Am 12.06.2018 um 23:45 schrieb
On Mon, 2018-06-11 at 21:07 +0100, J. Gareth Moreton wrote:
Thanks David,

I'm still learning some of the nuances of the Intel and AMD
processors, but most of it is just logical analysis.  Admittedly my
main drive has been to shrink down the size of the binary, since
Delphi and Free Pascal have always been a little bit bloated in
comparison.  Not that it is necessarily a bad thing, but saving space
without sacrificing performance can only be a good thing, especially
for those with limited bandwidth or for saving those few precious
bytes when burning files to a CD or DVD.

There have been a few instances in the compiled compiler (my main
test case) where an entire register is freed up due to my deep
optimisation, and that means the corresponding "push" and "pop" at
either end of the procedure can be removed (along with the
corresponding stack unwinding information), although I haven't
started programming that yet.

Isn't it better to perform this optimization before register
allocation. Then, when this happens, the corresponding "push" and "pop"
wouldn't even be put by the compiler, because the register wouldn't
have to be spilled.

Yes, this is what I already started once, a peephole optimizer pass being able to be run before register allocation which executes in particular optimizations which reduce register usage.
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