Re: nasm over gas?

[Jamie Lokier]

Jörn Engel wrote:
> - Why has Alan measured faster kernels with -Os than with -O2?
> 
> Code size *does* matter.

That's not just i-cache pressure.  It is partly a GCC problem, and
it's possible -Os would run faster than -O2 even with no i-cache.

I've observed -Os emitting exactly the same code as -O2 for some
trivial functions, except that -O2 has a few extra redundant
instructions.

Obvious the _intent_ of -O2 is to compile for speed, but it's clear
that GCC often emits trivially redundant instructions (like stack
adjustments) that don't serve to speed up the program at all.

-- Jamie
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