Seeing that the current C++ draft has been approved, I'd like to submit
this for mainline, and get the proper review everyone's being quietly
avoiding :).
To refresh everyone's memory, here is the problem:
struct
{
unsigned int a : 4;
unsigned char b;
unsigned int c: 6;
} var;
void seta(){
var.a = 12;
}
In the new C++ standard, stores into <a> cannot touch <b>, so we can't
store with anything wider (e.g. a 32 bit store) that will touch <b>.
This problem can be seen on strictly aligned targets such as ARM, where
we store the above sequence with a 32-bit store. Or on x86-64 with <a>
being volatile (PR48124).
This patch fixes both problems, but only for the C++ memory model. This
is NOT a generic fix PR48124, only a fix when using "--param
allow-store-data-races=0". I will gladly change the parameter name, if
another is preferred.
The gist of this patch is in max_field_size(), where we calculate the
maximum number of bits we can store into. In doing this calculation I
assume we can store into the padding without causing any races. So,
padding between fields and at the end of the structure are included.
Tested on x86-64 both with and without "--param
allow-store-data-races=0", and visually inspecting the assembly on
arm-linux and ia64-linux.
OK for trunk?
Aldy
* params.h (ALLOW_STORE_DATA_RACES): New.
* params.def (PARAM_ALLOW_STORE_DATA_RACES): New.
* Makefile.in (expr.o): Depend on PARAMS_H.
* machmode.h (get_best_mode): Add argument.
* fold-const.c (optimize_bit_field_compare): Add argument to
get_best_mode.
(fold_truthop): Same.
* ifcvt.c (noce_emit_move_insn): Add argument to store_bit_field.
* expr.c (emit_group_store): Same.
(copy_blkmode_from_reg): Same.
(write_complex_part): Same.
(optimize_bitfield_assignment_op): Add argument.
Add argument to get_best_mode.
(max_field_size): New.
(expand_assignment): Calculate maxbits and pass it down
accordingly.
(store_field): New argument.
(expand_expr_real_2): New argument to store_field.
Include params.h.
* expr.h (store_bit_field): New argument.
* stor-layout.c (get_best_mode): Restrict mode expansion by taking
into account maxbits.
* calls.c (store_unaligned_arguments_into_pseudos): New argument
to store_bit_field.
* expmed.c (store_bit_field_1): New argument. Use it.
(store_bit_field): Same.
(store_fixed_bit_field): Same.
(store_split_bit_field): Same.
(extract_bit_field_1): Pass new argument to get_best_mode.
(extract_bit_field): Same.
* stmt.c (store_bit_field): Pass new argument to store_bit_field.
* tree.h (DECL_THREAD_VISIBLE_P): New.
* doc/invoke.texi: Document parameter allow-store-data-races.
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 173263)
+++ doc/invoke.texi (working copy)
@@ -8886,6 +8886,11 @@ The maximum number of conditional stores
if either vectorization (@option{-ftree-vectorize}) or if-conversion
(@option{-ftree-loop-if-convert}) is disabled. The default is 2.
+@item allow-store-data-races
+Allow optimizers to introduce new data races on stores.
+Set to 1 to allow, otherwise to 0. This option is enabled by default
+unless implicitly set by the @option{-fmemory-model=} option.
