[ARM64EC 3/?] Mark reserved registers specific to ARM64EC ABI.

[efriedma]

Summary

Part of patchset to add initial support for ARM64EC.

I'm not completely sure I understand the reason for this restriction, but Microsoft documentation says that asynchronous signals clobber these registers, so we can't ever use them.

As far as I know, none of these registers have any hardcoded meaning, so reserving them shouldn't have any significant side-effects.

[mstorsjo]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

The comment says v16-v31 but the code seems to go from 15 to 31 - is that a typo? (Based on the comment in the testcase, the code is right and the comment above is the one that is wrong.)

[efriedma]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

Microsoft docs say v16-v31. Will fix.

[DavidSpickett]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

Are you using the "B" name here so that all the various size registers up to "V" get marked as reserved too? (if not you could use "V" to match the comment)

[efriedma]

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

331

Yes, using the "B" name so markSuperRegs finds all the registers.

[efriedma]

Fix v15/v16 confusion

[dpaoliello]

You may also want to use the exiting llvm/test/CodeGen/AArch64/arm64-platform-reg.ll test case.

[efriedma]

Rebased

[efriedma]

https://reviews.llvm.org/rG4658366d95d5e398baad956225cc4ba339d5b037 . (phab didn't pick it up due to misspelling)