Status: Accepted
Owner: ----
CC: [email protected], [email protected]
Labels: Type-Bug Priority-Medium
New issue 3176 by [email protected]: Optimistic bounds check
generalization leads to repetetive deoptimization
http://code.google.com/p/v8/issues/detail?id=3176
In the code below optimizer optimistically generalizes bounds check at (*)
to perform both i and i - 5 checks. This leads to a deopt at the very first
loop iteration. Optimizer never learns anything from the deopt and will
continue to repeat the mistake.
function foo(a) {
var sum = 0;
for (var i = 0; i < 10; i++) {
sum += a[i]; // (*)
if (i > 6) {
sum -= a[i - 4];
sum -= a[i - 5];
}
}
return sum;
}
var a = new Int32Array(10);
foo(a);
foo(a);
%OptimizeFunctionOnNextCall(foo);
foo(a);
%OptimizeFunctionOnNextCall(foo);
foo(a);
Most probably related to r19475 hence CCing Sven and Jakob.
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