678377 - IonMonkey: LICM makes recursive calls

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Ryan Pearl [:rpearl]]

Loop::iterateLoopBlocks() makes non-tailcalls to Loop::iterateLoopBlocks() when this can be done without recursive calls. At the very least, an explicit stack should be used (to manage memory in a way that is OOM-safe), but it is possible that simply iterating over the blocks in the loop may be sufficient?

Comment 1

[Andrew Scheff]

It was determined that you can't iterate over blocks in the loop because there's no guarantee on the range of block ids contained in the loop.  You have to follow pred pointers.  It would be easy to change this to an explicit stack though...

Comment 2

[Hannes Verschore [:h4writer]]

Attachment: Transform to use stack

This removes the iterative way LICM worked. In the progress I also found a small fault, where we could iterate blocks multiple times and have the same instructions multiple times in the worklist.

Comment 3

[Hannes Verschore [:h4writer]]

Comment on attachment 742355 [details] [diff] [review]
Transform to use stack

s/iterative/recursief/

Comment 4

[Hannes Verschore [:h4writer]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/082445b83eba

Comment 5

[Hannes Verschore [:h4writer]]

Attachment: Fix regression

Very stupid bug in this patch (i++ != i--).
In my quest I did find 2 extra fixes for wrong behavior of the original code.

Comment 6

[Hannes Verschore [:h4writer]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/827a95147b4f

Comment 7

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/082445b83eba
https://hg.mozilla.org/mozilla-central/rev/827a95147b4f