[Bug middle-end/45739] New: [missed optimization] static evaluation of SSE intrinsics (pxor)

[Bug middle-end/45739] New: [missed optimization] static evaluation of SSE intrinsics (pxor)

[kretz at kde dot org]

Testcase:
#include <emmintrin.h>
__m128i foo;
int main()
{
    foo = _mm_xor_si128(_mm_setzero_si128(), foo);
    return 0;
}

Resulting Assembly (with -O3):
pxor    %xmm0, %xmm0
xorl    %eax, %eax
pxor    foo(%rip), %xmm0
movdqa  %xmm0, foo(%rip)
ret

Expected Result:
since any value xor zero does not change the value the static evaluation step
of GCC should eliminate the pxor instruction altogether.

Likewise the call to _mm_xor_si128 on two constants should be statically
evaluated and if the destination register would not change the call should be
eliminated.

Rationale:
a) of course removing unnecessary code is always nice
b) the implementation of correct unsigned integer compare can be done with pxor
and 0x80000000. All unsigned compares against constant values can thus be
improved.


-- 
           Summary: [missed optimization] static evaluation of SSE
                    intrinsics (pxor)
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kretz at kde dot org
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug target/45739] static evaluation of SSE intrinsics (pxor)

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2010-09-21 10:25 -------
Confirmed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
          Component|middle-end                  |target
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2010-09-21 10:25:16
               date|                            |
            Summary|[missed optimization] static|static evaluation of SSE
                   |evaluation of SSE intrinsics|intrinsics (pxor)
                   |(pxor)                      |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug target/45739] static evaluation of SSE intrinsics (pxor)

[jakub at gcc dot gnu dot org]

-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2010-09-21 10:25:16         |2010-09-21 11:27:37
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug rtl-optimization/45739] static evaluation of SSE intrinsics (pxor)

[jakub at gcc dot gnu dot org]

------- Comment #2 from jakub at gcc dot gnu dot org  2010-09-21 12:23 -------
Created an attachment (id=21856)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21856&action=view)
gcc46-pr45739.patch

Fix.  For further optimizations (like vector A | ~0, A | ~A, A ^ ~0, A & ~0), I
guess we'd need something like CONST_ALL_ONES_RTX (mode) and sharing that in
const_tiny_rtx.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug rtl-optimization/45739] static evaluation of SSE intrinsics (pxor)

[jakub at gcc dot gnu dot org]

------- Comment #3 from jakub at gcc dot gnu dot org  2010-09-21 23:33 -------
Subject: Bug 45739

Author: jakub
Date: Tue Sep 21 23:33:01 2010
New Revision: 164501

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=164501
Log:
        PR rtl-optimization/45739
        * simplify-rtx.c (simplify_binary_operation_1): Optimize even
        vector mode | CONST0_RTX (mode) and ^ CONST0_RTX (mode).

        * gcc.target/i386/pr45739.c: New test.

Added:
    trunk/gcc/testsuite/gcc.target/i386/pr45739.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/simplify-rtx.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug rtl-optimization/45739] static evaluation of SSE intrinsics (pxor)

[jakub at gcc dot gnu dot org]

------- Comment #4 from jakub at gcc dot gnu dot org  2010-09-22 00:06 -------
Fixed.


-- 

jakub at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug rtl-optimization/45739] static evaluation of SSE intrinsics (pxor)

[howarth at nitro dot med dot uc dot edu]

------- Comment #5 from howarth at nitro dot med dot uc dot edu  2010-09-22 02:56 -------
(In reply to comment #4)
> Fixed.
> 

The new trunk/gcc/testsuite/gcc.target/i386/pr45739.c erroneously fails on
x86_64-apple-darwin10 as ...

FAIL: gcc.target/i386/pr45739.c scan-assembler-not por

since it is matching...

        .section
__TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support

Adding...

/* { dg-prune-output ".*live_support*" } */

to gcc.target/i386/pr45739.c solves this issue.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug rtl-optimization/45739] static evaluation of SSE intrinsics (pxor)

[howarth at nitro dot med dot uc dot edu]

------- Comment #6 from howarth at nitro dot med dot uc dot edu  2010-09-22 03:10 -------
My mistake... dg-prune-output is insufficient to prevent scan-assembler-not
from accidentally matching on live_support in the intel darwin assembly.


-- 

howarth at nitro dot med dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at redhat dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739

[Bug rtl-optimization/45739] static evaluation of SSE intrinsics (pxor)

[jakub at gcc dot gnu dot org]

------- Comment #7 from jakub at gcc dot gnu dot org  2010-09-22 08:57 -------
Subject: Bug 45739

Author: jakub
Date: Wed Sep 22 08:57:38 2010
New Revision: 164516

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=164516
Log:
        PR rtl-optimization/45739
        * gcc.target/i386/pr45739.c: Tighten up scan-assembler-not
        regexps.

Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.target/i386/pr45739.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45739