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[Bug target/70465] [4.9/5/6/7 Regression] Poor code for x87 asm
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 31 Mar 2016 17:36:13 +0000
- Subject: [Bug target/70465] [4.9/5/6/7 Regression] Poor code for x87 asm
- Auto-submitted: auto-generated
- References: <bug-70465-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70465
--- Comment #5 from UroÅ Bizjak <ubizjak at gmail dot com> ---
(In reply to Jeffrey A. Law from comment #4)
> No objections to deferring this to gcc-7. Not surprisingly, my response
> when this issue was raised on Red Hat's internal IRC was the same -- nobody
> cares about x87 math anymore ;-) IMHO it's really just a codesize issue
> anyway given how fxch is implemented on modern processors.
Related to PR 15492.
IMO, regstack.c should be taught to track loads to stack registers, so it would
be able to swap two FLDs, instead of emitting compensating FXCH right after two
FLDs.