diff options
Diffstat (limited to 'gcc/expr.c')
| -rw-r--r-- | gcc/expr.c | 119 |
1 files changed, 24 insertions, 95 deletions
@@ -4439,113 +4439,43 @@ optimize_bitfield_assignment_op (unsigned HOST_WIDE_INT bitsize, /* In the C++ memory model, consecutive bit fields in a structure are considered one memory location. - Given a COMPONENT_REF, this function returns the bit range of - consecutive bits in which this COMPONENT_REF belongs in. The - values are returned in *BITSTART and *BITEND. If either the C++ - memory model is not activated, or this memory access is not thread - visible, 0 is returned in *BITSTART and *BITEND. - - EXP is the COMPONENT_REF. - INNERDECL is the actual object being referenced. - BITPOS is the position in bits where the bit starts within the structure. - BITSIZE is size in bits of the field being referenced in EXP. - - For example, while storing into FOO.A here... - - struct { - BIT 0: - unsigned int a : 4; - unsigned int b : 1; - BIT 8: - unsigned char c; - unsigned int d : 6; - } foo; - - ...we are not allowed to store past <b>, so for the layout above, a - range of 0..7 (because no one cares if we store into the - padding). */ + Given a COMPONENT_REF EXP at bit position BITPOS, this function + returns the bit range of consecutive bits in which this COMPONENT_REF + belongs in. The values are returned in *BITSTART and *BITEND. + If the access does not need to be restricted 0 is returned in + *BITSTART and *BITEND. */ static void get_bit_range (unsigned HOST_WIDE_INT *bitstart, unsigned HOST_WIDE_INT *bitend, - tree exp, tree innerdecl, - HOST_WIDE_INT bitpos, HOST_WIDE_INT bitsize) + tree exp, + HOST_WIDE_INT bitpos) { - tree field, record_type, fld; - bool found_field = false; - bool prev_field_is_bitfield; + unsigned HOST_WIDE_INT bitoffset; + tree field, repr, offset; gcc_assert (TREE_CODE (exp) == COMPONENT_REF); - /* If other threads can't see this value, no need to restrict stores. */ - if (ALLOW_STORE_DATA_RACES - || ((TREE_CODE (innerdecl) == MEM_REF - || TREE_CODE (innerdecl) == TARGET_MEM_REF) - && !ptr_deref_may_alias_global_p (TREE_OPERAND (innerdecl, 0))) - || (DECL_P (innerdecl) - && ((TREE_CODE (innerdecl) == VAR_DECL - && DECL_THREAD_LOCAL_P (innerdecl)) - || !TREE_STATIC (innerdecl)))) + field = TREE_OPERAND (exp, 1); + repr = DECL_BIT_FIELD_REPRESENTATIVE (field); + /* If we do not have a DECL_BIT_FIELD_REPRESENTATIVE there is no + need to limit the range we can access. */ + if (!repr) { *bitstart = *bitend = 0; return; } - /* Bit field we're storing into. */ - field = TREE_OPERAND (exp, 1); - record_type = DECL_FIELD_CONTEXT (field); - - /* Count the contiguous bitfields for the memory location that - contains FIELD. */ - *bitstart = 0; - prev_field_is_bitfield = true; - for (fld = TYPE_FIELDS (record_type); fld; fld = DECL_CHAIN (fld)) - { - tree t, offset; - enum machine_mode mode; - int unsignedp, volatilep; - - if (TREE_CODE (fld) != FIELD_DECL) - continue; - - t = build3 (COMPONENT_REF, TREE_TYPE (exp), - unshare_expr (TREE_OPERAND (exp, 0)), - fld, NULL_TREE); - get_inner_reference (t, &bitsize, &bitpos, &offset, - &mode, &unsignedp, &volatilep, true); - - if (field == fld) - found_field = true; - - if (DECL_BIT_FIELD_TYPE (fld) && bitsize > 0) - { - if (prev_field_is_bitfield == false) - { - *bitstart = bitpos; - prev_field_is_bitfield = true; - } - } - else - { - prev_field_is_bitfield = false; - if (found_field) - break; - } - } - gcc_assert (found_field); + /* Compute the adjustment to bitpos from the offset of the field + relative to the representative. */ + offset = size_diffop (DECL_FIELD_OFFSET (field), + DECL_FIELD_OFFSET (repr)); + bitoffset = (tree_low_cst (offset, 1) * BITS_PER_UNIT + + tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1) + - tree_low_cst (DECL_FIELD_BIT_OFFSET (repr), 1)); - if (fld) - { - /* We found the end of the bit field sequence. Include the - padding up to the next field and be done. */ - *bitend = bitpos - 1; - } - else - { - /* If this is the last element in the structure, include the padding - at the end of structure. */ - *bitend = TREE_INT_CST_LOW (TYPE_SIZE (record_type)) - 1; - } + *bitstart = bitpos - bitoffset; + *bitend = *bitstart + tree_low_cst (DECL_SIZE (repr), 1) - 1; } /* Returns true if the MEM_REF REF refers to an object that does not @@ -4682,8 +4612,7 @@ expand_assignment (tree to, tree from, bool nontemporal) if (TREE_CODE (to) == COMPONENT_REF && DECL_BIT_FIELD_TYPE (TREE_OPERAND (to, 1))) - get_bit_range (&bitregion_start, &bitregion_end, - to, tem, bitpos, bitsize); + get_bit_range (&bitregion_start, &bitregion_end, to, bitpos); /* If we are going to use store_bit_field and extract_bit_field, make sure to_rtx will be safe for multiple use. */ |