411284 - TASK: use one stack region and have the rstack grow downwards

Status: VERIFIED WONTFIX

(Tamarin Graveyard :: Tracing Virtual Machine, enhancement, P4)

Description

[Edwin Smith]

There are two forth stacks, one for operands and one for return values and local variables and AS3 stack frames.  Two stacks both grow upwards, require two stack overflow checks at each AS3 call, and two separate stack regions.

We could just have one region, with the return stack growing downwards, which is conventional anyway.  then, only one stack overflow check is required and only one region to manage.

with rstack growing downwards, rp[0] should be the topmost valid entry, and push/pop use pre-decrement and post-increment.