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[VPlan] Convert BuildVector with all-equal values to Broadcast. #165826

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Merged
merged 2 commits into from
Nov 2, 2025
Merged

[VPlan] Convert BuildVector with all-equal values to Broadcast. #165826

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c9a9ea9
[VPlan] Convert BuildVector with all-equal values to Broadcast.
fhahn Oct 30, 2025
c73c5cf
Merge branch 'main' into vplan-buildvector-to-broadcast
fhahn Nov 1, 2025
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6 changes: 6 additions & 0 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
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Expand Up @@ -1281,6 +1281,12 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
return;
}

if (match(Def, m_BuildVector()) && all_equal(R.operands())) {
Def->replaceAllUsesWith(
Builder.createNaryOp(VPInstruction::Broadcast, Def->getOperand(0)));
return;
}

Comment on lines +1284 to +1289
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@ayalz ayalz Nov 3, 2025

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Good to place this BuildVector-to-Broadcast replacement after folding Extract-from-BuildVector patterns; would it (still) be useful to fold Extract-from-Broadcast patterns?

if (auto *Phi = dyn_cast<VPPhi>(Def)) {
if (Phi->getNumOperands() == 1)
Phi->replaceAllUsesWith(Phi->getOperand(0));
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4 changes: 2 additions & 2 deletions llvm/test/Transforms/LoopVectorize/AArch64/force-target-instruction-cost.ll
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Expand Up @@ -365,8 +365,8 @@ define void @invalid_legacy_cost(i64 %N, ptr %x) #0 {
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP6:%.*]] = alloca i8, i64 0, align 16
; CHECK-NEXT: [[TMP7:%.*]] = insertelement <2 x ptr> poison, ptr [[TMP6]], i32 0
; CHECK-NEXT: [[TMP8:%.*]] = insertelement <2 x ptr> [[TMP7]], ptr [[TMP6]], i32 1
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x ptr> poison, ptr [[TMP6]], i64 0
; CHECK-NEXT: [[TMP8:%.*]] = shufflevector <2 x ptr> [[BROADCAST_SPLATINSERT]], <2 x ptr> poison, <2 x i32> zeroinitializer
; CHECK-NEXT: [[TMP9:%.*]] = getelementptr ptr, ptr [[X]], i64 [[INDEX]]
; CHECK-NEXT: store <2 x ptr> [[TMP8]], ptr [[TMP9]], align 8
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
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4 changes: 2 additions & 2 deletions llvm/test/Transforms/LoopVectorize/AArch64/licm-calls.ll
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Expand Up @@ -10,8 +10,8 @@ define void @licm_replicate_call(double %x, ptr %dst) {
; CHECK-NEXT: br label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[TMP1:%.*]] = tail call double @llvm.pow.f64(double [[X]], double 3.000000e+00)
; CHECK-NEXT: [[TMP2:%.*]] = insertelement <2 x double> poison, double [[TMP1]], i32 0
; CHECK-NEXT: [[TMP3:%.*]] = insertelement <2 x double> [[TMP2]], double [[TMP1]], i32 1
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x double> poison, double [[TMP1]], i64 0
; CHECK-NEXT: [[TMP3:%.*]] = shufflevector <2 x double> [[BROADCAST_SPLATINSERT]], <2 x double> poison, <2 x i32> zeroinitializer
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
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18 changes: 9 additions & 9 deletions llvm/test/Transforms/LoopVectorize/AArch64/masked-call-scalarize.ll
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Expand Up @@ -64,9 +64,9 @@ define void @test_widen_exp_v2(ptr noalias %p2, ptr noalias %p, i64 %n) #5 {
; TFCOMMON-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDEX_NEXT:%.*]], [[PRED_STORE_CONTINUE6:%.*]] ]
; TFCOMMON-NEXT: [[ACTIVE_LANE_MASK:%.*]] = phi <2 x i1> [ [[ACTIVE_LANE_MASK_ENTRY]], [[ENTRY]] ], [ [[ACTIVE_LANE_MASK_NEXT:%.*]], [[PRED_STORE_CONTINUE6]] ]
; TFCOMMON-NEXT: [[LD:%.*]] = load double, ptr [[P2:%.*]], align 8
; TFCOMMON-NEXT: [[TMP5:%.*]] = tail call double @llvm.exp.f64(double [[LD]]) #[[ATTR3:[0-9]+]]
; TFCOMMON-NEXT: [[TMP7:%.*]] = insertelement <2 x double> poison, double [[TMP5]], i32 0
