DAGCombiner::Run infinite loop / memory leak

[llvmbot]

Bugzilla Link	45186
Resolution	FIXED
Resolved on	Jun 23, 2020 14:17
Version	trunk
OS	FreeBSD
Blocks	#44654
Attachments	reproduce files from manually crashing compiler with SIGBUS.
Reporter	LLVM Bugzilla Contributor
CC	@chmeeedalf,@DimitryAndric,@hfinkel,@nemanjai,@pkubaj,@tstellar
Fixed by commit(s)	099a875 177a9ac

Extended Description

FreeBSD clang 9.0.1 could compile this code OK, but FreeBSD clang 10.0.0 llvmorg-10.0.0-rc3-1-gc290cb61fdc gets stuck in an infinite loop, and so does current llvm master.

Code is from FreeBSD security/nss package building on powerpc64.

[llvmbot]

assigned to @hfinkel

[pkubaj]

The same bug affects also multimedia/x264.

[pkubaj]

Adding dim@ to cc.

[DimitryAndric]

Reduced to:

// clang -cc1 -triple powerpc64-- -S -target-feature +vsx -O2 -std=c99 -vectorize-loops gcm-min.c
struct {
long b, c;
} d;
long e(unsigned char *f) {
return (long)f[0] << 56 | (long)f[1] << 48 | (long)f[2] << 40 |
(long)f[3] << 32 | (long)f[4] << 24 | f[5] << 16 | f[6] << 8 | f[7];
}
void g(void) {
d.c = e((unsigned char *)g + 8);
d.b = e((unsigned char *)g);
}

[DimitryAndric]

Regression caused by https://reviews.llvm.org/rGa9ad65a2b34 aka https://reviews.llvm.org/D71954 ("[PowerPC] Change default for unaligned FP access for older subtargets"), which was a fix for bug 40554.

[nemanjai]

Ah, this really was only supposed to be used for scalar types.

[nemanjai]

Is this something you need backported to 10.0.1?

[DimitryAndric]

Is this something you need backported to 10.0.1?

Yes, that would be nice, thanks for the fix!. I'm certainly going to import it into FreeBSD when the upcoming 10.0.1-rc2 drops. Or I'll cherry-pick it separately, so it can be merged back to older FreeBSD branches.

[nemanjai]

Can we get this merged into 10.0.1?

[nemanjai]

Sorry, that would mean that both commits need to be merged in:
a9ad65a
099a875

[tstellar]

Sorry, that would mean that both commits need to be merged in:
a9ad65a

This patch is from December and already in the branch.

099a875

[tstellar]

Hal, what do you think about backporting this?

https://reviews.llvm.org/rG099a875f28d0131a6ae85af91b9eb8627917fbbe

[pkubaj]

Reopened for merging.

[hfinkel]

Hal, what do you think about backporting this?

https://reviews.llvm.org/rG099a875f28d0131a6ae85af91b9eb8627917fbbe

LGTM.

[tstellar]

Merged: 177a9ac