Re: [PATCH][Middle-end][version 3]2nd patch of PR78809 and PR83026

[Jeff Law <law at redhat dot com>]

On 05/29/2018 06:08 PM, Qing Zhao wrote:
> Hi, Jeff,
> 
> Thanks a lot for your review and comments.
> 
> I have updated my patch based on your suggestion, and retested this whole patch on both X86 and aarch64.
> 
> please take a look at the patch again.
> 
> thanks.
> 
> Qing
> 
>> On May 25, 2018, at 3:38 PM, Jeff Law <law@redhat.com> wrote:
>> So I originally thought you had the core logic wrong in the immediate
>> uses loop.  But it's actually the case that the return value is the
>> exact opposite of what I expected.
>>
>> ie, I expected "TRUE" to mean the call was transformed, "FALSE" if it
>> was not transformed.
>>
>> Can you fix that so it's not so confusing?
>>
>> I think with that change we'll be good to go, but please repost for a
>> final looksie.
>>
>> THanks,
>> Jeff
> 
> 
> 0001-2nd-Patch-for-PR78009.patch
> 
> 
> From 750f44ee0777d55b568f07e263babdedd532d315 Mon Sep 17 00:00:00 2001
> From: qing zhao <qing.zhao@oracle.com>
> Date: Tue, 29 May 2018 16:15:21 -0400
> Subject: [PATCH] 2nd Patch for PR78009 Patch for PR83026
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809
> Inline strcmp with small constant strings
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83026
> missing strlen optimization for strcmp of unequal strings
> 
> The design doc for PR78809 is at:
> https://www.mail-archive.com/gcc@gcc.gnu.org/msg83822.html
> 
> this patch is for the second part of change of PR78809 and PR83026:
> 
> B. for strncmp (s1, s2, n) (!)= 0 or strcmp (s1, s2) (!)= 0
> 
>    B.1. (PR83026) When the lengths of both arguments are constant and
>         it's a strcmp:
>       * if the lengths are NOT equal, we can safely fold the call
>         to a non-zero value.
>       * otherwise, do nothing now.
> 
>    B.2. (PR78809) When the length of one argument is constant, try to replace
>    the call with a __builtin_str(n)cmp_eq call where possible, i.e:
> 
>    strncmp (s, STR, C) (!)= 0 in which, s is a pointer to a string, STR is a
>    string with constant length, C is a constant.
>      if (C <= strlen(STR) && sizeof_array(s) > C)
>        {
>          replace this call with
>          __builtin_strncmp_eq (s, STR, C) (!)= 0
>        }
>      if (C > strlen(STR)
>        {
>          it can be safely treated as a call to strcmp (s, STR) (!)= 0
>          can handled by the following strcmp.
>        }
> 
>    strcmp (s, STR) (!)= 0 in which, s is a pointer to a string, STR is a
>    string with constant length.
>      if  (sizeof_array(s) > strlen(STR))
>        {
>          replace this call with
>          __builtin_strcmp_eq (s, STR, strlen(STR)+1) (!)= 0
>        }
> 
>    later when expanding the new __builtin_str(n)cmp_eq calls, first expand them
>    as __builtin_memcmp_eq, if the expansion does not succeed, change them back
>    to call to __builtin_str(n)cmp.
> 
> adding test case strcmpopt_2.c and strcmpopt_4.c into gcc.dg for part B of
> PR78809 adding test case strcmpopt_3.c into gcc.dg for PR83026
> 
> bootstraped and tested on both X86 and Aarch64. no regression.
> ---
>  gcc/builtins.c                     |  33 ++++
>  gcc/builtins.def                   |   5 +
>  gcc/gimple-fold.c                  |   5 +
>  gcc/testsuite/gcc.dg/strcmpopt_2.c |  67 ++++++++
>  gcc/testsuite/gcc.dg/strcmpopt_3.c |  31 ++++
>  gcc/testsuite/gcc.dg/strcmpopt_4.c |  16 ++
>  gcc/tree-ssa-strlen.c              | 304 ++++++++++++++++++++++++++++++++++---
>  gcc/tree-ssa-structalias.c         |   2 +
>  gcc/tree.c                         |   8 +
>  9 files changed, 454 insertions(+), 17 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/strcmpopt_2.c
>  create mode 100644 gcc/testsuite/gcc.dg/strcmpopt_3.c
>  create mode 100644 gcc/testsuite/gcc.dg/strcmpopt_4.c
Sorry for the long delay.  This needs a ChangeLog.  With the ChangeLog
it is OK for the trunk.

Jeff