It is the intent for all_ones_mask_p to return true when 64 bits of ones in an
unsigned type of width 64 when size is 64, right? Currently the code uses a
signed type for tmask, which sets the upper bits to 1, when the value includes
the sign bit set and the equality code does check all 128 bits of the the value
for equality. This results in the current code returning false in this case.
The below change is the behavior change I'm talking about.
We're fixing this in the wide-int branch, and just wanted to see if someone
wanted to argue this isn't a bug.
If you want to see a small test case:
typedef enum
{
DK_ERROR,
DK_SORRY,
DK_LAST_DIAGNOSTIC_KIND
} diagnostic_t;
struct diagnostic_context
{
int diagnostic_count[DK_LAST_DIAGNOSTIC_KIND];
diagnostic_t *classify_diagnostic;
};
extern diagnostic_context *global_dc;
bool
seen_error (void)
{
return (global_dc)->diagnostic_count[(int) (DK_ERROR)] ||
(global_dc)->diagnostic_count[(int) (DK_SORRY)];
}
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 6506ae7..9b17d1d 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -3702,12 +3702,23 @@ all_ones_mask_p (const_tree mask, int size)
tmask = build_int_cst_type (signed_type_for (type), -1);
- return
- tree_int_cst_equal (mask,
- const_binop (RSHIFT_EXPR,
- const_binop (LSHIFT_EXPR, tmask,
- size_int (precision - size)),
- size_int (precision - size)));
+ if (tree_int_cst_equal (mask,
+ const_binop (RSHIFT_EXPR,
+ const_binop (LSHIFT_EXPR, tmask,
+ size_int (precision -
size)),
+ size_int (precision - size))))
+ return true;
+
+ tmask = build_int_cst_type (unsigned_type_for (type), -1);
+
+ if (tree_int_cst_equal (mask,
+ const_binop (RSHIFT_EXPR,
+ const_binop (LSHIFT_EXPR, tmask,
+ size_int (precision -
size)),
+ size_int (precision - size))))
+ return true;
+
+ return false;
}
/* Subroutine for fold: determine if VAL is the INTEGER_CONST that
