Re: [new-regalloc-branch] patch: subreg things 2/2

[Michael Matz <matzmich at cs dot tu-berlin dot de>]

Hi,

On 21 Jun 2001, Daniel Berlin wrote:

> Michael,
> Just FYI, I plan on getting rid of the conservative coalescing part.
> Until optimistic coalescing is fully implemented, this will mainly
> consist of commenting out the call to the conservative test, and
> freezing of moves.

Note also, that some code in ra.c canīt correctly handle spilled nodes, if
they result from coalescing (i.e. something which is not possible right
now, which explains this fact).

Iīve also read a paper about optimistic coalescing (and then added the
TODO item ;-)), but this involves some things and bookkeeping (e.g.
breaking coalesced webs, if that coalescing results in spilling
afterwards).  I would like to have this (switching off conservative
coalescing) optional, may be based on a -fra-xxx flag, so performance
impact of this is easier measurable.

> This has also been shown in the paper on optimistic register
> coalescing, among other papers.

If this is the same paper I was refering above (I donīt have the title
handy here at university), then this (the betterness as iterated
coalescing) was reached by the man above, the reconsidering of coalscing
if that rsulted in spilling.  This is also, what I want to implement one
of those days.


Ciao,
Michael.