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LSV: document hang reported in #37865 (#102479)

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LoadStoreVectorizer hangs on certain examples, when its reorder function
goes into a cycle. Detect this cycle and explicitly forbid it, using an
assert, and document the resulting crash in a test-case under AArch64.
This commit is contained in:
Ramkumar Ramachandra
2024-08-09 11:34:09 +01:00
committed by GitHub
parent ccb2b011e5
commit 199d6f2c0c
2 changed files with 17 additions and 0 deletions
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2
llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
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@@ -216,6 +216,8 @@ void reorder(Instruction *I) {
if (IM->getParent() != I->getParent())
continue;
assert(IM != I && "Unexpected cycle while re-ordering instructions");
if (!IM->comesBefore(I)) {
InstructionsToMove.insert(IM);
Worklist.push_back(IM);

15
llvm/test/Transforms/LoadStoreVectorizer/AArch64/pr37865.ll Normal file
View File

@@ -0,0 +1,15 @@
; REQUIRES: asserts
; RUN: not --crash opt -mtriple=aarch64 -passes=load-store-vectorizer \
; RUN: -disable-output %s 2>&1 | FileCheck %s
define i32 @load_cycle(ptr %x) {
; CHECK: Unexpected cycle while re-ordering instructions
entry:
%gep.x.1 = getelementptr inbounds [2 x i32], ptr %x, i32 0, i32 1
%load.x.1 = load i32, ptr %gep.x.1
%rem = urem i32 %load.x.1, 1
%gep.x.2 = getelementptr inbounds [2 x i32], ptr %x, i32 %rem, i32 0
%load.x.2 = load i32, ptr %gep.x.2
%ret = add i32 %load.x.2, %load.x.1
ret i32 %ret
}