[llvm] [LV] Ensure VPInstruction::usesFirstLaneOnly behaves correctly for WidePtrAdd (PR #169344)
David Sherwood via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 24 07:53:47 PST 2025
https://github.com/david-arm created https://github.com/llvm/llvm-project/pull/169344
While attempting to remove the use of undef from more loop vectoriser tests I discovered a bug where this assert was firing:
llvm::Constant* llvm::Constant::getSplatValue(bool) const: Assertion `this->getType()->isVectorTy() && "Only valid for vectors!"' failed. ...
#8 0x0000aaaab9e2fba4 llvm::Constant::getSplatValue
#9 0x0000aaaab9dfb844 llvm::ConstantFoldBinaryInstruction
This seems to be happening because we do not handle the WidePtrAdd case correctly in usesFirstLaneOnly when the VF is 1.
This PR also removes the use of undef from the test `both` in Transforms/LoopVectorize/iv_outside_user.ll, which is what started triggering the assert.
Fixes #169334
>From a040f2401950ceffb6cbae093bb2d09fdc1c8807 Mon Sep 17 00:00:00 2001
From: David Sherwood <david.sherwood at arm.com>
Date: Mon, 24 Nov 2025 15:51:24 +0000
Subject: [PATCH] [LV] Ensure VPInstruction::usesFirstLaneOnly behaves
correctly for WidePtrAdd
While attempting to remove the use of undef from more loop
vectoriser tests I discovered a bug where this assert was firing:
llvm::Constant* llvm::Constant::getSplatValue(bool) const: Assertion
`this->getType()->isVectorTy() && "Only valid for vectors!"' failed.
...
#8 0x0000aaaab9e2fba4 llvm::Constant::getSplatValue
#9 0x0000aaaab9dfb844 llvm::ConstantFoldBinaryInstruction
This seems to be happening because we do not handle the WidePtrAdd
case correctly in usesFirstLaneOnly when the VF is 1.
This PR also removes the use of undef from the test `both` in
Transforms/LoopVectorize/iv_outside_user.ll, which is what started
triggering the assert.
Fixes #169334
---
.../lib/Transforms/Vectorize/VPlanRecipes.cpp | 2 +-
.../LoopVectorize/iv_outside_user.ll | 140 ++++++++++++------
2 files changed, 95 insertions(+), 47 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index b27f2f8a3c8cb..c3482d7c1932e 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -1360,7 +1360,7 @@ bool VPInstruction::usesFirstLaneOnly(const VPValue *Op) const {
return Op == getOperand(0) || vputils::onlyFirstLaneUsed(this);
case VPInstruction::WidePtrAdd:
// WidePtrAdd supports scalar and vector base addresses.
- return false;
+ return vputils::onlyFirstLaneUsed(this);
case VPInstruction::ComputeAnyOfResult:
case VPInstruction::ComputeFindIVResult:
return Op == getOperand(1);
diff --git a/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll b/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll
index 162803a377bc0..e7a819dc6474d 100644
--- a/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll
+++ b/llvm/test/Transforms/LoopVectorize/iv_outside_user.ll
@@ -152,59 +152,107 @@ for.end:
ret ptr %ptr.phi
}
-define ptr @both(i32 %k) {
-; CHECK-LABEL: define ptr @both(
-; CHECK-SAME: i32 [[K:%.*]]) {
-; CHECK-NEXT: [[ENTRY:.*]]:
-; CHECK-NEXT: [[BASE:%.*]] = getelementptr inbounds i32, ptr undef, i64 1
-; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[K]], -1
