Fix unsafe use of 'allocate' where 'allocate_zero' should be used

The more aggressive optimizations of 'allocate_zero' introduced
in cb6fc15c35c7e could produce unsafe code such as the following:

    {allocate,0,1}.
    {bif,element,{f,0},[{integer,1},{x,0}],{x,0}}.

The code is not safe because if element/2 fails, the runtime
system may scan the stack and find garbage that looks like a
catch tag, and would most probably crash.

Fix the problem by making beam_utils:is_killed/3 be more conservative
when asked whether a Y register will be killed.

Also fix an unsafe move upwards of an allocation instruction
in beam_block.

0 files changed, 0 insertions, 0 deletions