The following fixes a mistake in an earlier patch of mine fixing
PR71002. fold-const.c make_bit_field_ref doesn't care about alias
sets of references it merges but as it commons to a common base
it assumed the original refs were aliased by the new one. The
testcase of PR71002 shows this is not true for union references
which are punned to alias-set zero. Now my fix retained the
alias-set of (one of!) the original refs if it wasn't equal to
the alias-set of the common inner ref. That obviously breaks
things if the alias sets of the other original refs do not alias
this one.
The following rectifies this by only handling the alias-set zero
case as required by the original PR.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk
and branch.
Richard.
2016-10-28 Richard Biener <rguent...@suse.de>
PR middle-end/78128
PR middle-end/71002
* fold-const.c (make_bit_field_ref): Only adjust alias set
when the original alias set was zero.
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 241642)
+++ gcc/fold-const.c (working copy)
@@ -3787,11 +3787,11 @@ make_bit_field_ref (location_t loc, tree
{
tree result, bftype;
- if (get_alias_set (inner) != get_alias_set (orig_inner))
+ alias_set_type iset = get_alias_set (orig_inner);
+ if (iset == 0 && get_alias_set (inner) != iset)
inner = fold_build2 (MEM_REF, TREE_TYPE (inner),
build_fold_addr_expr (inner),
- build_int_cst
- (reference_alias_ptr_type (orig_inner), 0));
+ build_int_cst (ptr_type_node, 0));
if (bitpos == 0 && !reversep)
{
