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From: "g.peterhoff@t-online.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107432] New: __builtin_convertvector generates inefficient code
Date: Thu, 27 Oct 2022 10:02:40 +0000	[thread overview]
Message-ID: <bug-107432-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107432

            Bug ID: 107432
           Summary: __builtin_convertvector generates inefficient code
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: g.peterhoff@t-online.de
  Target Milestone: ---

Example: conversion int64_t -> int32_t

avx512f + avx512vl
HW conversions are available.

avx2
There is a correctly working 32-bit-permutation
(_mm256_permutevar8x32_epi32/vpermd) that can be used.

I have not (yet) evaluated whether other conversions (larger int -> smaller
int) are also affected.
PS: On x86 it's already hell to optimize all cases depending on the instruction
set.
PPS: What about -march=znver4 ?

https://godbolt.org/z/3s79bnh7v

thx
Gero

             reply	other threads:[~2022-10-27 10:02 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-27 10:02 g.peterhoff@t-online.de [this message]
2022-10-27 15:12 ` [Bug target/107432] " pinskia at gcc dot gnu.org
2022-10-27 16:14 ` g.peterhoff@t-online.de
2022-10-28  3:33 ` crazylht at gmail dot com
2022-10-28  3:36 ` crazylht at gmail dot com
2022-10-28  5:22 ` crazylht at gmail dot com
2022-10-28  5:33 ` crazylht at gmail dot com
2022-10-28  6:55 ` crazylht at gmail dot com
2022-10-28 11:41 ` rguenth at gcc dot gnu.org
2022-10-31 13:02 ` rsandifo at gcc dot gnu.org

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