diff options
Diffstat (limited to 'gcc/convert.c')
| -rw-r--r-- | gcc/convert.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/gcc/convert.c b/gcc/convert.c index e440e35f575..aa0d0fb4140 100644 --- a/gcc/convert.c +++ b/gcc/convert.c @@ -182,7 +182,27 @@ convert_to_integer (type, expr) we are truncating EXPR. */ else if (outprec >= inprec) - return build1 (NOP_EXPR, type, expr); + { + enum tree_code code; + + /* If the precision of the EXPR's type is K bits and the + destination mode has more bits, and the sign is changing, + it is not safe to use a NOP_EXPR. For example, suppose + that EXPR's type is a 3-bit unsigned integer type, the + TYPE is a 3-bit signed integer type, and the machine mode + for the types is 8-bit QImode. In that case, the + conversion necessitates an explicit sign-extension. In + the signed-to-unsigned case the high-order bits have to + be cleared. */ + if (TREE_UNSIGNED (type) != TREE_UNSIGNED (TREE_TYPE (expr)) + && (TYPE_PRECISION (TREE_TYPE (expr)) + != GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (expr))))) + code = CONVERT_EXPR; + else + code = NOP_EXPR; + + return build1 (code, type, expr); + } /* If TYPE is an enumeral type or a type with a precision less than the number of bits in its mode, do the conversion to the |