Fix extra nonzero call for chained comparisons

[kmod]

See compare_ordering.py

The issue is that for chanined comparisons (a < b < c), we do something like:

def chained_compare(a, b, c):
  t1 = a < b
  if not bool(t1):
    return t1
  else:
    t2 = b < c
    nonzero(t2)
    return t2

Where that final nonzero(t2) call is extraneous and should be removed.

[benhoyt]

@kmod FYI, that link is broken. Should it be here?

[kmod]

Oops yes, thanks :)

[sizeoftank]

Hi @kmod
I found your comments in remapCompare() when I debugging for this issue.
So can we add a check to skip the last branch here? (is there any related code needed to change?)

    // TODO: this branch is unused for the last comparison
    AST_Branch* br = new AST_Branch();
    br->test = callNonzero(makeLoad(name, node));
    push_back(br);

    CFGBlock* was_block = curblock;
    CFGBlock* next_block = cfg->addBlock();
    CFGBlock* crit_break_block = cfg->addBlock();
    was_block->connectTo(next_block);
    was_block->connectTo(crit_break_block);

    br->iffalse = crit_break_block;
    br->iftrue = next_block;

    curblock = crit_break_block;
    pushJump(exit_block);

    curblock = next_block;

    left = right;

[kmod]

Closed via #1301