Only propagate if both inputs poison

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp

@@ -719,7 +719,8 @@ GCNTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
     Value *Src0 = II.getArgOperand(0);
     Value *Src1 = II.getArgOperand(1);
 
-    if (isa<PoisonValue>(Src0) || isa<PoisonValue>(Src1))
+    // TODO: Replace call with scalar operation if only one element is poison.
+    if (isa<PoisonValue>(Src0) && isa<PoisonValue>(Src1))
       return IC.replaceInstUsesWith(II, PoisonValue::get(II.getType()));
 
     if (isa<UndefValue>(Src0) && isa<UndefValue>(Src1)) {

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

@@ -1322,15 +1322,17 @@ define <2 x i16> @undef_cvt_pknorm_i16() {
 
 define <2 x i16> @poison_lhs_cvt_pknorm_i16(float %y) {
 ; CHECK-LABEL: @poison_lhs_cvt_pknorm_i16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pknorm.i16(float poison, float [[Y:%.*]])
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pknorm.i16(float poison, float %y)
   ret <2 x i16> %cvt
 }
 
 define <2 x i16> @poison_rhs_cvt_pknorm_i16(float %x) {
 ; CHECK-LABEL: @poison_rhs_cvt_pknorm_i16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pknorm.i16(float [[X:%.*]], float poison)
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pknorm.i16(float %x, float poison)
   ret <2 x i16> %cvt
@@ -1378,15 +1380,17 @@ define <2 x i16> @undef_cvt_pknorm_u16() {
 
 define <2 x i16> @poison_lhs_cvt_pknorm_u16(float %y) {
 ; CHECK-LABEL: @poison_lhs_cvt_pknorm_u16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pknorm.u16(float poison, float [[Y:%.*]])
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pknorm.u16(float poison, float %y)
   ret <2 x i16> %cvt
 }
 
 define <2 x i16> @poison_rhs_cvt_pknorm_u16(float %x) {
 ; CHECK-LABEL: @poison_rhs_cvt_pknorm_u16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pknorm.u16(float [[X:%.*]], float poison)
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pknorm.u16(float %x, float poison)
   ret <2 x i16> %cvt
@@ -1434,15 +1438,17 @@ define <2 x i16> @undef_cvt_pk_i16() {
 
 define <2 x i16> @poison_lhs_cvt_pk_i16(i32 %y) {
 ; CHECK-LABEL: @poison_lhs_cvt_pk_i16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pk.i16(i32 poison, i32 [[Y:%.*]])
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pk.i16(i32 poison, i32 %y)
   ret <2 x i16> %cvt
 }
 
 define <2 x i16> @poison_rhs_cvt_pk_i16(i32 %x) {
 ; CHECK-LABEL: @poison_rhs_cvt_pk_i16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pk.i16(i32 [[X:%.*]], i32 poison)
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pk.i16(i32 %x, i32 poison)
   ret <2 x i16> %cvt
@@ -1490,15 +1496,17 @@ define <2 x i16> @undef_cvt_pk_u16() {
 
 define <2 x i16> @poison_lhs_cvt_pk_u16(i32 %y) {
 ; CHECK-LABEL: @poison_lhs_cvt_pk_u16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pk.u16(i32 poison, i32 [[Y:%.*]])
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pk.u16(i32 poison, i32 %y)
   ret <2 x i16> %cvt
 }
 
 define <2 x i16> @poison_rhs_cvt_pk_u16(i32 %x) {
 ; CHECK-LABEL: @poison_rhs_cvt_pk_u16(
-; CHECK-NEXT:    ret <2 x i16> poison
+; CHECK-NEXT:    [[CVT:%.*]] = call <2 x i16> @llvm.amdgcn.cvt.pk.u16(i32 [[X:%.*]], i32 poison)
+; CHECK-NEXT:    ret <2 x i16> [[CVT]]
 ;
   %cvt = call <2 x i16> @llvm.amdgcn.cvt.pk.u16(i32 %x, i32 poison)
   ret <2 x i16> %cvt