[Tarantool-patches] [PATCH luajit 4/4] ARM64: Fix xpcall() error case (really).

[Igor Munkin]

Sergey,

Thanks for the patch! There are still typos left after fixing Sergos
review comments (the commit message is taken from the branch).
Otherwise, LGTM.

| ARM64: Fix xpcall() error case (really).
|
| Thanks to François Perrad and Stefan Pejic.
|
| (cherry picked from commit d417ded17945b4211608d497d50b509e0274f5e0)
|
| Premature decrement of VM's RC register before switch to fff_fallback
| handler during processing `xpcall()` fast function leads to incorrect
| stack layout (not enough arguments on stack), when `xpcall()` calls

Typo: s/calls/is called/.

| without a second argument or if it is not a function (see
| <test/lua-Harness-tests/301-basic.t:832>

Typo: looks like line underfull (in LaTeX terms).

| test in lua-Harness test suite). While further error processing it leads
| to incorrect error message, due to stack inconsistency.
|
| This patch stores intermediate result into TMP1 register (it does not
| determine fallback's behaviour and there is no way to return from
| fallback back to xpcall processing with spoiled TMP1) and moves RC
| setting after the switch to the fallback handler.
|
| Sergey Kaplun:
| * added the description for the problem
|
| Resolves tarantool/tarantool#6093
| Part of tarantool/tarantool#5629

-- 
Best regards,
IM