+
@end table
@end table
Index: machmode.h
===================================================================
--- machmode.h (revision 173263)
+++ machmode.h (working copy)
@@ -248,7 +248,9 @@ extern enum machine_mode mode_for_vector
/* Find the best mode to use to access a bit field. */
-extern enum machine_mode get_best_mode (int, int, unsigned int,
+extern enum machine_mode get_best_mode (int, int,
+ unsigned HOST_WIDE_INT,
+ unsigned int,
enum machine_mode, int);
/* Determine alignment, 1<=result<=BIGGEST_ALIGNMENT. */
Index: tree.h
===================================================================
--- tree.h (revision 173263)
+++ tree.h (working copy)
@@ -3156,6 +3156,10 @@ struct GTY(()) tree_parm_decl {
#define DECL_THREAD_LOCAL_P(NODE) \
(VAR_DECL_CHECK (NODE)->decl_with_vis.tls_model >= TLS_MODEL_REAL)
+/* Return true if a VAR_DECL is visible from another thread. */
+#define DECL_THREAD_VISIBLE_P(NODE) \
+ (TREE_STATIC (NODE) && !DECL_THREAD_LOCAL_P (NODE))
+
/* In a non-local VAR_DECL with static storage duration, true if the
variable has an initialization priority. If false, the variable
will be initialized at the DEFAULT_INIT_PRIORITY. */
Index: fold-const.c
===================================================================
--- fold-const.c (revision 173263)
+++ fold-const.c (working copy)
@@ -3409,7 +3409,7 @@ optimize_bit_field_compare (location_t l
&& flag_strict_volatile_bitfields > 0)
nmode = lmode;
else
- nmode = get_best_mode (lbitsize, lbitpos,
+ nmode = get_best_mode (lbitsize, lbitpos, 0,
const_p ? TYPE_ALIGN (TREE_TYPE (linner))
: MIN (TYPE_ALIGN (TREE_TYPE (linner)),
TYPE_ALIGN (TREE_TYPE (rinner))),
@@ -5237,7 +5237,7 @@ fold_truthop (location_t loc, enum tree_
to be relative to a field of that size. */
first_bit = MIN (ll_bitpos, rl_bitpos);
end_bit = MAX (ll_bitpos + ll_bitsize, rl_bitpos + rl_bitsize);
- lnmode = get_best_mode (end_bit - first_bit, first_bit,
+ lnmode = get_best_mode (end_bit - first_bit, first_bit, 0,
TYPE_ALIGN (TREE_TYPE (ll_inner)), word_mode,
volatilep);
if (lnmode == VOIDmode)
@@ -5302,7 +5302,7 @@ fold_truthop (location_t loc, enum tree_
first_bit = MIN (lr_bitpos, rr_bitpos);
end_bit = MAX (lr_bitpos + lr_bitsize, rr_bitpos + rr_bitsize);
- rnmode = get_best_mode (end_bit - first_bit, first_bit,
+ rnmode = get_best_mode (end_bit - first_bit, first_bit, 0,
TYPE_ALIGN (TREE_TYPE (lr_inner)), word_mode,
volatilep);
if (rnmode == VOIDmode)
Index: params.h
===================================================================
--- params.h (revision 173263)
+++ params.h (working copy)
@@ -206,4 +206,6 @@ extern void init_param_values (int *para
PARAM_VALUE (PARAM_MIN_NONDEBUG_INSN_UID)
#define MAX_STORES_TO_SINK \
PARAM_VALUE (PARAM_MAX_STORES_TO_SINK)
+#define ALLOW_STORE_DATA_RACES \
+ PARAM_VALUE (PARAM_ALLOW_STORE_DATA_RACES)
#endif /* ! GCC_PARAMS_H */
Index: ifcvt.c
===================================================================
--- ifcvt.c (revision 173263)
+++ ifcvt.c (working copy)
@@ -885,7 +885,7 @@ noce_emit_move_insn (rtx x, rtx y)
}
gcc_assert (start < (MEM_P (op) ? BITS_PER_UNIT : BITS_PER_WORD));
- store_bit_field (op, size, start, GET_MODE (x), y);
+ store_bit_field (op, size, start, 0, GET_MODE (x), y);
return;
}
@@ -939,7 +939,7 @@ noce_emit_move_insn (rtx x, rtx y)
inner = XEXP (outer, 0);
outmode = GET_MODE (outer);
bitpos = SUBREG_BYTE (outer) * BITS_PER_UNIT;
- store_bit_field (inner, GET_MODE_BITSIZE (outmode), bitpos, outmode, y);
+ store_bit_field (inner, GET_MODE_BITSIZE (outmode), bitpos, 0, outmode, y);
}
/* Return sequence of instructions generated by if conversion. This
Index: expr.c
===================================================================
--- expr.c (revision 173263)
+++ expr.c (working copy)
@@ -54,6 +54,7 @@ along with GCC; see the file COPYING3.