-; CHECK-NEXT: [[TMP1:%.*]] = zext i32 [[TMP0]] to i64
-; CHECK-NEXT: [[TMP2:%.*]] = add nuw nsw i64 [[TMP1]], 1
-; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP2]], 2
-; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
-; CHECK: [[VECTOR_PH]]:
-; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP2]], 2
-; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP2]], [[N_MOD_VF]]
-; CHECK-NEXT: [[IND_END:%.*]] = trunc i64 [[N_VEC]] to i32
-; CHECK-NEXT: [[TMP3:%.*]] = mul i64 [[N_VEC]], 4
-; CHECK-NEXT: [[IND_END1:%.*]] = getelementptr i8, ptr [[BASE]], i64 [[TMP3]]
-; CHECK-NEXT: [[TMP4:%.*]] = mul i64 [[N_VEC]], 4
-; CHECK-NEXT: [[IND_END2:%.*]] = getelementptr i8, ptr undef, i64 [[TMP4]]
-; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
-; CHECK: [[VECTOR_BODY]]:
-; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
-; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
-; CHECK-NEXT: [[TMP5:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
-; CHECK-NEXT: br i1 [[TMP5]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], {{!llvm.loop ![0-9]+}}
-; CHECK: [[MIDDLE_BLOCK]]:
-; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP2]], [[N_VEC]]
-; CHECK-NEXT: [[IND_ESCAPE:%.*]] = getelementptr i8, ptr [[IND_END1]], i64 -4
-; CHECK-NEXT: br i1 [[CMP_N]], label %[[FOR_END:.*]], label %[[SCALAR_PH]]
-; CHECK: [[SCALAR_PH]]:
-; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i32 [ [[IND_END]], %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
-; CHECK-NEXT: [[BC_RESUME_VAL1:%.*]] = phi ptr [ [[IND_END1]], %[[MIDDLE_BLOCK]] ], [ [[BASE]], %[[ENTRY]] ]
-; CHECK-NEXT: [[BC_RESUME_VAL2:%.*]] = phi ptr [ [[IND_END2]], %[[MIDDLE_BLOCK]] ], [ undef, %[[ENTRY]] ]
-; CHECK-NEXT: br label %[[FOR_BODY:.*]]
-; CHECK: [[FOR_BODY]]:
-; CHECK-NEXT: [[INC_PHI:%.*]] = phi i32 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[INC:%.*]], %[[FOR_BODY]] ]
-; CHECK-NEXT: [[INC_LAG1:%.*]] = phi ptr [ [[BC_RESUME_VAL1]], %[[SCALAR_PH]] ], [ [[TMP:%.*]], %[[FOR_BODY]] ]
-; CHECK-NEXT: [[INC_LAG2:%.*]] = phi ptr [ [[BC_RESUME_VAL2]], %[[SCALAR_PH]] ], [ [[INC_LAG1]], %[[FOR_BODY]] ]
-; CHECK-NEXT: [[TMP]] = getelementptr inbounds i32, ptr [[INC_LAG1]], i64 1
-; CHECK-NEXT: [[INC]] = add nsw i32 [[INC_PHI]], 1
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[INC]], [[K]]
-; CHECK-NEXT: br i1 [[CMP]], label %[[FOR_END]], label %[[FOR_BODY]], {{!llvm.loop ![0-9]+}}
-; CHECK: [[FOR_END]]:
-; CHECK-NEXT: [[INC_LAG1_LCSSA:%.*]] = phi ptr [ [[INC_LAG1]], %[[FOR_BODY]] ], [ [[IND_ESCAPE]], %[[MIDDLE_BLOCK]] ]
-; CHECK-NEXT: ret ptr [[INC_LAG1_LCSSA]]
+define ptr @both(ptr %p, i32 %k) {
+; VEC-LABEL: define ptr @both(
+; VEC-SAME: ptr [[P:%.*]], i32 [[K:%.*]]) {
+; VEC-NEXT: [[ENTRY:.*]]:
+; VEC-NEXT: [[BASE:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 1
+; VEC-NEXT: [[TMP0:%.*]] = add i32 [[K]], -1
+; VEC-NEXT: [[TMP1:%.*]] = zext i32 [[TMP0]] to i64
+; VEC-NEXT: [[TMP2:%.*]] = add nuw nsw i64 [[TMP1]], 1
+; VEC-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP2]], 2
+; VEC-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; VEC: [[VECTOR_PH]]:
+; VEC-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP2]], 2
