llvm dev - Sep 2008 - [LLVMdev] A question about instruction operands.

> >>>
> >> It's enclosed inside :
> >>
> >> let isTwoAddress = 1 in {
> >> ...
> >> }
> >>
> >> (you'll need to scroll up a fair amount to find this).
> >>
> >>
> > That means, it gets converted to
> > dst = src;
> > dst = dst + 1;
> >
> > Right ?
> >
> > - Sanjiv
> >
> Yes, I believe the two address instruction pass performs exactly this
> transformation.
> 
Thanks.
How do I communicate if my CopyRegToReg instruction clobbers a register
of another register class? Is it through let Defs = [REG]  { ... } while
defining the instr pattern?

- Sanjiv
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On Sep 23, 2008, at 9:05 AM, Sanjiv.Gupta at microchip.com wrote:
>>>>>
>>>> It's enclosed inside :
>>>>
>>>> let isTwoAddress = 1 in {
>>>> ...
>>>> }
>>>>
>>>> (you'll need to scroll up a fair amount to find this).
>>>>
>>>>
>>> That means, it gets converted to
>>> dst = src;
>>> dst = dst + 1;
>>>
>>> Right ?
>>>
>>> - Sanjiv
>>>
>> Yes, I believe the two address instruction pass performs exactly this
>> transformation.
>>
> Thanks.
> How do I communicate if my CopyRegToReg instruction clobbers a  
> register
> of another register class? Is it through let Defs = [REG]  { ... }  
> while
> defining the instr pattern?
That won't work. You don't know what physical registers are clobbered  
until you know the register assignments, right? One possibility is to  
add implicit defs when you create these instructions.

Evan
>
>
> - Sanjiv
>
>> _______________________________________________
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>
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On Wed, 2008-09-24 at 10:26 -0700, Evan Cheng wrote:
> > How do I communicate if my CopyRegToReg instruction clobbers a  
> > register
> > of another register class? Is it through let Defs = [REG]  { ... }  
> > while
> > defining the instr pattern?
> 
> That won't work. You don't know what physical registers are
clobbered
> until you know the register assignments, right? One possibility is to  
> add implicit defs when you create these instructions.
> 
In our case that isn't a problem because we have only one register.
> Evan
> 
> >
> >
> > - Sanjiv
> >
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
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