[Bug tree-optimization/36318] New: SRA pessimizes struct copies without -Os

[Bug tree-optimization/36318] New: SRA pessimizes struct copies without -Os

[astrange at ithinksw dot com]

> /usr/local/gcc44/bin/gcc -v
Using built-in specs.
Target: i386-apple-darwin9.2.2
Configured with: ../gcc/configure --prefix=/usr/local/gcc44
--enable-threads=posix --with-arch=core2 --with-tune=core2 --with-gmp=/sw
--with-mpfr=/sw --disable-nls --disable-bootstrap --enable-checking=yes,rtl
--enable-languages=c,c++,objc
Thread model: posix
gcc version 4.4.0 20080523 (experimental) (GCC) 

and these options:
> gcc -fno-pic -fomit-frame-pointer -O3 -S wc.c

For the attached source, gcc generates good code for global variable
assignment:
_foo0:
        subl    $12, %esp
        movl    _b, %eax
        movl    %eax, _a
        addl    $12, %esp
        ret

but uses byte copies for pointer assignment:
_foo1:
        subl    $12, %esp
        movl    %ebx, 4(%esp)
        movl    %esi, 8(%esp)
        movl    20(%esp), %eax
        movl    16(%esp), %edx
        movzbl  (%eax), %esi
        movzbl  1(%eax), %ebx
        movzbl  2(%eax), %ecx
        movzbl  3(%eax), %eax
        movb    %cl, 2(%edx)
        movb    %al, 3(%edx)
        movb    %bl, 1(%edx)
        movl    %esi, %eax
        movb    %al, (%edx)
        movl    4(%esp), %ebx
        movl    8(%esp), %esi
        addl    $12, %esp
        ret

Using either -Os or -fno-tree-sra fixes it.


-- 
           Summary: SRA pessimizes struct copies without -Os
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: astrange at ithinksw dot com
GCC target triplet: i?86-*-*


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36318

[Bug tree-optimization/36318] SRA pessimizes struct copies without -Os

[astrange at ithinksw dot com]

------- Comment #1 from astrange at ithinksw dot com  2008-05-23 21:37 -------
Created an attachment (id=15678)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15678&action=view)
testcase


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36318

[Bug tree-optimization/36318] SRA pessimizes struct copies without -Os

[astrange at ithinksw dot com]

------- Comment #2 from astrange at ithinksw dot com  2009-05-30 00:19 -------
Fixed with new SRA:
_foo1:
        subl    $12, %esp
        movl    20(%esp), %eax
        movl    (%eax), %edx
        movl    16(%esp), %eax
        movl    %edx, (%eax)
        addl    $12, %esp
        ret


-- 

astrange at ithinksw dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36318

[Bug tree-optimization/36318] SRA pessimizes struct copies without -Os

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2009-05-30 09:49 -------
Can you provide a testcase suitable for inclusion in the testsuite?


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36318

[Bug tree-optimization/36318] SRA pessimizes struct copies without -Os

[astrange at ithinksw dot com]

------- Comment #4 from astrange at ithinksw dot com  2009-06-05 04:31 -------
This bug must have been weaker than I remembered it; when I used 4 char fields
instead of one char[4], 4.4 behaved properly too.

How about:
Alexander Strange <astrange@ithinksw.com

        PR tree-optimization/36318
        * gcc.dg/tree-ssa/sra-7.c: New test.

/* { dg-do compile } */
/* { dg-options "-O1 -fdump-tree-sra-details" } */

typedef struct {char f[4];} __attribute__((aligned (4))) s;

void a(s *s1, s *s2)
{
    *s1 = *s2;
}

/* Struct copies should not be split into members */
/* { dg-final { scan-tree-dump "= \\\*s2"  "sra"} } */
/* { dg-final { cleanup-tree-dump "sra" } } */

I checked sra instead of esra since it runs last and this is a negative test.
Hopefully this is trivial?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36318

[Bug tree-optimization/36318] SRA pessimizes struct copies without -Os

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2009-06-05 08:30 -------
Subject: Bug 36318

Author: rguenth
Date: Fri Jun  5 08:30:21 2009
New Revision: 148203

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=148203
Log:
2009-06-05  Alexander Strange <astrange@ithinksw.com>

        PR tree-optimization/36318
        * gcc.dg/tree-ssa/sra-7.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/sra-7.c
Modified:
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36318