[llvm] 9b1e953 - [InstSimplify] Remove select ?, undef, X -> X and select ?, X, undef -> X transforms
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 8 12:53:56 PDT 2020
Author: Craig Topper
Date: 2020-07-08T12:53:05-07:00
New Revision: 9b1e95329af7bb005275f18225b2c130ec3ea98d
URL: https://github.com/llvm/llvm-project/commit/9b1e95329af7bb005275f18225b2c130ec3ea98d
DIFF: https://github.com/llvm/llvm-project/commit/9b1e95329af7bb005275f18225b2c130ec3ea98d.diff
LOG: [InstSimplify] Remove select ?, undef, X -> X and select ?, X, undef -> X transforms
As noted here https://lists.llvm.org/pipermail/llvm-dev/2016-October/106182.html and by alive2, this transform isn't valid. If X is poison this potentially propagates poison when it shouldn't.
This same transform still exists in DAGCombiner.
Differential Revision: https://reviews.llvm.org/D83360
Added:
Modified:
clang/test/CodeGen/arm-mve-intrinsics/dup.c
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstCombine/select.ll
llvm/test/Transforms/InstSimplify/select.ll
Removed:
################################################################################
diff --git a/clang/test/CodeGen/arm-mve-intrinsics/dup.c b/clang/test/CodeGen/arm-mve-intrinsics/dup.c
index 283c08257005..b443917cb258 100644
--- a/clang/test/CodeGen/arm-mve-intrinsics/dup.c
+++ b/clang/test/CodeGen/arm-mve-intrinsics/dup.c
@@ -242,7 +242,8 @@ uint32x4_t test_vdupq_m_n_u32(uint32x4_t inactive, uint32_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <8 x i1> @llvm.arm.mve.pred.i2v.v8i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <8 x half> undef, half [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <8 x half> [[DOTSPLATINSERT]], <8 x half> undef, <8 x i32> zeroinitializer
-// CHECK-NEXT: ret <8 x half> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <8 x i1> [[TMP1]], <8 x half> [[DOTSPLAT]], <8 x half> undef
+// CHECK-NEXT: ret <8 x half> [[TMP2]]
//
float16x8_t test_vdupq_x_n_f16(float16_t a, mve_pred16_t p)
{
@@ -255,7 +256,8 @@ float16x8_t test_vdupq_x_n_f16(float16_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <4 x i1> @llvm.arm.mve.pred.i2v.v4i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x float> undef, float [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <4 x float> [[DOTSPLATINSERT]], <4 x float> undef, <4 x i32> zeroinitializer
-// CHECK-NEXT: ret <4 x float> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x float> [[DOTSPLAT]], <4 x float> undef
+// CHECK-NEXT: ret <4 x float> [[TMP2]]
//
float32x4_t test_vdupq_x_n_f32(float32_t a, mve_pred16_t p)
{
@@ -268,7 +270,8 @@ float32x4_t test_vdupq_x_n_f32(float32_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <16 x i1> @llvm.arm.mve.pred.i2v.v16i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <16 x i8> undef, i8 [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <16 x i8> [[DOTSPLATINSERT]], <16 x i8> undef, <16 x i32> zeroinitializer
-// CHECK-NEXT: ret <16 x i8> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <16 x i1> [[TMP1]], <16 x i8> [[DOTSPLAT]], <16 x i8> undef
+// CHECK-NEXT: ret <16 x i8> [[TMP2]]
//
int8x16_t test_vdupq_x_n_s8(int8_t a, mve_pred16_t p)
{
@@ -281,7 +284,8 @@ int8x16_t test_vdupq_x_n_s8(int8_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <8 x i1> @llvm.arm.mve.pred.i2v.v8i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <8 x i16> undef, i16 [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <8 x i16> [[DOTSPLATINSERT]], <8 x i16> undef, <8 x i32> zeroinitializer
