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Make sure the isolate hidden class is constant #6892

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floitschG opened this issue Nov 23, 2012 · 7 comments
Closed

Make sure the isolate hidden class is constant #6892

floitschG opened this issue Nov 23, 2012 · 7 comments
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@floitschG
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type-task web-dart2js

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@floitschG
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V8 optimizes function instantiations by moving constant functions into the hidden class.
for example function A() { this.foo = function() { return 499; }; }
Afaik this will move the function into the hidden class of the newly allocated object.
However if 'foo' changes this means that we have a map-transition. Normally this doesn't happen for dart2js generated code, but we should probably make sure that non-final statics don't have this problem:
===
bar() => 499;
var foo = bar;
// later in code:
... foo = (() => 42);
===
@peter-ahe-google
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Added this to the Later milestone.

@kasperl
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kasperl commented May 23, 2013

Added TriageForM5 label.

@kasperl
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kasperl commented May 28, 2013

Removed TriageForM5 label.

@kasperl
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kasperl commented Jul 10, 2014

Removed this from the Later milestone.
Added Oldschool-Milestone-Later label.

@kasperl
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kasperl commented Aug 4, 2014

Removed Oldschool-Milestone-Later label.

@karlklose
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@floitschG Could you update the status of this bug?

@floitschG
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Current version of dart2js seems to do the right thing. Deferred loading of libraries destroys the hidden map of global objects, but that's a different issue.

final x = (() { return 499; }) ();
final y = (() { return 42; }) ();

foo() {
  var sum = 0;
  for (int i = 0; i < 100000; i++) {
    sum += x;
    sum = sum & 0xFFFFFF;
  }
  return sum;
}

main() {
  for (int j = 0; j < 1000; j++) { foo(); }

  var sw = new Stopwatch()..start();
  for (int j = 0; j < 1000; j++) { foo(); }
  print(sw.elapsedMilliseconds);
  print(y);
  for (int j = 0; j < 1000; j++) { foo(); }
  sw.reset();
  for (int j = 0; j < 1000; j++) { foo(); }
  print(sw.elapsedMilliseconds);
}

@kevmoo kevmoo removed the triaged label Mar 1, 2016
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@kevmoo @kasperl @peter-ahe-google @karlklose @floitschG