[llvm] 1089158 - [ConstantFolding] propagate poison through vector reduction intrinsics

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2021-04-29T12:54:20-04:00
New Revision: 1089158c5a0f7a30100159b7d9b57238578caeaf

URL: https://github.com/llvm/llvm-project/commit/1089158c5a0f7a30100159b7d9b57238578caeaf
DIFF: https://github.com/llvm/llvm-project/commit/1089158c5a0f7a30100159b7d9b57238578caeaf.diff

LOG: [ConstantFolding] propagate poison through vector reduction intrinsics

Added: 
    

Modified: 
    llvm/lib/Analysis/ConstantFolding.cpp
    llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index cfc1fc4055c5..d53c02fe34c3 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1712,7 +1712,11 @@ Constant *constantFoldVectorReduce(Intrinsic::ID IID, Constant *Op) {
   if (isa<ConstantAggregateZero>(Op))
     return ConstantInt::get(VT->getElementType(), 0);
 
-  // TODO: Handle undef and poison.
+  // This is the same as the underlying binops - poison propagates.
+  if (isa<PoisonValue>(Op))
+    return PoisonValue::get(VT->getElementType());
+
+  // TODO: Handle undef.
   if (!isa<ConstantVector>(Op) && !isa<ConstantDataVector>(Op))
     return nullptr;
 

diff  --git a/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll b/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
index 877a2ad29580..5ace64ee78e2 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
@@ -73,8 +73,7 @@ define i32 @add_undef1() {
 
 define i32 @add_poison() {
 ; CHECK-LABEL: @add_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -134,8 +133,7 @@ define i32 @mul_undef1() {
 
 define i32 @mul_poison() {
 ; CHECK-LABEL: @mul_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.mul.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.mul.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -194,8 +192,7 @@ define i32 @and_undef1() {
 
 define i32 @and_poison() {
 ; CHECK-LABEL: @and_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.and.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.and.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -254,8 +251,7 @@ define i32 @or_undef1() {
 
 define i32 @or_poison() {
 ; CHECK-LABEL: @or_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.or.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.or.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -314,8 +310,7 @@ define i32 @xor_undef1() {
 
 define i32 @xor_poison() {
 ; CHECK-LABEL: @xor_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.xor.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.xor.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -374,8 +369,7 @@ define i32 @smin_undef1() {
 
 define i32 @smin_poison() {
 ; CHECK-LABEL: @smin_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.smin.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.smin.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -434,8 +428,7 @@ define i32 @smax_undef1() {
 
 define i32 @smax_poison() {
 ; CHECK-LABEL: @smax_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.smax.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.smax.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -494,8 +487,7 @@ define i32 @umin_undef1() {
 
 define i32 @umin_poison() {
 ; CHECK-LABEL: @umin_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.umin.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.umin.v8i32(<8 x i32> poison)
   ret i32 %x
@@ -554,8 +546,7 @@ define i32 @umax_undef1d() {
 
 define i32 @umax_poison() {
 ; CHECK-LABEL: @umax_poison(
-; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.umax.v8i32(<8 x i32> poison)
-; CHECK-NEXT:    ret i32 [[X]]
+; CHECK-NEXT:    ret i32 poison
 ;
   %x = call i32 @llvm.vector.reduce.umax.v8i32(<8 x i32> poison)
   ret i32 %x