Repost: RFA [4.1]: improvement to if-conversion and cross-jumping (PR20070)

[Bernd Schmidt]

Joern RENNECKE wrote:
> I've just thought of another thing that won't work right with the 
> current infrastructure:
> when we call validate_change, the change is installed instantly.  Thus, 
> when we try to match
> the same register again, we will fail.  That is easy to fix for 
> PRE_MODIFY - just save the
> register before doing the first potential change - but much harder when 
> you have a PARALLEL
> where any SET_DEST could be a STRICT_LOW_PART, ZERO_EXTEND or SIGN_EXTEND.
> 
> I see four possible approaches here:

Maybe we could extend RVALUE to also describe the case that we have an 
in-out operand, and the REG handling could be changed to handle this 
case as well?  Then we'd have to scan each part of the insn only once.


Bernd