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Date: Mon, 23 Oct 2006 15:59:11 +0200
From: Avi Kivity <avi@qumranet.com>
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Subject: Re: [Qemu-devel] qemu vs gcc4
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To: paul@codesourcery.com
Cc: qemu-devel@nongnu.org

Paul Brook wrote:
> On Monday 23 October 2006 09:16, Martin Guy wrote:
>   
>>> Now, gcc4 can produce code with several return instructions (with no
>>> option to turn that of, as far as I understand). You cannot cut them out,
>>> and therefore you cannot chain the simple functions.
>>>       
>> ...unless you also map return instructions within the generated
>> functions into branches to the soon-to-be-dropped final "return"? Not
>> that I know anything about qemu internals mind u...
>>     
>
> That's exactly what my gcc4 hacks do.
>
> It gets complicated because a x86 uses variable length insn encodings so you 
> don't know where insn boundaries are, and a jmp instruction is larger than a 
> ret instruction so it's not always possible to do a straight replacement.
>   

how about

void some_generated_instruction(u32 a1, u32 s2)
{
       // code
       asm volatile ( "" );
}


that will force the code to fall through to the null asm code, avoiding 
premature returns.

if the code uses 'return' explicitly, turn it to a goto just before the 
'asm volatile'.


-- 
error compiling committee.c: too many arguments to function