• Simon Marlow's avatar
    Rolling back: Make FastString thread-safe. · 479b0241
    Simon Marlow authored
    This patch was the cause of the compile-time performance regression in
    #3796.  My guess is that it is due to the use of unsafePerformIO which
    traverses the stack up to the first update frame, and perhaps we have
    a deep stack when reading the dictionary from a .hi file.  In any
    case, since we're not relying on thread safety for FastStrings, I
    think the safest thing to do is back this out until we can investigate