Author: spatel Date: Wed Dec 2 19:25:12 2015 New Revision: 254573 URL: http://llvm.org/viewvc/llvm-project?rev=254573&view=rev Log: 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 Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp cfe/trunk/test/CodeGen/fp-contract-pragma.cpp Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=254573&r1=254572&r2=254573&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original) +++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Wed Dec 2 19:25:12 2015 @@ -2564,19 +2564,17 @@ static Value* tryEmitFMulAdd(const BinOp return nullptr; // 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)) { - if (LHSBinOp->getOpcode() == llvm::Instruction::FMul) { - assert(LHSBinOp->getNumUses() == 0 && - "Operations with multiple uses shouldn't be contracted."); + // Also, make sure that the mul result isn't used directly. In that case, + // there's no point creating a muladd operation. + if (auto *LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) { + if (LHSBinOp->getOpcode() == llvm::Instruction::FMul && + LHSBinOp->use_empty()) 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 (auto *RHSBinOp = dyn_cast<llvm::BinaryOperator>(op.RHS)) { + if (RHSBinOp->getOpcode() == llvm::Instruction::FMul && + RHSBinOp->use_empty()) return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false); - } } return nullptr; Modified: cfe/trunk/test/CodeGen/fp-contract-pragma.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/fp-contract-pragma.cpp?rev=254573&r1=254572&r2=254573&view=diff ============================================================================== --- cfe/trunk/test/CodeGen/fp-contract-pragma.cpp (original) +++ cfe/trunk/test/CodeGen/fp-contract-pragma.cpp Wed Dec 2 19:25:12 2015 @@ -62,3 +62,15 @@ float fp_contract_6(float a, float b, fl 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; +} + _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
