DEFAULT_CALLER_SAVES doesn't work on the mac

[Muhammed Fawzy]

Ian, thanks for your reply.
However, I think I wasn't clear in my question, please let me try to 
explain.
the problem I am trying to solve  is that I want to save  ecx, edx registers 
around a specific function call, In my case I want to save them around 
mcount call ( when you compile with -pg switch, mcount is inserted after the 
prolog of each function ).

the problem is that mcount and moncount implementation on the MAC trashes 
the value of ecx register, and gcc doesn't emit code to save registers 
around mcount calls..  I was hoping to find a gcc code gen option to force 
gcc to save and restore register values around mcount call.

I tried -fcall-saved-REG and -fcall-used-REG but this didn't work around 
each function call

I hope anyone can help with this issue.
Thanks


--------------------------------------------------
From: "Ian Lance Taylor" <iant@google.com>
Sent: Tuesday, December 22, 2009 7:55 AM
To: "Muhammed Fawzy" <mfawzymkh@hotmail.com>
Cc: <gcc-help@gcc.gnu.org>
Subject: Re: DEFAULT_CALLER_SAVES doesn't work on the mac

> "Muhammed Fawzy" <mfawzymkh@hotmail.com> writes:
>
>>    I am trying to force GCC to save ALL registers before functions
>> calls. I am running GCC 4.0.1 on MAC OS X leopard.
>> I am trying to achieve this by defining DEFAULT_CALLER_SAVES as well
>> as compiling with -fcaller-saves.  however, disassemble of a simple
>> helloworld program that calls functions a from main doesn't show any
>> difference.
>> is there any special thing needed to force gcc to save all registers ?
>
> -fcaller-saves is the default when optimizing.
>
> Try using -fcall-used-REG for all your registers.
>
> Ian
>