[Bug c/15869] New: No NOP after LW (with -mips1 -O0)

[Bug c/15869] New: No NOP after LW (with -mips1 -O0)

[niva at niisi dot msk dot ru]

* the complete command line that triggers the bug;

mips64-none-elf-gcc bar.c -v -O0 -G0 -mips1 -mabi=32 -S -v

     * The resultant code works incorrectly because there is no NOP between
       the following commands:

	lw	$2,%lo(lastc.1)($2)
	xor	$2,$3,$2



     * the  preprocessed  file (*.i*) that triggers the bug, generated by
       adding -save-temps to the complete compilation command, or, in the
       case  of  a  bug  report for the GNAT front end, a complete set of
       source files (see below).

void bar (int n, int c)
{
  static int lastn = -1, lastc = -1;

  if (lastn != n)
    {
      if (lastc != lastn)
	abort ();
      lastc = 0;
      lastn = n;
    }

  if (c != (char) (lastc ^ (n << 3)))
    abort ();
  lastc++;
}

     * The resultant assembler code

	.file	1 "bar.c"
	.section .mdebug.abi32
	.previous
	.data
	.align	2
	.type	lastn.0, @object
	.size	lastn.0, 4
lastn.0:
	.word	-1
	.align	2
	.type	lastc.1, @object
	.size	lastc.1, 4
lastc.1:
	.word	-1
	.text
	.align	2
	.globl	bar
	.ent	bar
bar:
	.frame	$fp,24,$31		# vars= 0, regs= 2/0, args= 16, gp= 0
	.mask	0xc0000000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	
	addiu	$sp,$sp,-24
	sw	$31,20($sp)
	sw	$fp,16($sp)
	move	$fp,$sp
	sw	$4,24($fp)
	sw	$5,28($fp)
	lui	$2,%hi(lastn.0)
	lw	$3,%lo(lastn.0)($2)
	lw	$2,24($fp)
	nop
	beq	$3,$2,$L2
	nop

	lui	$2,%hi(lastc.1)
	lui	$3,%hi(lastn.0)
	lw	$4,%lo(lastc.1)($2)
	lw	$2,%lo(lastn.0)($3)
	nop
	beq	$4,$2,$L3
	nop

	jal	abort
	nop

$L3:
	lui	$2,%hi(lastc.1)
	sw	$0,%lo(lastc.1)($2)
	lui	$3,%hi(lastn.0)
	lw	$2,24($fp)
	nop
	sw	$2,%lo(lastn.0)($3)
$L2:
	lw	$2,24($fp)
	nop
	sll	$3,$2,3
	lui	$2,%hi(lastc.1)
	lw	$2,%lo(lastc.1)($2)
	xor	$2,$3,$2
	sll	$3,$2,24
	sra	$3,$3,24
	lw	$2,28($fp)
	nop
	beq	$3,$2,$L4
	nop

	jal	abort
	nop

$L4:
	lui	$3,%hi(lastc.1)
	lui	$2,%hi(lastc.1)
	lw	$2,%lo(lastc.1)($2)
	nop
	addiu	$2,$2,1
	sw	$2,%lo(lastc.1)($3)
	move	$sp,$fp
	lw	$31,20($sp)
	lw	$fp,16($sp)
	addiu	$sp,$sp,24
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	bar

-- 
           Summary: No NOP after LW (with -mips1 -O0)
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: niva at niisi dot msk dot ru
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: mips64-none-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] No NOP after LW (with -mips1 -O0)

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |target


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] No NOP after LW (with -mips1 -O0)

[rsandifo at gcc dot gnu dot org]

------- Additional Comments From rsandifo at gcc dot gnu dot org  2004-06-22 08:18 -------
Confirmed.  Seems to be caused by some no-op moves that get deleted
after machine_dependent_reorg.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rsandifo at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] No NOP after LW (with -mips1 -O0)

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-06-22 21:28 -------
Subject: Bug 15869

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rsandifo@gcc.gnu.org	2004-06-22 21:28:06

Modified files:
	gcc            : ChangeLog 
	gcc/config/mips: mips.c 

Log message:
	PR target/15869
	* config/mips/mips.c (mips_avoid_hazards): Call split_all_insns_noflow.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.4081&r2=2.4082
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/mips/mips.c.diff?cvsroot=gcc&r1=1.418&r2=1.419



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] No NOP after LW (with -mips1 -O0)

[rsandifo at gcc dot gnu dot org]

