The following patch is necessary to make DECL_BIT_FIELD_REPRESENTATIVE
useable in COMPONENT_REFs (which is the easiest way to get
some bitfield lowering).
An earlier patch passed bootstrapped and testing on
x86_64-unknown-linux-gnu (with bitfield lowering), re-testing
after minor changes.
2013-11-11 Richard Biener <rguent...@suse.de>
* tree-ssa-alias.c (nonoverlapping_component_refs_of_decl_p):
Properly handle DECL_BIT_FIELD_REPRESENTATIVE occuring as
COMPONENT_REF operand.
* alias.c (nonoverlapping_component_refs_p): Likewise.
* stor-layout.c (start_bitfield_representative): Mark
DECL_BIT_FIELD_REPRESENTATIVE as DECL_NONADDRESSABLE_P.
Index: gcc/tree-ssa-alias.c
===================================================================
*** gcc/tree-ssa-alias.c.orig 2013-11-11 10:32:25.000000000 +0100
--- gcc/tree-ssa-alias.c 2013-11-11 11:35:16.042386275 +0100
*************** nonoverlapping_component_refs_of_decl_p
*** 829,841 ****
if (type1 != type2 || TREE_CODE (type1) != RECORD_TYPE)
goto may_overlap;
- /* Different fields of the same record type cannot overlap.
- ??? Bitfields can overlap at RTL level so punt on them. */
if (field1 != field2)
{
component_refs1.release ();
component_refs2.release ();
! return !(DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2));
}
}
--- 829,848 ----
if (type1 != type2 || TREE_CODE (type1) != RECORD_TYPE)
goto may_overlap;
if (field1 != field2)
{
component_refs1.release ();
component_refs2.release ();
! /* A field and its representative need to be considered the
! same. */
! if (DECL_BIT_FIELD_REPRESENTATIVE (field1) == field2
! || DECL_BIT_FIELD_REPRESENTATIVE (field2) == field1)
! return false;
! /* Different fields of the same record type cannot overlap.
! ??? Bitfields can overlap at RTL level so punt on them. */
! if (DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2))
! return false;
! return true;
}
}
Index: gcc/stor-layout.c
===================================================================
*** gcc/stor-layout.c.orig 2013-11-11 12:05:16.000000000 +0100
--- gcc/stor-layout.c 2013-11-11 13:42:14.947161958 +0100
*************** start_bitfield_representative (tree fiel
*** 1747,1752 ****
--- 1747,1757 ----
DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field);
DECL_PACKED (repr) = DECL_PACKED (field);
DECL_CONTEXT (repr) = DECL_CONTEXT (field);
+ /* There are no indirect accesses to this field. If we introduce
+ some then they have to use the record alias set. This makes
+ sure to properly conflict with [indirect] accesses to addressable
+ fields of the bitfield group. */
+ DECL_NONADDRESSABLE_P (repr) = 1;
return repr;
}
Index: gcc/alias.c
===================================================================
*** gcc/alias.c.orig 2013-11-11 15:29:12.000000000 +0100
--- gcc/alias.c 2013-11-11 15:29:17.054068720 +0100
*************** nonoverlapping_component_refs_p (const_r
*** 2302,2310 ****
found:
/* If we're left with accessing different fields of a structure, then no
! possible overlap, unless they are both bitfields. */
if (TREE_CODE (typex) == RECORD_TYPE && fieldx != fieldy)
! return !(DECL_BIT_FIELD (fieldx) && DECL_BIT_FIELD (fieldy));
/* The comparison on the current field failed. If we're accessing
a very nested structure, look at the next outer level. */
--- 2302,2316 ----
found:
/* If we're left with accessing different fields of a structure, then no
! possible overlap, unless they are both bitfields or one is
! the representative of the other. */
if (TREE_CODE (typex) == RECORD_TYPE && fieldx != fieldy)
! {
! if (DECL_BIT_FIELD_REPRESENTATIVE (fieldx) == fieldy
! || DECL_BIT_FIELD_REPRESENTATIVE (fieldy) == fieldx)
! return false;
! return !(DECL_BIT_FIELD (fieldx) && DECL_BIT_FIELD (fieldy));
! }
/* The comparison on the current field failed. If we're accessing
a very nested structure, look at the next outer level. */
