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Set FMF for -ffp-contract=fast 

With this, FMF(contract) becomes an alternative way to express the request to
contract.

These are currently only propagated for FMul, FAdd and FSub.  The rest will be
added as more FMFs are hooked up for this.

This is toward fixing PR25721.

Differential Revision: https://reviews.llvm.org/D31168

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@299469 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Adam Nemet 2017-04-04 21:18:30 +00:00
parent dad9866deb
commit a51d8c8b11
2 changed files with 53 additions and 4 deletions
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28
lib/CodeGen/CGExprScalar.cpp
View File

@ -113,6 +113,22 @@ static bool CanElideOverflowCheck(const ASTContext &Ctx, const BinOpInfo &Op) {
(2 * Ctx.getTypeSize(RHSTy)) < PromotedSize;
}
/// Update the FastMathFlags of LLVM IR from the FPOptions in LangOptions.
static void updateFastMathFlags(llvm::FastMathFlags &FMF,
FPOptions FPFeatures) {
FMF.setAllowContract(FPFeatures.allowFPContractAcrossStatement());
}
/// Propagate fast-math flags from \p Op to the instruction in \p V.
static Value *propagateFMFlags(Value *V, const BinOpInfo &Op) {
if (auto *I = dyn_cast<llvm::Instruction>(V)) {
llvm::FastMathFlags FMF = I->getFastMathFlags();
updateFastMathFlags(FMF, Op.FPFeatures);
I->setFastMathFlags(FMF);
}
return V;
}
class ScalarExprEmitter
: public StmtVisitor<ScalarExprEmitter, Value*> {
CodeGenFunction &CGF;
@ -553,8 +569,10 @@ public:
!CanElideOverflowCheck(CGF.getContext(), Ops))
return EmitOverflowCheckedBinOp(Ops);
if (Ops.LHS->getType()->isFPOrFPVectorTy())
return Builder.CreateFMul(Ops.LHS, Ops.RHS, "mul");
if (Ops.LHS->getType()->isFPOrFPVectorTy()) {
Value *V = Builder.CreateFMul(Ops.LHS, Ops.RHS, "mul");
return propagateFMFlags(V, Ops);
}
return Builder.CreateMul(Ops.LHS, Ops.RHS, "mul");
}
/// Create a binary op that checks for overflow.
@ -2722,7 +2740,8 @@ Value *ScalarExprEmitter::EmitAdd(const BinOpInfo &op) {
if (Value *FMulAdd = tryEmitFMulAdd(op, CGF, Builder))
return FMulAdd;
return Builder.CreateFAdd(op.LHS, op.RHS, "add");
Value *V = Builder.CreateFAdd(op.LHS, op.RHS, "add");
return propagateFMFlags(V, op);
}
return Builder.CreateAdd(op.LHS, op.RHS, "add");
@ -2755,7 +2774,8 @@ Value *ScalarExprEmitter::EmitSub(const BinOpInfo &op) {
// Try to form an fmuladd.
if (Value *FMulAdd = tryEmitFMulAdd(op, CGF, Builder, true))
return FMulAdd;
return Builder.CreateFSub(op.LHS, op.RHS, "sub");
Value *V = Builder.CreateFSub(op.LHS, op.RHS, "sub");
return propagateFMFlags(V, op);
}
return Builder.CreateSub(op.LHS, op.RHS, "sub");

29
test/CodeGen/ffp-contract-fast-option.cpp Normal file
View File

@ -0,0 +1,29 @@
// RUN: %clang_cc1 -O3 -ffp-contract=fast -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck %s
float fp_contract_1(float a, float b, float c) {
// CHECK-LABEL: fp_contract_1fff(
// CHECK: fmul contract float
// CHECK: fadd contract float
return a * b + c;
}
float fp_contract_2(float a, float b, float c) {
// CHECK-LABEL: fp_contract_2fff(
// CHECK: fmul contract float
// CHECK: fsub contract float
return a * b - c;
}
void fp_contract_3(float *a, float b, float c) {
// CHECK-LABEL: fp_contract_3Pfff(
// CHECK: fmul contract float
// CHECK: fadd contract float
a[0] += b * c;
}
void fp_contract_4(float *a, float b, float c) {
// CHECK-LABEL: fp_contract_4Pfff(
// CHECK: fmul contract float
// CHECK: fsub contract float
a[0] -= b * c;
}