1125185 - MOZ_COLD attribute for infrequently executed functions

Status: RESOLVED FIXED

(Core :: MFBT, enhancement)

Description

[Dan Gohman [:sunfish]]

Attachment: cold-attribute.patch

The attached patch adds a MOZ_COLD macro, which is __attribute__((cold)) on GCC and clang, which decorates functions with a hint to compiler optimizers that they are infrequently executed.

It also adds MOZ_COLD to a handful of what I believe are fairly obvious cold functions.

I'm primarily adding this in preparation for a patch in bug 986981, since it adds a bunch of code that's only run from the asm.js signal handler for out-of-bounds accesses, which should be cold in practice.

Comment 1

[Dan Gohman [:sunfish]]

Attachment: cold-attribute.patch

Minor update to move MOZ_COLD out of the C++-only section of Attributes.h as apparently there are some C things in a full mozilla-central build too.

Comment 2

[Jeff Walden [:Waldo]]

Comment on attachment 8553790 [details] [diff] [review]
cold-attribute.patch

Review of attachment 8553790 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/gc/StoreBuffer.h
@@ +24,1 @@
>  CrashAtUnhandlableOOM(const char *reason);

Just remove this declaration.  This header already includes LifoAlloc.h, so this is unnecessary.  Although, to be honest, I think this probably belongs most properly in jsutil.h -- move the single declaration there?  LifoAlloc.h includes jsutil.h, so this shouldn't require any other adjustments.

Comment 3

[Dan Gohman [:sunfish]]

Ok, I moved the CrashAtUnhandlableOOM declaration as reuqested.

https://hg.mozilla.org/integration/mozilla-inbound/rev/780d7bb5eb82

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/780d7bb5eb82