diff options
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 25069c5..3cc01ea 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -2625,6 +2625,7 @@ decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize, HOST_WIDE_INT *pbitpo enum machine_mode *pmode, int *punsignedp, int *pvolatilep, tree *pmask, tree *pand_mask) { + tree outer_type = 0; tree and_mask = 0; tree mask, inner, offset; tree unsigned_type; @@ -2636,6 +2637,13 @@ decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize, HOST_WIDE_INT *pbitpo if (! INTEGRAL_TYPE_P (TREE_TYPE (exp))) return 0; + /* We are interested in the bare arrangement of bits, so strip everything + that doesn't affect the machine mode. However, record the type of the + outermost expression if it may matter below. */ + if (TREE_CODE (exp) == NOP_EXPR + || TREE_CODE (exp) == CONVERT_EXPR + || TREE_CODE (exp) == NON_LVALUE_EXPR) + outer_type = TREE_TYPE (exp); STRIP_NOPS (exp); if (TREE_CODE (exp) == BIT_AND_EXPR) @@ -2654,6 +2662,12 @@ decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize, HOST_WIDE_INT *pbitpo || TREE_CODE (inner) == PLACEHOLDER_EXPR) return 0; + /* If the number of bits in the reference is the same as the bitsize of + the outer type, then the outer type gives the signedness. Otherwise + (in case of a small bitfield) the signedness is unchanged. */ + if (outer_type && *pbitsize == tree_low_cst (TYPE_SIZE (outer_type), 1)) + *punsignedp = TREE_UNSIGNED (outer_type); + /* Compute the mask to access the bitfield. */ unsigned_type = (*lang_hooks.types.type_for_size) (*pbitsize, 1); precision = TYPE_PRECISION (unsigned_type); |