https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66142
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |rguenth at gcc dot gnu.org
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I guess it depends on what exactly SCCVN uses the operand vectors
created/optimized by copy_reference_ops_from_ref/valueize_refs_1 for.
If it is used only for tracking what is the value of the reference (the value
stored into that piece of memory), or also for canonicalization of references
to certain more canonical form, or both. If only the value of the reference,
then
supposedly it would be nice to get far more canonicalization in the references
(e.g. turn (perhaps multiple nested) COMPONENT_REFs into MEM_REFs with offset
(except perhaps for bitfields, perhaps even do something about ARRAY_REFs, so
that say even:
struct A { float x, y; };
struct B { struct A u; };
void bar (struct A *);
float
f2 (struct B *x, int y)
{
struct A p;
p.x = 1.0f;
p.y = 2.0f;
char *z = (char *) x;
z += y * sizeof (struct B);
z += __builtin_offsetof (struct B, u.y);
x[y].u = p;
float f = *(float *) z;
bar (&p);
return f;
}
is handled). But, supposedly it would be undesirable to canonicalize all the
COMPONENT_REFs to the MEM_REFs (at least early on, e.g. for
__builtin_object_size (, 1) purposes, or aliasing etc.).
Richi, any thoughts on this?
