1501310 - Consider moving Baseline fallback IC stub code to JSRuntime

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P3)

Description

[Ted Campbell [:tcampbell]]

As we complete the migration of ICs to CacheIR, the remaining ICs are primarily fallbacks. We should investigate moving this JitCode to the JSRuntime to be shared.

This would simplify parts of baseline compilation and we may be able to eliminate the fallback IC stub space.

Comment 1

[Jan de Mooij [:jandem]]

Let's do this after bug 1499644 lands to avoid bitrotting that (and this patch will look nicer on top of that).

Comment 2

[Jan de Mooij [:jandem]]

I've been thinking a bit about the right design for this.

* We probably need a FallbackStubKind enum class so we can store an EnumeratedArray<FallbackStubKind, uint32_t> in JitRuntime - storing the offset in a shared JitCode* instance, similar to (other) runtime trampolines.

* The stub compiler class for each stub is currently responsible for (1) Compiling stub code and (2) allocating the stub.

For (1) I think it might be nice to use a shared FallbackStubCompiler class that compiles all the fallback stub codes. It could call a static method on each fallback stub class to compile the code for it, for example we would have:

  static void emitCode(FallbackStubCompiler& compiler);

on ICTypeOf_Fallback, ICGetProp_Fallback, etc.

For (2) I think we can probably allocate the stub directly in ICScript::Create, once bug 1499644 is done. Maybe with some helper lambda and perfect forwarding.

Comment 3

[Jan de Mooij [:jandem]]

I started working on this as first step to speed up ICScript allocation.

Having this in JitRealm instead of JitRuntime is just wasteful and after this and Ian's work converting the Call IC to CacheIR we should be able to remove a lot of the old ICStubCompiler infrastructure.

Comment 4

[Jan de Mooij [:jandem]]

Attachment: Bug 1501310 - Move Baseline IC fallback code from JitRealm to JitRuntime. r?tcampbell!

Fallback code is now generated (as a single JitCode instance) when we create the
JitRuntime.

In ICScript::Create we can now allocate the fallback stubs directly (we no
longer need a Compiler class for each fallback stub) because we no longer have
to handle the compile-code case.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d6fb444fa553
Move Baseline IC fallback code from JitRealm to JitRuntime. r=tcampbell

Comment 6

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/d6fb444fa553