v8/test/mjsunit/compiler/regress-3218915.js

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// Flags: --allow-natives-syntax

// Regression test for failure to deoptimize properly when the most recent
// side effect occurred in a comma expression in an effect context.

// An unoptimizable function, calling it is a side effect.
function side_effect() { try {} finally {} return "wrong"; }

// A function to observe the value of its first argument.
function observe(x, y) { try {} finally {} return x; }

// If we optimize for x a smi, then x a string will deopt.  The side effect
// immediately before the deopt is in a comma expresion in an effect context
// (i.e., itself the left subexpression of a comma expression).
function test(x) { return observe(this, ((0, side_effect()), x + 1)); }

// Run test enough times to get it optimized.
%PrepareFunctionForOptimization(test);
for (var i = 0; i < 5; ++i) test(0);
%OptimizeFunctionOnNextCall(test);
test(0);

// Force test to deopt.  If it behaves normally, it should return the global
// object.  If the value of the call to side_effect() is lingering after the
// deopt, it will return the string "wrong".
assertFalse(test("a") === "wrong");