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[InstSimplify] Cast folding can be made more generic
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Use isEliminableCastPair to determine if a pair of casts are foldable.

llvm-svn: 276777
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@majnemer
majnemer committed Jul 26, 2016
1 parent 2f2bd8c commit 6774d61
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Showing 3 changed files with 51 additions and 61 deletions.
20 changes: 7 additions & 13 deletions llvm/include/llvm/Analysis/InstructionSimplify.h
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Original file line number Diff line number Diff line change
Expand Up @@ -238,19 +238,13 @@ namespace llvm {
AssumptionCache *AC = nullptr,
const Instruction *CxtI = nullptr);

/// Given operands for an TruncInst, fold the result or return null.
Value *SimplifyTruncInst(Value *Op, Type *Ty, const DataLayout &DL,
const TargetLibraryInfo *TLI = nullptr,
const DominatorTree *DT = nullptr,
AssumptionCache *AC = nullptr,
const Instruction *CxtI = nullptr);

/// Given operands for an BitCastInst, fold the result or return null.
Value *SimplifyBitCastInst(Value *Op, Type *Ty, const DataLayout &DL,
const TargetLibraryInfo *TLI = nullptr,
const DominatorTree *DT = nullptr,
AssumptionCache *AC = nullptr,
const Instruction *CxtI = nullptr);
/// Given operands for a CastInst, fold the result or return null.
Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
const DataLayout &DL,
const TargetLibraryInfo *TLI = nullptr,
const DominatorTree *DT = nullptr,
AssumptionCache *AC = nullptr,
const Instruction *CxtI = nullptr);

//=== Helper functions for higher up the class hierarchy.

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89 changes: 43 additions & 46 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -69,8 +69,8 @@ static Value *SimplifyCmpInst(unsigned, Value *, Value *, const Query &,
unsigned);
static Value *SimplifyOrInst(Value *, Value *, const Query &, unsigned);
static Value *SimplifyXorInst(Value *, Value *, const Query &, unsigned);
static Value *SimplifyTruncInst(Value *, Type *, const Query &, unsigned);
static Value *SimplifyBitCastInst(Value *, Type *, const Query &, unsigned);
static Value *SimplifyCastInst(unsigned, Value *, Type *,
const Query &, unsigned);

/// For a boolean type, or a vector of boolean type, return false, or
/// a vector with every element false, as appropriate for the type.
Expand Down Expand Up @@ -748,7 +748,8 @@ static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
// See if "V === X - Y" simplifies.
if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, Q, MaxRecurse-1))
// It does! Now see if "trunc V" simplifies.
if (Value *W = SimplifyTruncInst(V, Op0->getType(), Q, MaxRecurse-1))
if (Value *W = SimplifyCastInst(Instruction::Trunc, V, Op0->getType(),
Q, MaxRecurse - 1))
// It does, return the simplified "trunc V".
return W;

Expand Down Expand Up @@ -3790,49 +3791,47 @@ static Value *SimplifyPHINode(PHINode *PN, const Query &Q) {
return CommonValue;
}

static Value *SimplifyTruncInst(Value *Op, Type *Ty, const Query &Q, unsigned) {
static Value *SimplifyCastInst(unsigned CastOpc, Value *Op,
Type *Ty, const Query &Q, unsigned MaxRecurse) {
if (auto *C = dyn_cast<Constant>(Op))
return ConstantFoldCastOperand(Instruction::Trunc, C, Ty, Q.DL);

// trunc([zs]ext(x)) -> x if the trunc undoes the work of the [zs]ext.
if (auto *CI = dyn_cast<CastInst>(Op))
if (isa<ZExtInst>(CI) || isa<SExtInst>(CI))
if (CI->getOperand(0)->getType() == Ty)
return CI->getOperand(0);

return nullptr;
}

Value *llvm::SimplifyTruncInst(Value *Op, Type *Ty, const DataLayout &DL,
const TargetLibraryInfo *TLI,
const DominatorTree *DT, AssumptionCache *AC,
const Instruction *CxtI) {
return ::SimplifyTruncInst(Op, Ty, Query(DL, TLI, DT, AC, CxtI),
RecursionLimit);
}

