llvm dev - Jul 2008 - [LLVMdev] IMPLICIT_DEF's

Guys,

     I think I figure out the way that the current LLVM allocators are 
handling IMPLICIT_DEF's. One question more: why are you adding null length 
intervals to IMPLICIT_DEF instructions? If they were non-null, I think the 
code to handle them would be more homogeneous, e.g a traversal of the 
intervals during register allocation would already reveal virtuals defined 
implicitly.

best,

Fernando

On Jul 19, 2008, at 9:14 AM, Fernando Magno Quintao Pereira wrote:
>
> Guys,
>
>     I think I figure out the way that the current LLVM allocators are
> handling IMPLICIT_DEF's. One question more: why are you adding null  
> length
> intervals to IMPLICIT_DEF instructions? If they were non-null, I  
> think the
> code to handle them would be more homogeneous, e.g a traversal of the
> intervals during register allocation would already reveal virtuals  
> defined
> implicitly.
Assigning IMPLICIT_DEF defined interval a null length interval is an  
optimization. It enables more coalescing since an implicitly defined  
register should not conflict with anything else.

Evan
>
>
> best,
>
> Fernando
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