Avoids overriding the v0 register (which containins the result of the
tested function) in checkasm_call_checked.

Loads from this strictly doesn't require alignment, but specify it
just for consistency with the arm version.
Signed-off-by: Martin Storsjö <martin@martin.st>

x29 (FP) is a callee saved register and should be restored on
return. Instead of backing up x29 and restoring it here, back up
sp in a register that we are allowed to overwrite.

This fixes crashes in checkasm on aarch64 since f1b3e131.
For some reason, gcc builds didn't crash, but clang builds do.
Signed-off-by: Martin Storsjö <martin@martin.st>

They only contain one line and will never contain more.

This, combined with clobbering the stack space prior to the call,
increases the chances of finding cases where 32 bit parameters
are erroneously treated as 64 bit.
Signed-off-by: Martin Storsjö <martin@martin.st>

Signed-off-by: Martin Storsjö <martin@martin.st>

Even if MAX_ARGS - 2 (for arm) or MAX_ARGS - 7 (for aarch64) parameters
are passed on the stack to checkasm_checked_call, we actually only
need to store MAX_ARGS - 4 (for arm) or MAX_ARGS - 8 (for aarch64)
parameters on the stack when calling the tested function.
Signed-off-by: Martin Storsjö <martin@martin.st>

This is disabled on iOS, since iOS uses a slightly different ABI
for vararg parameters.
Signed-off-by: Martin Storsjö <martin@martin.st>