static Value *SimplifyBitCastInst(Value *Op, Type *Ty, const Query &Q, unsigned) {
if (auto *C = dyn_cast<Constant>(Op))
return ConstantFoldCastOperand(Instruction::BitCast, C, Ty, Q.DL);
return ConstantFoldCastOperand(CastOpc, C, Ty, Q.DL);

if (auto *CI = dyn_cast<CastInst>(Op)) {
auto *Src = CI->getOperand(0);
Type *SrcTy = Src->getType();
Type *MidTy = CI->getType();
Type *DstTy = Ty;
if (Src->getType() == Ty) {
auto FirstOp = static_cast<Instruction::CastOps>(CI->getOpcode());
auto SecondOp = static_cast<Instruction::CastOps>(CastOpc);
Type *SrcIntPtrTy =
SrcTy->isPtrOrPtrVectorTy() ? Q.DL.getIntPtrType(SrcTy) : nullptr;
Type *MidIntPtrTy =
MidTy->isPtrOrPtrVectorTy() ? Q.DL.getIntPtrType(MidTy) : nullptr;
Type *DstIntPtrTy =
DstTy->isPtrOrPtrVectorTy() ? Q.DL.getIntPtrType(DstTy) : nullptr;
if (CastInst::isEliminableCastPair(FirstOp, SecondOp, SrcTy, MidTy, DstTy,
SrcIntPtrTy, MidIntPtrTy,
DstIntPtrTy) == Instruction::BitCast)
return Src;
}
}

// bitcast x -> x
if (Op->getType() == Ty)
return Op;

// bitcast(bitcast x) -> x
if (auto *BC = dyn_cast<BitCastInst>(Op))
if (BC->getOperand(0)->getType() == Ty)
return BC->getOperand(0);
if (CastOpc == Instruction::BitCast)
if (Op->getType() == Ty)
return Op;

return nullptr;
}

Value *llvm::SimplifyBitCastInst(Value *Op, Type *Ty, const DataLayout &DL,
const TargetLibraryInfo *TLI,
const DominatorTree *DT, AssumptionCache *AC,
const Instruction *CxtI) {
return ::SimplifyBitCastInst(Op, Ty, Query(DL, TLI, DT, AC, CxtI),
RecursionLimit);
Value *llvm::SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
const DataLayout &DL,
const TargetLibraryInfo *TLI,
const DominatorTree *DT, AssumptionCache *AC,
const Instruction *CxtI) {
return ::SimplifyCastInst(CastOpc, Op, Ty, Query(DL, TLI, DT, AC, CxtI),
RecursionLimit);
}

//=== Helper functions for higher up the class hierarchy.
Expand Down Expand Up @@ -4301,13 +4300,11 @@ Value *llvm::SimplifyInstruction(Instruction *I, const DataLayout &DL,
TLI, DT, AC, I);
break;
}
case Instruction::Trunc:
Result =
SimplifyTruncInst(I->getOperand(0), I->getType(), DL, TLI, DT, AC, I);
break;
case Instruction::BitCast:
Result =
SimplifyBitCastInst(I->getOperand(0), I->getType(), DL, TLI, DT, AC, I);
#define HANDLE_CAST_INST(num, opc, clas) case Instruction::opc:
#include "llvm/IR/Instruction.def"
#undef HANDLE_CAST_INST
Result = SimplifyCastInst(I->getOpcode(), I->getOperand(0), I->getType(),
DL, TLI, DT, AC, I);
break;
}

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3 changes: 1 addition & 2 deletions llvm/test/Transforms/GVN/pr14166.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -17,8 +17,7 @@ define <2 x i32> @test1() {
; CHECK: %v3 = inttoptr <2 x i32> %v2 to <2 x i8*>
; CHECK: %v4 = bitcast <2 x i32>* %v1 to <2 x i8*>*
; CHECK: store <2 x i8*> %v3, <2 x i8*>* %v4
; CHECK: %1 = ptrtoint <2 x i8*> %v3 to <2 x i32>
; CHECK: ret <2 x i32> %1
; CHECK: ret <2 x i32> %v2
}

declare void @anything(<2 x i32>*)
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