http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56965
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |ebotcazou at gcc dot gnu.org
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Besides that nonoverlapping_component_refs_p is O(3) in the size of the refs
involved.
It also seems to ignore inner VIEW_CONVERT_EXPRs which means that doing the
struct X vs. struct Y dance with a VIEW_CONVERT_EXPR exposes a similar issue
(insert suitable Ada testcase here).
In the end I'd like to get rid of nonoverlapping_component_refs_p by moving
it to the tree oracle (where there is a similar but less aggressive
aliasing_component_refs_p).
It appears to me that nonoverlapping_component_refs_p could avoid its O(3)
complexity by doing sth like
... search for innermost VIEW_CONVERT_EXPR and start at its base ...
vec<pair<tree, tree>> comprefs1;
while (handled_component_ref_p (ref))
{
if (TREE_CODE (ref) == COMPONENT_REF)
comprefs.safe_push (pair (ref, TYPE_MAIN_VARIANT (TYPE_CONTEXT
(TREE_OPERAND (ref, 1)))));
ref = TREE_OPERAND (ref, 0);
}
same for the other ref. Then sort the two vectors after the context type
(using TYPE_UID as key for example) and then comparing the two vectors
in lock-step.
-> O (n * log (n))
(and we can skip over non-component-handled-components as in the code above).
