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Re: combine permutations in gimple
On Mon, 13 Aug 2012, Richard Guenther wrote:
+ /* Check that it is only used here. We cannot use has_single_use
+ since the expression is using it twice itself... */
Ah ... so then
|| num_imm_uses (op0) != 2
Ah, ok, that's simpler indeed, but there were such dire warnings to never
use that evil function unless absolutely necessary that I didn't dare use
it... Thanks for the permission.
If your new predicate would match more places (can you do a quick search?)
You mean: if there are more optimizations that either already check for
double use in the same statement, or could benefit from doing so? I'll
take a look.
then we want it in tree-flow-inline.h instead of in
tree-ssa-forwprop.c. But yes,
num_imm_uses can be expensive. For now just stick with the above.
I assume "the above" means "num_imm_uses (op0) != 2", since both versions
are above ;-)
The natural SSA (and forwprop) way is to look for BIT_FIELD_REF and see
if the def stmt is a VEC_PERM_EXPR.