[Bug tree-optimization/54295] New: [4.7 regression] Widening multiply-accumulate operation uses wrong value extension

[Bug tree-optimization/54295] New: [4.7 regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

             Bug #: 54295
           Summary: [4.7 regression] Widening multiply-accumulate
                    operation uses wrong value extension
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rearnsha@gcc.gnu.org
            Target: arm aarch64


A widening multiply-accumulate operation can generate an incorrect result if
there are casts in expression.

Compile the attached test-case on ARM at -O2, the result is:

$./a.out 
<aborted>

Correct result, as seen at -O1 is

$./a.out
$

[Bug tree-optimization/54295] [4.7 regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

--- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-08-17 12:47:35 UTC ---
Created attachment 28042
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28042
Testcase

[Bug tree-optimization/54295] [4.7 regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

--- Comment #2 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-08-17 12:50:32 UTC ---
Testing a fix

[Bug tree-optimization/54295] [4.7/4.8 regression] Widening multiply-accumulate operation uses wrong value extension

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.2
            Summary|[4.7 regression] Widening   |[4.7/4.8 regression]
                   |multiply-accumulate         |Widening
                   |operation uses wrong value  |multiply-accumulate
                   |extension                   |operation uses wrong value
                   |                            |extension

[Bug tree-optimization/54295] [4.7/4.8 regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

--- Comment #3 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-08-20 12:49:55 UTC ---
Author: rearnsha
Date: Mon Aug 20 12:49:47 2012
New Revision: 190533

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=190533
Log:
    PR tree-ssa/54295
    * tree-ssa-math-opts.c (widening_mult_conversion_strippable_p):
    New function.
    (is_widening_mult_rhs_p): Use it.

    * gcc.c-torture/execute/20120817-1.c: New test.


Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/20120817-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-math-opts.c

[Bug tree-optimization/54295] [4.7/4.8 regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

--- Comment #4 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-08-20 14:13:40 UTC ---
Author: rearnsha
Date: Mon Aug 20 14:13:16 2012
New Revision: 190534

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=190534
Log:
    PR tree-ssa/54295
    * tree-ssa-math-opts.c (is_widening_mult_rhs_p): Delete rhs_code
    declaration and setter.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-ssa-math-opts.c

[Bug tree-optimization/54295] [4.7/4.8 regression] Widening multiply-accumulate operation uses wrong value extension

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-09-04
                 CC|                            |ramana at gcc dot gnu.org
     Ever Confirmed|0                           |1

[Bug tree-optimization/54295] [4.7 Regression] Widening multiply-accumulate operation uses wrong value extension

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
            Summary|[4.7/4.8 regression]        |[4.7 Regression] Widening
                   |Widening                    |multiply-accumulate
                   |multiply-accumulate         |operation uses wrong value
                   |operation uses wrong value  |extension
                   |extension                   |

--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-09-07 10:31:13 UTC ---
Fixed on trunk sofar.

[Bug tree-optimization/54295] [4.7 Regression] Widening multiply-accumulate operation uses wrong value extension

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

--- Comment #6 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-09-07 10:37:12 UTC ---
Author: rearnsha
Date: Fri Sep  7 10:37:08 2012
New Revision: 191066

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=191066
Log:
    PR tree-ssa/54295
    * tree-ssa-math-opts.c (widening_mult_conversion_strippable_p):
    Sign-extension of a zero-extended value can be simplified to
    just zero-extension.

testsuite:
    * gcc.target/arm/pr50318-1.c: Scan for smlal.
    * gcc.target/arm/smlaltb-1.c: XFAIL test.
    * gcc.target/arm/smlaltt-1.c: Likewise.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.target/arm/pr50318-1.c
    trunk/gcc/testsuite/gcc.target/arm/smlaltb-1.c
    trunk/gcc/testsuite/gcc.target/arm/smlaltt-1.c
    trunk/gcc/tree-ssa-math-opts.c

[Bug tree-optimization/54295] [4.7 Regression] Widening multiply-accumulate operation uses wrong value extension

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.2                       |4.7.3

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-20 10:14:21 UTC ---
GCC 4.7.2 has been released.

[Bug tree-optimization/54295] [4.7 Regression] Widening multiply-accumulate operation uses wrong value extension

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.3                       |4.7.4

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-11 07:59:05 UTC ---
GCC 4.7.3 is being released, adjusting target milestone.

[Bug tree-optimization/54295] [4.7 Regression] Widening multiply-accumulate operation uses wrong value extension

[jogo at openwrt dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Jonas Gorski <jogo at openwrt dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jogo at openwrt dot org

--- Comment #9 from Jonas Gorski <jogo at openwrt dot org> 2013-04-29 12:56:23 UTC ---
I want to confirm that this is still an issue in 4.7.3, also applies to at
least mips32 (did not test mips64) and causes miscompilations in the linux
kernel there.

[Bug tree-optimization/54295] [4.7 Regression] Widening multiply-accumulate operation uses wrong value extension

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54295

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
      Known to work|                            |4.8.0
         Resolution|---                         |FIXED
   Target Milestone|4.7.4                       |4.8.0

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for 4.8.0.