660002 - TI: "Assertion failure: copied == 0,"

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Gary Kwong [:gkw] [:nth10sd] (NOT official MoCo now)]

Attachment: stack

(function() {
    let V = x(x, x = w), x
})()

asserts js debug shell on JM changeset 8bcb569c9bf9 with -m, -a and -n at Assertion failure: copied == 0,

autoBisect shows this is probably related to the following changeset:

The first bad revision is:
changeset:   69535:9e0bab2c04b4
user:        Brian Hackett
date:        Sat May 14 10:30:03 2011 -0700
summary:     [INFER] Don't learn types for dead entries at join points, bug 656591, learn argument types at script entry and mark monitored call ICs, bug 656920.

Comment 1

[Gary Kwong [:gkw] [:nth10sd] (NOT official MoCo now)]

See bug 659438.

Comment 2

[Brian Hackett [Laid off!]]

To simplify handling of most ops which expect objects, we forget information about the incoming stack values if they are known non-objects.  This broke invariants if the stack value was copied by other stack values popped in the opcode, we need to uncopy first in such cases.

http://hg.mozilla.org/projects/jaegermonkey/rev/e62ab4bbe727

Comment 3

[Christian Holler (:decoder)]

A testcase for this bug was automatically identified at js/src/jit-test/tests/jaeger/bug660002.js.