[PATCH] Enable FastISel on ARM for Linux and NaCl, not MCJIT

[Renato Golin]

On 13 June 2013 01:34, JF Bastien <jfb at google.com> wrote:

> This is a resubmit of r182877, which was reverted because it broken MCJIT
> tests on ARM. The patch leaves MCJIT on ARM as it was before: only enabled
> for iOS. I've CC'ed people from the original review and revert.
>

Nice tests! Good to see that so many things were working all along, but
never tested properly. ;)

I can't vow for the support quality, as I was not following FastISel that
closely, but if all those tests pass, than something is working and we
should keep tests running to make sure we don't regress, and that alone is
a great change. Thanks for working on this!



> FastISel was only enabled for iOS ARM and Thumb2, this patch enables it
> for ARM (not Thumb2) on Linux and NaCl, but not MCJIT.
>
> Thumb2 support needs a bit more work, mainly around register class
> restrictions.
>
> The patch punts to SelectionDAG when doing TLS relocation on non-Darwin
> targets. I will fix this and other FastISel-to-SelectionDAG failures in a
> separate patch.
>
The patch also forces FastISel to retain frame pointers: iOS always keeps
> them for backtracking (so emitted code won't change because of this), but
> Linux was getting much worse code that was incorrect when using big frames
> (such as test-suite's lencod). I'll also fix this in a later patch, it will
> probably require a peephole so that FastISel doesn't rematerialize frame
> pointers back-to-back.
>

I know it's a bit of a pain, but can you create some generic place-holder
bugs for those? At least we have an explicit list of broken things, rather
than on the back of some people's minds. ;)


I ran all of lnt test-suite on A15 hardware with --optimize-option=-O0 and
> all the tests pass. All the tests also pass on x86 make check-all. I also
> re-ran the check-all tests that failed on ARM, and they all seem to pass.
>

Our buildbots run on -O3, would be good to know if they also pass on higher
optimization levels.

cheers,
--renato
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