[Bug c/37990] New: -Os produces redundant instructions

[Bug c/37990] New: -Os produces redundant instructions

[reza at parvan dot net]

DESCRIPTION:
----------------------------------------
Simple test case is below.
There is redundant stack manipulation in the assembly output.
Use gcc -Wall -Os -S test.c
-----------------------------------------

VERSION INFO:
----------------------------------
gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --enable-mpfr --enable-checking=release i486-linux-gnu
Thread model: posix
gcc version 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5)
-----------------------------------

SOURCE CODE:
----------------------------------
extern int ii(int i);

void 
mm()
{
    int i=99;
more:
    i = ii(i);
    goto inc;
inc:
    if(i==0)
        goto more;
    i++;
    goto more;
}
---------------------------------------


-- 
           Summary: -Os produces redundant instructions
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: reza at parvan dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37990

[Bug c/37990] -Os produces redundant instructions

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-11-02 10:33 -------
What exactly do you mean with redundant stack manipulation?  Note that the
ABI requires the stack to be aligned properly at function entry which makes
stack adjustment necessary before the call.  Note also that you can use
-maccumulate-outgoing-args to reduce the number of stack operations, but that
may cause bigger code in some cases.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37990

[Bug c/37990] -Os produces redundant instructions

[reza at parvan dot net]

------- Comment #2 from reza at parvan dot net  2008-11-02 11:01 -------
Arrrg!  I'm very sorry.  Please ignore this bug report.

I'll change the status to INVALID if that's okay.

Thanks for your response.

Reza.


-- 

reza at parvan dot net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37990