#include "diagnostic.h"
#include "ssaexpand.h"
#include "target-globals.h"
+#include "params.h"
/* Decide whether a function's arguments should be processed
from first to last or from last to first.
@@ -142,7 +143,8 @@ static void store_constructor_field (rtx
HOST_WIDE_INT, enum machine_mode,
tree, tree, int, alias_set_type);
static void store_constructor (tree, rtx, int, HOST_WIDE_INT);
-static rtx store_field (rtx, HOST_WIDE_INT, HOST_WIDE_INT, enum machine_mode,
+static rtx store_field (rtx, HOST_WIDE_INT, HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT, enum machine_mode,
tree, tree, alias_set_type, bool);
static unsigned HOST_WIDE_INT highest_pow2_factor_for_target (const_tree,
const_tree);
@@ -2063,7 +2065,7 @@ emit_group_store (rtx orig_dst, rtx src,
emit_move_insn (adjust_address (dest, mode, bytepos), tmps[i]);
else
store_bit_field (dest, bytelen * BITS_PER_UNIT, bytepos * BITS_PER_UNIT,
- mode, tmps[i]);
+ 0, mode, tmps[i]);
}
/* Copy from the pseudo into the (probable) hard reg. */
@@ -2157,7 +2159,7 @@ copy_blkmode_from_reg (rtx tgtblk, rtx s
/* Use xbitpos for the source extraction (right justified) and
bitpos for the destination store (left justified). */
- store_bit_field (dst, bitsize, bitpos % BITS_PER_WORD, copy_mode,
+ store_bit_field (dst, bitsize, bitpos % BITS_PER_WORD, 0, copy_mode,
extract_bit_field (src, bitsize,
xbitpos % BITS_PER_WORD, 1, false,
NULL_RTX, copy_mode, copy_mode));
@@ -2794,7 +2796,7 @@ write_complex_part (rtx cplx, rtx val, b
gcc_assert (MEM_P (cplx) && ibitsize < BITS_PER_WORD);
}
- store_bit_field (cplx, ibitsize, imag_p ? ibitsize : 0, imode, val);
+ store_bit_field (cplx, ibitsize, imag_p ? ibitsize : 0, 0, imode, val);
}
/* Extract one of the components of the complex value CPLX. Extract the
@@ -3929,6 +3931,7 @@ get_subtarget (rtx x)
static bool
optimize_bitfield_assignment_op (unsigned HOST_WIDE_INT bitsize,
unsigned HOST_WIDE_INT bitpos,
+ unsigned HOST_WIDE_INT maxbits,
enum machine_mode mode1, rtx str_rtx,
tree to, tree src)
{
@@ -3989,7 +3992,7 @@ optimize_bitfield_assignment_op (unsigne
if (str_bitsize == 0 || str_bitsize > BITS_PER_WORD)
str_mode = word_mode;
- str_mode = get_best_mode (bitsize, bitpos,
+ str_mode = get_best_mode (bitsize, bitpos, maxbits,
MEM_ALIGN (str_rtx), str_mode, 0);
if (str_mode == VOIDmode)
return false;
@@ -4098,6 +4101,92 @@ optimize_bitfield_assignment_op (unsigne
return false;
}
+/* In the C++ memory model, consecutive bit fields in a structure are
+ considered one memory location.
+
+ Given a COMPONENT_REF, this function returns the maximum number of
+ bits we are allowed to store into, when storing into the
+ COMPONENT_REF. We return 0, if there is no restriction.
+
+ EXP is the COMPONENT_REF.
