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Re: [PATCH] PR target/72839: Increase MOVE_RATIO to 17 for Lakemont
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 18 Aug 2016 08:16:29 +0200
- Subject: Re: [PATCH] PR target/72839: Increase MOVE_RATIO to 17 for Lakemont
- Authentication-results: sourceware.org; auth=none
- References: <20160817182636.GA16702@intel.com>
On Wed, Aug 17, 2016 at 8:26 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> Larger MOVE_RATIO will always make code faster. 17 is the number with
> smaller code sizes for Lakemont.
>
> Tested on x86-64. OK for trunk?
OK, I assume that the patch is based on some benchmark.
Thanks,
Uros.
>
> H.J.
> ---
> gcc/
>
> PR target/72839
> * config/i386/i386.c (lakemont_cost): Set MOVE_RATIO to 17.
>
> gcc/testsuite/
>
> PR target/72839
> * gcc.target/i386/pr72839.c: New test.
> ---
> gcc/config/i386/i386.c | 2 +-
> gcc/testsuite/gcc.target/i386/pr72839.c | 17 +++++++++++++++++
> 2 files changed, 18 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr72839.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 3805817..8fe3821 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -426,7 +426,7 @@ struct processor_costs lakemont_cost = {
> COSTS_N_INSNS (3), /* cost of movsx */
> COSTS_N_INSNS (2), /* cost of movzx */
> 8, /* "large" insn */
> - 9, /* MOVE_RATIO */
> + 17, /* MOVE_RATIO */
> 6, /* cost for loading QImode using movzbl */
> {2, 4, 2}, /* cost of loading integer registers
> in QImode, HImode and SImode.
> diff --git a/gcc/testsuite/gcc.target/i386/pr72839.c b/gcc/testsuite/gcc.target/i386/pr72839.c
> new file mode 100644
> index 0000000..ea724f7
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr72839.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target ia32 } */
> +/* { dg-options "-O2 -mtune=lakemont" } */
> +
> +extern char *strcpy (char *, const char *);
> +
> +void
> +foo (char *s)
> +{
> + strcpy (s,
> + "12345678123456781234567812345678123456781234567812345678"
> + "1234567");
> +}
> +
> +/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\$\[0-9\]+, \[0-9\]*\\(%\[^,\]+\\)" 16 } } */
> +/* { dg-final { scan-assembler-not "rep movsl" } } */
> +/* { dg-final { scan-assembler-not "rep movsb" } } */
> --
> 2.7.4
>