AMDGPU: Fix fdiv lowering when f32 denormals supported

Also fix test not actually using function labels.

llvm-svn: 274969

2 files changed, 15 insertions, 22 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);
diff --git a/llvm/test/CodeGen/AMDGPU/fdiv.ll b/llvm/test/CodeGen/AMDGPU/fdiv.ll
index 33e865f3218..4021233e778 100644
--- a/llvm/test/CodeGen/AMDGPU/fdiv.ll
+++ b/llvm/test/CodeGen/AMDGPU/fdiv.ll
@@ -1,8 +1,9 @@
-; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=SI %s
-; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs -amdgpu-fast-fdiv < %s | FileCheck -check-prefix=SI %s
-; RUN: llc -march=amdgcn -mcpu=fiji -verify-machineinstrs < %s | FileCheck -check-prefix=I754 %s
-; RUN: llc -march=amdgcn -mcpu=fiji -verify-machineinstrs -enable-unsafe-fp-math < %s | FileCheck -check-prefix=UNSAFE-FP %s
-; RUN: llc -march=r600 -mcpu=redwood < %s | FileCheck -check-prefix=R600 %s
+; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=tonga -mattr=+fp32-denormals -verify-machineinstrs < %s | FileCheck -check-prefix=I754 -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs -amdgpu-fast-fdiv < %s | FileCheck -check-prefix=SI -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=fiji -verify-machineinstrs < %s | FileCheck -check-prefix=I754 -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=fiji -verify-machineinstrs -enable-unsafe-fp-math < %s | FileCheck -check-prefix=UNSAFE-FP -check-prefix=FUNC %s
+; RUN: llc -march=r600 -mcpu=redwood < %s | FileCheck -check-prefix=R600 -check-prefix=FUNC %s
 
 ; These tests check that fdiv is expanded correctly and also test that the
 ; scheduler is scheduling the RECIP_IEEE and MUL_IEEE instructions in separate
@@ -11,10 +12,8 @@
 ; These test check that fdiv using unsafe_fp_math, coarse fp div, and IEEE754 fp div.
 
 ; FUNC-LABEL: {{^}}fdiv_f32:
-; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[3].Z
-; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[3].Y
-; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[3].X, PS
-; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[2].W, PS
+; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[2].W
+; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[2].Z, PS
 
 ; UNSAFE-FP: v_rcp_f32
 ; UNSAFE-FP: v_mul_f32_e32
@@ -36,10 +35,8 @@ entry:
 }
 
 ; FUNC-LABEL: {{^}}fdiv_f32_fast_math:
-; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[3].Z
-; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[3].Y
-; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[3].X, PS
-; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[2].W, PS
+; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[2].W
+; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[2].Z, PS
 
 ; UNSAFE-FP: v_rcp_f32
 ; UNSAFE-FP: v_mul_f32_e32
@@ -54,10 +51,8 @@ entry:
 }
 
 ; FUNC-LABEL: {{^}}fdiv_f32_arcp_math:
-; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[3].Z
-; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[3].Y
-; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[3].X, PS
-; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[2].W, PS
+; R600-DAG: RECIP_IEEE * T{{[0-9]+\.[XYZW]}}, KC0[2].W
+; R600-DAG: MUL_IEEE {{\** *}}T{{[0-9]+\.[XYZW]}}, KC0[2].Z, PS
 
 ; UNSAFE-FP: v_rcp_f32
 ; UNSAFE-FP: v_mul_f32_e32