+
+ 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,
+ we would return 8 maximum bits (because who cares if we store into
+ the padding). */
+
+
+static unsigned HOST_WIDE_INT
+max_field_size (tree exp, HOST_WIDE_INT bitpos, HOST_WIDE_INT bitsize)
+{
+ tree field, record_type, fld;
+ HOST_WIDE_INT maxbits = bitsize;
+
+ 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
+ || !DECL_THREAD_VISIBLE_P (TREE_OPERAND (exp, 0)))
+ return 0;
+
+ field = TREE_OPERAND (exp, 1);
+ record_type = DECL_FIELD_CONTEXT (field);
+
+ /* Find the original field within the structure. */
+ for (fld = TYPE_FIELDS (record_type); fld; fld = DECL_CHAIN (fld))
+ if (fld == field)
+ break;
+ gcc_assert (fld == field);
+
+ /* If this is the last element in the structure, we can touch from
+ BITPOS to the end of the structure (including the padding). */
+ if (!DECL_CHAIN (fld))
+ return TREE_INT_CST_LOW (TYPE_SIZE (record_type)) - bitpos;
+
+ /* Count contiguous bit fields not separated by a 0-length bit-field. */
+ for (fld = DECL_CHAIN (fld); 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);
+
+ /* Only count contiguous bit fields, that are not separated by a
+ zero-length bit field. */
+ if (!DECL_BIT_FIELD (fld)
+ || bitsize == 0)
+ {
+ /* Include the padding up to the next field. */
+ maxbits += bitpos - maxbits;
+ break;
+ }
+
+ maxbits += bitsize;
+ }
+
+ return maxbits;
+}
/* Expand an assignment that stores the value of FROM into TO. If NONTEMPORAL
is true, try generating a nontemporal store. */
@@ -4197,6 +4286,9 @@ expand_assignment (tree to, tree from, b
{
enum machine_mode mode1;
HOST_WIDE_INT bitsize, bitpos;
+ /* Max consecutive bits we are allowed to touch while storing
+ into TO. */
+ HOST_WIDE_INT maxbits = 0;
tree offset;
int unsignedp;
int volatilep = 0;
@@ -4206,6 +4298,10 @@ expand_assignment (tree to, tree from, b
tem = get_inner_reference (to, &bitsize, &bitpos, &offset, &mode1,
&unsignedp, &volatilep, true);
+ if (TREE_CODE (to) == COMPONENT_REF
+ && DECL_BIT_FIELD (TREE_OPERAND (to, 1)))
+ maxbits = max_field_size (to, bitpos, bitsize);
+
/* If we are going to use store_bit_field and extract_bit_field,
make sure to_rtx will be safe for multiple use. */
@@ -4286,12 +4382,13 @@ expand_assignment (tree to, tree from, b
result = store_expr (from, XEXP (to_rtx, bitpos != 0), false,
nontemporal);
else if (bitpos + bitsize <= mode_bitsize / 2)
- result = store_field (XEXP (to_rtx, 0), bitsize, bitpos,
+ result = store_field (XEXP (to_rtx, 0), bitsize, bitpos, maxbits,
mode1, from, TREE_TYPE (tem),
get_alias_set (to), nontemporal);
else if (bitpos >= mode_bitsize / 2)
result = store_field (XEXP (to_rtx, 1), bitsize,
- bitpos - mode_bitsize / 2, mode1, from,
+ bitpos - mode_bitsize / 2, maxbits,
+ mode1, from,
TREE_TYPE (tem), get_alias_set (to),
nontemporal);
else if (bitpos == 0 && bitsize == mode_bitsize)
@@ -4312,7 +4409,8 @@ expand_assignment (tree to, tree from, b
0);
write_complex_part (temp, XEXP (to_rtx, 0), false);
write_complex_part (temp, XEXP (to_rtx, 1), true);
- result = store_field (temp, bitsize, bitpos, mode1, from,
+ result = store_field (temp, bitsize, bitpos, maxbits,
+ mode1, from,
TREE_TYPE (tem), get_alias_set (to),
nontemporal);
emit_move_insn (XEXP (to_rtx, 0), read_complex_part (temp,
false));
@@ -4337,11 +4435,12 @@ expand_assignment (tree to, tree from, b
MEM_KEEP_ALIAS_SET_P (to_rtx) = 1;
