compute_stack_effects() is called in add_safepoint_edges(). In debug build, C2 invokes it for almost all bytecodes in Parse::do_one_block().

There are 2 places that we can optimize it.

1. rsize is not used by many bytecodes. we could use a lambda to wrap it up. only evaluate the lambda on demand.

here is the code snippet.
    BasicType rtype = T_ILLEGAL;
    int rsize = 0;

    if (code != Bytecodes::_illegal) {
     depth = Bytecodes::depth(code); // checkcast=0, athrow=-1
     rtype = Bytecodes::result_type(code); // checkcast=P, athrow=V
     if (rtype < T_CONFLICT)
       rsize = type2size[rtype];
    }

it requires 2 loads and 2 comparisons every time. We will skip the computation if it is not in use and 2 loads and 1 comparison when it's used.

2. we could leverage assertion to skip computation.
if asserts that resize is -depth, we could use it directly
     assert(rsize == -depth, "");
     inputs = rsize;