// (fneg (fmul c, x)) -> (fmul -c, x)
if (N0.getOpcode() == ISD::FMUL) {
ConstantFPSDNode *CFP1 = dyn_cast<ConstantFPSDNode>(N0.getOperand(1));
- if (CFP1)
- return DAG.getNode(ISD::FMUL, SDLoc(N), VT,
- N0.getOperand(0),
- DAG.getNode(ISD::FNEG, SDLoc(N), VT,
- N0.getOperand(1)));
+ if (CFP1) {
+ APFloat CVal = CFP1->getValueAPF();
+ CVal.changeSign();
+ if (Level >= AfterLegalizeDAG &&
+ (TLI.isFPImmLegal(CVal, N->getValueType(0)) ||
+ TLI.isOperationLegal(ISD::ConstantFP, N->getValueType(0))))
+ return DAG.getNode(
+ ISD::FMUL, SDLoc(N), VT, N0.getOperand(0),
+ DAG.getNode(ISD::FNEG, SDLoc(N), VT, N0.getOperand(1)));
+ }
}
return SDValue();
--- /dev/null
+; RUN: llc -mtriple=arm64 -fp-contract=fast -o - %s | FileCheck %s
+
+
+; Make sure we don't try to fold an fneg into +0.0, creating an illegal constant
+; -0.0. It's also good, though not essential, that we don't resort to a litpool.
+define double @test_fms_fold(double %a, double %b) {
+; CHECK-LABEL: test_fms_fold:
+; CHECK: fmov {{d[0-9]+}}, xzr
+; CHECK: ret
+ %mul = fmul double %a, 0.000000e+00
+ %mul1 = fmul double %b, 0.000000e+00
+ %sub = fsub double %mul, %mul1
+ ret double %sub
+}
\ No newline at end of file