Closed Bug 754713 Opened 11 years ago Closed 11 years ago

IonMonkey: Assertion failure: [infer failure] Missing type pushed 0: void, at js/src/jsinfer.cpp:353


(Core :: JavaScript Engine, defect)

Other Branch
Not set



Tracking Status
firefox-esr10 --- unaffected


(Reporter: decoder, Assigned: jandem)



(Keywords: assertion, testcase, Whiteboard: [jsbugmon:update])


(1 file, 1 obsolete file)

The following testcase asserts on ionmonkey revision e8de64e7e9fe (run with --ion -n):

var t = 100;
function foo(ox) {
  var x = ox;
  var n = 0;
  for (var i = 0; i < 90; i++) {
    n += x.f.g;
    if (i >= 80)
function f() {}
function g() {}
f.prototype = {f:g};
foo(new f());
The problem is that IonBuilder::jsop_getprop pushes a constant value for "x.f" and therefore "x" has no SSA uses. IsPhiObservable does not like this:

    // Note that this skips reading resume points, which we don't count as
    // actual uses. This is safe as long as the SSA still mimics the actual
    // bytecode, i.e. no elimination has occurred. If the only uses are resume
    // points, then the SSA name is never consumed by the program.

So it's basically the same issue as bug 724517. Requiring SSA uses to mimic bytecode uses seems too error-prone. I will change IsPhiObservable to not skip resume points and see if it hurts benchmark performance.
Assignee: general → jdemooij
Bug 741203 has another great testcase, I reduced it to:

function f(x) {
    var y = (x < 0) ? 1 : 2;
    Math.floor(0); // bailout

Here we eliminate the phi for "y", then bailout and resume at SETLOCAL y. The type check fails because we set y to |undefined| instead of 2.
Attached patch Patch (obsolete) — Splinter Review
This is one of the simpler solutions we discussed yesterday. My initial patch fixed all places manually and modified traverseBytecode to ensure that if there's a bytecode use there must be at least one SSA use. The final patch is much simpler though: if a bytecode instruction uses a phi, it marks that phi as having bytecode uses and we always consider such phis observable. It fixes all testcases I found and does not noticeably regress performance.
Attachment #624442 - Flags: review?(dvander)
Attachment #624442 - Flags: review?(dvander)
Attached patch PatchSplinter Review
Attachment #624442 - Attachment is obsolete: true
Attachment #624454 - Flags: review?(dvander)
Comment on attachment 624454 [details] [diff] [review]

Review of attachment 624454 [details] [diff] [review]:

Nice - glad to see there was both a simple and generic fix.

::: js/src/ion/IonBuilder.cpp
@@ +622,5 @@
> +void
> +IonBuilder::markPhiBytecodeUses(JSOp op)
> +{
> +    unsigned nuses = analyze::GetUseCount(script, pc - script->code);

What's the difference between this and js_CodeSpec[op].nuses?
Attachment #624454 - Flags: review?(dvander) → review+
(In reply to David Anderson [:dvander] from comment #6)
> What's the difference between this and js_CodeSpec[op].nuses?

js_CodeSpec[op].nuses is -1 if the number of uses is dynamic (JSOP_CALL, JSOP_POPN etc). GetUseCount returns the right value in these cases.
Closed: 11 years ago
Resolution: --- → FIXED
Group: core-security
A testcase for this bug was automatically identified at js/src/jit-test/tests/ion/bug754713-2.js.
Flags: in-testsuite+
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