Multi-Threading GCC Continuation

[Segher Boessenkool]

Hi Nick,

On Sun, Dec 08, 2019 at 03:03:56PM -0500, Nicholas Krause wrote:
> The first questions are:
> 1. What current heuristics do we have as it seems none for figuring out 
> what state is shared
> as it seems none? If I correct the first thing to do is discuss what 
> bits/bitmasks we want
> for figuring out shared state or other ways.

Shared between what and what?

> 2. MD files seem to be a major source of shared state or reading them.  
> Is it possible
> to read from them async? Doesn't seem to be a problem but the current 
> docs don't
> mention it nor does it seem easy to do.

MD files are not read *at all* by the compiler itself; they aren't
installed, even.  They are read by the gen* programs when the compiler
itself is built, to create the insn-*.c files and the like.

> 3. There are two ways to write this for RTL either one class for all the 
> state or a core
> class will each major part being a subclass like delayed branch 
> scheduling e.t.c.Not sure
> which is better so thought I would ask.

RTL as it is is pretty efficient.  Please keep it that way.  It also is
a dumb (and very "open") data structure, by design.  See how "XEXP" and
similar work.

That could be changed of course, for non-trivial cost, but what for?


Segher