[VPlan] Extend licm to hoist assumes #162636

artagnon · 2025-10-09T11:23:40Z

Assumes are safe to hoist if they're guaranteed to execute, since they don't alias, and don't throw. This mirrors what the IR-LICM does.

llvmbot · 2025-10-09T11:24:14Z

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: Ramkumar Ramachandra (artagnon)

Changes

Assumes are always safe to hoist, since they don't alias, and don't throw.

-- 8< --
Based on #162486.

Full diff: https://github.com/llvm/llvm-project/pull/162636.diff

7 Files Affected:

(modified) llvm/lib/Transforms/Vectorize/VPlan.h (+9)
(modified) llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp (+22-3)
(modified) llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll (+8-6)
(modified) llvm/test/Transforms/LoopVectorize/X86/cost-model.ll (+2-8)
(modified) llvm/test/Transforms/LoopVectorize/X86/funclet.ll (+25-4)
(modified) llvm/test/Transforms/LoopVectorize/assume.ll (+10-10)
(modified) llvm/test/Transforms/LoopVectorize/scalable-assume.ll (+2-4)

diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index fb696bea671af..6ac46e62cbaf5 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1554,6 +1554,9 @@ class VPWidenIntrinsicRecipe : public VPRecipeWithIRFlags, public VPIRMetadata {
   /// True if the intrinsic may have side-effects.
   bool MayHaveSideEffects;
 
+  /// True if the intrinsic is safe to speculatively execute.
+  bool IsSafeToSpeculativelyExecute;
+
 public:
   VPWidenIntrinsicRecipe(CallInst &CI, Intrinsic::ID VectorIntrinsicID,
                          ArrayRef<VPValue *> CallArguments, Type *Ty,
@@ -1577,6 +1580,7 @@ class VPWidenIntrinsicRecipe : public VPRecipeWithIRFlags, public VPIRMetadata {
     MayHaveSideEffects = MayWriteToMemory ||
                          !Attrs.hasAttribute(Attribute::NoUnwind) ||
                          !Attrs.hasAttribute(Attribute::WillReturn);
+    IsSafeToSpeculativelyExecute = Attrs.hasAttribute(Attribute::Speculatable);
   }
 
   ~VPWidenIntrinsicRecipe() override = default;
@@ -1616,6 +1620,11 @@ class VPWidenIntrinsicRecipe : public VPRecipeWithIRFlags, public VPIRMetadata {
   /// Returns true if the intrinsic may have side-effects.
   bool mayHaveSideEffects() const { return MayHaveSideEffects; }
 
+  /// Returns true if the intrinsic is safe to speculatively execute.
+  bool isSafeToSpeculativelyExecute() const {
+    return IsSafeToSpeculativelyExecute;
+  }
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   /// Print the recipe.
   void print(raw_ostream &O, const Twine &Indent,
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index c8a2d84a535d3..8d2d16e8f9bec 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -30,6 +30,7 @@
 #include "llvm/Analysis/InstSimplifyFolder.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/ScalarEvolutionPatternMatch.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Analysis/VectorUtils.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/MDBuilder.h"
@@ -2087,6 +2088,16 @@ void VPlanTransforms::cse(VPlan &Plan) {
   }
 }
 
