bool &NeedsExtraction);
/// Canonicalize array indices to pointer-size integers. This helps to
/// simplify the logic of splitting a GEP. For example, if a + b is a
/// pointer-size integer, we have
/// gep base, a + b = gep (gep base, a), b
/// However, this equality may not hold if the size of a + b is smaller than
/// the pointer size, because LLVM conceptually sign-extends GEP indices to
/// pointer size before computing the address
/// (http://llvm.org/docs/LangRef.html#id181).
///
/// This canonicalization is very likely already done in clang and
/// instcombine. Therefore, the program will probably remain the same.
///
/// Verified in @i32_add in split-gep.ll
bool canonicalizeArrayIndicesToPointerSize(GetElementPtrInst *GEP);
const DataLayout *DL;
};
} // anonymous namespace
@ -553,8 +577,27 @@ bool ConstantOffsetExtractor::NoCommonBits(Value *LHS, Value *RHS) const {
return (LHSKnownZero | RHSKnownZero).isAllOnesValue();
}
int64_t SeparateConstOffsetFromGEP::accumulateByteOffset(
GetElementPtrInst *GEP, const DataLayout *DL, bool &NeedsExtraction) {
bool SeparateConstOffsetFromGEP::canonicalizeArrayIndicesToPointerSize(
GetElementPtrInst *GEP) {
bool Changed = false;
Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
gep_type_iterator GTI = gep_type_begin(*GEP);
for (User::op_iterator I = GEP->op_begin() + 1, E = GEP->op_end();
I != E; ++I, ++GTI) {
// Skip struct member indices which must be i32.
if (isa<SequentialType>(*GTI)) {
if ((*I)->getType() != IntPtrTy) {
*I = CastInst::CreateIntegerCast(*I, IntPtrTy, true, "idxprom", GEP);
Changed = true;
}
}
}
return Changed;
}
int64_t
SeparateConstOffsetFromGEP::accumulateByteOffset(GetElementPtrInst *GEP,
bool &NeedsExtraction) {
NeedsExtraction = false;
int64_t AccumulativeByteOffset = 0;
gep_type_iterator GTI = gep_type_begin(*GEP);
@ -587,35 +630,10 @@ bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
return false;
bool Changed = false;
// Canonicalize array indices to pointer-size integers. This helps to simplify
// the logic of splitting a GEP. For example, if a + b is a pointer-size
// integer, we have
// gep base, a + b = gep (gep base, a), b
// However, this equality may not hold if the size of a + b is smaller than
// the pointer size, because LLVM conceptually sign-extends GEP indices to
// pointer size before computing the address
// (http://llvm.org/docs/LangRef.html#id181).
//
// This canonicalization is very likely already done in clang and instcombine.
// Therefore, the program will probably remain the same.
//
// Verified in @i32_add in split-gep.ll
const DataLayout *DL = &getAnalysis<DataLayoutPass>().getDataLayout();
Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
gep_type_iterator GTI = gep_type_begin(*GEP);
for (User::op_iterator I = GEP->op_begin() + 1, E = GEP->op_end();
I != E; ++I, ++GTI) {
if (isa<SequentialType>(*GTI)) {
if ((*I)->getType() != IntPtrTy) {
*I = CastInst::CreateIntegerCast(*I, IntPtrTy, true, "idxprom", GEP);
Changed = true;
}
}
}
Changed |= canonicalizeArrayIndicesToPointerSize(GEP);
bool NeedsExtraction;
int64_t AccumulativeByteOffset =
accumulateByteOffset(GEP, DL, NeedsExtraction);
int64_t AccumulativeByteOffset = accumulateByteOffset(GEP, NeedsExtraction);
if (!NeedsExtraction)
return Changed;
@ -631,7 +649,7 @@ bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
// Remove the constant offset in each GEP index. The resultant GEP computes
// the variadic base.
GTI = gep_type_begin(*GEP);
gep_type_iterator GTI = gep_type_begin(*GEP);
for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
if (isa<SequentialType>(*GTI)) {
Value *NewIdx = nullptr;
@ -699,6 +717,7 @@ bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
uint64_t ElementTypeSizeOfGEP =
DL->getTypeAllocSize(GEP->getType()->getElementType());
Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
if (AccumulativeByteOffset % ElementTypeSizeOfGEP == 0) {
// Very likely. As long as %gep is natually aligned, the byte offset we
// extracted should be a multiple of sizeof(*%gep).