-// CHECK-NEXT: ret <8 x i16> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <8 x i1> [[TMP1]], <8 x i16> [[DOTSPLAT]], <8 x i16> undef
+// CHECK-NEXT: ret <8 x i16> [[TMP2]]
//
int16x8_t test_vdupq_x_n_s16(int16_t a, mve_pred16_t p)
{
@@ -294,7 +298,8 @@ int16x8_t test_vdupq_x_n_s16(int16_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <4 x i1> @llvm.arm.mve.pred.i2v.v4i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x i32> undef, i32 [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <4 x i32> [[DOTSPLATINSERT]], <4 x i32> undef, <4 x i32> zeroinitializer
-// CHECK-NEXT: ret <4 x i32> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> [[DOTSPLAT]], <4 x i32> undef
+// CHECK-NEXT: ret <4 x i32> [[TMP2]]
//
int32x4_t test_vdupq_x_n_s32(int32_t a, mve_pred16_t p)
{
@@ -307,7 +312,8 @@ int32x4_t test_vdupq_x_n_s32(int32_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <16 x i1> @llvm.arm.mve.pred.i2v.v16i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <16 x i8> undef, i8 [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <16 x i8> [[DOTSPLATINSERT]], <16 x i8> undef, <16 x i32> zeroinitializer
-// CHECK-NEXT: ret <16 x i8> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <16 x i1> [[TMP1]], <16 x i8> [[DOTSPLAT]], <16 x i8> undef
+// CHECK-NEXT: ret <16 x i8> [[TMP2]]
//
uint8x16_t test_vdupq_x_n_u8(uint8_t a, mve_pred16_t p)
{
@@ -320,7 +326,8 @@ uint8x16_t test_vdupq_x_n_u8(uint8_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <8 x i1> @llvm.arm.mve.pred.i2v.v8i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <8 x i16> undef, i16 [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <8 x i16> [[DOTSPLATINSERT]], <8 x i16> undef, <8 x i32> zeroinitializer
-// CHECK-NEXT: ret <8 x i16> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <8 x i1> [[TMP1]], <8 x i16> [[DOTSPLAT]], <8 x i16> undef
+// CHECK-NEXT: ret <8 x i16> [[TMP2]]
//
uint16x8_t test_vdupq_x_n_u16(uint16_t a, mve_pred16_t p)
{
@@ -333,7 +340,8 @@ uint16x8_t test_vdupq_x_n_u16(uint16_t a, mve_pred16_t p)
// CHECK-NEXT: [[TMP1:%.*]] = call <4 x i1> @llvm.arm.mve.pred.i2v.v4i1(i32 [[TMP0]])
// CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x i32> undef, i32 [[A:%.*]], i32 0
// CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <4 x i32> [[DOTSPLATINSERT]], <4 x i32> undef, <4 x i32> zeroinitializer
-// CHECK-NEXT: ret <4 x i32> [[DOTSPLAT]]
+// CHECK-NEXT: [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> [[DOTSPLAT]], <4 x i32> undef
+// CHECK-NEXT: ret <4 x i32> [[TMP2]]
//
uint32x4_t test_vdupq_x_n_u32(uint32_t a, mve_pred16_t p)
{
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index d3bdf9d6aafd..8cd5d2034586 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4118,11 +4118,6 @@ static Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
if (TrueVal == FalseVal)
return TrueVal;
- if (isa<UndefValue>(TrueVal)) // select ?, undef, X -> X
- return FalseVal;
- if (isa<UndefValue>(FalseVal)) // select ?, X, undef -> X
- return TrueVal;
-
// Deal with partial undef vector constants: select ?, VecC, VecC' --> VecC''
Constant *TrueC, *FalseC;
if (TrueVal->getType()->isVectorTy() && match(TrueVal, m_Constant(TrueC)) &&
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 381a77bb8d78..f990a58f984c 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -2273,3 +2273,43 @@ exit:
%sel = select i1 %cond, i32 %phi, i32 %A
ret i32 %sel
}
+
+; Negative tests to ensure we don't remove selects with undef true/false values.
