[llvm] [VPlan] Remove dead recipes before simplifying blends (PR #157622)

[Mel Chen via llvm-commits]

https://github.com/Mel-Chen updated https://github.com/llvm/llvm-project/pull/157622

>From 2a7ba265f4a887e1ec49df13a76fefe43ce22acb Mon Sep 17 00:00:00 2001
From: Mel Chen <mel.chen at sifive.com>
Date: Mon, 8 Sep 2025 18:10:05 -0700
Subject: [PATCH] Do remove dead recipe before SimplifyBlend

---
 llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp    |  2 +-
 .../Transforms/LoopVectorize/if-pred-non-void.ll     | 12 +++---------
 llvm/test/Transforms/LoopVectorize/vplan-printing.ll |  4 +---
 3 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index 10b2f5df2e23e..696e0af040c8a 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -2214,8 +2214,8 @@ void VPlanTransforms::optimize(VPlan &Plan) {
   runPass(removeRedundantInductionCasts, Plan);
 
   runPass(simplifyRecipes, Plan);
-  runPass(simplifyBlends, Plan);
   runPass(removeDeadRecipes, Plan);
+  runPass(simplifyBlends, Plan);
   runPass(narrowToSingleScalarRecipes, Plan);
   runPass(legalizeAndOptimizeInductions, Plan);
   runPass(removeRedundantExpandSCEVRecipes, Plan);
diff --git a/llvm/test/Transforms/LoopVectorize/if-pred-non-void.ll b/llvm/test/Transforms/LoopVectorize/if-pred-non-void.ll
index 4811a77d53439..712fb5bfeaab9 100644
--- a/llvm/test/Transforms/LoopVectorize/if-pred-non-void.ll
+++ b/llvm/test/Transforms/LoopVectorize/if-pred-non-void.ll
@@ -562,9 +562,7 @@ define void @pr30172(ptr nocapture %asd, ptr nocapture %bsd) !dbg !5 {;
 ; CHECK-NEXT:    br label [[PRED_SDIV_CONTINUE4]]
 ; CHECK:       pred.sdiv.continue4:
 ; CHECK-NEXT:    [[TMP28:%.*]] = phi <2 x i32> [ [[TMP19]], [[PRED_SDIV_CONTINUE]] ], [ [[TMP26]], [[PRED_SDIV_IF3]] ]
-; CHECK-NEXT:    [[TMP27:%.*]] = xor <2 x i1> [[TMP8]], splat (i1 true), !dbg [[DBG35]]
-; CHECK-NEXT:    [[TMP30:%.*]] = select <2 x i1> [[TMP4]], <2 x i1> [[TMP27]], <2 x i1> zeroinitializer, !dbg [[DBG35]]
-; CHECK-NEXT:    [[PREDPHI:%.*]] = select <2 x i1> [[TMP30]], <2 x i32> [[TMP5]], <2 x i32> [[TMP28]]
+; CHECK-NEXT:    [[PREDPHI:%.*]] = select <2 x i1> [[TMP10]], <2 x i32> [[TMP28]], <2 x i32> [[TMP5]]
 ; CHECK-NEXT:    store <2 x i32> [[PREDPHI]], ptr [[TMP1]], align 4, !alias.scope [[META29]], !noalias [[META32]]
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
 ; CHECK-NEXT:    [[TMP32:%.*]] = icmp eq i64 [[INDEX_NEXT]], 128
@@ -642,12 +640,8 @@ define void @pr30172(ptr nocapture %asd, ptr nocapture %bsd) !dbg !5 {;
 ; UNROLL-NO-VF-NEXT:    br label [[PRED_SDIV_CONTINUE3]]
 ; UNROLL-NO-VF:       pred.sdiv.continue3:
 ; UNROLL-NO-VF-NEXT:    [[TMP29:%.*]] = phi i32 [ poison, [[PRED_SDIV_CONTINUE]] ], [ [[TMP27]], [[PRED_SDIV_IF2]] ]
-; UNROLL-NO-VF-NEXT:    [[TMP30:%.*]] = xor i1 [[TMP15]], true, !dbg [[DBG35]]
-; UNROLL-NO-VF-NEXT:    [[TMP28:%.*]] = xor i1 [[TMP16]], true, !dbg [[DBG35]]
-; UNROLL-NO-VF-NEXT:    [[TMP32:%.*]] = select i1 [[TMP17]], i1 [[TMP30]], i1 false, !dbg [[DBG35]]
-; UNROLL-NO-VF-NEXT:    [[TMP33:%.*]] = select i1 [[TMP14]], i1 [[TMP28]], i1 false, !dbg [[DBG35]]
-; UNROLL-NO-VF-NEXT:    [[PREDPHI:%.*]] = select i1 [[TMP32]], i32 [[TMP10]], i32 [[TMP25]]
-; UNROLL-NO-VF-NEXT:    [[PREDPHI4:%.*]] = select i1 [[TMP33]], i32 [[TMP11]], i32 [[TMP29]]
+; UNROLL-NO-VF-NEXT:    [[PREDPHI:%.*]] = select i1 [[TMP20]], i32 [[TMP25]], i32 [[TMP10]]
+; UNROLL-NO-VF-NEXT:    [[PREDPHI4:%.*]] = select i1 [[TMP21]], i32 [[TMP29]], i32 [[TMP11]]
 ; UNROLL-NO-VF-NEXT:    store i32 [[PREDPHI]], ptr [[TMP2]], align 4, !alias.scope [[META29]], !noalias [[META32]]
 ; UNROLL-NO-VF-NEXT:    store i32 [[PREDPHI4]], ptr [[TMP3]], align 4, !alias.scope [[META29]], !noalias [[META32]]
 ; UNROLL-NO-VF-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
diff --git a/llvm/test/Transforms/LoopVectorize/vplan-printing.ll b/llvm/test/Transforms/LoopVectorize/vplan-printing.ll
index 87b11dc77d417..5018a9b185d31 100644
--- a/llvm/test/Transforms/LoopVectorize/vplan-printing.ll
+++ b/llvm/test/Transforms/LoopVectorize/vplan-printing.ll
@@ -374,9 +374,7 @@ define void @debug_loc_vpinstruction(ptr nocapture %asd, ptr nocapture %bsd) !db
 ; CHECK-NEXT:  Successor(s): if.then.0
 ; CHECK-EMPTY:
 ; CHECK-NEXT:  if.then.0:
-; CHECK-NEXT:    EMIT vp<[[NOT2:%.+]]> = not ir<%cmp2>
-; CHECK-NEXT:    EMIT vp<[[SEL2:%.+]]> = logical-and vp<[[NOT1]]>, vp<[[NOT2]]>
-; CHECK-NEXT:    BLEND ir<%ysd.0> = vp<[[PHI]]> ir<%psd>/vp<[[SEL2]]>
+; CHECK-NEXT:    BLEND ir<%ysd.0> = ir<%psd> vp<[[PHI]]>/vp<[[OR1]]>
 ; CHECK-NEXT:    vp<[[VEC_PTR2:%.+]]> = vector-pointer ir<%isd>
 ; CHECK-NEXT:    WIDEN store vp<[[VEC_PTR2]]>, ir<%ysd.0>
 ; CHECK-NEXT:    EMIT vp<[[CAN_IV_NEXT]]> = add nuw vp<[[CAN_IV]]>, vp<[[VFxUF]]>