On 11/02/2009 08:49 AM, Joern Rennecke wrote:
This would only be valid if the comparison is in an equality context
(or for special input operand ranges).
So (unless the target is CC0) you'd either have to use dataflow analysis
to look at all the contexts the comparison result is used in, or you'd need
a target hook to classify CCmode modes to check if they are used only
for equality comparisons and can have their inputs altered.
Yes, that's why I suggested doing it on the tree level instead.
This is not implemented but IMHO obsolete, most of the targets will
just use an AND to implement zero extension.
If the target can actually write to partial registers and refer to the
entire register without undue delay, you won't need and zero_extend or
AND operation at all. So this is obsolete only to the extent that such
targets have become fewer / more arcane.
Yes, that's what I meant. The implementation effort is much less justified.
Paolo