; TFCOMMON-NEXT: [[TMP8:%.*]] = insertelement <2 x double> [[TMP7]], double [[TMP5]], i32 1
; TFCOMMON-NEXT: [[TMP5:%.*]] = tail call double @llvm.exp.f64(double [[LD]]) #[[ATTR2:[0-9]+]]
; TFCOMMON-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x double> poison, double [[TMP5]], i64 0
; TFCOMMON-NEXT: [[TMP8:%.*]] = shufflevector <2 x double> [[BROADCAST_SPLATINSERT]], <2 x double> poison, <2 x i32> zeroinitializer
; TFCOMMON-NEXT: [[TMP9:%.*]] = fcmp ogt <2 x double> [[TMP8]], zeroinitializer
; TFCOMMON-NEXT: [[PREDPHI:%.*]] = select <2 x i1> [[TMP9]], <2 x double> zeroinitializer, <2 x double> splat (double 1.000000e+00)
; TFCOMMON-NEXT: [[TMP16:%.*]] = extractelement <2 x i1> [[ACTIVE_LANE_MASK]], i32 0
Expand All @@ -79,7 +79,7 @@ define void @test_widen_exp_v2(ptr noalias %p2, ptr noalias %p, i64 %n) #5 {
; TFCOMMON-NEXT: [[TMP14:%.*]] = extractelement <2 x i1> [[ACTIVE_LANE_MASK]], i32 1
; TFCOMMON-NEXT: br i1 [[TMP14]], label [[PRED_STORE_IF1:%.*]], label [[PRED_STORE_CONTINUE6]]
; TFCOMMON: pred.store.if1:
; TFCOMMON-NEXT: [[TMP19:%.*]] = extractelement <2 x double> [[PREDPHI]], i32 1
; TFCOMMON-NEXT: [[TMP19:%.*]] = extractelement <2 x double> [[PREDPHI]], i32 0
; TFCOMMON-NEXT: store double [[TMP19]], ptr [[P]], align 8
; TFCOMMON-NEXT: br label [[PRED_STORE_CONTINUE6]]
; TFCOMMON: pred.store.continue2:
Expand All @@ -105,9 +105,9 @@ define void @test_widen_exp_v2(ptr noalias %p2, ptr noalias %p, i64 %n) #5 {
; TFA_INTERLEAVE-NEXT: [[ACTIVE_LANE_MASK:%.*]] = phi <2 x i1> [ [[ACTIVE_LANE_MASK_ENTRY]], [[ENTRY]] ], [ [[ACTIVE_LANE_MASK_NEXT:%.*]], [[PRED_STORE_CONTINUE9]] ]
; TFA_INTERLEAVE-NEXT: [[ACTIVE_LANE_MASK2:%.*]] = phi <2 x i1> [ [[ACTIVE_LANE_MASK_ENTRY1]], [[ENTRY]] ], [ [[ACTIVE_LANE_MASK_NEXT10:%.*]], [[PRED_STORE_CONTINUE9]] ]
; TFA_INTERLEAVE-NEXT: [[TMP4:%.*]] = load double, ptr [[P2:%.*]], align 8
; TFA_INTERLEAVE-NEXT: [[TMP9:%.*]] = tail call double @llvm.exp.f64(double [[TMP4]]) #[[ATTR3:[0-9]+]]
; TFA_INTERLEAVE-NEXT: [[TMP11:%.*]] = insertelement <2 x double> poison, double [[TMP9]], i32 0
; TFA_INTERLEAVE-NEXT: [[TMP12:%.*]] = insertelement <2 x double> [[TMP11]], double [[TMP9]], i32 1
; TFA_INTERLEAVE-NEXT: [[TMP5:%.*]] = tail call double @llvm.exp.f64(double [[TMP4]]) #[[ATTR2:[0-9]+]]
; TFA_INTERLEAVE-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x double> poison, double [[TMP5]], i64 0
; TFA_INTERLEAVE-NEXT: [[TMP12:%.*]] = shufflevector <2 x double> [[BROADCAST_SPLATINSERT]], <2 x double> poison, <2 x i32> zeroinitializer
; TFA_INTERLEAVE-NEXT: [[TMP14:%.*]] = fcmp ogt <2 x double> [[TMP12]], zeroinitializer
; TFA_INTERLEAVE-NEXT: [[PREDPHI3:%.*]] = select <2 x i1> [[TMP14]], <2 x double> zeroinitializer, <2 x double> splat (double 1.000000e+00)
; TFA_INTERLEAVE-NEXT: [[TMP19:%.*]] = extractelement <2 x i1> [[ACTIVE_LANE_MASK]], i32 0
Expand All @@ -120,7 +120,7 @@ define void @test_widen_exp_v2(ptr noalias %p2, ptr noalias %p, i64 %n) #5 {
; TFA_INTERLEAVE-NEXT: [[TMP29:%.*]] = extractelement <2 x i1> [[ACTIVE_LANE_MASK]], i32 1
; TFA_INTERLEAVE-NEXT: br i1 [[TMP29]], label [[PRED_STORE_IF4:%.*]], label [[PRED_STORE_CONTINUE5:%.*]]
; TFA_INTERLEAVE: pred.store.if3:
; TFA_INTERLEAVE-NEXT: [[TMP22:%.*]] = extractelement <2 x double> [[PREDPHI3]], i32 1
; TFA_INTERLEAVE-NEXT: [[TMP22:%.*]] = extractelement <2 x double> [[PREDPHI3]], i32 0
; TFA_INTERLEAVE-NEXT: store double [[TMP22]], ptr [[P]], align 8
; TFA_INTERLEAVE-NEXT: br label [[PRED_STORE_CONTINUE5]]
; TFA_INTERLEAVE: pred.store.continue4:
Expand All @@ -134,7 +134,7 @@ define void @test_widen_exp_v2(ptr noalias %p2, ptr noalias %p, i64 %n) #5 {
; TFA_INTERLEAVE-NEXT: [[TMP25:%.*]] = extractelement <2 x i1> [[ACTIVE_LANE_MASK2]], i32 1
; TFA_INTERLEAVE-NEXT: br i1 [[TMP25]], label [[PRED_STORE_IF8:%.*]], label [[PRED_STORE_CONTINUE9]]
; TFA_INTERLEAVE: pred.store.if7:
; TFA_INTERLEAVE-NEXT: [[TMP34:%.*]] = extractelement <2 x double> [[PREDPHI3]], i32 1
; TFA_INTERLEAVE-NEXT: [[TMP34:%.*]] = extractelement <2 x double> [[PREDPHI3]], i32 0
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@ayalz ayalz Nov 3, 2025