+static bool isSafeToSpeculativelyExecute(VPRecipeBase *R) {
+  if (auto *WC = dyn_cast<VPWidenCallRecipe>(R))
+    return WC->getCalledScalarFunction()->isSpeculatable();
+  if (auto *WI = dyn_cast<VPWidenIntrinsicRecipe>(R))
+    return WI->isSafeToSpeculativelyExecute();
+  if (auto *RepR = dyn_cast<VPReplicateRecipe>(R))
+    return isSafeToSpeculativelyExecute(RepR->getUnderlyingInstr());
+  return !R->mayHaveSideEffects();
+}
+
 /// Move loop-invariant recipes out of the vector loop region in \p Plan.
 static void licm(VPlan &Plan) {
   VPBasicBlock *Preheader = Plan.getVectorPreheader();
@@ -2095,6 +2106,15 @@ static void licm(VPlan &Plan) {
   // out of a loop region. Does not address legality concerns such as aliasing
   // or speculation safety.
   auto CannotHoistRecipe = [](VPRecipeBase &R) {
+    // Assumes don't alias anything or throw.
+    if (match(&R, m_Intrinsic<Intrinsic::assume>()))
+      return false;
+
+    // TODO: Relax checks in the future, e.g. we could also hoist reads, if
+    // their memory location is not modified in the vector loop.
+    if (R.mayReadOrWriteMemory() || R.isPhi())
+      return true;
+
     // Allocas cannot be hoisted.
     auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
     return RepR && RepR->getOpcode() == Instruction::Alloca;
@@ -2104,14 +2124,13 @@ static void licm(VPlan &Plan) {
   // preheader. Preform a shallow traversal of the vector loop region, to
   // exclude recipes in replicate regions.
   VPRegionBlock *LoopRegion = Plan.getVectorLoopRegion();
+  bool GuaranteedToExecute = Preheader->getSingleSuccessor() == LoopRegion;
   for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
            vp_depth_first_shallow(LoopRegion->getEntry()))) {
     for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
       if (CannotHoistRecipe(R))
         continue;
-      // TODO: Relax checks in the future, e.g. we could also hoist reads, if
-      // their memory location is not modified in the vector loop.
-      if (R.mayHaveSideEffects() || R.mayReadFromMemory() || R.isPhi() ||
+      if ((!GuaranteedToExecute && !isSafeToSpeculativelyExecute(&R)) ||
           any_of(R.operands(), [](VPValue *Op) {
             return !Op->isDefinedOutsideLoopRegions();
           }))
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll b/llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll
index 5970608794b55..48e64771ac152 100644
--- a/llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll
@@ -45,8 +45,9 @@ define void @test1(ptr %dst, {i64, i64} %sv) {
 ; FORCED-NEXT:    [[TMP3:%.*]] = icmp eq i32 [[INDEX_NEXT]], 1000
 ; FORCED-NEXT:    br i1 [[TMP3]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
 ; FORCED:       [[MIDDLE_BLOCK]]:
-; FORCED-NEXT:    br [[EXIT:label %.*]]
-; FORCED:       [[SCALAR_PH:.*:]]
+; FORCED-NEXT:    br label %[[EXIT:.*]]
+; FORCED:       [[EXIT]]:
+; FORCED-NEXT:    ret void
 ;
 entry:
   br label %loop.body
@@ -91,18 +92,19 @@ define void @test_getVectorCallCost(ptr %dst, {float, float} %sv) {
 ; FORCED-NEXT:    [[TMP4:%.*]] = extractvalue { float, float } [[SV]], 1
 ; FORCED-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <2 x float> poison, float [[TMP4]], i64 0
 ; FORCED-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <2 x float> [[BROADCAST_SPLATINSERT1]], <2 x float> poison, <2 x i32> zeroinitializer
+; FORCED-NEXT:    [[TMP2:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> [[BROADCAST_SPLAT]], <2 x float> [[BROADCAST_SPLAT2]])
 ; FORCED-NEXT:    br label %[[VECTOR_BODY:.*]]
 ; FORCED:       [[VECTOR_BODY]]:
 ; FORCED-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
 ; FORCED-NEXT:    [[TMP1:%.*]] = getelementptr float, ptr [[DST]], i32 [[INDEX]]
-; FORCED-NEXT:    [[TMP2:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> [[BROADCAST_SPLAT]], <2 x float> [[BROADCAST_SPLAT2]])
 ; FORCED-NEXT:    store <2 x float> [[TMP2]], ptr [[TMP1]], align 4
 ; FORCED-NEXT:    [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 2
 ; FORCED-NEXT:    [[TMP3:%.*]] = icmp eq i32 [[INDEX_NEXT]], 1000
-; FORCED-NEXT:    br i1 [[TMP3]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
+; FORCED-NEXT:    br i1 [[TMP3]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP3:![0-9]+]]
 ; FORCED:       [[MIDDLE_BLOCK]]:
-; FORCED-NEXT:    br [[EXIT:label %.*]]
-; FORCED:       [[SCALAR_PH:.*:]]
+; FORCED-NEXT:    br label %[[EXIT:.*]]
+; FORCED:       [[EXIT]]:
+; FORCED-NEXT:    ret void
 ;
 entry:
   br label %loop.body
diff --git a/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll b/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
index 9453ad7c61f68..725fa49c0930c 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
@@ -540,6 +540,8 @@ define i64 @cost_assume(ptr %end, i64 %N) {
 ; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[TMP2]], 8
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[TMP2]], [[N_MOD_VF]]
 ; CHECK-NEXT:    [[TMP11:%.*]] = icmp ne i64 [[N:%.*]], 0
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
 ; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
 ; CHECK:       vector.body:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
@@ -551,14 +553,6 @@ define i64 @cost_assume(ptr %end, i64 %N) {
 ; CHECK-NEXT:    [[TMP8]] = add <2 x i64> [[VEC_PHI2]], splat (i64 1)
 ; CHECK-NEXT:    [[TMP9]] = add <2 x i64> [[VEC_PHI3]], splat (i64 1)
 ; CHECK-NEXT:    [[TMP10]] = add <2 x i64> [[VEC_PHI4]], splat (i64 1)
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[TMP11]])
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 8
 ; CHECK-NEXT:    [[TMP13:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[TMP13]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP18:![0-9]+]]
diff --git a/llvm/test/Transforms/LoopVectorize/X86/funclet.ll b/llvm/test/Transforms/LoopVectorize/X86/funclet.ll
index 84d21110e8da9..f5a30bef177df 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/funclet.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/funclet.ll
@@ -1,11 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
 ; RUN: opt -S -passes=loop-vectorize < %s | FileCheck %s
 target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
 target triple = "i686-pc-windows-msvc18.0.0"
 
