On 02/29/12 03:22, Richard Guenther wrote:

So fixing up individual passes is easier - I can only think of PRE being
problematic right now, I am not aware that any other pass moves loads
or stores.  So I'd simply pre-compute the stmt bit in PRE and adjust

           if (gimple_has_volatile_ops (stmt)
               || stmt_could_throw_p (stmt))

in compute_avail accordingly.

Initially I thought PRE would be problematic for transactions, but perhaps it isn't. As I understand, for PRE we hoist loads/computations that are mostly redundant, but will be performed on every path:

        if (flag)
                a = b + c;
        d = b + c;              <-- [b + c] always computed

Even if we hoist [b + c] before the flag, [b + c] will be computed on every path out of "if (flag)...". So... we can allow this transformation within transactions, right?


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