}
- if (optimize_bitfield_assignment_op (bitsize, bitpos, mode1,
+ if (optimize_bitfield_assignment_op (bitsize, bitpos, maxbits, mode1,
to_rtx, to, from))
result = NULL;
else
- result = store_field (to_rtx, bitsize, bitpos, mode1, from,
+ result = store_field (to_rtx, bitsize, bitpos, maxbits,
+ mode1, from,
TREE_TYPE (tem), get_alias_set (to),
nontemporal);
}
@@ -4734,7 +4833,7 @@ store_expr (tree exp, rtx target, int ca
: BLOCK_OP_NORMAL));
else if (GET_MODE (target) == BLKmode)
store_bit_field (target, INTVAL (expr_size (exp)) * BITS_PER_UNIT,
- 0, GET_MODE (temp), temp);
+ 0, 0, GET_MODE (temp), temp);
else
convert_move (target, temp, unsignedp);
}
@@ -5177,7 +5276,8 @@ store_constructor_field (rtx target, uns
store_constructor (exp, target, cleared, bitsize / BITS_PER_UNIT);
}
else
- store_field (target, bitsize, bitpos, mode, exp, type, alias_set, false);
+ store_field (target, bitsize, bitpos, 0, mode, exp, type, alias_set,
+ false);
}
/* Store the value of constructor EXP into the rtx TARGET.
@@ -5751,6 +5851,8 @@ store_constructor (tree exp, rtx target,
BITSIZE bits, starting BITPOS bits from the start of TARGET.
If MODE is VOIDmode, it means that we are storing into a bit-field.
+ MAXBITS is the number of bits we can store into, 0 if no limit.
+
Always return const0_rtx unless we have something particular to
return.
@@ -5764,6 +5866,7 @@ store_constructor (tree exp, rtx target,
static rtx
store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
+ unsigned HOST_WIDE_INT maxbits,
enum machine_mode mode, tree exp, tree type,
alias_set_type alias_set, bool nontemporal)
{
@@ -5796,8 +5899,8 @@ store_field (rtx target, HOST_WIDE_INT b
if (bitsize != (HOST_WIDE_INT) GET_MODE_BITSIZE (GET_MODE (target)))
emit_move_insn (object, target);
- store_field (blk_object, bitsize, bitpos, mode, exp, type, alias_set,
- nontemporal);
+ store_field (blk_object, bitsize, bitpos, maxbits,
+ mode, exp, type, alias_set, nontemporal);
emit_move_insn (target, object);
@@ -5911,7 +6014,7 @@ store_field (rtx target, HOST_WIDE_INT b
}
/* Store the value in the bitfield. */
- store_bit_field (target, bitsize, bitpos, mode, temp);
+ store_bit_field (target, bitsize, bitpos, maxbits, mode, temp);
return const0_rtx;
}
@@ -7323,7 +7426,7 @@ expand_expr_real_2 (sepops ops, rtx targ
(treeop0))
* BITS_PER_UNIT),
(HOST_WIDE_INT) GET_MODE_BITSIZE (mode)),
- 0, TYPE_MODE (valtype), treeop0,
+ 0, 0, TYPE_MODE (valtype), treeop0,
type, 0, false);
}
Index: expr.h
===================================================================
--- expr.h (revision 173263)
+++ expr.h (working copy)
@@ -665,7 +665,8 @@ extern enum machine_mode
mode_for_extraction (enum extraction_pattern, int);
extern void store_bit_field (rtx, unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT, enum machine_mode, rtx);
+ unsigned HOST_WIDE_INT, unsigned HOST_WIDE_INT,
+ enum machine_mode, rtx);
extern rtx extract_bit_field (rtx, unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT, int, bool, rtx,
enum machine_mode, enum machine_mode);
Index: stor-layout.c
===================================================================
--- stor-layout.c (revision 173263)
+++ stor-layout.c (working copy)
@@ -2428,6 +2428,9 @@ fixup_unsigned_type (tree type)
/* Find the best machine mode to use when referencing a bit field of length
BITSIZE bits starting at BITPOS.
