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Posted: **Mon Sep 05, 2011 12:25 am**

Except for when doing whole program optimization and with at least hidden symbols, the compiler can't assign variables to specific register slots across function calls in a safe manner. The register globals extension is used to allow e.g. the VM program counter or (for a stack machine) stack pointer to be placed in registers across multiple functions.

You can think of this as, almost, a custom calling convention exteennsion. Indeed, if you had one (e.g. Watcom's pragma based method) this would probably not be necessary (though, then again, it may still produce cleaner code)

Posted: **Mon Sep 05, 2011 12:32 am**

That's what optimizing linkers are for---making things clean (e.g., LLVM gold plugin)

Posted: **Mon Sep 05, 2011 2:03 am**

Hi,

Just putting this for informational purposes only, the good old Turbo / Borland C++ had the feature of accessing registers like this. I do not have access to a Borland compiler right now , but i guess newer versions allows access to 32 bit registers

Code: Select all

_AX = 2 ;
_BX = 3 ;
_CX  = _AX + _BX ;

--Thomas

Posted: **Mon Sep 05, 2011 2:07 am**

Yes, miker00lz already mentioned that. At least what Owen (who will get his 5th start after just two more posts from the time I post this

) mentions is useful for a sucky toolchain...

Posted: **Mon Sep 05, 2011 2:15 am**

Yes, miker00lz already mentioned that. At least what Owen (who will get his 5th start after just two more posts from the time I post this ) mentions is useful for a sucky toolchain...

Sorry , missed that

. However redundancy does improve reliability at times

--Thomas

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better registers representation in C?

Re: better registers representation in C?

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Re: better registers representation in C?

Re: better registers representation in C?

Re: better registers representation in C?