[llvm] [VPlan] Simplify select with constant condition (PR #150357)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 23 18:50:06 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Luke Lau (lukel97)
<details>
<summary>Changes</summary>
This helps simplify VPBlendRecipes that are expanded to selects in another patch.
---
Full diff: https://github.com/llvm/llvm-project/pull/150357.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp (+6)
- (modified) llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll (+8-10)
``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index 5da43b61c672e..be5bc6fdbd1e8 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -1079,6 +1079,12 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
return;
}
+ if (match(Def, m_Select(m_True(), m_VPValue(X), m_VPValue())))
+ return Def->replaceAllUsesWith(X);
+
+ if (match(Def, m_Select(m_False(), m_VPValue(), m_VPValue(X))))
+ return Def->replaceAllUsesWith(X);
+
if (match(Def, m_Select(m_VPValue(), m_VPValue(X), m_Deferred(X))))
return Def->replaceAllUsesWith(X);
diff --git a/llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll b/llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll
index 05a495d51c458..86b28c3183166 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll
@@ -67,17 +67,16 @@ define void @redundant_or_1(ptr %dst, i1 %c.0, i1 %c.1) {
; CHECK: vector.ph:
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i1> poison, i1 [[C_0:%.*]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT]], <4 x i1> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT: [[TMP0:%.*]] = xor <4 x i1> [[BROADCAST_SPLAT]], splat (i1 true)
; CHECK-NEXT: [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <4 x i1> poison, i1 [[C_1:%.*]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT2:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT1]], <4 x i1> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT: [[TMP0:%.*]] = xor <4 x i1> [[BROADCAST_SPLAT2]], splat (i1 true)
-; CHECK-NEXT: [[TMP4:%.*]] = select i1 true, <4 x i1> [[BROADCAST_SPLAT]], <4 x i1> zeroinitializer
; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[PRED_STORE_CONTINUE8:%.*]] ]
; CHECK-NEXT: [[VEC_IND:%.*]] = phi <4 x i8> [ <i8 0, i8 1, i8 2, i8 3>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[PRED_STORE_CONTINUE8]] ]
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule <4 x i8> [[VEC_IND]], splat (i8 2)
; CHECK-NEXT: [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x i1> [[TMP0]], <4 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP5:%.*]] = select <4 x i1> [[TMP2]], <4 x i1> [[TMP4]], <4 x i1> zeroinitializer
+; CHECK-NEXT: [[TMP5:%.*]] = select <4 x i1> [[TMP2]], <4 x i1> [[BROADCAST_SPLAT2]], <4 x i1> zeroinitializer
; CHECK-NEXT: [[TMP6:%.*]] = extractelement <4 x i1> [[TMP5]], i32 0
; CHECK-NEXT: br i1 [[TMP6]], label [[PRED_STORE_IF:%.*]], label [[PRED_STORE_CONTINUE:%.*]]
; CHECK: pred.store.if:
@@ -120,11 +119,11 @@ define void @redundant_or_1(ptr %dst, i1 %c.0, i1 %c.1) {
; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
; CHECK: loop.header:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[LOOP_LATCH:%.*]] ]
-; CHECK-NEXT: br i1 [[C_1]], label [[LOOP_LATCH]], label [[THEN_1:%.*]]
+; CHECK-NEXT: br i1 [[C_0]], label [[LOOP_LATCH]], label [[THEN_1:%.*]]
; CHECK: then.1:
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[IV]], 2
; CHECK-NEXT: [[OR:%.*]] = or i1 [[CMP]], true
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR]], i1 [[C_0]], i1 false
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR]], i1 [[C_1]], i1 false
; CHECK-NEXT: br i1 [[COND]], label [[THEN_2:%.*]], label [[LOOP_LATCH]]
; CHECK: then.2:
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i32, ptr [[DST]], i32 [[IV]]
@@ -171,17 +170,16 @@ define void @redundant_or_2(ptr %dst, i1 %c.0, i1 %c.1) {
; CHECK: vector.ph:
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i1> poison, i1 [[C_1:%.*]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT]], <4 x i1> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT: [[TMP0:%.*]] = xor <4 x i1> [[BROADCAST_SPLAT]], splat (i1 true)
; CHECK-NEXT: [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <4 x i1> poison, i1 [[C_0:%.*]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT2:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT1]], <4 x i1> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT: [[TMP0:%.*]] = xor <4 x i1> [[BROADCAST_SPLAT2]], splat (i1 true)
-; CHECK-NEXT: [[TMP1:%.*]] = select i1 true, <4 x i1> [[BROADCAST_SPLAT]], <4 x i1> zeroinitializer
; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[PRED_STORE_CONTINUE8:%.*]] ]
; CHECK-NEXT: [[VEC_IND:%.*]] = phi <4 x i8> [ <i8 0, i8 1, i8 2, i8 3>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[PRED_STORE_CONTINUE8]] ]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ule <4 x i8> [[VEC_IND]], splat (i8 2)
; CHECK-NEXT: [[TMP3:%.*]] = select <4 x i1> [[TMP2]], <4 x i1> [[TMP0]], <4 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP4:%.*]] = select <4 x i1> [[TMP3]], <4 x i1> [[TMP1]], <4 x i1> zeroinitializer
+; CHECK-NEXT: [[TMP4:%.*]] = select <4 x i1> [[TMP3]], <4 x i1> [[BROADCAST_SPLAT2]], <4 x i1> zeroinitializer
; CHECK-NEXT: [[TMP5:%.*]] = extractelement <4 x i1> [[TMP4]], i32 0
; CHECK-NEXT: br i1 [[TMP5]], label [[PRED_STORE_IF:%.*]], label [[PRED_STORE_CONTINUE:%.*]]
; CHECK: pred.store.if:
@@ -224,11 +222,11 @@ define void @redundant_or_2(ptr %dst, i1 %c.0, i1 %c.1) {
; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
; CHECK: loop.header:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[LOOP_LATCH:%.*]] ]
-; CHECK-NEXT: br i1 [[C_0]], label [[LOOP_LATCH]], label [[THEN_1:%.*]]
+; CHECK-NEXT: br i1 [[C_1]], label [[LOOP_LATCH]], label [[THEN_1:%.*]]
; CHECK: then.1:
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[IV]], 2
; CHECK-NEXT: [[OR:%.*]] = or i1 true, [[CMP]]
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR]], i1 [[C_1]], i1 false
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR]], i1 [[C_0]], i1 false
; CHECK-NEXT: br i1 [[COND]], label [[THEN_2:%.*]], label [[LOOP_LATCH]]
; CHECK: then.2:
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i32, ptr [[DST]], i32 [[IV]]
``````````
</details>
https://github.com/llvm/llvm-project/pull/150357
More information about the llvm-commits
mailing list