+ MAXBITS is the maximum number of bits we are allowed to touch, when
+ referencing this bit field. MAXBITS is 0 if there is no limit.
+
The underlying object is known to be aligned to a boundary of ALIGN bits.
If LARGEST_MODE is not VOIDmode, it means that we should not use a mode
larger than LARGEST_MODE (usually SImode).
@@ -2445,7 +2448,8 @@ fixup_unsigned_type (tree type)
decide which of the above modes should be used. */
enum machine_mode
-get_best_mode (int bitsize, int bitpos, unsigned int align,
+get_best_mode (int bitsize, int bitpos, unsigned HOST_WIDE_INT maxbits,
+ unsigned int align,
enum machine_mode largest_mode, int volatilep)
{
enum machine_mode mode;
@@ -2484,6 +2488,7 @@ get_best_mode (int bitsize, int bitpos,
if (bitpos / unit == (bitpos + bitsize - 1) / unit
&& unit <= BITS_PER_WORD
&& unit <= MIN (align, BIGGEST_ALIGNMENT)
+ && (!maxbits || unit <= maxbits)
&& (largest_mode == VOIDmode
|| unit <= GET_MODE_BITSIZE (largest_mode)))
wide_mode = tmode;
Index: calls.c
===================================================================
--- calls.c (revision 173263)
+++ calls.c (working copy)
@@ -909,7 +909,7 @@ store_unaligned_arguments_into_pseudos (
emit_move_insn (reg, const0_rtx);
bytes -= bitsize / BITS_PER_UNIT;
- store_bit_field (reg, bitsize, endian_correction, word_mode,
+ store_bit_field (reg, bitsize, endian_correction, 0, word_mode,
word);
}
}
Index: expmed.c
===================================================================
--- expmed.c (revision 173263)
+++ expmed.c (working copy)
@@ -47,9 +47,13 @@ struct target_expmed *this_target_expmed
static void store_fixed_bit_field (rtx, unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT, rtx);
+ unsigned HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT,
+ rtx);
static void store_split_bit_field (rtx, unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT, rtx);
+ unsigned HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT,
+ rtx);
static rtx extract_fixed_bit_field (enum machine_mode, rtx,
unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT,
@@ -333,7 +337,9 @@ mode_for_extraction (enum extraction_pat
static bool
store_bit_field_1 (rtx str_rtx, unsigned HOST_WIDE_INT bitsize,
- unsigned HOST_WIDE_INT bitnum, enum machine_mode fieldmode,
+ unsigned HOST_WIDE_INT bitnum,
+ unsigned HOST_WIDE_INT maxbits,
+ enum machine_mode fieldmode,
rtx value, bool fallback_p)
{
unsigned int unit
@@ -547,7 +553,9 @@ store_bit_field_1 (rtx str_rtx, unsigned
if (!store_bit_field_1 (op0, MIN (BITS_PER_WORD,
bitsize - i * BITS_PER_WORD),
- bitnum + bit_offset, word_mode,
+ bitnum + bit_offset,
+ maxbits,
+ word_mode,
value_word, fallback_p))
{
delete_insns_since (last);
@@ -718,9 +726,10 @@ store_bit_field_1 (rtx str_rtx, unsigned
mode. Otherwise, use the smallest mode containing the field. */
if (GET_MODE (op0) == BLKmode
+ || (maxbits && GET_MODE_BITSIZE (GET_MODE (op0)) > maxbits)
|| (op_mode != MAX_MACHINE_MODE
&& GET_MODE_SIZE (GET_MODE (op0)) > GET_MODE_SIZE (op_mode)))
- bestmode = get_best_mode (bitsize, bitnum, MEM_ALIGN (op0),
+ bestmode = get_best_mode (bitsize, bitnum, maxbits, MEM_ALIGN (op0),
(op_mode == MAX_MACHINE_MODE
? VOIDmode : op_mode),
MEM_VOLATILE_P (op0));
@@ -748,7 +757,7 @@ store_bit_field_1 (rtx str_rtx, unsigned
/* Fetch that unit, store the bitfield in it, then store
the unit. */
tempreg = copy_to_reg (xop0);
- if (store_bit_field_1 (tempreg, bitsize, xbitpos,
+ if (store_bit_field_1 (tempreg, bitsize, xbitpos, maxbits,
fieldmode, orig_value, false))
{
emit_move_insn (xop0, tempreg);
@@ -761,21 +770,28 @@ store_bit_field_1 (rtx str_rtx, unsigned
if (!fallback_p)
return false;
- store_fixed_bit_field (op0, offset, bitsize, bitpos, value);
+ store_fixed_bit_field (op0, offset, bitsize, bitpos, maxbits, value);
return true;
}
/* Generate code to store value from rtx VALUE
into a bit-field within structure STR_RTX
containing BITSIZE bits starting at bit BITNUM.
