ppc64/clang: save/restore vector register vr31.

This fixes crashes in the test cases when TXR is built with
clang on little-endian PPC64. Clang uses vector instructions,
but our jmp.S does not save any vector registers. In some
places this causes a problem.

I've noticed much of the code just uses vrs0, vrs1 and vrs63
for doing small things, like initializing small structures
with a single instruction. The functions that use more of these
registers don't call anything that saves and restores a
context.

In this patch we just save/restore vrs63, which maps to vr31.
The vrs0 and vrs1 don't have to be saved and restored; the
setjmp function doesn't do it. Everything is conditional on
__ALTIVEC__.

* unwind.h (jmp): We add vr31 to the PPC64 version of
struct jmp. The instructions which load and store this
requires 32 byte alignment, so we assert that. Note that the
alignment leaves 8 bytes of padding at the end of the structure
since there are 23 other registers to save.

* jmp.S (jmp_save, jmp_restore): We save and restore v31 first
and then move the pointer past it by 32 bytes to do the rest
of the registers exactly as before. In jmp_save, we save
an extra copy of the r11 register into the padding so that
it is initialized. We don't like to encourage padding in the
stack because in light of our GC's conservative scan of
the stack, it promotes spurious retention of objects.

0 files changed, 0 insertions, 0 deletions