Cleanup and improve PPC fsel generation

First, we should not cheat: fsel-based lowering of select_cc is a
finite-math-only optimization (the ISA manual, section F.3 of v2.06, makes
this clear, as does a note in our own README).

This also adds fsel-based lowering of EQ and NE condition codes. As it turned
out, fsel generation was covered by a grand total of zero regression test
cases. I've added some test cases to cover the existing behavior (which is now
finite-math only), as well as the new EQ cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179000 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 33 insertions, 7 deletions

diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index cec0b8f..333976b 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -4673,10 +4673,14 @@ SDValue PPCTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
       !Op.getOperand(2).getValueType().isFloatingPoint())
     return Op;
 
-  ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
+  // We might be able to do better than this under some circumstances, but in
+  // general, fsel-based lowering of select is a finite-math-only optimization.
+  // For more information, see section F.3 of the 2.06 ISA specification.
+  if (!DAG.getTarget().Options.NoInfsFPMath ||
+      !DAG.getTarget().Options.NoNaNsFPMath)
+    return Op;
 
-  // Cannot handle SETEQ/SETNE.
-  if (CC == ISD::SETEQ || CC == ISD::SETNE) return Op;
+  ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
 
   EVT ResVT = Op.getValueType();
   EVT CmpVT = Op.getOperand(0).getValueType();
@@ -4686,9 +4690,20 @@ SDValue PPCTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
 
   // If the RHS of the comparison is a 0.0, we don't need to do the
   // subtraction at all.
+  SDValue Sel1;
   if (isFloatingPointZero(RHS))
     switch (CC) {
     default: break;       // SETUO etc aren't handled by fsel.
+    case ISD::SETNE:
+      std::swap(TV, FV);
+    case ISD::SETEQ:
+      if (LHS.getValueType() == MVT::f32)   // Comparison is always 64-bits
+        LHS = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, LHS);
+      Sel1 = DAG.getNode(PPCISD::FSEL, dl, ResVT, LHS, TV, FV);
+      if (Sel1.getValueType() == MVT::f32)   // Comparison is always 64-bits
+        Sel1 = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Sel1);
+      return DAG.getNode(PPCISD::FSEL, dl, ResVT,
+                         DAG.getNode(ISD::FNEG, dl, MVT::f64, LHS), Sel1, FV);
     case ISD::SETULT:
     case ISD::SETLT:
       std::swap(TV, FV);  // fsel is natively setge, swap operands for setlt
@@ -4711,30 +4726,41 @@ SDValue PPCTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
   SDValue Cmp;
   switch (CC) {
   default: break;       // SETUO etc aren't handled by fsel.
+  case ISD::SETNE:
+    std::swap(TV, FV);
+  case ISD::SETEQ:
+    Cmp = DAG.getNode(ISD::FSUB, dl, CmpVT, LHS, RHS);
+    if (Cmp.getValueType() == MVT::f32)   // Comparison is always 64-bits
+      Cmp = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Cmp);
+    Sel1 = DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, TV, FV);
+    if (Sel1.getValueType() == MVT::f32)   // Comparison is always 64-bits
+      Sel1 = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Sel1);
+    return DAG.getNode(PPCISD::FSEL, dl, ResVT,
+                       DAG.getNode(ISD::FNEG, dl, MVT::f64, Cmp), Sel1, FV);
   case ISD::SETULT:
   case ISD::SETLT:
     Cmp = DAG.getNode(ISD::FSUB, dl, CmpVT, LHS, RHS);
     if (Cmp.getValueType() == MVT::f32)   // Comparison is always 64-bits
       Cmp = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Cmp);
-      return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, FV, TV);
+    return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, FV, TV);
   case ISD::SETOGE:
   case ISD::SETGE:
     Cmp = DAG.getNode(ISD::FSUB, dl, CmpVT, LHS, RHS);
     if (Cmp.getValueType() == MVT::f32)   // Comparison is always 64-bits
       Cmp = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Cmp);
-      return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, TV, FV);
+    return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, TV, FV);
   case ISD::SETUGT:
   case ISD::SETGT:
     Cmp = DAG.getNode(ISD::FSUB, dl, CmpVT, RHS, LHS);
     if (Cmp.getValueType() == MVT::f32)   // Comparison is always 64-bits
       Cmp = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Cmp);
-      return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, FV, TV);
+    return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, FV, TV);
   case ISD::SETOLE:
   case ISD::SETLE:
     Cmp = DAG.getNode(ISD::FSUB, dl, CmpVT, RHS, LHS);
     if (Cmp.getValueType() == MVT::f32)   // Comparison is always 64-bits
       Cmp = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Cmp);
-      return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, TV, FV);
+    return DAG.getNode(PPCISD::FSEL, dl, ResVT, Cmp, TV, FV);
   }
   return Op;
 }