diff -r 000000000000 -r 6474c204b198 js/src/jit-test/lib/jitopts.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/lib/jitopts.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,69 @@
+// These predicates are for tests that require a particular set of JIT options.
+
+// Check if toggles match. Useful for tests that shouldn't be run if a
+// different set of JIT toggles are set, since TBPL runs each jit-test
+// multiple times with a variety of flags.
+function jitTogglesMatch(opts) {
+  var currentOpts = getJitCompilerOptions();
+  for (var k in opts) {
+    if (k.indexOf(".enable") > 0 && opts[k] != currentOpts[k])
+      return false;
+  }
+  return true;
+}
+
+// Run fn under a particular set of JIT options.
+function withJitOptions(opts, fn) {
+  var oldOpts = getJitCompilerOptions();
+  for (var k in opts)
+    setJitCompilerOption(k, opts[k]);
+  try {
+    fn();
+  } finally {
+    for (var k in oldOpts)
+      setJitCompilerOption(k, oldOpts[k]);
+  }
+}
+
+// N.B. Ion opts *must come before* baseline opts because there's some kind of
+// "undo eager compilation" logic. If we don't set the baseline usecount
+// *after* the Ion usecount we end up setting the baseline usecount to be the
+// default if we hit the "undo eager compilation" logic.
+var Opts_BaselineEager =
+    {
+      'ion.enable': 1,
+      'baseline.enable': 1,
+      'baseline.usecount.trigger': 0,
+      'parallel-compilation.enable': 1
+    };
+
+// Checking for parallel compilation being off is often helpful if the test
+// requires a function be Ion compiled. Each individual test will usually
+// finish before the Ion compilation thread has a chance to attach the
+// compiled code.
+var Opts_IonEagerNoParallelCompilation =
+    {
+      'ion.enable': 1,
+      'ion.usecount.trigger': 0,
+      'baseline.enable': 1,
+      'baseline.usecount.trigger': 0,
+      'parallel-compilation.enable': 0,
+    };
+
+var Opts_Ion2NoParallelCompilation =
+    {
+      'ion.enable': 1,
+      'ion.usecount.trigger': 2,
+      'baseline.enable': 1,
+      'baseline.usecount.trigger': 1,
+      'parallel-compilation.enable': 0
+    };
+
+var Opts_NoJits =
+    {
+      'ion.enable': 0,
+      'ion.usecount.trigger': 0,
+      'baseline.usecount.trigger': 0,
+      'baseline.enable': 0,
+      'parallel-compilation.enable': 0
+    };