public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/98647] New: Failure to optimize out convertion from float to vector type
Date: Wed, 13 Jan 2021 00:57:05 +0000	[thread overview]
Message-ID: <bug-98647-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98647

            Bug ID: 98647
           Summary: Failure to optimize out convertion from float to
                    vector type
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

float f(float val)
{
    return _mm_cvtss_f32(_mm_and_ps(_mm_set_ss(val),
_mm_castsi128_ps(_mm_set1_epi32(0x7fffffff))));
}

This can be optimized to avoid the conversions in the emitted assembly code.
This optimization is done by LLVM, but not by GCC.

LLVM code generation :

.LCPI1_0:
  .long 0x7fffffff # float NaN
  .long 0x7fffffff # float NaN
  .long 0x7fffffff # float NaN
  .long 0x7fffffff # float NaN
f(float): # @f(float)
  andps xmm0, xmmword ptr [rip + .LCPI1_0]
  ret

GCC code generation :

f(float):
  pxor xmm1, xmm1
  movss xmm1, xmm0
  movaps xmm0, XMMWORD PTR .LC1[rip]
  andps xmm0, xmm1
  ret

.LC1:
  .long 2147483647
  .long 2147483647
  .long 2147483647
  .long 2147483647

             reply	other threads:[~2021-01-13  0:57 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-13  0:57 gabravier at gmail dot com [this message]
2021-01-13  1:07 ` [Bug target/98647] " pinskia at gcc dot gnu.org
2021-01-13  1:24 ` gabravier at gmail dot com
2021-01-13  7:01 ` jakub 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-98647-4@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).