src/v8/test/mjsunit/unary-minus-deopt.js

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// Flags: --allow-natives-syntax --opt --no-always-opt

// This is a boiled-down example happening in the Epic Citadel demo:
// After deopting, the multiplication for unary minus stayed in Smi
// mode instead of going to double mode, leading to deopt loops.

function unaryMinusTest(x) {
  var g = (1 << x) | 0;
  // Optimized code will contain a LMulI with -1 as right operand.
  return (g & -g) - 1 | 0;
}

%PrepareFunctionForOptimization(unaryMinusTest);
unaryMinusTest(3);
unaryMinusTest(3);
%OptimizeFunctionOnNextCall(unaryMinusTest);
unaryMinusTest(3);
assertOptimized(unaryMinusTest);

// Deopt on kMinInt
unaryMinusTest(31);
// The following is normally true, but not with --stress-opt. :-/
// assertUnoptimized(unaryMinusTest);
%PrepareFunctionForOptimization(unaryMinusTest);

// We should have learned something from the deopt.
unaryMinusTest(31);
%OptimizeFunctionOnNextCall(unaryMinusTest);
unaryMinusTest(31);
assertOptimized(unaryMinusTest);