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[X86] Don't rely on global contraction flag #167252

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Merged
merged 8 commits into from
Nov 13, 2025
Merged

[X86] Don't rely on global contraction flag #167252

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b8dcc44
Make X86 backend not rely on global contract flag
mikolaj-pirog Nov 9, 2025
591d77e
Formatting
mikolaj-pirog Nov 9, 2025
2279803
remove unused
mikolaj-pirog Nov 9, 2025
22ff3fd
Reviewer suggestions
mikolaj-pirog Nov 10, 2025
c8ce070
Formatting
mikolaj-pirog Nov 10, 2025
cef9fa0
Add warning on using fp-contract on x86
mikolaj-pirog Nov 12, 2025
52fd57b
Add test, fix last test using fp-contract=fast
mikolaj-pirog Nov 12, 2025
59e4ae7
Add missing contract
mikolaj-pirog Nov 13, 2025
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15 changes: 4 additions & 11 deletions llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8432,9 +8432,7 @@ static bool isFMAddSubOrFMSubAdd(const X86Subtarget &Subtarget,
// DAGCombiner::visitFADDForFMACombine. It would be good to have one
// function that would answer if it is Ok to fuse MUL + ADD to FMADD
// or MUL + ADDSUB to FMADDSUB.
const TargetOptions &Options = DAG.getTarget().Options;
bool AllowFusion =
Options.AllowFPOpFusion == FPOpFusion::Fast ||
(AllowSubAddOrAddSubContract && Opnd0->getFlags().hasAllowContract());
if (!AllowFusion)
return false;
Expand Down Expand Up @@ -54160,11 +54158,7 @@ static SDValue combineFMulcFCMulc(SDNode *N, SelectionDAG &DAG,
// FADD(A, FMA(B, C, 0)) and FADD(A, FMUL(B, C)) to FMA(B, C, A)
static SDValue combineFaddCFmul(SDNode *N, SelectionDAG &DAG,
const X86Subtarget &Subtarget) {
auto AllowContract = [&DAG](const SDNodeFlags &Flags) {
return DAG.getTarget().Options.AllowFPOpFusion == FPOpFusion::Fast ||
Flags.hasAllowContract();
};

bool AllowContract = N->getFlags().hasAllowContract();
auto HasNoSignedZero = [&DAG](const SDNodeFlags &Flags) {
return DAG.getTarget().Options.NoSignedZerosFPMath ||
Flags.hasNoSignedZeros();
Expand All @@ -54176,8 +54170,7 @@ static SDValue combineFaddCFmul(SDNode *N, SelectionDAG &DAG,
Bits.getConstant() == AI;
};

if (N->getOpcode() != ISD::FADD || !Subtarget.hasFP16() ||
!AllowContract(N->getFlags()))
if (N->getOpcode() != ISD::FADD || !Subtarget.hasFP16() || !AllowContract)
return SDValue();

EVT VT = N->getValueType(0);
Expand All @@ -54188,14 +54181,14 @@ static SDValue combineFaddCFmul(SDNode *N, SelectionDAG &DAG,
SDValue RHS = N->getOperand(1);
bool IsConj;
SDValue FAddOp1, MulOp0, MulOp1;
auto GetCFmulFrom = [&MulOp0, &MulOp1, &IsConj, &AllowContract,
auto GetCFmulFrom = [&MulOp0, &MulOp1, &IsConj, AllowContract,
&IsVectorAllNegativeZero,
&HasNoSignedZero](SDValue N) -> bool {
if (!N.hasOneUse() || N.getOpcode() != ISD::BITCAST)
return false;
SDValue Op0 = N.getOperand(0);
unsigned Opcode = Op0.getOpcode();
if (Op0.hasOneUse() && AllowContract(Op0->getFlags())) {
if (Op0.hasOneUse() && AllowContract) {
if ((Opcode == X86ISD::VFMULC || Opcode == X86ISD::VFCMULC)) {
MulOp0 = Op0.getOperand(0);
MulOp1 = Op0.getOperand(1);
Expand Down