AMDGPU: Fix fdiv lowering when f32 denormals supported

Also fix test not actually using function labels.

llvm-svn: 274969

1 files changed, 3 insertions, 5 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index f224e197ea4..29c40851ea9 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -2073,17 +2073,13 @@ SDValue SITargetLowering::LowerFDIV32(SDValue Op, SelectionDAG &DAG) const {
   if (SDValue FastLowered = LowerFastFDIV(Op, DAG))
     return FastLowered;
 
-  // This uses v_rcp_f32 which does not handle denormals. Let this hit a
-  // selection error for now rather than do something incorrect.
-  if (Subtarget->hasFP32Denormals())
-    return SDValue();
-
   SDLoc SL(Op);
   SDValue LHS = Op.getOperand(0);
   SDValue RHS = Op.getOperand(1);
 
   // faster 2.5 ulp fdiv when using -amdgpu-fast-fdiv flag
   if (EnableAMDGPUFastFDIV) {
+    // This does not support denormals.
     SDValue r1 = DAG.getNode(ISD::FABS, SL, MVT::f32, RHS);
 
     const APFloat K0Val(BitsToFloat(0x6f800000));
@@ -2105,6 +2101,7 @@ SDValue SITargetLowering::LowerFDIV32(SDValue Op, SelectionDAG &DAG) const {
 
     r1 = DAG.getNode(ISD::FMUL, SL, MVT::f32, RHS, r3);
 
+    // rcp does not support denormals.
     SDValue r0 = DAG.getNode(AMDGPUISD::RCP, SL, MVT::f32, r1);
 
     SDValue Mul = DAG.getNode(ISD::FMUL, SL, MVT::f32, LHS, r0);
@@ -2120,6 +2117,7 @@ SDValue SITargetLowering::LowerFDIV32(SDValue Op, SelectionDAG &DAG) const {
   SDValue DenominatorScaled = DAG.getNode(AMDGPUISD::DIV_SCALE, SL, ScaleVT, RHS, RHS, LHS);
   SDValue NumeratorScaled = DAG.getNode(AMDGPUISD::DIV_SCALE, SL, ScaleVT, LHS, RHS, LHS);
 
+  // Denominator is scaled to not be denormal, so using rcp is ok.
   SDValue ApproxRcp = DAG.getNode(AMDGPUISD::RCP, SL, MVT::f32, DenominatorScaled);
 
   SDValue NegDivScale0 = DAG.getNode(ISD::FNEG, SL, MVT::f32, DenominatorScaled);