Infinite recursion in loop vectorizer

[d0k]

Bugzilla Link	28541
Resolution	FIXED
Resolved on	Aug 12, 2016 17:48
Version	trunk
OS	All
Blocks	#28974
CC	@zmodem,@hfinkel

Extended Description

$ cat t.c
a, b, c;
fn1() {
while (b--) {
c = a;
switch (a & 3)
case 0:
do
case 3:
case 2:
case 1:
;
while (--c)
;
}
}

$ clang -O2 t.c
...
#​8 0x00000000019ffbaa (anonymous namespace)::InnerLoopVectorizer::createBlockInMask(llvm::BasicBlock*) (bin/clang)
#​9 0x0000000001a000d4 (anonymous namespace)::InnerLoopVectorizer::createEdgeMask(llvm::BasicBlock*, llvm::BasicBlock*) (bin/clang)
... repeats 100+ times ...

1.  <eof> parser at end of file
   

2.  Per-module optimization passes
   

3.  Running pass 'Function Pass Manager' on module 't.c'.
   

4.  Running pass 'Loop Vectorization' on function '@fn1'
   

clang: error: unable to execute command: Segmentation fault (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 3.9.0 (trunk 275303) (llvm/trunk 275304)

The crash only occurs at -O2, the bug comes from the interaction of multiple passes.

[d0k]

Bisection points at r264697.

This code is coming from real code (pygame) even though it looks like fuzzer output ;)

[d0k]

*** Bug llvm/llvm-bugzilla-archive#28716 has been marked as a duplicate of this bug. ***

[zmodem]

Sounds like this is a 3.8 -> 3.9 regression.

[llvmbot]

*** Bug #28564 has been marked as a duplicate of this bug. ***

[zmodem]

mkuper pointed out there's a fix up for review: http://reviews.llvm.org/D22952

[llvmbot]

Fixed by r278573.

[zmodem]

mentioned in issue #28974

[d0k]

mentioned in issue llvm/llvm-bugzilla-archive#28716