AMDGPU: Fold fneg into fmed3

[rampitec]

LGTM

[arsenm]

r339821

lib/Target/AMDGPU/AMDGPUISelLowering.cpp

static bool fnegFoldsIntoOp(unsigned Opc) {
   case ISD::FCANONICALIZE:
   case AMDGPUISD::RCP:
   case AMDGPUISD::RCP_LEGACY:
   case AMDGPUISD::RCP_IFLAG:
   case AMDGPUISD::SIN_HW:
   case AMDGPUISD::FMUL_LEGACY:
   case AMDGPUISD::FMIN_LEGACY:
   case AMDGPUISD::FMAX_LEGACY:
+  case AMDGPUISD::FMED3:
     return true;
   default:
     return false;
   }
 }
 
 /// \p returns true if the operation will definitely need to use a 64-bit
 /// encoding, and thus will use a VOP3 encoding regardless of the source
case AMDGPUISD::FMIN_LEGACY: {
     SDValue NegRHS = DAG.getNode(ISD::FNEG, SL, VT, RHS);
     unsigned Opposite = inverseMinMax(Opc);
 
     SDValue Res = DAG.getNode(Opposite, SL, VT, NegLHS, NegRHS, N0->getFlags());
     if (!N0.hasOneUse())
       DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
     return Res;
   }
+  case AMDGPUISD::FMED3: {
+    SDValue Ops[3];
+    for (unsigned I = 0; I < 3; ++I)
+      Ops[I] = DAG.getNode(ISD::FNEG, SL, VT, N0->getOperand(I), N0->getFlags());
+
+    SDValue Res = DAG.getNode(AMDGPUISD::FMED3, SL, VT, Ops, N0->getFlags());
+    if (!N0.hasOneUse())
+      DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
+    return Res;
+  }
   case ISD::FP_EXTEND:
   case ISD::FTRUNC:
   case ISD::FRINT:
   case ISD::FNEARBYINT: // XXX - Should fround be handled?
   case ISD::FSIN:
   case ISD::FCANONICALIZE:
   case AMDGPUISD::RCP:
   case AMDGPUISD::RCP_LEGACY:

test/CodeGen/AMDGPU/llvm.amdgcn.fmed3.ll

 ; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
 ; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
 
 ; GCN-LABEL: {{^}}test_fmed3:
 ; GCN: v_med3_f32 v{{[0-9]+}}, s{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}
 define amdgpu_kernel void @test_fmed3(float addrspace(1)* %out, float %src0, float %src1, float %src2) #1 {
-  %mad = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float %src2)
-  store float %mad, float addrspace(1)* %out
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float %src2)
+  store float %med3, float addrspace(1)* %out
   ret void
 }
 
