[LLVMdev] implicit register usage

[Jim Grosbach]

I'm not sure. It certainly seems reasonable to me that the building could/should set default Define flags on operands based on the MCInstrDesc. Dunno why it doesn't.

-Jim

On Feb 19, 2013, at 7:14 PM, reed kotler <rkotler at mips.com> wrote:

> Hi Jim,
> 
> One thing that seems strange to me is that if do a BuildMI, if you put a register inside the first parens, then it will treat it as a def, but if you just .addReg it won't (by default), even though it should know from the instruction definition.
> 
> Seems like it should do that.
> 
> Why would you want it to not do that?
> 
> Reed
> 
> 
> 
> On 02/18/2013 01:22 PM, Jim Grosbach wrote:
>> Hi Reed,
>> 
>> The .td file "Defs = …" should be sufficient. The implicit uses and implicit defs are part of the MCInstrDesc data structure, which is shared by all instances of a given instruction.
>> 
>> -Jim
>> 
>> On Feb 17, 2013, at 2:22 PM, reed kotler <rkotler at mips.com> wrote:
>> 
>>> If I put in my tablegen td file that a certain instruction implicitly sets a register, do I need to also do the same if I am using BuildMI or can I assume that further passes and such will now know that this register is implicitly set or used?
>>> 
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> 
>