[LLVMbugs] [Bug 8200] MMX unpack instructions no longer get selected

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Oct 29 11:35:31 PDT 2010


http://llvm.org/bugs/show_bug.cgi?id=8200

chromium at hybridsource.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |chromium at hybridsource.org
         Resolution|FIXED                       |

--- Comment #12 from chromium at hybridsource.org 2010-10-29 13:35:31 CDT ---
It appears that this patch 115298 broke mmx in other ways, as I've noticed that
some HTML5 video scaling code in Chromium doesn't work right after this patch
was applied.  I bisected the llvm release_28 branch before and after this patch
and found that this mmx change was the culprit.  Here's the video scaling code
that it likely broke:

http://src.chromium.org/viewvc/chrome/trunk/src/media/base/yuv_row_posix.cc?view=markup

I wonder why this patch was never applied to llvm trunk, does it have known
issues?  As it was never applied to llvm trunk, I just built Chromium with
trunk llvm-117647/clang-117645 and wasn't able to reproduce, so the problem
only crops up with the final llvm 2.8 release.  I build Chromium 7-9 on FreeBSD
7, I've attached screenshots of the resulting video scaling problem.  As I
noted on this Chromium-clang thread, the problem goes away if I trigger another
code path that doesn't use the assembly/mmx code:

http://groups.google.com/a/chromium.org/group/clang/browse_thread/thread/bfafbc62871caa55#

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