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[VPlan] Extend licm to hoist assumes #162636

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Merged
merged 3 commits into from
Oct 16, 2025
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[VPlan] Extend licm to hoist assumes #162636

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25ca3f6
[VPlan] Extend licm to hoist assumes
artagnon Oct 9, 2025
180e515
[VPlan] Tweak comment around assume
artagnon Oct 16, 2025
18aea31
[LV] Test update after rebase
artagnon Oct 16, 2025
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5 changes: 5 additions & 0 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
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Expand Up @@ -2124,6 +2124,11 @@ static void licm(VPlan &Plan) {
// Return true if we do not know how to (mechanically) hoist a given recipe
// out of a loop region.
auto CannotHoistRecipe = [](VPRecipeBase &R) {
// Assumes don't alias anything or throw; as long as they're guaranteed to
// execute, they're safe to hoist.
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.mayHaveSideEffects() || R.mayReadFromMemory() || R.isPhi())
Expand Down
10 changes: 2 additions & 8 deletions llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
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Expand Up @@ -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]] ]
Expand All @@ -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]+]]
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20 changes: 10 additions & 10 deletions llvm/test/Transforms/LoopVectorize/assume.ll
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Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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]]
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/LoopVectorize/operand-bundles.ll
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Expand Up @@ -189,12 +189,12 @@ define void @assume_cold_operand_bundle(ptr noalias %a, ptr noalias %b) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: br label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: tail call void @llvm.assume(i1 true) [ "cold"() ]
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr inbounds float, ptr [[B]], i64 [[INDEX]]
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = load <4 x float>, ptr [[TMP0]], align 4
; CHECK-NEXT: tail call void @llvm.assume(i1 true) [ "cold"() ]
; CHECK-NEXT: [[TMP1:%.*]] = fadd <4 x float> [[WIDE_LOAD]], splat (float 1.000000e+00)
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds float, ptr [[A]], i64 [[INDEX]]
; CHECK-NEXT: store <4 x float> [[TMP1]], ptr [[TMP2]], align 4
Expand Down
6 changes: 2 additions & 4 deletions llvm/test/Transforms/LoopVectorize/scalable-assume.ll
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Expand Up @@ -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
Expand All @@ -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
Expand Down
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