[Bug optimization/12305] New: processor return register saved/restore unnecessarily in leaf function

[Bug optimization/12305] New: processor return register saved/restore unnecessarily in leaf function

[tm at kloo dot net]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305

           Summary: processor return register saved/restore unnecessarily in
                    leaf function
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tm at kloo dot net
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-linux
  GCC host triplet: i386-linux
GCC target triplet: sh-elf

When this function is compiled:

int a, b; int foo(void) { return a + b; }

using -O2 -m4 -fPIC -S, the following code is created:

_foo:
        mov.l   r12,@-r15
        mova    .L3,r0
        mov.l   .L3,r12
        mov.l   r14,@-r15
        add     r0,r12
        mov.l   .L4,r0
        sts.l   pr,@-r15		<- PR saved unnecessarily
        mov.l   @(r0,r12),r1
        mov     r12,r0
        mov     r15,r14
        mov.l   @r1,r2
        mov.l   .L5,r1
        mov.l   @(r0,r1),r1
        mov.l   @r1,r1
        add     r1,r2
        mov     r2,r0
        mov     r14,r15
        lds.l   @r15+,pr		<- PR restored unnecessarily
        mov.l   @r15+,r14
        rts
        mov.l   @r15+,r12

[Bug optimization/12305] processor return register saved/restore unnecessarily in leaf function

[pinskia at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305


pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
  GCC build triplet|i386-linux                  |
   GCC host triplet|i386-linux                  |
           Keywords|                            |pessimizes-code

[Bug optimization/12305] processor return register saved/restore unnecessarily in leaf function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-08 21:17 -------
This version did not have the store/restore of the return register:
./cc1 --version
GNU C version 3.4 20030718 (experimental) (sh4-hardhat-linux)
        compiled by GNU C version 3.4 20030718 (experimental).
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305

[Bug optimization/12305] processor return register saved/restore unnecessarily in leaf function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-08 21:46 -------
I can confirm this on the mainline (20031108), looks like sh-linux does do the saving or 
restoring of the return register for some reason.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-11-08 21:46:12
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305

[Bug target/12305] processor return register saved/restore unnecessarily in leaf function

[anilp1 at kpitcummins dot com]

------- Additional Comments From anilp1 at kpitcummins dot com  2004-04-28 07:26 -------
(In reply to comment #2)
> I can confirm this on the mainline (20031108), looks like sh-linux does do 
the saving or 
> restoring of the return register for some reason.

Hi,

Above mentioned bug is solved in gcc 3.5 mainline (snapshot dated 27-03-2004). 
But this bug is still there in released gcc 3.4.

Can anybody tell me which patch will fix this bug in gcc 3.4 ?

Regards,
Anil Paranjpe


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305

[Bug target/12305] processor return register saved/restore unnecessarily in leaf function

[dhananjayd at kpitcummins dot com]

------- Additional Comments From dhananjayd at kpitcummins dot com  2004-04-28 09:29 -------
Fixed with - 

http://gcc.gnu.org/ml/gcc-patches/2004-02/msg02248.html

http://gcc.gnu.org/ml/gcc-cvs/2004-02/msg01310.html

This PR can be closed.

-Dhananjay

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305

[Bug target/12305] processor return register saved/restore unnecessarily in leaf function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-04-28 11:24 -------
Fixed for 3.5.0.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12305