Eliminate potential unsafe use of general destination

a3407eaa2104d6 eliminated the -gen_dest flag for macros in ops.tab.

It turns out that the new implementation (taking the address of the
X or X destination register) is unsafe if the destination is a Y
register and there can be a GC. The problem is that the address to
the Y register will change if there is a GC.

Fortunately, the few instructions in OTP 20 that have a general
destinations are safe. The put_list_ssd instruction never does a GC.
The bit syntax instructions that may do a GC will always store the
result to an X register.

To be completely sure, rewrite the destination register from 'd' to
'x' for the bit syntax instructions. That means that a bit syntax
instruction with a Y register destionation will abort the loading
if it is encountered.

0 files changed, 0 insertions, 0 deletions