Re: [PATCH] AArch64: Improve GOT addressing

[Richard Sandiford <richard.sandiford@arm.com>]

Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
> Hi Richard,
>
>> Normally we should only put two instructions in the same define_insn
>> if there's a specific ABI or architectural reason for not separating
>> them.  Doing it purely for optimisation reasons is going against the
>> general direction of travel.  So I think the first question is: why
>> don't we simply delay the split until after reload instead, since
>> that's the more normal way of handling this kind of thing?
>
> Well there are no optimizations that benefit from them being split, and there
> is no gain from scheduling them independently. Keeping them together
> means the linker could perform relaxations on the pair without adding new
> relocations. So if we split after reload we'd still want to keep them together.

The burden of proof is the other way though: there has to be a specific
reason for keeping the instructions together, rather than a specific
reason for splitting them.  How we optimise things after RA changes
with time.

Thanks,
Richard