938246 - getJSReturnTypeTag returns incorrect value for booleans

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Boris Zbarsky [:bzbarsky]]

We return JSVAL_TYPE_INT32, not JSVAL_TYPE_BOOLEAN.  That means the jit can't optimize away its type guards, since it knows it's seen types other than this one.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Attachment: Don't try to tell the JIT that our booleans are 32-bit integers, when they're actually booleans.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Attachment: Don't try to tell the JIT that our booleans are 32-bit integers, when they're actually booleans.

Comment 3

[Eric Faust [:efaust]]

Comment on attachment 831678 [details] [diff] [review]
Don't try to tell the JIT that our booleans are 32-bit integers, when they're actually booleans.

Nice catch. This looks like it might have been very unpleasant to track down. r=me

Comment 4

[Boris Zbarsky [:bzbarsky]]

I actually saw it while reading the code in Codegen.py...

Comment 5

[Boris Zbarsky [:bzbarsky]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/a90375867a74

Comment 6

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

https://hg.mozilla.org/mozilla-central/rev/a90375867a74