[Bug tree-optimization/20204] New: [4.0 regression] miscompilation of asm-declared registers

[Bug tree-optimization/20204] New: [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

Between LAST_UPDATED: "Thu Feb 24 08:05:18 UTC 2005"
and "Thu Feb 24 14:59:24 UTC 2005" I see lots of testsuite regressions.
For GCC, they are (as per Mike Stump's script): 

Tests that now fail, but worked before:

21_strings/basic_string/insert/char/2.cc execution test
21_strings/basic_string/replace/char/3.cc execution test
22_locale/money_get/get/char/14.cc execution test
22_locale/money_get/get/char/6.cc execution test
23_containers/vector/check_construct_destroy.cc execution test
23_containers/vector/invalidation/3.cc execution test
25_algorithms/sort.cc execution test

Tests that now fail, but worked before:

gcc.c-torture/execute/20010124-1.c execution,  -O0
gcc.c-torture/execute/20010124-1.c execution,  -O1
gcc.c-torture/execute/20010124-1.c execution,  -O2
gcc.c-torture/execute/20010124-1.c execution,  -Os

(also failures in newlib sanity tests).
It seems that the cause is that memmove is miscompiled.
Here's a slightly minimized test-case.  Note the use of asm-declared registers:
void *x (void *pdst, const void *psrc, unsigned int pn)
{
  register void *return_dst __asm__ ("r10") = pdst;
  register unsigned char *dst __asm__ ("r13") = pdst;
  register unsigned const char *src __asm__ ("r11") = psrc;
  register int n __asm__ ("r12") = pn;

  if (src < dst && dst < src + n)
    {
      src += n;
      dst += n;
      while (n--)
        *--dst = *--src;
      return return_dst;
    }

  while (n >= 16) n--;

  return return_dst;
}
extern void abort ();
extern void exit (int);
char xx[30] = "abc";
int main (void)
{
  char yy[30] = "aab";

  if (x (xx + 1, xx, 2) != xx + 1 || memcmp (xx, yy, sizeof (yy)) != 0)
    abort ();
  exit (0);
}

The moving while-loop results in this code (pruned;
assembly syntax should be understandable enough knowing that
destinations are to the right):
_x:
        cmp.d $r11,$r10
        bls .L2
        nop
        add.d $r12,$r11
        cmp.d $r11,$r10
        blo .L14
        move.d $r10,$r9

.L2:
        cmpq 15,$r12
        ble .L17
        clear.d $r9

        subq 15,$r12
        addq 1,$r9
.L16:
        cmp.d $r9,$r12
        bne .L16
        addq 1,$r9

.L17:
        ret
        nop
.L14:
        test.d $r12
        beq .L17
        add.d $r12,$r9

.L10:
        subq 1,$r9
        subq 1,$r11
        move.b [$r11],$r13
        cmpq 1,$r12
        beq .L17
        move.b $r13,[$r9]

        subq 1,$r9
        subq 1,$r11
        move.b [$r11],$r13
        cmpq 1,$r12
        bne .L10
        move.b $r13,[$r9]

        ba .L17
        nop
        .size   _x, .-_x

Note the absence of update of R12.

-- 
           Summary: [4.0 regression] miscompilation of asm-declared
                    registers
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: critical
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hp at gcc dot gnu dot org
                CC: dnovillo at gcc dot gnu dot org,gcc-bugs at gcc dot gnu
                    dot org
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: cris-axis-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 01:00 -------
I also forgot to mention that this was observed with -O2.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 00:59 -------
I forgot to mention that this is the only suspect patch in this time-frame:

+ 2005-02-24  Diego Novillo  <dnovillo@redhat.com>
+
+       * tree-into-ssa.c: Re-organize internal functions.
+
+

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[dnovillo at redhat dot com]

------- Additional Comments From dnovillo at redhat dot com  2005-02-25 01:05 -------
Subject: Re:  [4.0 regression] miscompilation
 of asm-declared registers

hp at gcc dot gnu dot org wrote:
> ------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 00:59 -------
> I forgot to mention that this is the only suspect patch in this time-frame:
> 
> + 2005-02-24  Diego Novillo  <dnovillo@redhat.com>
> +
> +       * tree-into-ssa.c: Re-organize internal functions.
> +
> +
> 
I find this very hard to believe.  The only thing this patch did is move 
  text around the file.  It added no code and removed no code.


Diego.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 01:12 -------
Well, I can't follow the code, but here are all the gcc changes in that
time-frame:

diff -p -c -r2.7576 -r2.7578
*** ChangeLog   24 Feb 2005 01:54:58 -0000      2.7576
--- ChangeLog   24 Feb 2005 14:17:25 -0000      2.7578
***************
*** 1,3 ****
--- 1,19 ----
+ 2005-02-24  Diego Novillo  <dnovillo@redhat.com>
+
+       * tree-into-ssa.c: Re-organize internal functions.
+
+ 2005-02-24  Richard Henderson  <rth@redhat.com>
+
+       PR middle-end/18902
+       * c-opts.c (c_common_post_options): Set flag_complex_method to 2
+       for c99.
+       * common.opt (fcx-limited-range): New.
+       * opts.c (set_fast_math_flags): Set flag_cx_limited_range.
+       * toplev.c (flag_complex_method): Initialize to 1.
+       (process_options): Set flag_complex_method to 0 if
+       flag_cx_limited_range.
+       * doc/invoke.texi (-fcx-limited-range): New.
+
  2005-02-24  Kazu Hirata  <kazu@cs.umass.edu>

        * cse.c (delete_trivially_dead_insns): Speed up by using

I can certainly understand that a typo changed some assigmnent such that
asm-declared registers are mishandled.  Pretty please.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[dnovillo at redhat dot com]

------- Additional Comments From dnovillo at redhat dot com  2005-02-25 01:21 -------
Subject: Re:  [4.0 regression] miscompilation
 of asm-declared registers

hp at gcc dot gnu dot org wrote:

> I can certainly understand that a typo changed some assigmnent such that
> asm-declared registers are mishandled.  Pretty please.
> 
I've had this patch in TCB for over 3 weeks now, but don't worry, I'll 
take a peek tomorrow.


