> On Thu, 12 Nov 2020, Jan Hubicka wrote:
>
> > Hi,
> > this is updated patch I am re-testing and plan to commit if it suceeds.
> >
> > * fold-const.c (operand_compare::operand_equal_p): Compare
> > offsets of fields in component_refs when comparing addresses.
> > (operand_compare::hash_operand): Likewise.
> > diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> > index c47557daeba..273ee25ceda 100644
> > --- a/gcc/fold-const.c
> > +++ b/gcc/fold-const.c
> > @@ -3312,11 +3312,36 @@ operand_compare::operand_equal_p (const_tree arg0,
> > const_tree arg1,
> > case COMPONENT_REF:
> > /* Handle operand 2 the same as for ARRAY_REF. Operand 0
> > may be NULL when we're called to compare MEM_EXPRs. */
> > - if (!OP_SAME_WITH_NULL (0)
> > - || !OP_SAME (1))
> > + if (!OP_SAME_WITH_NULL (0))
> > return false;
> > - flags &= ~OEP_ADDRESS_OF;
> > - return OP_SAME_WITH_NULL (2);
> > + /* Most of time we only need to compare FIELD_DECLs for equality.
> > + However when determining address look into actual offsets.
> > + These may match for unions and unshared record types. */
>
> looks like you can simplify by doing
>
> flags &= ~OEP_ADDRESS_OF;
>
> here. Neither the FIELD_DECL compare nor the offsets need it
Yep
>
> You elided
>
> flags &= ~OEP_ADDRESS_OF;
> - return OP_SAME_WITH_NULL (2);
>
> that was here when OP_SAME (1), please re-instantiate.
Sorry for that, that was not very careful.
Here is updated patch I re-tested x86_64-linux.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index c47557daeba..ddf18f27cb7 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -3312,10 +3312,32 @@ operand_compare::operand_equal_p (const_tree arg0,
const_tree arg1,
case COMPONENT_REF:
/* Handle operand 2 the same as for ARRAY_REF. Operand 0
may be NULL when we're called to compare MEM_EXPRs. */
- if (!OP_SAME_WITH_NULL (0)
- || !OP_SAME (1))
+ if (!OP_SAME_WITH_NULL (0))
return false;
+ /* Most of time we only need to compare FIELD_DECLs for equality.
+ However when determining address look into actual offsets.
+ These may match for unions and unshared record types. */
flags &= ~OEP_ADDRESS_OF;
+ if (!OP_SAME (1))
+ {
+ if (flags & OEP_ADDRESS_OF)
+ {
+ if (TREE_OPERAND (arg0, 2)
+ || TREE_OPERAND (arg1, 2))
+ return OP_SAME_WITH_NULL (2);
+ tree field0 = TREE_OPERAND (arg0, 1);
+ tree field1 = TREE_OPERAND (arg1, 1);
+
+ if (!operand_equal_p (DECL_FIELD_OFFSET (field0),
+ DECL_FIELD_OFFSET (field1), flags)
+ || !operand_equal_p (DECL_FIELD_BIT_OFFSET (field0),
+ DECL_FIELD_BIT_OFFSET (field1),
+ flags))
+ return false;
+ }
+ else
+ return false;
+ }
return OP_SAME_WITH_NULL (2);
case BIT_FIELD_REF:
@@ -3787,9 +3809,26 @@ operand_compare::hash_operand (const_tree t,
inchash::hash &hstate,
sflags = flags;
break;
+ case COMPONENT_REF:
+ if (sflags & OEP_ADDRESS_OF)
+ {
+ hash_operand (TREE_OPERAND (t, 0), hstate, flags);
+ if (TREE_OPERAND (t, 2))
+ hash_operand (TREE_OPERAND (t, 2), hstate,
+ flags & ~OEP_ADDRESS_OF);
+ else
+ {
+ tree field = TREE_OPERAND (t, 1);
+ hash_operand (DECL_FIELD_OFFSET (field),
+ hstate, flags & ~OEP_ADDRESS_OF);
+ hash_operand (DECL_FIELD_BIT_OFFSET (field),
+ hstate, flags & ~OEP_ADDRESS_OF);
+ }
+ return;
+ }
+ break;
case ARRAY_REF:
case ARRAY_RANGE_REF:
- case COMPONENT_REF:
case BIT_FIELD_REF:
sflags &= ~OEP_ADDRESS_OF;
break;
