Andrew Pinski wrote:

Actually they will with multi threaded program, since you can have a case
where it works and now it is broken because one thread has speed up so much it
writes to a variable which had a copy on another thread's stack.  So the 
argument
about it being too strong is wrong because timming matters now a days.  
Instruction
scheduling can cause the same issue as it forces a write too early for another 
thread
to act on.

But the behavior of such programs is typically fundamentally non-deterministic. I don't think it is useful to lump in this
kind of change with other functional changes. Remember that
the standard has NOTHING to say about instruction speeds and
even informally, any program depending on relative speeds of
two instruction streams is just TOO far out to consider.

Thanks,
Andrew Pinski

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