On Wed, 2020-04-22 at 15:50 -0500, Segher Boessenkool wrote: > > > > In some ways it feels like it would be easier to resurrect RTL SSA :-) > > Why was RTL SSA abandoned? > > It might well work to keep everything in SSA form all the way to RA. > Hrm, that doesn't sound bad at all :-) > > (The PHIs need to be made explicit to something that resembles the > machine code we will end up with, very early in the pipeline, but it > could still also be some valid SSA form; and we can of course also > have hard registers in all RTL, so that needs to be dealt with sanely > some way as well Lots of details, I don't see a crucial problem though, > probably means I need to look harder ;-) ) Lack of time mostly. There's some complications like subregs, argument registers and the like. But you can restrict ssa based analysis & optimizations to just the set of pseudos that are in SSA form and do something more conservative on the rest.
Jeff
