[tree-ssa] reaching def. question

[Diego Novillo]

On Tue, 2004-03-16 at 16:39, Devang Patel wrote:
> How do I find out reaching definitions of 'a' at statement S1?
> 
> S1:      a = b;
> 
> What I want to know is whether S1 is defining 'a' first time
> or killing earlier def of 'a'. compute_reaching_defs () is not
> yet implemented. Is there any other alternative API?
> 
compute_reaching_defs() wouldn't help you.  There are no uses of 'a' in
S1.

You need to do a dominator walk and stop when you find the first
definition.  But, there can be more than one:

	if (...)
	   a = b;
	else
	   a = c;

Both defs to 'a' are defininig 'a' for the "first time".  Besides, in
our current framework.  Every definition is a different variable.

What are you trying to solve?


Diego.