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[LegacyPM] Fix PR37888 by teaching the legacy loop pass manager how to

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clear out deleted loops from the current queue beyond just the current
loop.

This is important because SimpleLoopUnswitch will now enqueue the same
loop to be re-processed. When it does this with the legacy PM, we don't
have a way of canceling the rest of the pipeline and so we can end up
deleting the loop before we reprocess it. =/

This change also makes it easy to support deleting other loops in the
queue to process, although I don't have any use cases for that.

Differential Revision: https://reviews.llvm.org/D48470

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335317 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2018-06-22 02:43:41 +00:00
parent 20f413f83a
commit 762b38dd8c
2 changed files with 48 additions and 1 deletions
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11
lib/Analysis/LoopPass.cpp
View File

@ -142,8 +142,17 @@ void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
void LPPassManager::markLoopAsDeleted(Loop &L) {
assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
"Must not delete loop outside the current loop tree!");
if (&L == CurrentLoop)
// If this loop appears elsewhere within the queue, we also need to remove it
// there. However, we have to be careful to not remove the back of the queue
// as that is assumed to match the current loop.
assert(LQ.back() == CurrentLoop && "Loop queue back isn't the current loop!");
LQ.erase(std::remove(LQ.begin(), LQ.end(), &L), LQ.end());
if (&L == CurrentLoop) {
CurrentLoopDeleted = true;
// Add this loop back onto the back of the queue to preserve our invariants.
LQ.push_back(&L);
}
}
/// run - Execute all of the passes scheduled for execution. Keep track of

38
test/Transforms/SimpleLoopUnswitch/pr37888.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: opt -simple-loop-unswitch -loop-deletion -S < %s | FileCheck %s
;
; Check that when we do unswitching where we re-enqueue the loop to be processed
; again, but manage to delete the loop before ever getting to iterate on it, it
; doesn't crash the legacy pass manager.
target triple = "x86_64-unknown-linux-gnu"
define void @pr37888() {
; CHECK-LABEL: define void @pr37888()
entry:
%tobool = icmp ne i16 undef, 0
br label %for.body
; CHECK: %[[TOBOOL:.*]] = icmp ne
; CHECK-NEXT: br i1 %[[TOBOOL]], label %if.then, label %[[ENTRY_SPLIT:.*]]
;
; CHECK: [[ENTRY_SPLIT]]:
; CHECK-NEXT: br label %for.end
for.body:
br i1 %tobool, label %if.then, label %if.end
if.then:
unreachable
; CHECK: if.then:
; CHECK-NEXT: unreachable
if.end:
br label %for.inc
for.inc:
br i1 undef, label %for.body, label %for.end
for.end:
ret void
; CHECK: for.end:
; CHECK-NEXT: ret void
}