 define void @test1() #0 personality ptr @__CxxFrameHandler3 {
+; CHECK-LABEL: define void @test1(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] personality ptr @__CxxFrameHandler3 {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    invoke void @_CxxThrowException(ptr null, ptr null)
+; CHECK-NEXT:            to label %[[UNREACHABLE:.*]] unwind label %[[CATCH_DISPATCH:.*]]
+; CHECK:       [[CATCH_DISPATCH]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = catchswitch within none [label %catch] unwind to caller
+; CHECK:       [[CATCH:.*]]:
+; CHECK-NEXT:    [[TMP1:%.*]] = catchpad within [[TMP0]] [ptr null, i32 64, ptr null]
+; CHECK-NEXT:    br label %[[FOR_BODY:.*]]
+; CHECK:       [[FOR_COND_CLEANUP:.*]]:
+; CHECK-NEXT:    catchret from [[TMP1]] to label %[[TRY_CONT:.*]]
+; CHECK:       [[FOR_BODY]]:
+; CHECK-NEXT:    [[I_07:%.*]] = phi i32 [ 0, %[[CATCH]] ], [ [[INC:%.*]], %[[FOR_BODY]] ]
+; CHECK-NEXT:    [[CALL:%.*]] = call double @floor(double 1.000000e+00) #[[ATTR1:[0-9]+]] [ "funclet"(token [[TMP1]]) ]
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I_07]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 1024
+; CHECK-NEXT:    br i1 [[EXITCOND]], label %[[FOR_COND_CLEANUP]], label %[[FOR_BODY]]
+; CHECK:       [[TRY_CONT]]:
+; CHECK-NEXT:    ret void
+; CHECK:       [[UNREACHABLE]]:
+; CHECK-NEXT:    unreachable
+;
 entry:
   invoke void @_CxxThrowException(ptr null, ptr null)
-          to label %unreachable unwind label %catch.dispatch
+  to label %unreachable unwind label %catch.dispatch
 
 catch.dispatch:                                   ; preds = %entry
   %0 = catchswitch within none [label %catch] unwind to caller
@@ -31,9 +55,6 @@ unreachable:                                      ; preds = %entry
   unreachable
 }
 