+; VEC-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP2]], [[N_MOD_VF]]
+; VEC-NEXT: [[TMP3:%.*]] = trunc i64 [[N_VEC]] to i32
+; VEC-NEXT: [[TMP4:%.*]] = mul i64 [[N_VEC]], 4
+; VEC-NEXT: [[TMP5:%.*]] = getelementptr i8, ptr [[BASE]], i64 [[TMP4]]
+; VEC-NEXT: br label %[[VECTOR_BODY:.*]]
+; VEC: [[VECTOR_BODY]]:
+; VEC-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; VEC-NEXT: [[POINTER_PHI:%.*]] = phi ptr [ [[BASE]], %[[VECTOR_PH]] ], [ [[PTR_IND:%.*]], %[[VECTOR_BODY]] ]
+; VEC-NEXT: [[VECTOR_GEP:%.*]] = getelementptr i8, ptr [[POINTER_PHI]], <2 x i64> <i64 0, i64 4>
+; VEC-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
+; VEC-NEXT: [[PTR_IND]] = getelementptr i8, ptr [[POINTER_PHI]], i64 8
+; VEC-NEXT: [[TMP6:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
+; VEC-NEXT: br i1 [[TMP6]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], {{!llvm.loop ![0-9]+}}
+; VEC: [[MIDDLE_BLOCK]]:
+; VEC-NEXT: [[VECTOR_RECUR_EXTRACT:%.*]] = extractelement <2 x ptr> [[VECTOR_GEP]], i32 1
+; VEC-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP2]], [[N_VEC]]
+; VEC-NEXT: [[IND_ESCAPE:%.*]] = getelementptr i8, ptr [[TMP5]], i64 -4
+; VEC-NEXT: br i1 [[CMP_N]], label %[[FOR_END:.*]], label %[[SCALAR_PH]]
+; VEC: [[SCALAR_PH]]:
+; VEC-NEXT: [[BC_RESUME_VAL:%.*]] = phi i32 [ [[TMP3]], %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
+; VEC-NEXT: [[BC_RESUME_VAL1:%.*]] = phi ptr [ [[TMP5]], %[[MIDDLE_BLOCK]] ], [ [[BASE]], %[[ENTRY]] ]
+; VEC-NEXT: [[SCALAR_RECUR_INIT:%.*]] = phi ptr [ [[VECTOR_RECUR_EXTRACT]], %[[MIDDLE_BLOCK]] ], [ [[BASE]], %[[ENTRY]] ]
+; VEC-NEXT: br label %[[FOR_BODY:.*]]
+; VEC: [[FOR_BODY]]:
+; VEC-NEXT: [[INC_PHI:%.*]] = phi i32 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[INC:%.*]], %[[FOR_BODY]] ]
+; VEC-NEXT: [[INC_LAG1:%.*]] = phi ptr [ [[BC_RESUME_VAL1]], %[[SCALAR_PH]] ], [ [[TMP:%.*]], %[[FOR_BODY]] ]
+; VEC-NEXT: [[INC_LAG2:%.*]] = phi ptr [ [[SCALAR_RECUR_INIT]], %[[SCALAR_PH]] ], [ [[INC_LAG1]], %[[FOR_BODY]] ]
+; VEC-NEXT: [[TMP]] = getelementptr inbounds i32, ptr [[INC_LAG1]], i64 1
+; VEC-NEXT: [[INC]] = add nsw i32 [[INC_PHI]], 1
+; VEC-NEXT: [[CMP:%.*]] = icmp eq i32 [[INC]], [[K]]
+; VEC-NEXT: br i1 [[CMP]], label %[[FOR_END]], label %[[FOR_BODY]], {{!llvm.loop ![0-9]+}}
+; VEC: [[FOR_END]]:
+; VEC-NEXT: [[INC_LAG1_LCSSA:%.*]] = phi ptr [ [[INC_LAG1]], %[[FOR_BODY]] ], [ [[IND_ESCAPE]], %[[MIDDLE_BLOCK]] ]
+; VEC-NEXT: ret ptr [[INC_LAG1_LCSSA]]
+;
+; INTERLEAVE-LABEL: define ptr @both(
+; INTERLEAVE-SAME: ptr [[P:%.*]], i32 [[K:%.*]]) {
+; INTERLEAVE-NEXT: [[ENTRY:.*]]:
+; INTERLEAVE-NEXT: [[BASE:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 1
+; INTERLEAVE-NEXT: [[TMP0:%.*]] = add i32 [[K]], -1
+; INTERLEAVE-NEXT: [[TMP1:%.*]] = zext i32 [[TMP0]] to i64
+; INTERLEAVE-NEXT: [[TMP2:%.*]] = add nuw nsw i64 [[TMP1]], 1
+; INTERLEAVE-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP2]], 2
+; INTERLEAVE-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; INTERLEAVE: [[VECTOR_PH]]:
+; INTERLEAVE-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP2]], 2
+; INTERLEAVE-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP2]], [[N_MOD_VF]]
