VM library tweaks to avoid megamorphic calls in dart2js

VM library tweaks to avoid megamorphic calls in dart2js

Problems this addresses:

1. dart2js has hashCode functions like

   get hashCode = this.x.hashCode + 17 * this.y.hashCode

When x and y are ints or bools VM optimizing compiler inlined the call
to Object.hashCode and generated MegamorphicLookups for
Object._identityHashCode.

2. HashMaps with _Smi keys had a double MegamorphicLookup: The hash
table reasonably calls MegamorphicLookup(get:hashCode) which returns
Object.hashCode; the compiled Object.hashCode is essentially
MegamorphicLookup(get:_identityHashCode), which returns
_Smi._identityHashCode which finally returns 'this'.

3. _interpolateSingle's call to o.toString() is megamorphic. We can
avoid it for the common case of String arguments, this is often
comming from StringBuffer.write() with a literal or interpolated
argument.

R=srdjan@google.com

Committed: https://github.com/dart-lang/sdk/commit/dce10bba79f388932e5fb912db4c78701343c57b

[sra1, 2016-03-19 23:43:02]

sra@google.com changed reviewers:
+ srdjan@google.com

[kevmoo, 2016-03-21 14:32:18]

kevmoo@google.com changed reviewers:
+ kevmoo@google.com

[kevmoo, 2016-03-21 14:32:19]

DBC: out of curiosity tried this with pop-pop-win.

4% speed improvement. Cool!

[srdjan, 2016-03-21 14:54:38]

lgtm

[sra1, 2016-03-21 16:38:27]

Description was changed from

==========
VM library tweaks to avoid megamorphic calls in dart2js

Problems this addresses:

1. dart2js has hashCode functions like

   get hashCode = this.x.hashCode + 17 * this.y.hashCode

When x and y are ints or bools VM optimizing compiler inlined the call
to Object.hashCode and generated MegamorphicLookups for
Object._identityHashCode.

2. HashMaps with _Smi keys had a double MegamorphicLookup: The hash
table reasonably calls MegamorphicLookup(get:hashCode) which returns
Object.hashCode; the compiled Object.hashCode is essentially
MegamorphicLookup(get:_identityHashCode), which returns
_Smi._identityHashCode which finally returns 'this'.

3. _interpolateSingle's call to o.toString() is megamorphic. We can
avoid it for the common case of String arguments, this is often
comming from StringBuffer.write() with a literal or interpolated
argument.
==========

to

==========
VM library tweaks to avoid megamorphic calls in dart2js

Problems this addresses:

1. dart2js has hashCode functions like

   get hashCode = this.x.hashCode + 17 * this.y.hashCode

When x and y are ints or bools VM optimizing compiler inlined the call
to Object.hashCode and generated MegamorphicLookups for
Object._identityHashCode.

2. HashMaps with _Smi keys had a double MegamorphicLookup: The hash
table reasonably calls MegamorphicLookup(get:hashCode) which returns
Object.hashCode; the compiled Object.hashCode is essentially
MegamorphicLookup(get:_identityHashCode), which returns
_Smi._identityHashCode which finally returns 'this'.

3. _interpolateSingle's call to o.toString() is megamorphic. We can
avoid it for the common case of String arguments, this is often
comming from StringBuffer.write() with a literal or interpolated
argument.

R=srdjan@google.com

Committed:
https://github.com/dart-lang/sdk/commit/dce10bba79f388932e5fb912db4c78701343c57b
==========

[sra1, 2016-03-21 16:38:28]

Committed patchset #1 (id:1) manually as
dce10bba79f388932e5fb912db4c78701343c57b (presubmit successful).