> Exactly, that's what I meant to say when I said "when loop
> conditionals are runtime dependent". To ensure safety in
> PromoteValuesInLoop(), one needs to prove that basic-block is executed
> at least once. The question is how ?
The most general way to do this is to convert loops like this:
while (x) {
body;
}
to this:
if (x) {
do {
body;
} while (x);
}
In the second form, code hoisted/sunk/promoted out of the loop will
still be under the guard of the if. Also see tree-ssa-loop-ch.c in GCC,
for example.
Dan
--
Dan Gohman, Cray Inc.
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