463258 - Simplify guard record at LIR_loop

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, enhancement)

Description

[David Mandelin [:dmandelin]]

Given that LIR_loop does not in fact exit, it seems that a guard record and side exit are unnecessary. Ideally, can we eliminate the need for them entirely? Or, failing that, a simple API that will insert the minimal data and close the loop?

Comment 1

[Graydon Hoare :graydon]

LIR_loop exits now, conditionally; depends if its hot-patched by a timeout handler. But a side exit gets generated, and is used.

Comment 2

[Andreas Gal :gal]

LIR_loop has to be a guard for 2 reasons, one is the StackFilter (need the start state for the stack water-level analysis) and the other one is timeout handling. We can remove a lot of the SideExit state though and provide a SideExit base class and optional and separate extensions for the tracer and regexp.

Comment 3

[David Mandelin [:dmandelin]]

Hmm. I guess the hot-patching mechanism should behave identically on regexp native code loops to how it does for TM loops.

Comment 4

[Ryan VanderMeulen [:RyanVM]]

Obsolete with the removal of tracejit.