[Transforms] Let amdgcn take advantage of sin(-x) --> -sin(x) (#79700)

We do it for amdgcn_cos, and we should do it for amdgcn_sin as well.

Author: AZero13

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -2579,14 +2579,13 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
     }
     break;
   }
-  case Intrinsic::sin: {
+  case Intrinsic::sin:
+  case Intrinsic::amdgcn_sin: {
     Value *X;
     if (match(II->getArgOperand(0), m_OneUse(m_FNeg(m_Value(X))))) {
       // sin(-x) --> -sin(x)
-      Value *NewSin = Builder.CreateUnaryIntrinsic(Intrinsic::sin, X, II);
-      Instruction *FNeg = UnaryOperator::CreateFNeg(NewSin);
-      FNeg->copyFastMathFlags(II);
-      return FNeg;
+      Value *NewSin = Builder.CreateUnaryIntrinsic(IID, X, II);
+      return UnaryOperator::CreateFNegFMF(NewSin, II);
     }
     break;
   }

llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll

@@ -1023,6 +1023,60 @@ define float @cos_fabs_unary_fneg_f32(float %x) {
   ret float %cos
 }
 
+
+; --------------------------------------------------------------------
+; llvm.amdgcn.sin
+; --------------------------------------------------------------------
+declare float @llvm.amdgcn.sin.f32(float) nounwind readnone
+
+define float @sin_fneg_f32(float %x) {
+; CHECK-LABEL: @sin_fneg_f32(
+; CHECK-NEXT:    [[TMP1:%.*]] = call float @llvm.amdgcn.sin.f32(float [[X:%.*]])
+; CHECK-NEXT:    [[SIN:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT:    ret float [[SIN]]
+;
+  %x.fneg = fneg float %x
+  %sin = call float @llvm.amdgcn.sin.f32(float %x.fneg)
+  ret float %sin
+}
+
+define float @sin_fabs_f32(float %x) {
+; CHECK-LABEL: @sin_fabs_f32(
+; CHECK-NEXT:    [[X_FABS:%.*]] = call float @llvm.fabs.f32(float [[X:%.*]])
+; CHECK-NEXT:    [[SIN:%.*]] = call float @llvm.amdgcn.sin.f32(float [[X_FABS]])
+; CHECK-NEXT:    ret float [[SIN]]
+;
+  %x.fabs = call float @llvm.fabs.f32(float %x)
+  %sin = call float @llvm.amdgcn.sin.f32(float %x.fabs)
+  ret float %sin
+}
+
+define float @sin_fabs_fneg_f32(float %x) {
+; CHECK-LABEL: @sin_fabs_fneg_f32(
+; CHECK-NEXT:    [[X_FABS:%.*]] = call float @llvm.fabs.f32(float [[X:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call float @llvm.amdgcn.sin.f32(float [[X_FABS]])
+; CHECK-NEXT:    [[SIN:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT:    ret float [[SIN]]
+;
+  %x.fabs = call float @llvm.fabs.f32(float %x)
+  %x.fabs.fneg = fneg float %x.fabs
+  %sin = call float @llvm.amdgcn.sin.f32(float %x.fabs.fneg)
+  ret float %sin
+}
+
+define float @sin_fabs_fneg_fast_f32(float %x) {
+; CHECK-LABEL: @sin_fabs_fneg_fast_f32(
+; CHECK-NEXT:    [[X_FABS:%.*]] = call fast float @llvm.fabs.f32(float [[X:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call fast float @llvm.amdgcn.sin.f32(float [[X_FABS]])
+; CHECK-NEXT:    [[SIN:%.*]] = fneg fast float [[TMP1]]
+; CHECK-NEXT:    ret float [[SIN]]
+;
+  %x.fabs = call fast float @llvm.fabs.f32(float %x)
+  %x.fabs.fneg = fneg float %x.fabs
+  %sin = call fast float @llvm.amdgcn.sin.f32(float %x.fabs.fneg)
+  ret float %sin
+}
+
 ; --------------------------------------------------------------------
 ; llvm.amdgcn.cvt.pkrtz
 ; --------------------------------------------------------------------