Török Edvin 99536a178c Insert timeout checks directly into the JITed code. ...

pthread_cancel is broken on Mac OS X (it only works if the thread
you want to kill calls pthread_testcancel, which is never the situation
when you need async cancelation).
Anyway async cancelation is risky, it may leave bc_ctx in an inconsistent state.
So rather than doing using pthread_cancel (or pthread_kill+siglongjmp)
just insert the timeout checks into the JITed code directly.

These are inserted in each loop, if the loop's tripcount is unknown, or
higher than a threshold. They are also inserted after a certain amount
of APIcalls are made (even in absence of loops).
Note that 'loop' in this sense is not LLVM's notion of a natural loop,
it is simply a BB which is reachable both directly and via a backedge.

For example this doesn't contain natural loops but contains backedges (and a
potential infinite loop):
int foo(int a)
{
    int x=4;
    if (a == 42)
        goto head2;
head:
    x++;
head2:
    if (a >= 2) {
        x += 3;
        goto head;
    } else if (a >= 0) {
        x += 9;
        goto head;
    }
    return x;
}

2010-03-23 15:54:41 +02:00

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