+; See https://bugs.llvm.org/show_bug.cgi?id=31633
+; https://lists.llvm.org/pipermail/llvm-dev/2016-October/106182.html
+; https://reviews.llvm.org/D83360
+define i32 @false_undef(i1 %cond, i32 %x) {
+; CHECK-LABEL: @false_undef(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], i32 [[X:%.*]], i32 undef
+; CHECK-NEXT: ret i32 [[S]]
+;
+ %s = select i1 %cond, i32 %x, i32 undef
+ ret i32 %s
+}
+
+define i32 @true_undef(i1 %cond, i32 %x) {
+; CHECK-LABEL: @true_undef(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], i32 undef, i32 [[X:%.*]]
+; CHECK-NEXT: ret i32 [[S]]
+;
+ %s = select i1 %cond, i32 undef, i32 %x
+ ret i32 %s
+}
+
+define <2 x i32> @false_undef_vec(i1 %cond, <2 x i32> %x) {
+; CHECK-LABEL: @false_undef_vec(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], <2 x i32> [[X:%.*]], <2 x i32> undef
+; CHECK-NEXT: ret <2 x i32> [[S]]
+;
+ %s = select i1 %cond, <2 x i32> %x, <2 x i32> undef
+ ret <2 x i32> %s
+}
+
+define <2 x i32> @true_undef_vec(i1 %cond, <2 x i32> %x) {
+; CHECK-LABEL: @true_undef_vec(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], <2 x i32> undef, <2 x i32> [[X:%.*]]
+; CHECK-NEXT: ret <2 x i32> [[S]]
+;
+ %s = select i1 %cond, <2 x i32> undef, <2 x i32> %x
+ ret <2 x i32> %s
+}
diff --git a/llvm/test/Transforms/InstSimplify/select.ll b/llvm/test/Transforms/InstSimplify/select.ll
index 139f5e3c3c23..81fc3ff186cd 100644
--- a/llvm/test/Transforms/InstSimplify/select.ll
+++ b/llvm/test/Transforms/InstSimplify/select.ll
@@ -750,3 +750,43 @@ define i1 @y_might_be_poison(float %x, float %y) {
%c3 = select i1 %c1, i1 %c2, i1 false
ret i1 %c3
}
+
+; Negative tests to ensure we don't remove selects with undef true/false values.
+; See https://bugs.llvm.org/show_bug.cgi?id=31633
+; https://lists.llvm.org/pipermail/llvm-dev/2016-October/106182.html
+; https://reviews.llvm.org/D83360
+define i32 @false_undef(i1 %cond, i32 %x) {
+; CHECK-LABEL: @false_undef(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], i32 [[X:%.*]], i32 undef
+; CHECK-NEXT: ret i32 [[S]]
+;
+ %s = select i1 %cond, i32 %x, i32 undef
+ ret i32 %s
+}
+
+define i32 @true_undef(i1 %cond, i32 %x) {
+; CHECK-LABEL: @true_undef(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], i32 undef, i32 [[X:%.*]]
+; CHECK-NEXT: ret i32 [[S]]
+;
+ %s = select i1 %cond, i32 undef, i32 %x
+ ret i32 %s
+}
+
+define <2 x i32> @false_undef_vec(i1 %cond, <2 x i32> %x) {
+; CHECK-LABEL: @false_undef_vec(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], <2 x i32> [[X:%.*]], <2 x i32> undef
+; CHECK-NEXT: ret <2 x i32> [[S]]
+;
+ %s = select i1 %cond, <2 x i32> %x, <2 x i32> undef
+ ret <2 x i32> %s
+}
+
+define <2 x i32> @true_undef_vec(i1 %cond, <2 x i32> %x) {
+; CHECK-LABEL: @true_undef_vec(
+; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], <2 x i32> undef, <2 x i32> [[X:%.*]]
+; CHECK-NEXT: ret <2 x i32> [[S]]
+;
+ %s = select i1 %cond, <2 x i32> undef, <2 x i32> %x
+ ret <2 x i32> %s
+}
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