Open Bug 1436427 Opened 6 years ago Updated 2 years ago

Consider optimizing MBoundsCheck followed by MSpectreMaskIndex

Categories

(Core :: JavaScript Engine: JIT, enhancement, P2)

Product:
Core
Component:
JavaScript Engine: JIT
Type:
enhancement

Tracking

()

Tracking Flags:
Tracking Status
firefox60 --- fix-optional

People

(Reporter: jandem, Unassigned)

References

(Blocks 1 open bug)

Details

Before/during lowering we could check for MBoundsCheck followed by MSpectreMaskIndex with the same index/length operands. In that case we could lower it to a LIR op that does a single cmp followed by a jump + cmov (instead of doing two cmp instructions).

This is just a follow-up perf optimization. A good first step would be to instrument a shell build and see if this optimization would hit on benchmarks like Kraken/Octane.
Severity: normal → enhancement
status-firefox60: --- → fix-optional
Priority: -- → P2
Severity: normal → S3
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