This patch fixes PR18908, both the redundant bitfield truncation and
the allegedly missing tree simplification of Bool ^ 1 to ~Bool. The
former is because we for no reason truncate the result of bitwise
binary expressions again (not needed, operands are already truncated).
The latter is because integer_all_onesp uses the mode precision
to determine if all bits are set for an unsigned constant - that's
never true for all non-mode precision types (and thus Bool). There
is no reason for this restriction now that expansion of BIT_NOT_EXPR
is fixed.
Bootstrapped and tested on x86_64-unknown-linux-gnu, leaving a bit
for comments in case there are some.
Richard.
2011-07-19 Richard Guenther <rguent...@suse.de>
PR middle-end/18908
* tree.c (integer_all_onesp): Use TYPE_PRECISION, not MODE_PRECISION.
* expr.c (expand_expr_real_2): Do not unnecessarily truncate the
result of BIT_*_EXPR to bitfield precision.
Index: gcc/tree.c
===================================================================
--- gcc/tree.c (revision 176399)
+++ gcc/tree.c (working copy)
@@ -1759,9 +1759,7 @@ integer_all_onesp (const_tree expr)
if (!uns)
return 0;
- /* Note that using TYPE_PRECISION here is wrong. We care about the
- actual bits, not the (arbitrary) range of the type. */
- prec = GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (expr)));
+ prec = TYPE_PRECISION (TREE_TYPE (expr));
if (prec >= HOST_BITS_PER_WIDE_INT)
{
HOST_WIDE_INT high_value;
Index: gcc/expr.c
===================================================================
--- gcc/expr.c (revision 176399)
+++ gcc/expr.c (working copy)
@@ -8319,6 +8319,12 @@ expand_expr_real_2 (sepops ops, rtx targ
temp = expand_binop (mode, this_optab, op0, op1, target,
unsignedp, OPTAB_LIB_WIDEN);
gcc_assert (temp);
+ /* Bitwise operations do not need bitfield reduction as we expect their
+ operands being properly truncated. */
+ if (code == BIT_XOR_EXPR
+ || code == BIT_AND_EXPR
+ || code == BIT_IOR_EXPR)
+ return temp;
return REDUCE_BIT_FIELD (temp);
}
#undef REDUCE_BIT_FIELD
