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Re: Inline ASM and stack/base pointer
- From: Ian Lance Taylor <iant at google dot com>
- To: Daniel Mierswa <impulze at impulze dot org>
- Cc: gcc-help at gcc dot gnu dot org
- Date: Thu, 09 Jun 2011 10:49:23 -0700
- Subject: Re: Inline ASM and stack/base pointer
- References: <4DF0F706.5050803@impulze.org>
Daniel Mierswa <impulze@impulze.org> writes:
> I was wondering how to overcome the issue that evolves when parameters
> (inputs) to the inline assembly are passed relative to ebp/esp and
> modifying those pointers in the inline assembly. Basically
> __asm__("push %ecx\nmov %0, %edx\n"::"m"(variable)); could set '%0' to
> 4(%esp) or similar which would no longer represent the same location
> once I use push/pop in my asm. Is it possible to explicitly state that
> GCC passes those relative to esp _or_ ebp so I can safely modify at
> least one pointer (i.e. reserve stack space)? Or are there any other
> ways to overcome this issue? Thanks in advance.
Add "%esp" to your clobber list. That should force the compiler to pass
any stack variables using an offset from %ebp.
Ian