public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "jens.seifert at de dot ibm.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/95737] PPC: Unnecessary extsw after negative less than
Date: Fri, 19 Jun 2020 17:43:15 +0000 [thread overview]
Message-ID: <bug-95737-4-dmnOMiUmVr@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-95737-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95737
Jens Seifert <jens.seifert at de dot ibm.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |UNCONFIRMED
Resolution|DUPLICATE |---
--- Comment #3 from Jens Seifert <jens.seifert at de dot ibm.com> ---
This is different as the extsw also happens if the result gets used e.g.
followed by a andc, which is my case. I obviously oversimplified the sample. It
has nothing to do with function result and ABI requirements. gcc assume that
the result of -(a < b) implemented by subfc, subfe is signed 32-bit. But the
result is already 64-bit.
unsigned long long branchlesconditional(unsigned long long a, unsigned long
long b, unsigned long long c)
{
unsigned long long mask = -(a < b);
return c &~ mask;
}
results in
_Z20branchlesconditionalyyy:
.LFB1:
.cfi_startproc
subfc 4,4,3
subfe 3,3,3
not 3,3
extsw 3,3
and 3,3,5
blr
expected
subfc
subfe
andc
next prev parent reply other threads:[~2020-06-19 17:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 8:10 [Bug target/95737] New: " jens.seifert at de dot ibm.com
2020-06-19 16:40 ` [Bug target/95737] " wschmidt at gcc dot gnu.org
2020-06-19 16:42 ` wschmidt at gcc dot gnu.org
2020-06-19 17:43 ` jens.seifert at de dot ibm.com [this message]
2020-06-21 15:35 ` wschmidt at linux dot ibm.com
2020-06-21 16:30 ` segher at gcc dot gnu.org
2022-01-06 5:39 ` guihaoc at gcc dot gnu.org
2022-01-13 12:19 ` segher at gcc dot gnu.org
2022-01-13 16:34 ` segher at gcc dot gnu.org
2022-01-14 9:16 ` guihaoc at gcc dot gnu.org
2022-05-18 5:24 ` cvs-commit at gcc dot gnu.org
2022-07-29 2:52 ` guihaoc at gcc dot gnu.org
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bug-95737-4-dmnOMiUmVr@http.gcc.gnu.org/bugzilla/ \
--to=gcc-bugzilla@gcc.gnu.org \
--cc=gcc-bugs@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).