[Bug target/35258] two memcpy calls merged incorrectly with -O1

[krebbel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258

Andreas Krebbel krebbel at gcc dot gnu.org changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution||FIXED

--- Comment #7 from Andreas Krebbel krebbel at gcc dot gnu.org 2010-12-02 
09:41:57 UTC ---
Fixed.

[Bug target/35258] two memcpy calls merged incorrectly with -O1

[krebbel at gcc dot gnu dot org]

--- Comment #6 from krebbel at gcc dot gnu dot org  2008-02-25 15:08 ---
Subject: Bug 35258

Author: krebbel
Date: Mon Feb 25 15:07:17 2008
New Revision: 132628

URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=132628
Log:
2008-02-25  Andreas Krebbel  [EMAIL PROTECTED]

PR target/35258
* cse.c (cse_insn): Avoid creation of overlapping MEMs.
* alias.c (nonoverlapping_memrefs_p): Export for use in other modules.
* alias.h (nonoverlapping_memrefs_p): Likewise.

2008-02-25  Andreas Krebbel  [EMAIL PROTECTED]

PR target/35258
* gcc.dg/pr35258.c: New testcase.


Added:
trunk/gcc/testsuite/gcc.dg/pr35258.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/alias.c
trunk/gcc/alias.h
trunk/gcc/cse.c
trunk/gcc/testsuite/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258

[Bug target/35258] two memcpy calls merged incorrectly with -O1

[rguenth at gcc dot gnu dot org]

--- Comment #3 from rguenth at gcc dot gnu dot org  2008-02-20 09:43 ---
This would be an executable testcase:

extern void *memcpy (void *, const void *,  __SIZE_TYPE__);
extern int memcmp(const void *s1, const void *s2, __SIZE_TYPE__ n);
extern void abort(void);

char string1[9] = 1234;
char string2[9] = 1234;

void
bar (void)
{
  unsigned int temp;
  char *p = string1[2];

  memcpy (temp, string1[1], 4);
  memcpy (p, temp, 4);
  string1[1] = '.';
}

int main()
{
  bar();
  if (memcmp (string1, 1.234, 5) != 0)
abort ();
  return 0;
}

which I can confirm aborts on s390 but not x86_64.  bar looks like

bar:
.LFB2:
st  %r15,60(%r15)
.LCFI0:
larl%r5,.L3
ahi %r15,-104
.LCFI1:
larl%r1,string1+2
l   %r2,.L4-.L3(%r5)
mvc 0(4,%r1),0(%r2)
larl%r1,string1
mvi 1(%r1),46
l   %r15,164(%r15)
br  %r14


-- 

rguenth at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Keywords||wrong-code
   Last reconfirmed|-00-00 00:00:00 |2008-02-20 09:43:54
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258

[Bug target/35258] two memcpy calls merged incorrectly with -O1

[rguenth at gcc dot gnu dot org]

--- Comment #4 from rguenth at gcc dot gnu dot org  2008-02-20 09:52 ---
Actually the asm looks correct.  mvc is a memmove operation, moving 4 bytes
from string1+1 to string1+2.


-- 

rguenth at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||krebbel at gcc dot gnu dot
   ||org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258

[Bug target/35258] two memcpy calls merged incorrectly with -O1

[krebbel at gcc dot gnu dot org]

--- Comment #5 from krebbel at gcc dot gnu dot org  2008-02-20 12:59 ---
The assembler code is broken. In case of an overlap mvc copies one byte at a
time and continuing with the next after the first has been written. That's how
we use mvc for memsets.

The mvcs are merged by the dead store elimination pass. I'll try to understand
were it slips through the tests in dse and/or cse.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258

[Bug target/35258] two memcpy calls merged incorrectly with -O1

[janis at gcc dot gnu dot org]

--- Comment #1 from janis at gcc dot gnu dot org  2008-02-20 02:02 ---
Created an attachment (id=15185)
 -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15185action=view)
test case


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258

[Bug target/35258] two memcpy calls merged incorrectly with -O1

[pinskia at gcc dot gnu dot org]

--- Comment #2 from pinskia at gcc dot gnu dot org  2008-02-20 02:08 ---
Hmm, temp refers to the pointer to the array.

What happens if you use temp instead of temp?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35258