No, I looked out for any kind of errors during the build of the cross-compiler version 3.4.4, I am quite sure the tools are well built. Moreover, the leaf optimization procedure is embedded with other back-end routines (I mean, they reside into the same source files) and if something went wrong during the build, the whole cross-compiler would have been broken.
Well, I give you an example of the generated code with my gcc 3.4.4 cross-compiler (host: i686, target:sparc-elf).
- - - C source - - -
void myleafp() { return; }
int main(){
myleafp();
return 0;
}
- - -
sparc-elf-gcc issued with -O0 and -O2 gives the same machine code:
- - - obj dump - - -
40001170 <myleafp>:
40001170: 9d e3 bf 98 save %sp, -104, %sp
40001174: 81 c7 e0 08 ret
40001178: 81 e8 00 00 restore
4000117c <main>:
4000117c: 9d e3 bf 98 save %sp, -104, %sp
40001180: 7f ff ff fc call 40001170 <myleafp>
40001184: 01 00 00 00 nop
40001188: 82 10 20 00 clr %g1 ! 0 <_trap_table-0x40000000>
4000118c: b0 10 00 01 mov %g1, %i0
40001190: 81 c7 e0 08 ret
40001194: 81 e8 00 00 restore
- - -
Does your disassembly show a leaf procedure optimization?
Josef
--- On Fri, 10/22/10, Jorge PEREZ <jorge.perez@xxxxxxxx> wrote:
> From: Jorge PEREZ <jorge.perez@xxxxxxxx>
> Subject: Re: GCC and SPARC leaf procedures
> To: "Josef Ahmad" <josef_ahm@xxxxxxxxx>, gcc-help@xxxxxxxxxxx
> Date: Friday, October 22, 2010, 10:44 AM
> No problem Josef,
>
> however, I have tested that with GCC 3.4.4 and I'm pretty
> sure it does
> the optimization there too. Maybe you had an error during
> the
> cross-compiler build?
>
>
> PS: please always reply to the mailing list
>
>
>
>
> Josef Ahmad wrote:
> > Eh, you gave me the solution: I was using the version
> 3.4.4 of gcc.
> > I've just tried to compile my source code with gcc
> 4.4.2 and the optimization works.
> >
> > It's kind of weird, because there is an implementation
> for the leaf procedures optimization even in the former
> version, but perhaps it did not work yet.
> >
> > Now the problem is partially solved, because I am
> using a porting of gcc based on the version 3.4.4, and I
> would like to know how to obtain a leaf procedure
> optimization (if possible) on that version. Otherwise, I
> think I have to plan to update the porting to a newest
> version of gcc.
> >
> > Thank you!
> >
> > Josef
> >
> > --- On Fri, 10/22/10, Jorge PEREZ <jorge.perez@xxxxxxxx>
> wrote:
> >
> >ÂÂÂ
> >> From: Jorge PEREZ <jorge.perez@xxxxxxxx>
> >> Subject: GCC and SPARC leaf procedures
> >> To: gcc-help@xxxxxxxxxxx
> >> Cc: josef_ahm@xxxxxxxxx
> >> Date: Friday, October 22, 2010, 10:03 AM
> >> Hello Josef
> >>
> >> I was intrigued by your email since I actually
> think that
> >> GCC performs
> >> the leaf procedure optimization as indicated by
> the SPARC
> >> V8 manual (
> >> www.*sparc*.org/standards/*V8*.pdf p. 194)
> >>
> >> However, note that there are certain conditions
> that must
> >> be met in
> >> order to allow such optimizations, quoting the
> above
> >> referenced manual:
> >>
> >> Some leaf procedures can be made to operate
> without their
> >> own register
> >> window
> >> or stack frame, using their callerâs instead.
> This can be
> >> done when the
> >> candidate
> >> leaf procedure meets all of the following
> conditions13:
> >> Contains no references to %sp, except in its SAVE
> >> instruction
> >> Contains no references to %fp
> >> Refers to (or can be made to refer to) no more
> than 8 of
> >> the 32 integer
> >> regis-
> >> ters14, inclusive of %o7 (the âreturn
> addressâ).
> >>
> >> Actually there is a good example in a recent
> thread
> >> http://gcc.gnu.org/ml/gcc-help/2010-10/msg00249.html
> >> where you can see that in the function "somme",
> which I
> >> think is a leaf
> >> procedure, the SAVE and RESTORE instructions have
> been
> >> removed. What do
> >> you think?
> >>
> >>
> >> Otherwise, which GCC version are you using? I
> don't think
> >> that can be
> >> related to that, but just to be sure.
> >>
> >> Cheers,
> >>
> >>
> >> George
> >>
> >>
> >>Â ÂÂÂ
> >
> >
> >Â Â ÂÂÂ
> >
> >ÂÂÂ
>
>
>
