Closed
Bug 889825
Opened 11 years ago
Closed 11 years ago
IonMonkey: Eliminate more redundant bounds checks
Categories
(Core :: JavaScript Engine, defect)
Core
JavaScript Engine
Tracking
()
RESOLVED
FIXED
mozilla25
People
(Reporter: jandem, Assigned: jandem)
Details
Attachments
(1 file)
2.04 KB,
patch
|
h4writer
:
review+
|
Details | Diff | Splinter Review |
When we have something like this: x[a] = x[a] + 3; And we add an MConvertElementsToDouble instruction for the GETELEM, we're unable to eliminate the redundant bounds check for the SETELEM, because the MIR looks like this: GETELEM: BoundsCheck 1 -> InitializedLength 1 -> ConvertElementsToDouble -> Elements SETELEM: BoundsCheck 2 -> InitializedLength 2 -> Elements GVN does not know it can eliminate the second InitializedLength + BoundsCheck. The patch changes the GETELEM InitializedLength to have Elements as operand instead of ConvertElementsToDouble. This is safe because ConvertElementsToDouble will not change the initialized length. This wins about 15% on Kraken imaging-desaturate and 5% on audio-fft (where I noticed this).
Attachment #770798 -
Flags: review?(hv1989)
Comment 1•11 years ago
|
||
Comment on attachment 770798 [details] [diff] [review] Patch Review of attachment 770798 [details] [diff] [review]: ----------------------------------------------------------------- Nice find! Not entirely related, but I think I also saw gvn failing to merge the following (deltablue): Block 0 MTest "block 1", "block 2" Block 1 LoadFixedSlot 0 LoadFixedSlot 1 Block 2 LoadFixedSlot 1 LoadFixedSlot 0 So loading from the same elements but in different order. Nothing in between though.
Attachment #770798 -
Flags: review?(hv1989) → review+
Assignee | ||
Comment 2•11 years ago
|
||
https://hg.mozilla.org/integration/mozilla-inbound/rev/55497c1e7391 (In reply to Hannes Verschore [:h4writer] from comment #1) GVN will only do something if block 1 dominates block 2, it won't move these loads to block 0.
Comment 3•11 years ago
|
||
https://hg.mozilla.org/mozilla-central/rev/55497c1e7391
Status: ASSIGNED → RESOLVED
Closed: 11 years ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla25
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Description
•