src/v8/test/mjsunit/concurrent-initial-prototype-change.js

// Copyright 2013 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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// Flags: --allow-natives-syntax
// Flags: --concurrent-recompilation --block-concurrent-recompilation
// Flags: --nostress-opt --no-always-opt

// --nostress-opt is in place because this particular optimization
// (guaranteeing that the Array prototype chain has no elements) is
// maintained isolate-wide. Once it's been "broken" by the change
// to the Object prototype below, future compiles will not use the
// optimization anymore, and the code will remain optimized despite
// additional changes to the prototype chain.

if (!%IsConcurrentRecompilationSupported()) {
  print("Concurrent recompilation is disabled. Skipping this test.");
  quit();
}

function f1(a, i) {
  return a[i] + 0.5;
}

var arr = [0.0,,2.5];
assertEquals(0.5, f1(arr, 0));
assertEquals(0.5, f1(arr, 0));

// Optimized code of f1 depends on initial object and array maps.
%OptimizeFunctionOnNextCall(f1, "concurrent");
// Kick off recompilation;
assertEquals(0.5, f1(arr, 0));
// Invalidate current initial object map after compile graph has been created.
Object.prototype[1] = 1.5;
assertEquals(2, f1(arr, 1));
// Not yet optimized since concurrent recompilation is blocked.
assertUnoptimized(f1, "no sync");
// Let concurrent recompilation proceed.
%UnblockConcurrentRecompilation();
// Sync with background thread to conclude optimization, which bails out
// due to map dependency.
assertUnoptimized(f1, "sync");
//Clear type info for stress runs.
%ClearFunctionFeedback(f1);