+
+ MAXBITS is the maximum number of bits we are allowed to store into,
+ 0 if no limit.
+
FIELDMODE is the machine-mode of the FIELD_DECL node for this field. */
void
store_bit_field (rtx str_rtx, unsigned HOST_WIDE_INT bitsize,
- unsigned HOST_WIDE_INT bitnum, enum machine_mode fieldmode,
+ unsigned HOST_WIDE_INT bitnum,
+ unsigned HOST_WIDE_INT maxbits,
+ enum machine_mode fieldmode,
rtx value)
{
- if (!store_bit_field_1 (str_rtx, bitsize, bitnum, fieldmode, value, true))
+ if (!store_bit_field_1 (str_rtx, bitsize, bitnum, maxbits,
+ fieldmode, value, true))
gcc_unreachable ();
}
@@ -791,7 +807,9 @@ store_bit_field (rtx str_rtx, unsigned H
static void
store_fixed_bit_field (rtx op0, unsigned HOST_WIDE_INT offset,
unsigned HOST_WIDE_INT bitsize,
- unsigned HOST_WIDE_INT bitpos, rtx value)
+ unsigned HOST_WIDE_INT bitpos,
+ unsigned HOST_WIDE_INT maxbits,
+ rtx value)
{
enum machine_mode mode;
unsigned int total_bits = BITS_PER_WORD;
@@ -812,7 +830,7 @@ store_fixed_bit_field (rtx op0, unsigned
/* Special treatment for a bit field split across two registers. */
if (bitsize + bitpos > BITS_PER_WORD)
{
- store_split_bit_field (op0, bitsize, bitpos, value);
+ store_split_bit_field (op0, bitsize, bitpos, maxbits, value);
return;
}
}
@@ -830,10 +848,12 @@ store_fixed_bit_field (rtx op0, unsigned
if (MEM_VOLATILE_P (op0)
&& GET_MODE_BITSIZE (GET_MODE (op0)) > 0
+ && GET_MODE_BITSIZE (GET_MODE (op0)) <= maxbits
&& flag_strict_volatile_bitfields > 0)
mode = GET_MODE (op0);
else
mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT,
+ maxbits,
MEM_ALIGN (op0), mode, MEM_VOLATILE_P (op0));
if (mode == VOIDmode)
@@ -841,7 +861,7 @@ store_fixed_bit_field (rtx op0, unsigned
/* The only way this should occur is if the field spans word
boundaries. */
store_split_bit_field (op0, bitsize, bitpos + offset * BITS_PER_UNIT,
- value);
+ maxbits, value);
return;
}
@@ -961,7 +981,9 @@ store_fixed_bit_field (rtx op0, unsigned
static void
store_split_bit_field (rtx op0, unsigned HOST_WIDE_INT bitsize,
- unsigned HOST_WIDE_INT bitpos, rtx value)
+ unsigned HOST_WIDE_INT bitpos,
+ unsigned HOST_WIDE_INT maxbits,
+ rtx value)
{
unsigned int unit;
unsigned int bitsdone = 0;
@@ -1076,7 +1098,7 @@ store_split_bit_field (rtx op0, unsigned
it is just an out-of-bounds access. Ignore it. */
if (word != const0_rtx)
store_fixed_bit_field (word, offset * unit / BITS_PER_UNIT, thissize,
- thispos, part);
+ thispos, maxbits, part);
bitsdone += thissize;
}
}
