Hi Ben,
There has been some confusion here because I accidentally committed a
change to this file that then got reverted. The original fix was #9055,
making it so that on platforms with no registers, globalRegMaybe would
return Nothing (as it should). This wasn't necessary until recently
when we started using globalRegMaybe during optimisation in CmmSink.
Yes I think you should add MACHREGS_arm to the #if in that file, and
anywhere else where we do similar things.
Cheers,
Simon
On 23/07/2014 19:32, Ben Gamari wrote:
Hello Simon,
b0534f7 [1] and the subsequent reversion f0fcc41d7 touched
`includes/CodeGen.Platform.hs`, the former removing a panic in the case
of `globalRegMaybe` being undefined for a platform and replacing it with
`Nothing`.
Recently I've found that my ARM builds (with -fllvm) crash at this panic
whereas they did not as of the 7.8 release. Given that b0534f7 was
reverted this is no doubt due to another change that I haven't
identified yet. Do you have any idea what is happening here?
I'm currently attempting to build with a workaround setting
`globalRegMaybe _ = Nothing`, although this smells suspicously like what
would happen in the unregisterized case.
My other hypothesis is that MACHREGS_arm should be added to the
#if MACHREGS_i386 || MACHREGS_x86_64 || MACHREGS_sparc || MACHREGS_powerpc
which smells more like what a registerised architecture should do and it
seems the requisite macros are defined for ARM in
`stg/MachRegs.h`. Whatever happens for ARM should probably
also happen for AArch64.
How should `globalRegMaybe` and `freeReg` be defined for platforms that
rely exclusively on the LLVM backend? Both ARM and AArch64 appear to be
doing the wrong thing at present.
Cheers,
- Ben
[1]
https://github.com/ghc/ghc/commit/b0534f78a73f972e279eed4447a5687bd6a8308e#diff-4899eba6e173d5811d08d6c312da7752R741
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