-; CHECK-LABEL: define void @test1(
-; CHECK: %[[cpad:.*]] = catchpad within {{.*}} [ptr null, i32 64, ptr null]
-; CHECK: call <16 x double> @llvm.floor.v16f64(<16 x double> {{.*}}) [ "funclet"(token %[[cpad]]) ]
 
 declare x86_stdcallcc void @_CxxThrowException(ptr, ptr)
 
diff --git a/llvm/test/Transforms/LoopVectorize/assume.ll b/llvm/test/Transforms/LoopVectorize/assume.ll
index 65c12a15406ff..224ec4a6f7a90 100644
--- a/llvm/test/Transforms/LoopVectorize/assume.ll
+++ b/llvm/test/Transforms/LoopVectorize/assume.ll
@@ -34,8 +34,9 @@ define void @test1(ptr noalias nocapture %a, ptr noalias nocapture readonly %b)
 ; CHECK-NEXT:    [[TMP12:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1600
 ; CHECK-NEXT:    br i1 [[TMP12]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
 ; CHECK:       [[MIDDLE_BLOCK]]:
-; CHECK-NEXT:    br [[FOR_END:label %.*]]
-; CHECK:       [[SCALAR_PH:.*:]]
+; CHECK-NEXT:    br label %[[FOR_END:.*]]
+; CHECK:       [[FOR_END]]:
+; CHECK-NEXT:    ret void
 ;
 entry:
   br label %for.body
@@ -73,29 +74,28 @@ define void @test2(ptr noalias %a, ptr noalias %b) {
 ; CHECK-NEXT:    [[MASKCOND4:%.*]] = icmp eq i64 [[MASKEDPTR3]], 0
 ; CHECK-NEXT:    br label %[[VECTOR_PH:.*]]
 ; CHECK:       [[VECTOR_PH]]:
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND4]])
 ; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
 ; CHECK:       [[VECTOR_BODY]]:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
 ; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds float, ptr [[A]], i64 [[INDEX]]
 ; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds float, ptr [[TMP3]], i32 2
 ; CHECK-NEXT:    [[WIDE_LOAD:%.*]] = load <2 x float>, ptr [[TMP3]], align 4
 ; CHECK-NEXT:    [[WIDE_LOAD1:%.*]] = load <2 x float>, ptr [[TMP4]], align 4
 ; CHECK-NEXT:    [[TMP5:%.*]] = fadd <2 x float> [[WIDE_LOAD]], splat (float 1.000000e+00)
 ; CHECK-NEXT:    [[TMP6:%.*]] = fadd <2 x float> [[WIDE_LOAD1]], splat (float 1.000000e+00)
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND4]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND4]])
 ; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr inbounds float, ptr [[B]], i64 [[INDEX]]
 ; CHECK-NEXT:    [[TMP8:%.*]] = getelementptr inbounds float, ptr [[TMP7]], i32 2
 ; CHECK-NEXT:    store <2 x float> [[TMP5]], ptr [[TMP7]], align 4
 ; CHECK-NEXT:    store <2 x float> [[TMP6]], ptr [[TMP8]], align 4
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
 ; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1600
-; CHECK-NEXT:    br i1 [[TMP9]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
+; CHECK-NEXT:    br i1 [[TMP9]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP3:![0-9]+]]
 ; CHECK:       [[MIDDLE_BLOCK]]:
-; CHECK-NEXT:    br [[FOR_END:label %.*]]
-; CHECK:       [[SCALAR_PH:.*:]]
+; CHECK-NEXT:    br label %[[FOR_END:.*]]
+; CHECK:       [[FOR_END]]:
+; CHECK-NEXT:    ret void
 ;
 entry:
   %ptrint = ptrtoint ptr %a to i64
@@ -163,7 +163,7 @@ define void @predicated_assume(ptr noalias nocapture readonly %a, ptr noalias no
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
 ; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <2 x i64> [[STEP_ADD]], splat (i64 2)
 ; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
-; CHECK-NEXT:    br i1 [[TMP9]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP6:![0-9]+]]
+; CHECK-NEXT:    br i1 [[TMP9]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
 ; CHECK:       [[MIDDLE_BLOCK]]:
 ; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 [[TMP0]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[CMP_N]], [[FOR_COND_CLEANUP_LOOPEXIT:label %.*]], label %[[SCALAR_PH]]
diff --git a/llvm/test/Transforms/LoopVectorize/scalable-assume.ll b/llvm/test/Transforms/LoopVectorize/scalable-assume.ll
index ad8cd425cd6c2..667df3a6cc2a2 100644
--- a/llvm/test/Transforms/LoopVectorize/scalable-assume.ll
+++ b/llvm/test/Transforms/LoopVectorize/scalable-assume.ll
@@ -88,11 +88,11 @@ define void @test2(ptr %a, ptr noalias %b) {
 ; CHECK-NEXT:    [[TMP7:%.*]] = mul nuw i64 [[TMP6]], 4
 ; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 1600, [[TMP7]]
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 1600, [[N_MOD_VF]]
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND4]])
 ; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
 ; CHECK:       [[VECTOR_BODY]]:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
 ; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds float, ptr [[A]], i64 [[INDEX]]
 ; CHECK-NEXT:    [[TMP11:%.*]] = call i64 @llvm.vscale.i64()
 ; CHECK-NEXT:    [[TMP12:%.*]] = shl nuw i64 [[TMP11]], 1
@@ -101,8 +101,6 @@ define void @test2(ptr %a, ptr noalias %b) {
 ; CHECK-NEXT:    [[WIDE_LOAD3:%.*]] = load <vscale x 2 x float>, ptr [[TMP13]], align 4
 ; CHECK-NEXT:    [[TMP14:%.*]] = fadd <vscale x 2 x float> [[WIDE_LOAD]], splat (float 1.000000e+00)
 ; CHECK-NEXT:    [[TMP15:%.*]] = fadd <vscale x 2 x float> [[WIDE_LOAD3]], splat (float 1.000000e+00)
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND4]])
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND4]])
 ; CHECK-NEXT:    [[TMP16:%.*]] = getelementptr inbounds float, ptr [[B]], i64 [[INDEX]]
 ; CHECK-NEXT:    [[TMP17:%.*]] = call i64 @llvm.vscale.i64()
 ; CHECK-NEXT:    [[TMP18:%.*]] = shl nuw i64 [[TMP17]], 1

