Re: [Qemu-devel] [PATCH 2/4] tcg/i386: Remove unused registers from tcg_target_call_iarg_regs

[Stefan Weil <sw@weilnetz.de>]

Am 12.09.2012 23:18, schrieb Peter Maydell:
> On 12 September 2012 21:44, Stefan Weil <sw@weilnetz.de> wrote:
>> --- a/tcg/i386/tcg-target.c
>> +++ b/tcg/i386/tcg-target.c
>> @@ -75,9 +75,7 @@ static const int tcg_target_call_iarg_regs[] = {
>>       TCG_REG_R8,
>>       TCG_REG_R9,
>>   #else
>> -    TCG_REG_EAX,
>> -    TCG_REG_EDX,
>> -    TCG_REG_ECX
>> +    /* 32 bit mode uses stack based calling convention (GCC default). */
>>   #endif
>>   };
> This makes the array zero-length for 32 bit targets, but functions
> like tcg_out_tlb_load() and tcg_out_qemu_ld() still unconditionally
> access elements in it...
>
> -- PMM

Thanks for the hint. I'm afraid there are a lot more functions
of that kind in i386/tcg-target.c.

I could use conditional compilation for those accesses,
but first I'd like to understand why this works at all.

- sw