[NVPTX] Enable combineRepeatedFPDivisors for NVPTX.

[hfinkel]

LGTM

[jlebar]

Thank you for the review!

llvm/trunk/lib/Target/NVPTX/NVPTXISelLowering.h

public:
   // Get whether we should use instructions that flush floating-point denormals
   // to sign-preserving zero.
   bool useF32FTZ(const MachineFunction &MF) const;
 
   SDValue getSqrtEstimate(SDValue Operand, SelectionDAG &DAG, int Enabled,
                           int &ExtraSteps, bool &UseOneConst,
                           bool Reciprocal) const override;
 
+  unsigned combineRepeatedFPDivisors() const override { return 2; }
+
   bool allowFMA(MachineFunction &MF, CodeGenOpt::Level OptLevel) const;
   bool allowUnsafeFPMath(MachineFunction &MF) const;
 
   bool isFMAFasterThanFMulAndFAdd(EVT) const override { return true; }
 
   bool enableAggressiveFMAFusion(EVT VT) const override { return true; }
 
   // The default is to transform llvm.ctlz(x, false) (where false indicates that

llvm/trunk/test/CodeGen/NVPTX/fast-math.ll

 
 ; CHECK-LABEL: fcos_approx
 ; CHECK:       cos.approx.f32
 define float @fcos_approx(float %a) #0 {
   %r = tail call float @llvm.cos.f32(float %a)
   ret float %r
 }
 
+; CHECK-LABEL: repeated_div_recip_allowed
+define float @repeated_div_recip_allowed(i1 %pred, float %a, float %b, float %divisor) {
+; CHECK: rcp.rn.f32
+; CHECK: mul.rn.f32
+; CHECK: mul.rn.f32
+  %x = fdiv arcp float %a, %divisor
+  %y = fdiv arcp float %b, %divisor
+  %z = select i1 %pred, float %x, float %y
+  ret float %z
+}
+
+; CHECK-LABEL: repeated_div_recip_allowed_ftz
+define float @repeated_div_recip_allowed_ftz(i1 %pred, float %a, float %b, float %divisor) #1 {
+; CHECK: rcp.rn.ftz.f32
+; CHECK: mul.rn.ftz.f32
+; CHECK: mul.rn.ftz.f32
+  %x = fdiv arcp float %a, %divisor
+  %y = fdiv arcp float %b, %divisor
+  %z = select i1 %pred, float %x, float %y
+  ret float %z
+}
+
+; CHECK-LABEL: repeated_div_fast
+define float @repeated_div_fast(i1 %pred, float %a, float %b, float %divisor) #0 {
+; CHECK: rcp.approx.f32
+; CHECK: mul.f32
+; CHECK: mul.f32
+  %x = fdiv float %a, %divisor
+  %y = fdiv float %b, %divisor
+  %z = select i1 %pred, float %x, float %y
+  ret float %z
+}
+
+; CHECK-LABEL: repeated_div_fast_ftz
+define float @repeated_div_fast_ftz(i1 %pred, float %a, float %b, float %divisor) #0 #1 {
+; CHECK: rcp.approx.ftz.f32
+; CHECK: mul.ftz.f32
+; CHECK: mul.ftz.f32
+  %x = fdiv float %a, %divisor
+  %y = fdiv float %b, %divisor
+  %z = select i1 %pred, float %x, float %y
+  ret float %z
+}
+
 attributes #0 = { "unsafe-fp-math" = "true" }
 attributes #1 = { "nvptx-f32ftz" = "true" }