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From: Uros Bizjak <>
To: Roger Sayle <>
Subject: Re: [x86_64 PATCH] Two minor tweaks to ix86_expand_move.
Date: Sat, 17 Jun 2023 15:15:56 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <033d01d9a06f$6bdf2360$439d6a20$>

On Fri, Jun 16, 2023 at 6:27 PM Roger Sayle <> wrote:
> This patch splits out two (independent) minor changes to's
> ix86_expand_move from a larger patch, given that it's better to review
> and commit these independent pieces separately from a more complex patch.
> The first change is to test for CONST_WIDE_INT_P before calling
> ix86_convert_const_wide_int_to_broadcast.  Whilst stepping through
> this function in gdb, I was surprised that the code was continually
> jumping into this function with operands that obviously weren't
> appropriate.
> The second change is to generalize the optimization for efficiently
> moving a TImode value to V1TImode (via V2DImode), to cover all 128-bit
> vector modes.
> Hence for the test case:
> typedef unsigned long uv2di __attribute__ ((__vector_size__ (16)));
> uv2di foo2(__int128 x) { return (uv2di)x; }
> we'd previously move via memory with:
> foo2:   movq    %rdi, -24(%rsp)
>         movq    %rsi, -16(%rsp)
>         movdqa  -24(%rsp), %xmm0
>         ret
> with this patch we now generate with -O2 (the same as V1TImode):
> foo2:   movq    %rdi, %xmm0
>         movq    %rsi, %xmm1
>         punpcklqdq      %xmm1, %xmm0
>         ret
> and with -O2 -msse4 the even better:
> foo2:   movq    %rdi, %xmm0
>         pinsrq  $1, %rsi, %xmm0
>         ret
> The new test case is unimaginatively called sse2-v1ti-mov-2.c given
> the original test case just for V1TI mode was called sse2-v1ti-mov-1.c.
> This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> and make -k check, both with and without --target_board=unix{-m32}
> with no new failures.  Ok for mainline?
> 2023-06-16  Roger Sayle  <>
> gcc/ChangeLog
>         * config/i386/ (ix86_expand_move): Check that OP1 is
>         CONST_WIDE_INT_P before calling ix86_convert_wide_int_to_broadcast.
>         Generalize special case for converting TImode to V1TImode to handle
>         all 128-bit vector conversions.
> gcc/testsuite/ChangeLog
>         * New test case.



> Thanks in advance,
> Roger
> --

      reply	other threads:[~2023-06-17 13:16 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-06-16 16:27 Roger Sayle
2023-06-17 13:15 ` Uros Bizjak [this message]

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