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change an assert when generating fmuladd to an ordinary 'if' check (PR25719) 

We don't want to generate fmuladd if there's a use of the fmul expression, but this shouldn't be an assert.

The test case is derived from the commit message for r253337:
http://reviews.llvm.org/rL253337

That commit reverted r253269:
http://reviews.llvm.org/rL253269

...but the bug exists independently of the default fp-contract setting. It just became easier to hit with that change.

PR25719:
https://llvm.org/bugs/show_bug.cgi?id=25719

Differential Revision: http://reviews.llvm.org/D15165

llvm-svn: 254573
This commit is contained in:
Sanjay Patel 2015-12-03 01:25:12 +00:00
parent 0f87463676
commit a30cee6272
2 changed files with 21 additions and 11 deletions
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18
clang/lib/CodeGen/CGExprScalar.cpp
View File

@ -2564,20 +2564,18 @@ static Value* tryEmitFMulAdd(const BinOpInfo &op,
return nullptr; return nullptr;
// We have a potentially fusable op. Look for a mul on one of the operands. // We have a potentially fusable op. Look for a mul on one of the operands.
if (llvm::BinaryOperator* LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) { // Also, make sure that the mul result isn't used directly. In that case,
if (LHSBinOp->getOpcode() == llvm::Instruction::FMul) { // there's no point creating a muladd operation.
assert(LHSBinOp->getNumUses() == 0 && if (auto *LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) {
"Operations with multiple uses shouldn't be contracted."); if (LHSBinOp->getOpcode() == llvm::Instruction::FMul &&
LHSBinOp->use_empty())
return buildFMulAdd(LHSBinOp, op.RHS, CGF, Builder, false, isSub); return buildFMulAdd(LHSBinOp, op.RHS, CGF, Builder, false, isSub);
} }
} else if (llvm::BinaryOperator* RHSBinOp = if (auto *RHSBinOp = dyn_cast<llvm::BinaryOperator>(op.RHS)) {
dyn_cast<llvm::BinaryOperator>(op.RHS)) { if (RHSBinOp->getOpcode() == llvm::Instruction::FMul &&
if (RHSBinOp->getOpcode() == llvm::Instruction::FMul) { RHSBinOp->use_empty())
assert(RHSBinOp->getNumUses() == 0 &&
"Operations with multiple uses shouldn't be contracted.");
return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false); return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false);
} }
}
return nullptr; return nullptr;
} }

12
clang/test/CodeGen/fp-contract-pragma.cpp
View File

@ -62,3 +62,15 @@ float fp_contract_6(float a, float b, float c) {
return a * b + c; return a * b + c;
} }
// If the multiply has multiple uses, don't produce fmuladd.
// This used to assert (PR25719):
// https://llvm.org/bugs/show_bug.cgi?id=25719
float fp_contract_7(float a, float b, float c) {
// CHECK: _Z13fp_contract_7fff
// CHECK: %mul = fmul float %b, 2.000000e+00
// CHECK-NEXT: fsub float %mul, %c
#pragma STDC FP_CONTRACT ON
return (a = 2 * b) - c;
}