https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112706
Bug ID: 112706
Summary: missed simplification in FRE
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: hubicka at gcc dot gnu.org
Target Milestone: ---
Compiling the following testcase (simplified from repeated
std::vector::push_back expansion):
int *ptr;
void link_error ();
void
test ()
{
int *ptr1 = ptr + 10;
int *ptr2 = ptr + 20;
if (ptr1 == ptr2)
link_error ();
}
with gcc -O2 t.C -fdump-tree-all-details
one can check that link_error is optimized away really late:
jh@ryzen4:/tmp> grep link_error a-t.C*
....
a-t.C.106t.cunrolli: link_error ();
a-t.C.107t.backprop: link_error ();
a-t.C.108t.phiprop: link_error ();
a-t.C.109t.forwprop2:link_error ();
this is too late for some optimization to catch up (in the case of std::vector
we end up missing DSE since the transform is delayed to forwprop3)
I think this is something value numbering should catch.
