llvm dev - May 2006 - [LLVMdev] MRegisterInfo::storeRegToStackSlot question

Hi,
in LLVM CVS the afore-mentioned function has 'const
TargetRegisterClass*'
parameter, that is not documented.

Can somebody explain what does it mean?

Thanks,
Volodya

On Sat, 13 May 2006, Vladimir Prus wrote:
> in LLVM CVS the afore-mentioned function has 'const
TargetRegisterClass*'
> parameter, that is not documented.
>
> Can somebody explain what does it mean?
Basically, it gives the target more information about the spill.  In 
particular, it specifies the register class to use for the copy.  The 
target can choose to ignore this if it wants.

-Chris

-- 
http://nondot.org/sabre/
http://llvm.org/

Chris Lattner wrote:
> On Sat, 13 May 2006, Vladimir Prus wrote:
>> in LLVM CVS the afore-mentioned function has 'const
TargetRegisterClass*'
>> parameter, that is not documented.
>>
>> Can somebody explain what does it mean?
> 
> Basically, it gives the target more information about the spill.  In
> particular, it specifies the register class to use for the copy.  
I'm still missing something. The 'storeRegToStackSlot' saves
'SrcReg' (already specified) to stack (which is not a register). So,
what
does this register class applies to? 

Examining RegAllocLocal.cpp suggests that the argument actually specifies
the register class of the spilled virtual register. Can you give some
examples how that information can be helpful?

I'd like to send doc patch, but can't do that without understanding the
semantics ;-)

- Volodya