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Re: Simple Value Range Propagation
> How does this one differ from the one from John Wehle
> in <http://gcc.gnu.org/ml/gcc-patches/2000-07/msg00968.html>?
It is simpler and much faster. Basically it does not spend much time in
loops (it is not iterating as the old patch (it did 1000x times? in
"for (i = 0; i < 1000; i++)")).
The loop condition is a condition like every other condition for my VRP.
My VRP takes care only about simple sets:
(set (reg) (const_int))
(set (reg) (reg)
and simple conditions:
(cmp_operator (reg) (const_int))
(cmp_operator (reg) (reg))
It performs a data flow, the in and out sets contain a range for
each register (for saving memory and time the full ranges are not there,
i.e. when there is no range for a register the range is full
(i.e. [min_val,max_val])).
More detailed description is in
http://gcc.gnu.org/ml/gcc-patches/2003-06/msg00794.html
And also the overall comment in vrp.c in the patch:
http://gcc.gnu.org/ml/gcc-patches/2003-06/msg00730.html
Josef