davide created this revision.
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So, while trying to reduce a testcase I realized I can trigger a crash in LICM if I specify a given value of -opt-bisect-limit
(the repro is the one from https://llvm.org/bugs/show_bug.cgi?id=30708)
$ ./opt unopt.ll -opt-bisect-limit=53 -O3
[...]
BISECT: running pass (43) Loop Invariant Code Motion on loop │··························
BISECT: running pass (44) Unswitch loops on loop │··························
BISECT: running pass (45) Rotate Loops on loop │··························
BISECT: running pass (46) Loop Invariant Code Motion on loop │··························
BISECT: running pass (47) Unswitch loops on loop │··························
BISECT: running pass (48) Rotate Loops on loop │··························
BISECT: running pass (49) Loop Invariant Code Motion on loop │··························
BISECT: running pass (50) Unswitch loops on loop │··························
BISECT: running pass (51) Rotate Loops on loop │··························
BISECT: running pass (52) Loop Invariant Code Motion on loop │··························
BISECT: running pass (53) Unswitch loops on loop │··························
BISECT: NOT running pass (54) Rotate Loops on loop │··························
BISECT: NOT running pass (55) Loop Invariant Code Motion on loop │··························
BISECT: NOT running pass (56) Unswitch loops on loop │··························
BISECT: NOT running pass (57) Rotate Loops on loop │··························
[...]
opt: /home/davide/work/llvm-monorepo/llvm/lib/Transforms/Scalar/LICM.cpp:156: virtual bool {anonymous}::LegacyLICMPass::doFinalization(): Assertion `LICM.getLoopToAliasSetMap().empty() && "Didn't free loop alias sets"' failed.
I do think that the problem here is that if `skipLoop(L)` is true, we don't call the deleteSimpleAnalysisLoop() hook in the Loop Pass Manager, this leaves some pending elements inside LICM internal data structures -> `doFinalization()` checks for the map to be empty, and hits the assertion.
https://reviews.llvm.org/D25848
Files:
include/llvm/Analysis/LoopPass.h
lib/Analysis/LoopPass.cpp
Index: lib/Analysis/LoopPass.cpp
===================================================================
--- lib/Analysis/LoopPass.cpp
+++ lib/Analysis/LoopPass.cpp
@@ -205,7 +205,7 @@
: CurrentLoop->getHeader()->getName());
dumpPreservedSet(P);
- if (LoopWasDeleted) {
+ if (LoopWasDeleted || P->skipLoop(CurrentLoop)) {
// Notify passes that the loop is being deleted.
deleteSimpleAnalysisLoop(CurrentLoop);
} else {
Index: include/llvm/Analysis/LoopPass.h
===================================================================
--- include/llvm/Analysis/LoopPass.h
+++ include/llvm/Analysis/LoopPass.h
@@ -87,7 +87,7 @@
/// associated analysis values can be deleted.
virtual void deleteAnalysisLoop(Loop *L) {}
-protected:
+public:
/// Optional passes call this function to check whether the pass should be
/// skipped. This is the case when Attribute::OptimizeNone is set or when
/// optimization bisect is over the limit.
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