[LLVMdev] portable way to modify the FP register?

[James Molloy]

Hi,

To add to what Anton said, what if you're on a non-x86 target, or --no-frame-pointer is set?

Also, I'm intrigued as to how you guarantee that in the intervening time between the coroutine/generator function bar() returning one result and the next invocation of bar(), foo() doesn't call another function and overwrite bar()'s stack frame?

Cheers,

James Molloy
Graduate Compiler Engineer, ARM Ltd.


> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Salvador Abreu
> Sent: 13 December 2010 15:57
> To: llvmdev at cs.uiuc.edu
> Subject: [LLVMdev] portable way to modify the FP register?
>
> Hi,
>
> I'd like to know if there's a portable way of modifying the FP
> register, in LLVM.
>
> Suppose foo() calls bar(); bar emits a result but remains active and
> needs to be able to produce more results - a bit like a coroutine.  We
> want bar to restore FP to what it was inside foo before transferring
> control back to foo (bar's stack frame is not disposed of).
>
> We'd make sure that foo only accesses local variables via FP (SP
> addressing is disabled).
>
> What we'd like to do is something like (abstracted syntax and semantics
> :-)
>   (FP) = @llvm.frameaddress(1) ;
>
> So, is there a portable way to change FP?
>
> --
> Salvador Abreu       --  http://www.di.uevora.pt/~spa/
> Departamento de Informatica
> Universidade de Evora - PORTUGAL
>
>
>
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