------- Additional Comments From rsandifo at gcc dot gnu dot org  2004-06-22 21:32 -------
Patch applied to HEAD:

    http://gcc.gnu.org/ml/gcc-patches/2004-06/msg01798.html

CC'ing Mark since this is a 3.4 regression.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmitchel at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
      Known to fail|                            |3.4.0
      Known to work|                            |3.3.3 3.5.0
            Summary|No NOP after LW (with -mips1|[3.4 Regression] No NOP
                   |-O0)                        |after LW (with -mips1 -O0)
   Target Milestone|---                         |3.4.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[rsandifo at gcc dot gnu dot org]

------- Additional Comments From rsandifo at gcc dot gnu dot org  2004-06-23 06:46 -------
Adding a target milestone of 3.4.2 is probably just a formality,
and I seem to remember only Mark can set it to 3.4.1, but for
avoidance of doubt...I'd really like to see this go into 3.4.1
if possible.  It's entirely contained within the MIPS backend,
so there should be no risk to other targets.  And I think the
patch is low risk for MIPS too.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-06-23 06:55 -------
I think this one needs a bit more testing; apply it after 3.4.1 is out.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[rsandifo at redhat dot com]

------- Additional Comments From rsandifo at redhat dot com  2004-06-23 07:05 -------
Subject: Re:  [3.4 Regression] No NOP after LW (with
 -mips1 -O0)

"mmitchel at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:
> ------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-06-23 06:55 -------
> I think this one needs a bit more testing; apply it after 3.4.1 is out.

Sorry to be pushy, but from whom?  I don't think anyone other than me &
David Billinghurst are testing CVS sources at the moment.

If you're thinking about Maciej's offer to test on r3000 h/w: well,
that's going to be useful to see if there are more cases we're missing.
But it's easy to verify (by looking at assembler sources) that the
instance reported in the PR has been fixed.  And knowing the code
(and having written it myself ;) I don't think it can introduce
_more_ problems of the same kind.

Could I ask you to reconsider?  (Don't worry, if you say no, I won't
ask again.)

Richard


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[mark at codesourcery dot com]

------- Additional Comments From mark at codesourcery dot com  2004-06-23 15:54 -------
Subject: Re:  [3.4 Regression] No NOP after LW (with -mips1
 -O0)

rsandifo at redhat dot com wrote:

>------- Additional Comments From rsandifo at redhat dot com  2004-06-23 07:05 -------
>Subject: Re:  [3.4 Regression] No NOP after LW (with
> -mips1 -O0)
>
>"mmitchel at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:
>  
>
>>------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-06-23 06:55 -------
>>I think this one needs a bit more testing; apply it after 3.4.1 is out.
>>    
>>
>
>Sorry to be pushy, but from whom?  I don't think anyone other than me &
>David Billinghurst are testing CVS sources at the moment.
>  
>
 From whomever is using the MIPS toolchains, in general. :-)

Since this is on the mainline, people will be banging away on it, and if 
there are problems, they'll likely find them.

These things are judgement calls -- it's always hard to justify them 
precisely one way or the other.  My instincts with this patch are a 
little different from yours; I feel like it might cause problems, not 
because it's wrong per se, but because it might trigger some other 
weirdness.  If it had gone in a month ago, I'd feel different.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[rsandifo at redhat dot com]

------- Additional Comments From rsandifo at redhat dot com  2004-06-23 16:38 -------
Subject: Re:  [3.4 Regression] No NOP after LW (with
 -mips1 -O0)

"mark at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org> writes:
> These things are judgement calls -- it's always hard to justify them 
> precisely one way or the other.  My instincts with this patch are a 
> little different from yours; I feel like it might cause problems, not 
> because it's wrong per se, but because it might trigger some other 
> weirdness.  If it had gone in a month ago, I'd feel different.

Fair enough ;)  3.4.2 it is.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-07-07 06:28 -------
Subject: Bug 15869

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	rsandifo@gcc.gnu.org	2004-07-07 06:28:20

Modified files:
	gcc            : ChangeLog 
	gcc/config/mips: mips.c 

Log message:
	PR target/15869
	* config/mips/mips.c (mips_avoid_hazards): Call split_all_insns_noflow.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.533&r2=2.2326.2.534
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/mips/mips.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.362.4.13&r2=1.362.4.14



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869

[Bug target/15869] [3.4 Regression] No NOP after LW (with -mips1 -O0)

[rsandifo at gcc dot gnu dot org]

------- Additional Comments From rsandifo at gcc dot gnu dot org  2004-07-07 06:33 -------
Fixed for 3.4.2.


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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15869