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LoopVectorize: guard marking iv as scalar; fix bug (llvm#88730)
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When collecting loop scalars, LoopVectorize over-eagerly marks the
induction variable and its update as scalars after vectorization, even
if the induction variable update is a first-order recurrence. Guard the
process with this check, fixing a crash.

Fixes llvm#72969.
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@artagnon
artagnon authored Apr 18, 2024
1 parent 16fed31 commit 73e7f2f
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7 changes: 7 additions & 0 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3868,6 +3868,13 @@ void LoopVectorizationCostModel::collectLoopScalars(ElementCount VF) {
if (!ScalarInd)
continue;

// If the induction variable update is a fixed-order recurrence, neither the
// induction variable or its update should be marked scalar after
// vectorization.
auto *IndUpdatePhi = dyn_cast<PHINode>(IndUpdate);
if (IndUpdatePhi && Legal->isFixedOrderRecurrence(IndUpdatePhi))
continue;

// Determine if all users of the induction variable update instruction are
// scalar after vectorization.
auto ScalarIndUpdate =
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113 changes: 110 additions & 3 deletions llvm/test/Transforms/LoopVectorize/X86/pr72969.ll
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Original file line number Diff line number Diff line change
@@ -1,10 +1,111 @@
; REQUIRES: asserts
; RUN: not --crash opt -mtriple=x86_64 -mattr=-avx,-avx2,-avx512f,+sse,-sse2,-sse3,-sse4.2 -passes=loop-vectorize -S < %s
; RUN: not --crash opt -mtriple=x86_64 -mattr=-avx,-avx2,-avx512f,+sse,-sse2,-sse3,-sse4.2 -passes=loop-vectorize -force-vector-width=4 -S < %s
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
; RUN: opt -mtriple=x86_64 -mattr=-avx,-avx2,-avx512f,+sse,-sse2,-sse3,-sse4.2 -passes=loop-vectorize -S %s | FileCheck --check-prefix=NOVEC %s
; RUN: opt -mtriple=x86_64 -mattr=-avx,-avx2,-avx512f,+sse,-sse2,-sse3,-sse4.2 -passes=loop-vectorize -force-vector-width=4 -S %s | FileCheck --check-prefix=VEC %s

