Combine fcmp + select to fminnum / fmaxnum if no nans and legal
Also require unsafe FP math for no since there isn't a way to
test for signed zeros.
llvm-svn: 225744
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4f57032..56ba91f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4617,6 +4617,43 @@
return SDValue();
}
+
+/// \brief Generate Min/Max node
+static SDValue combineMinNumMaxNum(SDLoc DL, EVT VT, SDValue LHS, SDValue RHS,
+ SDValue True, SDValue False,
+ ISD::CondCode CC, const TargetLowering &TLI,
+ SelectionDAG &DAG) {
+ if (!(LHS == True && RHS == False) && !(LHS == False && RHS == True))
+ return SDValue();
+
+ switch (CC) {
+ case ISD::SETOLT:
+ case ISD::SETOLE:
+ case ISD::SETLT:
+ case ISD::SETLE:
+ case ISD::SETULT:
+ case ISD::SETULE: {
+ unsigned Opcode = (LHS == True) ? ISD::FMINNUM : ISD::FMAXNUM;
+ if (TLI.isOperationLegal(Opcode, VT))
+ return DAG.getNode(Opcode, DL, VT, LHS, RHS);
+ return SDValue();
+ }
+ case ISD::SETOGT:
+ case ISD::SETOGE:
+ case ISD::SETGT:
+ case ISD::SETGE:
+ case ISD::SETUGT:
+ case ISD::SETUGE: {
+ unsigned Opcode = (LHS == True) ? ISD::FMAXNUM : ISD::FMINNUM;
+ if (TLI.isOperationLegal(Opcode, VT))
+ return DAG.getNode(Opcode, DL, VT, LHS, RHS);
+ return SDValue();
+ }
+ default:
+ return SDValue();
+ }
+}
+
SDValue DAGCombiner::visitSELECT(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
@@ -4696,6 +4733,28 @@
// fold selects based on a setcc into other things, such as min/max/abs
if (N0.getOpcode() == ISD::SETCC) {
+ // select x, y (fcmp lt x, y) -> fminnum x, y
+ // select x, y (fcmp gt x, y) -> fmaxnum x, y
+ //
+ // This is OK if we don't care about what happens if either operand is a
+ // NaN.
+ //
+
+ // FIXME: Instead of testing for UnsafeFPMath, this should be checking for
+ // no signed zeros as well as no nans.
+ const TargetOptions &Options = DAG.getTarget().Options;
+ if (Options.UnsafeFPMath &&
+ VT.isFloatingPoint() && N0.hasOneUse() &&
+ DAG.isKnownNeverNaN(N1) && DAG.isKnownNeverNaN(N2)) {
+ ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
+
+ SDValue FMinMax =
+ combineMinNumMaxNum(SDLoc(N), VT, N0.getOperand(0), N0.getOperand(1),
+ N1, N2, CC, TLI, DAG);
+ if (FMinMax)
+ return FMinMax;
+ }
+
if ((!LegalOperations &&
TLI.isOperationLegalOrCustom(ISD::SELECT_CC, VT)) ||
TLI.isOperationLegal(ISD::SELECT_CC, VT))