[PATCH] D31068: [SDAG] Expand MergedConsecutiveStores to better handle Giving up in Chain Analysis

[Aditya Nandakumar via llvm-commits]

Managed to figure out what was different with x86_64 backend (and why it was not reproducing with the same test case).

The following test case should reproduce the issue of failing merging.

bin/llc -mtriple=x86_64-apple-darwin -o - test.ll  -disable-lsr
 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: test.ll
Type: application/octet-stream
Size: 1107 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170411/6e2cb851/attachment.obj>
-------------- next part --------------


I haven’t looked into why lsr hides the issue though.

Aditya
> On Apr 11, 2017, at 10:25 AM, Nirav Davé <niravd at google.com> wrote:
> 
> Hmm. This is disconcerting. It looks pretty clear that t50 improved it's chain from t18 to t0, but findBetterNeighborChains should be doing fixing all of the upper chains improved to t0 simultaneously. This is likely  be a nontrivial compiler slowdown. Would it possible to get the llvm code for this case? 
> ​