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Using lane 0 instead of 1 is fine because they are the same; missed-opportunities for vector-to-scalar narrowing of uniform values?

; TFA_INTERLEAVE-NEXT: store double [[TMP34]], ptr [[P]], align 8
; TFA_INTERLEAVE-NEXT: br label [[PRED_STORE_CONTINUE9]]
; TFA_INTERLEAVE: pred.store.continue8:
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6 changes: 2 additions & 4 deletions llvm/test/Transforms/LoopVectorize/X86/replicate-recipe-with-only-first-lane-used.ll
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Expand Up @@ -199,10 +199,8 @@ define float @uniform_load_replicating_select(ptr %A, ptr %B, i64 %1) {
; CHECK-NEXT: [[TMP5:%.*]] = add i64 [[INDEX]], 7
; CHECK-NEXT: [[TMP6:%.*]] = load float, ptr [[A]], align 4
; CHECK-NEXT: [[TMP10:%.*]] = fcmp ogt float [[TMP6]], 0.000000e+00
; CHECK-NEXT: [[TMP8:%.*]] = insertelement <4 x i1> poison, i1 [[TMP10]], i32 0
; CHECK-NEXT: [[TMP9:%.*]] = insertelement <4 x i1> [[TMP8]], i1 [[TMP10]], i32 1
; CHECK-NEXT: [[TMP13:%.*]] = insertelement <4 x i1> [[TMP9]], i1 [[TMP10]], i32 2
; CHECK-NEXT: [[TMP14:%.*]] = insertelement <4 x i1> [[TMP13]], i1 [[TMP10]], i32 3
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i1> poison, i1 [[TMP10]], i64 0
; CHECK-NEXT: [[TMP14:%.*]] = shufflevector <4 x i1> [[BROADCAST_SPLATINSERT]], <4 x i1> poison, <4 x i32> zeroinitializer
; CHECK-NEXT: [[TMP15:%.*]] = getelementptr inbounds float, ptr [[B]], i64 [[TMP2]]
; CHECK-NEXT: [[TMP16:%.*]] = getelementptr inbounds float, ptr [[B]], i64 [[TMP3]]
; CHECK-NEXT: [[TMP17:%.*]] = getelementptr inbounds float, ptr [[B]], i64 [[TMP4]]
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