diff options
Diffstat (limited to 'gcc/cp/class.c')
| -rw-r--r-- | gcc/cp/class.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/gcc/cp/class.c b/gcc/cp/class.c index cc26cb8..1cf87dc 100644 --- a/gcc/cp/class.c +++ b/gcc/cp/class.c @@ -4727,6 +4727,29 @@ layout_class_type (tree t, tree *virtuals_p) "classes to be placed at different locations in a " "future version of GCC", field); + /* The middle end uses the type of expressions to determine the + possible range of expression values. In order to optimize + "x.i > 7" to "false" for a 2-bit bitfield "i", the middle end + must be made aware of the width of "i", via its type. + + Because C++ does not have integer types of arbitrary width, + we must (for the purposes of the front end) convert from the + type assigned here to the declared type of the bitfield + whenever a bitfield expression is used as an rvalue. + Similarly, when assigning a value to a bitfield, the value + must be converted to the type given the bitfield here. */ + if (DECL_C_BIT_FIELD (field)) + { + tree ftype; + unsigned HOST_WIDE_INT width; + ftype = TREE_TYPE (field); + width = tree_low_cst (DECL_SIZE (field), /*unsignedp=*/1); + if (width != TYPE_PRECISION (ftype)) + TREE_TYPE (field) + = c_build_bitfield_integer_type (width, + TYPE_UNSIGNED (ftype)); + } + /* If we needed additional padding after this field, add it now. */ if (padding) |