469938 - TM: 19x slowdown due to questionable "unstable loop variable"

Status: RESOLVED DUPLICATE of bug 469044

(Core :: JavaScript Engine, defect)

Description

[Jesse Ruderman]

// c must be undeclared
for (var iter = 0; iter < 100000; ++iter) {
  c = "2";
  c = 3;
}

19x slower with -j than without.  The variable |c| has the same type at the end of each loop, so why does this keep triggering the "unstable loop variable" unhappiness?

Comment 1

[Jesse Ruderman]

Oh, is this what bug 469044 is about?

Comment 2

[Andreas Gal :gal]

./Darwin_DBG.OBJ/js -j x.js
recorder: started(33333), aborted(0), completed(0), different header(0), trees trashed(0), slot promoted(0), unstable loop variable(33333), breaks(0), returns(0), unstableInnerCalls(0)
monitor: triggered(0), exits(0), type mismatch(0), global mismatch(2)

33333 traces started? Blocker for sure.

Comment 3

[Andreas Gal :gal]

+1 for blocking from me, working on it

Comment 4

[Andreas Gal :gal]

This is a dup of 469044. c is an undeclared global, and it changes type from string to int so we end up flushing the cache every time we go through the code. 469044 fixes this.