diff options
Diffstat (limited to 'gcc/convert.c')
| -rw-r--r-- | gcc/convert.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/gcc/convert.c b/gcc/convert.c index 127b22b7eef..156c2cf40ae 100644 --- a/gcc/convert.c +++ b/gcc/convert.c @@ -227,9 +227,11 @@ convert_to_integer (type, expr) case LSHIFT_EXPR: /* We can pass truncation down through left shifting - when the shift count is a nonnegative constant. */ + when the shift count is a nonnegative constant and + the target type is unsigned. */ if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST && tree_int_cst_sgn (TREE_OPERAND (expr, 1)) >= 0 + && TREE_UNSIGNED (type) && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST) { /* If shift count is less than the width of the truncated type, @@ -311,12 +313,15 @@ convert_to_integer (type, expr) /* Don't do unsigned arithmetic where signed was wanted, or vice versa. Exception: if both of the original operands were - unsigned then can safely do the work as unsigned. + unsigned then we can safely do the work as unsigned; + if we are distributing through a LSHIFT_EXPR, we must + do the work as unsigned to avoid a signed overflow. And we may need to do it as unsigned if we truncate to the original size. */ typex = ((TREE_UNSIGNED (TREE_TYPE (expr)) || (TREE_UNSIGNED (TREE_TYPE (arg0)) - && TREE_UNSIGNED (TREE_TYPE (arg1)))) + && TREE_UNSIGNED (TREE_TYPE (arg1))) + || ex_form == LSHIFT_EXPR) ? unsigned_type (typex) : signed_type (typex)); return convert (type, fold (build (ex_form, typex, |