Commit Graph

8 Commits

Author SHA1 Message Date
Chandler Carruth 4a000883c7 [LoopSimplify] Re-instate r306081 with a bug fix w.r.t. indirectbr.
This was reverted in r306252, but I already had the bug fixed and was
just trying to form a test case.

The original commit factored the logic for forming dedicated exits
inside of LoopSimplify into a helper that could be used elsewhere and
with an approach that required fewer intermediate data structures. See
that commit for full details including the change to the statistic, etc.

The code looked fine to me and my reviewers, but in fact didn't handle
indirectbr correctly -- it left the 'InLoopPredecessors' vector dirty.

If you have code that looks *just* right, you can end up leaking these
predecessors into a subsequent rewrite, and crash deep down when trying
to update PHI nodes for predecessors that don't exist.

I've added an assert that makes the bug much more obvious, and then
changed the code to reliably clear the vector so we don't get this bug
again in some other form as the code changes.

I've also added a test case that *does* manage to catch this while also
giving some nice positive coverage in the face of indirectbr.

The real code that found this came out of what I think is CPython's
interpreter loop, but any code with really "creative" interpreter loops
mixing indirectbr and other exit paths could manage to tickle the bug.
I was hard to reduce the original test case because in addition to
having a particular pattern of IR, the whole thing depends on the order
of the predecessors which is in turn depends on use list order. The test
case added here was designed so that in multiple different predecessor
orderings it should always end up going down the same path and tripping
the same bug. I hope. At least, it tripped it for me without
manipulating the use list order which is better than anything bugpoint
could do...

llvm-svn: 306257
2017-06-25 22:45:31 +00:00
Chandler Carruth 73367b6a09 [LoopSimplify] Improve a test for loop simplify minorly. NFC.
I did some basic testing while looking for a bug in my recent change to
loop simplify and even though it didn't find the bug it seems like
a useful improvement anyways.

llvm-svn: 306256
2017-06-25 22:24:02 +00:00
Davide Italiano cd96cfd8df [PM] Port LoopSimplify to the new pass manager.
While here move simplifyLoop() function to the new header, as
suggested by Chandler in the review.

Differential Revision:  http://reviews.llvm.org/D21404

llvm-svn: 274959
2016-07-09 03:03:01 +00:00
Cameron Zwarich d8e66038f4 Rename 'loopsimplify' to 'loop-simplify'.
llvm-svn: 125317
2011-02-10 23:38:10 +00:00
Dan Gohman 1880092722 Change tests from "opt %s" to "opt < %s" so that opt doesn't see the
input filename so that opt doesn't print the input filename in the
output so that grep lines in the tests don't unintentionally match
strings in the input filename.

llvm-svn: 81537
2009-09-11 18:01:28 +00:00
Dan Gohman 9737a63ed8 Change these tests to feed the assembly files to opt directly, instead
of using llvm-as, now that opt supports this.

llvm-svn: 81226
2009-09-08 16:50:01 +00:00
Tanya Lattner 8bf97c2324 Byebye llvm-upgrade!
llvm-svn: 48762
2008-03-25 04:26:08 +00:00
Reid Spencer 83b3d82672 Regression is gone, don't try to find it on clean target.
llvm-svn: 33296
2007-01-17 07:59:14 +00:00