[Bug rtl-optimization/53141] New: [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[Bug rtl-optimization/53141] New: [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53141

             Bug #: 53141
           Summary: [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hjl.tools@gmail.com
                CC: areg.melikadamyan@gmail.com, krebbel@gcc.gnu.org,
                    ubizjak@gmail.com


On Linux/ia32, revision 186861

http://gcc.gnu.org/ml/gcc-cvs/2012-04/msg00814.html

caused:

FAIL: gcc.target/i386/bmi2-mulx32-1a.c scan-assembler-times bmi2_umulsidi3_1 1
FAIL: gcc.target/i386/bmi2-mulx32-2a.c scan-assembler-times mulx[ \\t]+[^\n]* 1

[Bug rtl-optimization/53141] [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[krebbel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53141

--- Comment #1 from Andreas Krebbel <krebbel at gcc dot gnu.org> 2012-04-27 14:32:23 UTC ---
That's because reload now will try with swapped operands before going to the
next alternative. So now the first alternative will be used instead of the
second.

This matches the behavior documented in the GCC internal manual:

http://gcc.gnu.org/onlinedocs/gccint/Multi_002dAlternative.html
"If two alternatives need the same amount of copying, the one that
comes first is chosen."

So if the second alternative is preferable then the back-end pattern needs to
be adjusted.

ira:
(insn 9 4 14 2 (parallel [
            (set (reg:DI 65 [ res ])
                (mult:DI (zero_extend:DI (reg/v:SI 64 [ b ]))
                    (zero_extend:DI (reg/v:SI 63 [ a ]))))
            (clobber (reg:CC 17 flags))
        ]) bmi2-mulx32-1.c:24 336 {*umulsidi3_1}
     (expr_list:REG_DEAD (reg/v:SI 64 [ b ])
        (expr_list:REG_DEAD (reg/v:SI 63 [ a ])
            (expr_list:REG_UNUSED (reg:CC 17 flags)
                (nil)))))

reload:
(insn 9 4 17 2 (parallel [
            (set (reg:DI 0 ax [orig:65 res ] [65])
                (mult:DI (zero_extend:DI (reg/v:SI 0 ax [orig:63 a ] [63]))
                    (zero_extend:DI (reg/v:SI 1 dx [orig:64 b ] [64]))))
            (clobber (reg:CC 17 flags))
        ]) bmi2-mulx32-1.c:24 336 {*umulsidi3_1}
     (nil))

back-end pattern:

(define_insn "*umul<mode><dwi>3_1"
  [(set (match_operand:<DWI> 0 "register_operand" "=A,r")
    (mult:<DWI>
      (zero_extend:<DWI>
        (match_operand:DWIH 1 "nonimmediate_operand" "%0,d"))
      (zero_extend:<DWI>
        (match_operand:DWIH 2 "nonimmediate_operand" "rm,rm"))))
   (clobber (reg:CC FLAGS_REG))]

[Bug rtl-optimization/53141] [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[krebbel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53141

--- Comment #2 from Andreas Krebbel <krebbel at gcc dot gnu.org> 2012-04-27 14:47:15 UTC ---
Created attachment 27252
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27252
Patch proposal

This patch should bring back the old behavior.

[Bug target/53141] [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53141

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-04-30
          Component|rtl-optimization            |target
   Target Milestone|---                         |4.8.0
     Ever Confirmed|0                           |1

--- Comment #3 from Uros Bizjak <ubizjak at gmail dot com> 2012-04-30 08:18:41 UTC ---
(In reply to comment #2)
> Created attachment 27252 [details]
> Patch proposal
> 
> This patch should bring back the old behavior.

The patch is OK, please submit it to gcc-patches@ mailing list.

[Bug target/53141] [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[uros at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53141

--- Comment #4 from uros at gcc dot gnu.org 2012-04-30 21:30:13 UTC ---
Author: uros
Date: Mon Apr 30 21:30:06 2012
New Revision: 187000

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=187000
Log:
    PR target/53141
    * config/i386/i386.md (*umul<mode><dwi>3_1): Switch places of
    constraints 0 and 1.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/i386.md

[Bug target/53141] [4.8 Regression] gcc.target/i386/bmi2-mulx32-[12]a.c

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53141

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                URL|                            |http://gcc.gnu.org/ml/gcc-p
                   |                            |atches/2012-04/msg01911.htm
                   |                            |l
         Resolution|                            |FIXED

--- Comment #5 from Uros Bizjak <ubizjak at gmail dot com> 2012-04-30 21:33:08 UTC ---
Fixed in a different way, by simply switching places of constraints.