@h = global i64 0

define void @test(ptr %p) {
; NOVEC-LABEL: define void @test(
; NOVEC-SAME: ptr [[P:%.*]]) #[[ATTR0:[0-9]+]] {
; NOVEC-NEXT: entry:
; NOVEC-NEXT: br label [[FOR_BODY:%.*]]
; NOVEC: for.body:
; NOVEC-NEXT: [[IDX_EXT_MERGE:%.*]] = phi i64 [ 1, [[ENTRY:%.*]] ], [ [[IDX:%.*]], [[FOR_BODY]] ]
; NOVEC-NEXT: [[INC_MERGE:%.*]] = phi i16 [ 1, [[ENTRY]] ], [ [[INC:%.*]], [[FOR_BODY]] ]
; NOVEC-NEXT: [[IDX_MERGE:%.*]] = phi i64 [ 0, [[ENTRY]] ], [ [[IDX_EXT_MERGE]], [[FOR_BODY]] ]
; NOVEC-NEXT: [[ADD:%.*]] = shl i64 [[IDX_MERGE]], 1
; NOVEC-NEXT: [[ARRAYIDX:%.*]] = getelementptr i64, ptr [[P]], i64 [[ADD]]
; NOVEC-NEXT: store i64 0, ptr [[ARRAYIDX]], align 8
; NOVEC-NEXT: [[INC]] = add i16 [[INC_MERGE]], 1
; NOVEC-NEXT: [[IDX]] = zext i16 [[INC]] to i64
; NOVEC-NEXT: [[GEP:%.*]] = getelementptr i64, ptr [[P]], i64 [[IDX]]
; NOVEC-NEXT: [[CMP:%.*]] = icmp ugt ptr [[GEP]], @h
; NOVEC-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[FOR_BODY]]
; NOVEC: exit:
; NOVEC-NEXT: ret void
;
; VEC-LABEL: define void @test(
; VEC-SAME: ptr [[P:%.*]]) #[[ATTR0:[0-9]+]] {
; VEC-NEXT: entry:
; VEC-NEXT: [[P1:%.*]] = ptrtoint ptr [[P]] to i64
; VEC-NEXT: [[TMP0:%.*]] = add i64 [[P1]], 16
; VEC-NEXT: [[UMAX2:%.*]] = call i64 @llvm.umax.i64(i64 [[TMP0]], i64 add (i64 ptrtoint (ptr @h to i64), i64 1))
; VEC-NEXT: [[TMP1:%.*]] = add i64 [[UMAX2]], -9
; VEC-NEXT: [[TMP2:%.*]] = sub i64 [[TMP1]], [[P1]]
; VEC-NEXT: [[TMP3:%.*]] = lshr i64 [[TMP2]], 3
; VEC-NEXT: [[TMP4:%.*]] = add nuw nsw i64 [[TMP3]], 1
; VEC-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP4]], 4
; VEC-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
; VEC: vector.scevcheck:
; VEC-NEXT: [[TMP5:%.*]] = add i64 [[P1]], 16
; VEC-NEXT: [[UMAX:%.*]] = call i64 @llvm.umax.i64(i64 [[TMP5]], i64 add (i64 ptrtoint (ptr @h to i64), i64 1))
; VEC-NEXT: [[TMP6:%.*]] = add i64 [[UMAX]], -9
; VEC-NEXT: [[TMP7:%.*]] = sub i64 [[TMP6]], [[P1]]
; VEC-NEXT: [[TMP8:%.*]] = lshr i64 [[TMP7]], 3
; VEC-NEXT: [[TMP9:%.*]] = icmp ugt i64 [[TMP8]], 65535
; VEC-NEXT: [[TMP10:%.*]] = trunc i64 [[TMP8]] to i16
; VEC-NEXT: [[TMP11:%.*]] = add i16 2, [[TMP10]]
; VEC-NEXT: [[TMP12:%.*]] = icmp ult i16 [[TMP11]], 2
; VEC-NEXT: [[TMP13:%.*]] = icmp ugt i64 [[TMP8]], 65535
; VEC-NEXT: [[TMP14:%.*]] = or i1 [[TMP12]], [[TMP13]]
; VEC-NEXT: br i1 [[TMP14]], label [[SCALAR_PH]], label [[VECTOR_PH:%.*]]
; VEC: vector.ph:
; VEC-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP4]], 4
; VEC-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP4]], [[N_MOD_VF]]
; VEC-NEXT: [[DOTCAST:%.*]] = trunc i64 [[N_VEC]] to i16
; VEC-NEXT: [[IND_END:%.*]] = add i16 1, [[DOTCAST]]
; VEC-NEXT: br label [[VECTOR_BODY:%.*]]
; VEC: vector.body:
; VEC-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
; VEC-NEXT: [[VECTOR_RECUR:%.*]] = phi <4 x i64> [ <i64 poison, i64 poison, i64 poison, i64 1>, [[VECTOR_PH]] ], [ [[TMP28:%.*]], [[VECTOR_BODY]] ]
; VEC-NEXT: [[VEC_IND:%.*]] = phi <4 x i16> [ <i16 1, i16 2, i16 3, i16 4>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
; VEC-NEXT: [[TMP15:%.*]] = add i64 [[INDEX]], 0
; VEC-NEXT: [[TMP16:%.*]] = add i64 [[INDEX]], 1
; VEC-NEXT: [[TMP17:%.*]] = add i64 [[INDEX]], 2
; VEC-NEXT: [[TMP18:%.*]] = add i64 [[INDEX]], 3
