[Bug middle-end/24929] long long shift/mask operations should be better optimized

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.3.0
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED
           Keywords|                            |missed-optimization

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed a long time ago.

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[aldot at gcc dot gnu dot org]

------- Comment #7 from aldot at gcc dot gnu dot org  2009-06-04 18:18 -------
(In reply to comment #5)

>         movzbl  18(%esp), %eax
> 
> could be used in this particular case.

4.3.3 onward seem to do that. Fixed?

$ for i in 4.2 4.3 4.4 4.5.orig-HEAD;do printf "### %s\n" $(gcc-$i
-dumpversion) ; gcc-$i -march=i386 -O2 -S -o- pr24929.c -fomit-frame-pointer |
awk 'BEGIN{yep=0;}/^f:/{yep=1;}/^\./{yep=0;}{if (yep){print $0}}';done
### 4.2.4
f:
        pushl   %edi
        pushl   %esi
        pushl   %ebx
        movl    16(%esp), %esi
        movl    20(%esp), %edi
        movl    24(%esp), %ecx
        movl    28(%esp), %ebx
        movl    %ebx, %ecx
        xorl    %ebx, %ebx
        shrl    $16, %ecx
        movzbl  %cl,%eax
        xorl    %edx, %edx
        shldl   $8, %esi, %edi
        sall    $8, %esi
        orl     %esi, %eax
        orl     %edi, %edx
        popl    %ebx
        popl    %esi
        popl    %edi
        ret
        .size   f, .-f
        .p2align 2,,3
### 4.3.3
f:
        movl    4(%esp), %edx
        movl    8(%esp), %ecx
        shldl   $8, %edx, %ecx
        sall    $8, %edx
        movzbl  18(%esp), %eax
        orl     %edx, %eax
        movl    %ecx, %edx
        ret
        .size   f, .-f
        .p2align 2,,3
### 4.4.0
f:
        movl    4(%esp), %edx
        movl    8(%esp), %ecx
        shldl   $8, %edx, %ecx
        sall    $8, %edx
        movzbl  18(%esp), %eax
        orl     %edx, %eax
        movl    %ecx, %edx
        ret
        .size   f, .-f
        .p2align 2,,3
### 4.5.0
f:
        movl    4(%esp), %edx
        movl    8(%esp), %ecx
        shldl   $8, %edx, %ecx
        sall    $8, %edx
        movzbl  18(%esp), %eax
        orl     %edx, %eax
        movl    %ecx, %edx
        ret
        .size   f, .-f
        .p2align 2,,3


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[steven at gcc dot gnu dot org]

------- Comment #6 from steven at gcc dot gnu dot org  2006-09-20 22:19 -------
*** Bug 28405 has been marked as a duplicate of this bug. ***


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vda dot linux at googlemail
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[uros at kss-loka dot si]

------- Comment #5 from uros at kss-loka dot si  2006-06-27 10:12 -------
(In reply to comment #4)

> which may be optimal.

        movzbl  18(%esp), %eax

could be used in this particular case.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[ian at airs dot com]

------- Comment #4 from ian at airs dot com  2006-06-27 06:05 -------
With my current version of the lower-subreg patch, I get this with -O2
-momit-leaf-frame-pointer:

f:
        movl    16(%esp), %eax
        movl    4(%esp), %ecx
        movl    8(%esp), %edx
        shrl    $16, %eax
        andl    $255, %eax
        shldl   $8, %ecx, %edx
        sall    $8, %ecx
        orl     %ecx, %eax
        ret

which may be optimal.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-02-02 18:16 -------
Confirmed.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-02-02 18:16:13
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[ian at airs dot com]

------- Comment #2 from ian at airs dot com  2006-02-02 18:14 -------
With an updated version of RTH's subreg lowering pass, I get this instruction
sequence:

f:
        movl    16(%esp), %eax
        movl    4(%esp), %edx
        movl    8(%esp), %ecx
        shrl    $16, %eax
        andl    $255, %eax
        shldl   $8, %edx, %ecx
        sall    $8, %edx
        orl     %edx, %eax
        movl    %ecx, %edx
        ret

This is one instruction shorter than the icc sequence, due to the use of shldl.
 It could be improved by switching the roles of %ecx and %edx to avoid the
final move, although that is complex to implement give the way the register
allocator currently handles pseudo-registers larger than word mode.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929

[Bug middle-end/24929] long long shift/mask operations should be better optimized

[tkho at ucla dot edu]

------- Comment #1 from tkho at ucla dot edu  2005-11-18 02:35 -------
Created an attachment (id=10273)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10273&action=view)
shift/mask long long testcase

Here is a rough instruction-count comparison for f() compiled at -O2,
march=pentiumpro between icc9 and gcc head 20051108 with the patch in PR 17886,
comment #16:

icc: 11
gcc: 23

`icc -O2 -march=pentiumpro -S test3.c` gives:
        movl      4(%esp), %eax
        movl      8(%esp), %ecx
        movl      %eax, %edx
        shrl      $24, %edx
        shll      $8, %eax
        shll      $8, %ecx
        orl       %ecx, %edx
        movzwl    18(%esp), %ecx
        movzbl    %cl, %ecx
        orl       %ecx, %eax
        ret

`gcc -c test3.c -save-temps -O2 -march=pentiumpro -momit-leaf-frame-pointer`
gives:
        subl    $12, %esp
        movl    %edi, 8(%esp)
        movl    28(%esp), %edi
        movl    16(%esp), %eax
        movl    20(%esp), %edx
        movl    %esi, 4(%esp)
        movl    24(%esp), %esi
        movl    %edi, %esi
        xorl    %edi, %edi
        movl    8(%esp), %edi
        movl    %ebx, (%esp)
        shrl    $16, %esi
        xorl    %ebx, %ebx
        shldl   $8, %eax, %edx
        movl    %esi, %ecx
        movl    4(%esp), %esi
        orl     %ebx, %edx
        movl    (%esp), %ebx
        andl    $255, %ecx
        sall    $8, %eax
        addl    $12, %esp
        orl     %ecx, %eax
        ret

For comparison, here's the code from gcc 2.95.3. It generates the same 18
instructions for both march=i386 and march=pentiumpro.
`gcc -c test3.c -save-temps -O2 -momit-leaf-frame-pointer -march=pentiumpro`:
        pushl %ebx
        movl 8(%esp),%ecx
        movl 12(%esp),%ebx
        movl 16(%esp),%eax
        movl 20(%esp),%edx
        shldl $8,%ecx,%ebx
        sall $8,%ecx
        movl %edx,%eax
        xorl %edx,%edx
        shrl $16,%eax
        andl $255,%eax
        andl $0,%edx
        orl %eax,%ecx
        orl %edx,%ebx
        movl %ecx,%eax
        movl %ebx,%edx
        popl %ebx
        ret


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929