1112641 - Re-enable regalloc optimizations when backtracking allocator is enabled by default

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine: JIT, enhancement, P5)

Description

[Dan Gohman [:sunfish]]

Bug 1100123, bug 1099216, bug 1103389, and bug 1096138 all require workarounds for limitations in the LSRA register allocator. Since the plan is to eventually make backtracking be enabled by default, when that happens, we should revisit those patches to see if the optimizations can be re-enabled.

Comment 1

[Paul Wright]

So can this be revisited at this point or is another bug taken the thunder out of this one?

Comment 2

[Till Schneidereit [:till]]

Seems like this should be doable now.

Comment 3

[Hannes Verschore [:h4writer]]

Seems only the workarounds for SIMD instructions are left. bug 1096138 is already fixed.
Benjamin can you take a look if removing the workarounds would give better code?

Comment 4

[Benjamin Bouvier [:bbouvier] (inactive)]

Tried to remove all of them, but it was crashing in some other places (MoveEmitter doesn't allow moves of registers from one type to another different type). At this point, considering that SIMD.js has stalled a bit, and until SIMD gets in wasm, we might probably invest in Cretonne instead of spending too much time on Spidermonkey's issues. Closing as WONTFIX, but if somebody else wanted to have a deeper look, feel free!