CGEN: Macro insns

[Dave Brolley]

Greg McGary wrote:

> 
> Months ago, I observed that macro-insns as currently implemented have
> very limited usefulness.  The args to `emit' are error-checked, but
> otherwise completely ignored.  The only thing you can do with a macro
> insn is omit some operands and have them be filled with zero, or
> change the order of operands in the syntax string.
> 
> I order to define short versions collapsed src & dest regs, I needed
> to define a multi-field with an inserter that dup'ed the reg#, and
> an extractor that ignored one sub-field.

Uggggghhh.....I'll keep this in mind should I not find time to fix the 
real problem. What is the ALIAS attribute? Does it keep the decode from 
complaining about the ambiguity?

Dave