Created attachment 8881984 [details] [diff] [review] Patch START_ASSERT_SAME_COMPARTMENT calls CurrentThreadIsHeapBusy which does an OOL call where we do a TLS lookup. Compartment checks are Nightly-only but this overhead makes it harder to profile. Here's a patch to just inline CurrentThreadIsHeapBusy in START_ASSERT_SAME_COMPARTMENT.
Pushed by email@example.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/e54513aa7922 Inline CurrentThreadIsHeapBusy in START_ASSERT_SAME_COMPARTMENT to avoid a TLS lookup for each compartment check. r=jonco