+; INTERLEAVE-NEXT: [[TMP3:%.*]] = trunc i64 [[N_VEC]] to i32
+; INTERLEAVE-NEXT: [[TMP6:%.*]] = mul i64 [[N_VEC]], 4
+; INTERLEAVE-NEXT: [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[BASE]], i64 [[TMP6]]
+; INTERLEAVE-NEXT: br label %[[VECTOR_BODY:.*]]
+; INTERLEAVE: [[VECTOR_BODY]]:
+; INTERLEAVE-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; INTERLEAVE-NEXT: [[POINTER_PHI:%.*]] = phi ptr [ [[BASE]], %[[VECTOR_PH]] ], [ [[PTR_IND:%.*]], %[[VECTOR_BODY]] ]
+; INTERLEAVE-NEXT: [[VECTOR_GEP:%.*]] = getelementptr i8, ptr [[POINTER_PHI]], i64 0
+; INTERLEAVE-NEXT: [[STEP_ADD:%.*]] = getelementptr i8, ptr [[VECTOR_GEP]], i64 4
+; INTERLEAVE-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
+; INTERLEAVE-NEXT: [[PTR_IND]] = getelementptr i8, ptr [[POINTER_PHI]], i64 8
+; INTERLEAVE-NEXT: [[TMP7:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
+; INTERLEAVE-NEXT: br i1 [[TMP7]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], {{!llvm.loop ![0-9]+}}
+; INTERLEAVE: [[MIDDLE_BLOCK]]:
+; INTERLEAVE-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP2]], [[N_VEC]]
+; INTERLEAVE-NEXT: [[IND_ESCAPE:%.*]] = getelementptr i8, ptr [[NEXT_GEP]], i64 -4
+; INTERLEAVE-NEXT: br i1 [[CMP_N]], label %[[FOR_END:.*]], label %[[SCALAR_PH]]
+; INTERLEAVE: [[SCALAR_PH]]:
+; INTERLEAVE-NEXT: [[BC_RESUME_VAL:%.*]] = phi i32 [ [[TMP3]], %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
+; INTERLEAVE-NEXT: [[BC_RESUME_VAL1:%.*]] = phi ptr [ [[NEXT_GEP]], %[[MIDDLE_BLOCK]] ], [ [[BASE]], %[[ENTRY]] ]
+; INTERLEAVE-NEXT: [[SCALAR_RECUR_INIT:%.*]] = phi ptr [ [[STEP_ADD]], %[[MIDDLE_BLOCK]] ], [ [[BASE]], %[[ENTRY]] ]
+; INTERLEAVE-NEXT: br label %[[FOR_BODY:.*]]
+; INTERLEAVE: [[FOR_BODY]]:
+; INTERLEAVE-NEXT: [[INC_PHI:%.*]] = phi i32 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[INC:%.*]], %[[FOR_BODY]] ]
+; INTERLEAVE-NEXT: [[INC_LAG1:%.*]] = phi ptr [ [[BC_RESUME_VAL1]], %[[SCALAR_PH]] ], [ [[TMP:%.*]], %[[FOR_BODY]] ]
+; INTERLEAVE-NEXT: [[INC_LAG2:%.*]] = phi ptr [ [[SCALAR_RECUR_INIT]], %[[SCALAR_PH]] ], [ [[INC_LAG1]], %[[FOR_BODY]] ]
+; INTERLEAVE-NEXT: [[TMP]] = getelementptr inbounds i32, ptr [[INC_LAG1]], i64 1
+; INTERLEAVE-NEXT: [[INC]] = add nsw i32 [[INC_PHI]], 1
+; INTERLEAVE-NEXT: [[CMP:%.*]] = icmp eq i32 [[INC]], [[K]]
+; INTERLEAVE-NEXT: br i1 [[CMP]], label %[[FOR_END]], label %[[FOR_BODY]], {{!llvm.loop ![0-9]+}}
+; INTERLEAVE: [[FOR_END]]:
+; INTERLEAVE-NEXT: [[INC_LAG1_LCSSA:%.*]] = phi ptr [ [[INC_LAG1]], %[[FOR_BODY]] ], [ [[IND_ESCAPE]], %[[MIDDLE_BLOCK]] ]
+; INTERLEAVE-NEXT: ret ptr [[INC_LAG1_LCSSA]]
;
entry:
- %base = getelementptr inbounds i32, ptr undef, i64 1
+ %base = getelementptr inbounds i32, ptr %p, i64 1
br label %for.body
for.body:
%inc.phi = phi i32 [ 0, %entry ], [ %inc, %for.body ]
%inc.lag1 = phi ptr [ %base, %entry ], [ %tmp, %for.body]
- %inc.lag2 = phi ptr [ undef, %entry ], [ %inc.lag1, %for.body]
+ %inc.lag2 = phi ptr [ %base, %entry ], [ %inc.lag1, %for.body]
%tmp = getelementptr inbounds i32, ptr %inc.lag1, i64 1
%inc = add nsw i32 %inc.phi, 1
%cmp = icmp eq i32 %inc, %k
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