@@ -1520,7 +1542,7 @@ extract_bit_field_1 (rtx str_rtx, unsign
if (GET_MODE (op0) == BLKmode
|| (ext_mode != MAX_MACHINE_MODE
&& GET_MODE_SIZE (GET_MODE (op0)) > GET_MODE_SIZE (ext_mode)))
- bestmode = get_best_mode (bitsize, bitnum, MEM_ALIGN (op0),
+ bestmode = get_best_mode (bitsize, bitnum, 0, MEM_ALIGN (op0),
(ext_mode == MAX_MACHINE_MODE
? VOIDmode : ext_mode),
MEM_VOLATILE_P (op0));
@@ -1646,7 +1668,7 @@ extract_fixed_bit_field (enum machine_mo
mode = tmode;
}
else
- mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT,
+ mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT, 0,
MEM_ALIGN (op0), word_mode, MEM_VOLATILE_P (op0));
if (mode == VOIDmode)
Index: Makefile.in
===================================================================
--- Makefile.in (revision 173263)
+++ Makefile.in (working copy)
@@ -2916,7 +2916,7 @@ expr.o : expr.c $(CONFIG_H) $(SYSTEM_H)
typeclass.h hard-reg-set.h toplev.h $(DIAGNOSTIC_CORE_H) hard-reg-set.h
$(EXCEPT_H) \
reload.h langhooks.h intl.h $(TM_P_H) $(TARGET_H) \
tree-iterator.h gt-expr.h $(MACHMODE_H) $(TIMEVAR_H) $(TREE_FLOW_H) \
- $(TREE_PASS_H) $(DF_H) $(DIAGNOSTIC_H) vecprim.h $(SSAEXPAND_H)
+ $(TREE_PASS_H) $(DF_H) $(DIAGNOSTIC_H) vecprim.h $(SSAEXPAND_H) $(PARAMS_H)
dojump.o : dojump.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H)
$(TREE_H) \
$(FLAGS_H) $(FUNCTION_H) $(EXPR_H) $(OPTABS_H) $(INSN_ATTR_H) insn-config.h
\
langhooks.h $(GGC_H) gt-dojump.h vecprim.h $(BASIC_BLOCK_H) output.h
Index: stmt.c
===================================================================
--- stmt.c (revision 173263)
+++ stmt.c (working copy)
@@ -1758,7 +1758,7 @@ expand_return (tree retval)
/* Use bitpos for the source extraction (left justified) and
xbitpos for the destination store (right justified). */
- store_bit_field (dst, bitsize, xbitpos % BITS_PER_WORD, word_mode,
+ store_bit_field (dst, bitsize, xbitpos % BITS_PER_WORD, 0, word_mode,
extract_bit_field (src, bitsize,
bitpos % BITS_PER_WORD, 1, false,
NULL_RTX, word_mode, word_mode));
Index: params.def
===================================================================
--- params.def (revision 173263)
+++ params.def (working copy)
@@ -884,6 +884,13 @@ DEFPARAM (PARAM_MAX_STORES_TO_SINK,
"Maximum number of conditional store pairs that can be sunk",
2, 0, 0)
+/* Data race flags for C++0x memory model compliance. */
+
+DEFPARAM (PARAM_ALLOW_STORE_DATA_RACES,
+ "allow-store-data-races",
+ "Allow new data races on stores to be introduced",
+ 1, 0, 1)
+
/*
Local variables:
