438376 - for-each-var code generation failure

Status: RESOLVED FIXED

(Tamarin Graveyard :: Self-hosting compiler (ESC), defect)

Description

[Lars T Hansen]

ESC generates code for the following fragment that fails verification (unbalanced stack depth).  If the var is manually hoisted then the code succeeds.

  function f() {
      if (x)
          for each (var md in x)
              print(md);
  }
  f();

Comment 1

[Lars T Hansen]

Note that the 'if' is necessary.  The CFG needs to have a flow graph that results in an unbalanced stack /and/ the unbalance needs to be detectable, as for the jump past the for loop when x is false.  The verifier does not complain if the loop leaves a nonempty stack and then returns.  This fact explains why all the for-each-var statements in eg abc-encode.es did not cause problems.

Comment 2

[Lars T Hansen]

Attachment: Patch

Comment 3

[Lars T Hansen]

(In reply to comment #1)
> Note that the 'if' is necessary.  The CFG needs to have a flow graph that
                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^
                                            needs to have an edge

Comment 4

[Lars T Hansen]

Changeset 582.