[Bug rtl-optimization/44404] New: auto-inc-dec generates an invalid assembly instruction

[Bug rtl-optimization/44404] New: auto-inc-dec generates an invalid assembly instruction

[kazu at gcc dot gnu dot org]

Consider:

char buf[128];

extern void bar (int a, const char *p);
extern char *strcpy (char *, const char *);

void
foo (int a)
{
  if (a)
    bar (0, buf);
  strcpy (buf, "0123456789abcdefghijklmnopqrstuvwxyz");
  bar (0, buf);
}

Compile this testcase with arm-none-linux-gnueabi-4.4.

strcpy above is inlined and unrolled like so:

        ldmia   r4!, {r0, r1, r2, r3}
        stmia   ip!, {r0, r1, r2, r3}
        ldmia   r4!, {r0, r1, r2, r3}
        stmia   ip!, {r0, r1, r2, r3}
        ldmia   r4, {r0, r1}
        str     r0, [ip], #4
        mov     r1, ip
        strb    r1, [r1], #-36

Notice that the last instruction looks strange.  R1 immediately after
the last ldmia contains the last character, namely the null
terminator, but that gets destroyed in "mov r1, ip".  Then strb
attempts to write r1 to the memory location pointed to by r1, which
doesn't make sense.

The last instruction comes from auto-inc-dec.c.

I've got a patch in testing.


-- 
           Summary: auto-inc-dec generates an invalid assembly instruction
           Product: gcc
           Version: 4.4.4
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: kazu at gcc dot gnu dot org
        ReportedBy: kazu at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: arm-none-linux-gnueabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2010-06-03 17:27 -------
Looks related to PR 20972.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[kazu at gcc dot gnu dot org]

------- Comment #2 from kazu at gcc dot gnu dot org  2010-06-03 18:18 -------
Andrew,

auto-inc-dec.c was introduced on Jul 2, 2006, and PR 20972 was filed
on April 12, 2005, so I'd think that PR 20972 is due to something
else.  They do both involve the same assembler message though.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2010-06-03 18:25 -------
(In reply to comment #2)
> auto-inc-dec.c was introduced on Jul 2, 2006, and PR 20972 was filed
> on April 12, 2005, so I'd think that PR 20972 is due to something
> else.  They do both involve the same assembler message though.

Yes but if you read that PR you will notice that auto-inc-dec.c included some
of the same issues as flow did.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[kazu at gcc dot gnu dot org]

------- Comment #4 from kazu at gcc dot gnu dot org  2010-06-07 11:35 -------
Posted a patch.


-- 

kazu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |http://gcc.gnu.org/ml/gcc-
                   |                            |patches/2010-
                   |                            |06/msg00514.html


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[kazu at gcc dot gnu dot org]

------- Comment #5 from kazu at gcc dot gnu dot org  2010-06-07 13:12 -------
Subject: Bug 44404

Author: kazu
Date: Mon Jun  7 13:12:42 2010
New Revision: 160372

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=160372
Log:
gcc/
        PR rtl-optimization/44404
        * auto-inc-dec.c (find_inc): Use reg_overlap_mentioned_p instead
        of count_occurrences to see if it's safe to modify mem_insn.insn.
        gcc/testsuite/

gcc/testsuite/
        PR rtl-optimization/44404
        * gcc.dg/pr44404.c: New.

Added:
    trunk/gcc/testsuite/gcc.dg/pr44404.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/auto-inc-dec.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[kazu at gcc dot gnu dot org]

------- Comment #6 from kazu at gcc dot gnu dot org  2010-06-07 13:15 -------
Fixed.


-- 

kazu at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[kazu at gcc dot gnu dot org]

------- Comment #7 from kazu at gcc dot gnu dot org  2010-06-07 13:17 -------
Subject: Bug 44404

Author: kazu
Date: Mon Jun  7 13:17:32 2010
New Revision: 160374

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=160374
Log:
gcc/
        PR rtl-optimization/44404
        * auto-inc-dec.c (find_inc): Use reg_overlap_mentioned_p instead
        of count_occurrences to see if it's safe to modify mem_insn.insn.
        gcc/testsuite/

gcc/testsuite/
        PR rtl-optimization/44404
        * gcc.dg/pr44404.c: New.

Modified:
    trunk/gcc/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[bernds at gcc dot gnu dot org]

------- Comment #8 from bernds at gcc dot gnu dot org  2010-07-07 15:27 -------
Subject: Bug 44404

Author: bernds
Date: Wed Jul  7 15:26:48 2010
New Revision: 161920

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=161920
Log:
        PR rtl-optimization/44404
        * auto-inc-dec.c (find_inc): Avoid calling count_occurrences if
        possible, use reg_overlap_mentioned_p instead.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/auto-inc-dec.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

[Bug rtl-optimization/44404] auto-inc-dec generates an invalid assembly instruction

[cbaylis at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44404

cbaylis at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gilles.chanteperdrix@xenoma
                   |                            |i.org

--- Comment #9 from cbaylis at gcc dot gnu.org ---
*** Bug 38674 has been marked as a duplicate of this bug. ***