Diego.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[dnovillo at gcc dot gnu dot org]

------- Additional Comments From dnovillo at gcc dot gnu dot org  2005-02-25 13:31 -------

Could you show me how to configure a cris-axis-elf target and build a simulator?  
Have you tried undoing the tree-into-ssa.c change?  It should be easy with:

$ cvs up -r 2.40 tree-into-ssa.c

If there had been a bug in the tree-into-ssa.c changes we would be seeing
widespread carnage on every target.  And that is just not the case:

http://gcc.gnu.org/ml/gcc-testresults/2005-02/msg01103.html
http://gcc.gnu.org/ml/gcc-testresults/2005-02/msg01100.html
http://gcc.gnu.org/ml/gcc-testresults/2005-02/msg01101.html

Diego.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 15:35 -------
In response to comment #6:
Building a CRIS toolchain with simulator (but see further below):
The general steps are exactly as any other simulator target,
follow <URL:http://gcc.gnu.org/simtest-howto.html>, though you need
the cris-sim.exp as per
<URL:http://gcc.gnu.org/ml/gcc-bugs/2005-02/msg00138.html>
(now in dejagnu CVS; not on sourceware).  Because the baseboard file
is not in the installed dir, special steps are necessary:
"mkdir ~/dejagnuboards"
Put cris-sim.exp in ~/dejagnurc
"echo 'set boards_dir ~/dejagnuboards' > ~/.dejagnurc"
Then proceed as per simtest-howto.html

But you actually just need to build cc1 and observe the assembly I posted.

And again, I think I need to point out that a bug in handling of
*asm-declared registers* is unlikely to show "widespread carnage".
But I certainly see how it can be overlooked and broken in tree-ssa
cleanup operations!

I have not tried reverting the patch but will do later, hoping it can
convince you that the "reorganization" caused this regression (whether
directly or indirectly exposing bugs elsewhere).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 15:59 -------
I was lucky enough to have a source tree from just before the suspected change
in the machine where I test using geoffk's script.  (It's a RH9 machine as
opposed to FC2, so thus we can supposedly also rule out miscompilation by the
host gcc.)  I have updated just the suspected change.  Test in progress.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2005-02-25 16:05 -------
I've confirmed on this other machine that the update caused the same breakage.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-02-25 16:05:49
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0 regression] miscompilation of asm-declared registers

[dnovillo at gcc dot gnu dot org]

------- Additional Comments From dnovillo at gcc dot gnu dot org  2005-02-25 16:48 -------
(In reply to comment #9)
> I've confirmed on this other machine that the update caused the same breakage.
> 
Ah, yes.  I see it now.  The reorg tickled a bug in the renamer:

# n_21 = V_MUST_DEF <n_18>
n = D.1158_28
...
n_48 = PHI <n_37, n21>
<L2>:
...
# VUSE <n_21>
n.5_40 = n;


That's wrong.  The last VUSE should be VUSE <n_48>.  Virtual operands should
always be in FUD-chain form.

Working on a fix.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dnovillo at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0/4.1 regression] miscompilation of asm-declared registers

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-02-25 21:10 -------
Subject: Bug 20204

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-4_0-branch
Changes by:	dnovillo@gcc.gnu.org	2005-02-25 21:10:30

Modified files:
	gcc            : ChangeLog tree-into-ssa.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.dg: pr20204.c 

Log message:
	PR tree-optimization/20204
	* tree-into-ssa.c (insert_phi_nodes_for): Do not use
	REWRITE_THIS_STMT markers on PHI nodes.
	(rewrite_initialize_block): Likewise.
	
	testsuite/ChangeLog
	
	PR tree-optimization/20204
	* testsuite/gcc.dg/pr20204.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=2.7592.2.2&r2=2.7592.2.3
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-into-ssa.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=2.41&r2=2.41.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.5084&r2=1.5084.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/pr20204.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=NONE&r2=1.1.2.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0/4.1 regression] miscompilation of asm-declared registers

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-02-25 21:12 -------
Subject: Bug 20204

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	dnovillo@gcc.gnu.org	2005-02-25 21:12:34

Modified files:
	gcc            : ChangeLog tree-into-ssa.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.dg: pr20204.c 

Log message:
	PR tree-optimization/20204
	* tree-into-ssa.c (insert_phi_nodes_for): Do not use
	REWRITE_THIS_STMT markers on PHI nodes.
	(rewrite_initialize_block): Likewise.
	
	testsuite/ChangeLog
	
	PR tree-optimization/20204
	* testsuite/gcc.dg/pr20204.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.7596&r2=2.7597
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-into-ssa.c.diff?cvsroot=gcc&r1=2.41&r2=2.42
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.5084&r2=1.5085
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/pr20204.c.diff?cvsroot=gcc&r1=1.1&r2=1.2



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0/4.1 regression] miscompilation of asm-declared registers

[dnovillo at gcc dot gnu dot org]

------- Additional Comments From dnovillo at gcc dot gnu dot org  2005-02-25 21:18 -------
Fixed.  http://gcc.gnu.org/ml/gcc-patches/2005-02/msg01625.html

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0/4.1 regression] miscompilation of asm-declared registers

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204

[Bug tree-optimization/20204] [4.0/4.1 regression] miscompilation of asm-declared registers

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.0                       |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20204