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Re: What happened to the IRA interprocedural reg-alloc work? (function_used_regs and friends)
Steven Bosscher <stevenb.gcc@gmail.com> writes:
>
> I suppose it's theoretically possible to make a good initial guess of
> what registers might be not-clobbered by a function even if the ABI
> says so. For instance, perhaps it's possible to assume that a function
> that doesn't touch any variables in a floating point mode also doesn't
> use/clobber any floating point registers. This assumption could be
> propagated via LTO/WHOPR. If the function turns out to clobber
> registers that were assumed to be untouched, you could just save and
> restore them in the function ("callee saved" so to speak). But I don't
> know how useful that would be.
>
There was a discussion on this some time ago. The conclusion was that
the partition should help: if the partitions works right the callers and
callees that are commonly should be commonly in the same partition, and
those need RA between themselves. Between partitions you couldn't do RA.
-Andi
--
ak@linux.intel.com -- Speaking for myself only