[Xen-devel] Re: [PATCH 4 of 7] x86/paravirt: selectively save/restore regs around pvops calls

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Rusty Russell wrote:
> On Thursday 29 January 2009 09:05:04 Jeremy Fitzhardinge wrote:
>   
> > +#define PV_SAVE_REGS(set)                      \
> > +       COND_PUSH(set, CLBR_RAX, rax);          \
> > +       COND_PUSH(set, CLBR_RCX, rcx);          \
> > +       COND_PUSH(set, CLBR_RDX, rdx);          \
> > +       COND_PUSH(set, CLBR_RSI, rsi);          \
> > +       COND_PUSH(set, CLBR_RDI, rdi);          \
> > +       COND_PUSH(set, CLBR_R8, r8);            \
> > +       COND_PUSH(set, CLBR_R9, r9);            \
> > +       COND_PUSH(set, CLBR_R10, r10);          \
> > +       COND_PUSH(set, CLBR_R11, r11)
> >     
> It's kind of messy.  Can we do something clever here with token pasting?
>   
I tried a few things, but no.  Passing in just RAX, and then pasting 
CLBR_##reg works, and the assembler accepts %RAX - but - the asm code 
also #defines RAX <some stack offset>, so the assembler ends up seeing 
%48.  I considered renaming all the CLBR_ defines to CLBR_rax, but that 
looks unhappy too.  So I stayed with this.
   J

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