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

lukel97

LGTM, this is to mirror what LICMPass does right?

Assumes are always safe to hoist, since they don't alias, and don't throw.

artagnon · 2025-10-16T13:28:12Z

LGTM, this is to mirror what LICMPass does right?

Yes, and I would appreciate it if you could also verify the test update after rebase.

fhahn

LGTM, thanks

artagnon requested review from fhahn and nikic October 9, 2025 11:23

llvmbot added vectorizers llvm:transforms labels Oct 9, 2025

artagnon mentioned this pull request Oct 9, 2025

[VPlan] Introduce cannotHoistOrSinkRecipe, fix miscompile #162674

Merged

fhahn reviewed Oct 14, 2025

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llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp Outdated Show resolved Hide resolved

artagnon force-pushed the vplan-licm-assume branch from 634aac0 to 7ca313e Compare October 16, 2025 12:46

artagnon requested a review from lukel97 October 16, 2025 12:47

lukel97 approved these changes Oct 16, 2025

View reviewed changes

artagnon added 3 commits October 16, 2025 14:24

[VPlan] Extend licm to hoist assumes

25ca3f6

Assumes are always safe to hoist, since they don't alias, and don't throw.

[VPlan] Tweak comment around assume

180e515

[LV] Test update after rebase

18aea31

artagnon force-pushed the vplan-licm-assume branch from 7ca313e to 18aea31 Compare October 16, 2025 13:27

fhahn approved these changes Oct 16, 2025

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artagnon enabled auto-merge (squash) October 16, 2025 13:41

artagnon merged commit b71515c into llvm:main Oct 16, 2025
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artagnon commented Oct 9, 2025 •

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llvmbot commented Oct 9, 2025 •

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