 ; GCN-LABEL: {{^}}test_fmed3_srcmods:
 ; GCN: v_med3_f32 v{{[0-9]+}}, -s{{[0-9]+}}, |v{{[0-9]+}}|, -|v{{[0-9]+}}|
 define amdgpu_kernel void @test_fmed3_srcmods(float addrspace(1)* %out, float %src0, float %src1, float %src2) #1 {
   %src0.fneg = fsub float -0.0, %src0
   %src1.fabs = call float @llvm.fabs.f32(float %src1)
   %src2.fabs = call float @llvm.fabs.f32(float %src2)
   %src2.fneg.fabs = fsub float -0.0, %src2.fabs
-  %mad = call float @llvm.amdgcn.fmed3.f32(float %src0.fneg, float %src1.fabs, float %src2.fneg.fabs)
-  store float %mad, float addrspace(1)* %out
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0.fneg, float %src1.fabs, float %src2.fneg.fabs)
+  store float %med3, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}test_fneg_fmed3:
+; GCN: v_med3_f32 v{{[0-9]+}}, -s{{[0-9]+}}, -v{{[0-9]+}}, -v{{[0-9]+}}
+define amdgpu_kernel void @test_fneg_fmed3(float addrspace(1)* %out, float %src0, float %src1, float %src2) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float %src2)
+  %neg.med3 = fsub float -0.0, %med3
+  store float %neg.med3, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}test_fneg_fmed3_multi_use:
+; GCN: v_med3_f32 [[MED3:v[0-9]+]], -s{{[0-9]+}}, -v{{[0-9]+}}, -v{{[0-9]+}}
+; GCN: v_mul_f32_e32 v{{[0-9]+}}, -4.0, [[MED3]]
+define amdgpu_kernel void @test_fneg_fmed3_multi_use(float addrspace(1)* %out, float %src0, float %src1, float %src2) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float %src2)
+  %neg.med3 = fsub float -0.0, %med3
+  %med3.user = fmul float %med3, 4.0
+  store volatile float %med3.user, float addrspace(1)* %out
+  store volatile float %neg.med3, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}test_fabs_fmed3:
+; GCN: v_med3_f32 [[MED3:v[0-9]+]], s{{[0-9]+}}, v{{[0-9]+}}, v{{[0-9]+}}
+; GCN: v_and_b32_e32 v{{[0-9]+}}, 0x7fffffff, [[MED3]]
+define amdgpu_kernel void @test_fabs_fmed3(float addrspace(1)* %out, float %src0, float %src1, float %src2) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float %src2)
+  %fabs.med3 = call float @llvm.fabs.f32(float %med3)
+  store float %fabs.med3, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}test_fneg_fmed3_rr_0:
+; GCN: v_bfrev_b32_e32 [[NEG0:v[0-9]+]], 1
+; GCN: v_med3_f32 v{{[0-9]+}}, -s{{[0-9]+}}, -v{{[0-9]+}}, [[NEG0]]
+define amdgpu_kernel void @test_fneg_fmed3_rr_0(float addrspace(1)* %out, float %src0, float %src1) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float 0.0)
+  %neg.med3 = fsub float -0.0, %med3
+  store float %neg.med3, float addrspace(1)* %out
+  ret void
+}
+
+; FIXME: Worse off from folding this
+; GCN-LABEL: {{^}}test_fneg_fmed3_rr_0_foldable_user:
+; GCN: v_bfrev_b32_e32 [[NEG0:v[0-9]+]], 1
+; GCN: v_med3_f32 [[MED3:v[0-9]+]], -s{{[0-9]+}}, -v{{[0-9]+}}, [[NEG0]]
+; GCN: v_mul_f32_e32 v{{[0-9]+}}, s{{[0-9]+}}, [[MED3]]
+define amdgpu_kernel void @test_fneg_fmed3_rr_0_foldable_user(float addrspace(1)* %out, float %src0, float %src1, float %mul.arg) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float %src1, float 0.0)
+  %neg.med3 = fsub float -0.0, %med3
+  %mul = fmul float %neg.med3, %mul.arg
+  store float %mul, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}test_fneg_fmed3_r_inv2pi_0:
+; GCN-DAG: v_bfrev_b32_e32 [[NEG0:v[0-9]+]], 1
+; GCN-DAG: v_mov_b32_e32 [[NEG_INV:v[0-9]+]], 0xbe22f983
+; GCN: v_med3_f32 v{{[0-9]+}}, -s{{[0-9]+}}, [[NEG_INV]], [[NEG0]]
+define amdgpu_kernel void @test_fneg_fmed3_r_inv2pi_0(float addrspace(1)* %out, float %src0) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float 0x3FC45F3060000000, float 0.0)
+  %neg.med3 = fsub float -0.0, %med3
+  store float %neg.med3, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}test_fneg_fmed3_r_inv2pi_0_foldable_user:
+; GCN-DAG: v_bfrev_b32_e32 [[NEG0:v[0-9]+]], 1
+; GCN-DAG: v_mov_b32_e32 [[NEG_INV:v[0-9]+]], 0xbe22f983
+; GCN: v_med3_f32 [[MED3:v[0-9]+]], -s{{[0-9]+}}, [[NEG_INV]], [[NEG0]]
+; GCN: v_mul_f32_e32 v{{[0-9]+}}, s{{[0-9]+}}, [[MED3]]
+define amdgpu_kernel void @test_fneg_fmed3_r_inv2pi_0_foldable_user(float addrspace(1)* %out, float %src0, float %mul.arg) #1 {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float %src0, float 0x3FC45F3060000000, float 0.0)
+  %neg.med3 = fsub float -0.0, %med3
+  %mul = fmul float %neg.med3, %mul.arg
+  store float %mul, float addrspace(1)* %out
   ret void
 }
 
 declare float @llvm.amdgcn.fmed3.f32(float, float, float) #0
 declare float @llvm.fabs.f32(float) #0
 
 attributes #0 = { nounwind readnone }
 attributes #1 = { nounwind }