; VEC-NEXT: [[TMP19:%.*]] = shl i64 [[TMP15]], 1
; VEC-NEXT: [[TMP20:%.*]] = shl i64 [[TMP16]], 1
; VEC-NEXT: [[TMP21:%.*]] = shl i64 [[TMP17]], 1
; VEC-NEXT: [[TMP22:%.*]] = shl i64 [[TMP18]], 1
; VEC-NEXT: [[TMP23:%.*]] = getelementptr i64, ptr [[P]], i64 [[TMP19]]
; VEC-NEXT: [[TMP24:%.*]] = getelementptr i64, ptr [[P]], i64 [[TMP20]]
; VEC-NEXT: [[TMP25:%.*]] = getelementptr i64, ptr [[P]], i64 [[TMP21]]
; VEC-NEXT: [[TMP26:%.*]] = getelementptr i64, ptr [[P]], i64 [[TMP22]]
; VEC-NEXT: store i64 0, ptr [[TMP23]], align 8
; VEC-NEXT: store i64 0, ptr [[TMP24]], align 8
; VEC-NEXT: store i64 0, ptr [[TMP25]], align 8
; VEC-NEXT: store i64 0, ptr [[TMP26]], align 8
; VEC-NEXT: [[TMP27:%.*]] = add <4 x i16> [[VEC_IND]], <i16 1, i16 1, i16 1, i16 1>
; VEC-NEXT: [[TMP28]] = zext <4 x i16> [[TMP27]] to <4 x i64>
; VEC-NEXT: [[TMP29:%.*]] = shufflevector <4 x i64> [[VECTOR_RECUR]], <4 x i64> [[TMP28]], <4 x i32> <i32 3, i32 4, i32 5, i32 6>
; VEC-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
; VEC-NEXT: [[VEC_IND_NEXT]] = add <4 x i16> [[VEC_IND]], <i16 4, i16 4, i16 4, i16 4>
; VEC-NEXT: [[TMP30:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
; VEC-NEXT: br i1 [[TMP30]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
; VEC: middle.block:
; VEC-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP4]], [[N_VEC]]
; VEC-NEXT: [[VECTOR_RECUR_EXTRACT:%.*]] = extractelement <4 x i64> [[TMP28]], i32 3
; VEC-NEXT: br i1 [[CMP_N]], label [[EXIT:%.*]], label [[SCALAR_PH]]
; VEC: scalar.ph:
; VEC-NEXT: [[SCALAR_RECUR_INIT:%.*]] = phi i64 [ 1, [[VECTOR_SCEVCHECK]] ], [ 1, [[ENTRY:%.*]] ], [ [[VECTOR_RECUR_EXTRACT]], [[MIDDLE_BLOCK]] ]
; VEC-NEXT: [[BC_RESUME_VAL:%.*]] = phi i16 [ [[IND_END]], [[MIDDLE_BLOCK]] ], [ 1, [[ENTRY]] ], [ 1, [[VECTOR_SCEVCHECK]] ]
; VEC-NEXT: [[BC_RESUME_VAL3:%.*]] = phi i64 [ [[N_VEC]], [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY]] ], [ 0, [[VECTOR_SCEVCHECK]] ]
; VEC-NEXT: br label [[FOR_BODY:%.*]]
; VEC: for.body:
; VEC-NEXT: [[SCALAR_RECUR:%.*]] = phi i64 [ [[SCALAR_RECUR_INIT]], [[SCALAR_PH]] ], [ [[IDX:%.*]], [[FOR_BODY]] ]
; VEC-NEXT: [[INC_MERGE:%.*]] = phi i16 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC:%.*]], [[FOR_BODY]] ]
; VEC-NEXT: [[IDX_MERGE:%.*]] = phi i64 [ [[BC_RESUME_VAL3]], [[SCALAR_PH]] ], [ [[SCALAR_RECUR]], [[FOR_BODY]] ]
; VEC-NEXT: [[ADD:%.*]] = shl i64 [[IDX_MERGE]], 1
; VEC-NEXT: [[ARRAYIDX:%.*]] = getelementptr i64, ptr [[P]], i64 [[ADD]]
; VEC-NEXT: store i64 0, ptr [[ARRAYIDX]], align 8
; VEC-NEXT: [[INC]] = add i16 [[INC_MERGE]], 1
; VEC-NEXT: [[IDX]] = zext i16 [[INC]] to i64
; VEC-NEXT: [[GEP:%.*]] = getelementptr i64, ptr [[P]], i64 [[IDX]]
; VEC-NEXT: [[CMP:%.*]] = icmp ugt ptr [[GEP]], @h
; VEC-NEXT: br i1 [[CMP]], label [[EXIT]], label [[FOR_BODY]], !llvm.loop [[LOOP3:![0-9]+]]
; VEC: exit:
; VEC-NEXT: ret void
;
entry:
br label %for.body

Expand All @@ -24,3 +125,9 @@ for.body:
exit:
ret void
}
;.
; VEC: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]], [[META2:![0-9]+]]}
; VEC: [[META1]] = !{!"llvm.loop.isvectorized", i32 1}
; VEC: [[META2]] = !{!"llvm.loop.unroll.runtime.disable"}
; VEC: [[LOOP3]] = distinct !{[[LOOP3]], [[META1]]}
;.

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