spatel created this revision. spatel added reviewers: lhames, scanon, hfinkel, klimek. spatel added a subscriber: cfe-commits.
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 http://reviews.llvm.org/D15165 Files: lib/CodeGen/CGExprScalar.cpp test/CodeGen/fp-contract-pragma.cpp Index: test/CodeGen/fp-contract-pragma.cpp =================================================================== --- test/CodeGen/fp-contract-pragma.cpp +++ test/CodeGen/fp-contract-pragma.cpp @@ -62,3 +62,15 @@ 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; +} + Index: lib/CodeGen/CGExprScalar.cpp =================================================================== --- lib/CodeGen/CGExprScalar.cpp +++ lib/CodeGen/CGExprScalar.cpp @@ -2564,17 +2564,17 @@ return nullptr; // We have a potentially fusable op. Look for a mul on one of the operands. + // Also, make sure that the mul result isn't used directly. In that case, + // there's no point creating a muladd operation. if (llvm::BinaryOperator* LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) { - if (LHSBinOp->getOpcode() == llvm::Instruction::FMul) { - assert(LHSBinOp->getNumUses() == 0 && - "Operations with multiple uses shouldn't be contracted."); + if (LHSBinOp->getOpcode() == llvm::Instruction::FMul && + LHSBinOp->getNumUses() == 0) { return buildFMulAdd(LHSBinOp, op.RHS, CGF, Builder, false, isSub); } } else if (llvm::BinaryOperator* RHSBinOp = dyn_cast<llvm::BinaryOperator>(op.RHS)) { - if (RHSBinOp->getOpcode() == llvm::Instruction::FMul) { - assert(RHSBinOp->getNumUses() == 0 && - "Operations with multiple uses shouldn't be contracted."); + if (RHSBinOp->getOpcode() == llvm::Instruction::FMul && + RHSBinOp->getNumUses() == 0) { return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false); } }
Index: test/CodeGen/fp-contract-pragma.cpp =================================================================== --- test/CodeGen/fp-contract-pragma.cpp +++ test/CodeGen/fp-contract-pragma.cpp @@ -62,3 +62,15 @@ 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; +} + Index: lib/CodeGen/CGExprScalar.cpp =================================================================== --- lib/CodeGen/CGExprScalar.cpp +++ lib/CodeGen/CGExprScalar.cpp @@ -2564,17 +2564,17 @@ return nullptr; // We have a potentially fusable op. Look for a mul on one of the operands. + // Also, make sure that the mul result isn't used directly. In that case, + // there's no point creating a muladd operation. if (llvm::BinaryOperator* LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) { - if (LHSBinOp->getOpcode() == llvm::Instruction::FMul) { - assert(LHSBinOp->getNumUses() == 0 && - "Operations with multiple uses shouldn't be contracted."); + if (LHSBinOp->getOpcode() == llvm::Instruction::FMul && + LHSBinOp->getNumUses() == 0) { return buildFMulAdd(LHSBinOp, op.RHS, CGF, Builder, false, isSub); } } else if (llvm::BinaryOperator* RHSBinOp = dyn_cast<llvm::BinaryOperator>(op.RHS)) { - if (RHSBinOp->getOpcode() == llvm::Instruction::FMul) { - assert(RHSBinOp->getNumUses() == 0 && - "Operations with multiple uses shouldn't be contracted."); + if (RHSBinOp->getOpcode() == llvm::Instruction::FMul && + RHSBinOp->getNumUses() == 0) { return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false); } }
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