Alright, I'm back and bearing patches. Firmly ready for the crucifixion
you will likely submit me to. :)
I've pretty much rewritten everything, taking into account all your
suggestions, and adding a handful of tests for corner cases we will now
handle correctly.
It seems the minimum needed is to calculate the byte offset of the start
of the bit region, and the length of the bit region. (Notice I say BYTE
offset, as the start of any bit region will happily coincide with a byte
boundary). These will of course be adjusted as various parts of the
bitfield infrastructure adjust offsets and memory addresses throughout.
First, it's not as easy as calling get_inner_reference() only once as
you've suggested. The only way to determine the padding at the end of a
field is getting the bit position of the field following the field in
question (or the size of the direct parent structure in the case where
the field in question is the last field in the structure). So we need
two calls to get_inner_reference for the general case. Which is at
least better than my original call to get_inner_reference() for every field.
I have clarified the comments and made it clear what the offsets are
relative to.
I am now handling large offsets that may appear as a tree OFFSET from
get_inner_reference, and have added a test for one such corner case,
including nested structures with head padding as you suggested. I am
still unsure that a variable length offset can happen before a bit field
region. So currently we assert that the final offset is host integer
representable. If you have a testcase that invalidates my assumption, I
will gladly add a test and fix the code.
Honestly, the code isn't pretty, but neither is the rest of the bit
field machinery. I tried to make due, but I'll gladly take suggestions
that are not in the form of "the entire bit field code needs to be
rewritten" :-).
To aid in reviewing, the crux of everything is in the rewritten
get_bit_range() and the first block of store_bit_field(). Everything
else is mostly noise. I have attached all of get_bit_range() as a
separate attachment to aid in reviewing, since that's the main engine,
and it has been largely rewritten.
This pacth handles all the testcases I could come up with, mostly
inspired by your suggestions. Eventually I would like to replace these
target specific tests with target-agnostic tests using the gdb simulated
thread test harness in the cxx-mem-model branch.
Finally, you had mentioned possible problems with tail padding in C++,
and suggested I use DECL_SIZE instead of calculating the padding using
the size of direct parent structure. DECL_SIZE doesn't include padding,
so I'm open to suggestions.
Fire away, but please be kind :).
* machmode.h (get_best_mode): Remove 2 arguments.
* fold-const.c (optimize_bit_field_compare): Same.
(fold_truthop): Same.
* expr.c (store_field): Change argument types in prototype.
(emit_group_store): Change argument types to store_bit_field call.
(copy_blkmode_from_reg): Same.
(write_complex_part): Same.
(optimize_bitfield_assignment_op): Change argument types.
Change arguments to get_best_mode.
(get_bit_range): Rewrite.
(expand_assignment): Adjust new call to get_bit_range.
Adjust bitregion_offset when to_rtx is changed.
Adjust calls to store_field with new argument types.
(store_field): New argument types.
Adjust calls to store_bit_field with new arguments.
* expr.h (store_bit_field): Change argument types.
* stor-layout.c (get_best_mode): Remove use of bitregion* arguments.
* expmed.c (store_bit_field_1): Change argument types.
Do not calculate maxbits.
Adjust bitregion_maxbits if offset changes.
(store_bit_field): Change argument types.
Adjust address taking into account bitregion_offset.
(store_fixed_bit_field): Change argument types.
Do not calculate maxbits.
(store_split_bit_field): Change argument types.
(extract_bit_field_1): Adjust arguments to get_best_mode.
(extract_fixed_bit_field): Same.
Index: machmode.h
===================================================================
--- machmode.h (revision 176891)
+++ machmode.h (working copy)
@@ -249,8 +249,6 @@ 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 HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
unsigned int,
enum machine_mode, int);
Index: fold-const.c
===================================================================
--- fold-const.c (revision 176891)
+++ fold-const.c (working copy)
@@ -3394,7 +3394,7 @@ optimize_bit_field_compare (location_t l
&& flag_strict_volatile_bitfields > 0)
nmode = lmode;
else
- nmode = get_best_mode (lbitsize, lbitpos, 0, 0,
+ nmode = get_best_mode (lbitsize, lbitpos,
const_p ? TYPE_ALIGN (TREE_TYPE (linner))
: MIN (TYPE_ALIGN (TREE_TYPE (linner)),
TYPE_ALIGN (TREE_TYPE (rinner))),
@@ -5221,7 +5221,7 @@ 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, 0, 0,
+ lnmode = get_best_mode (end_bit - first_bit, first_bit,
TYPE_ALIGN (TREE_TYPE (ll_inner)), word_mode,
volatilep);
if (lnmode == VOIDmode)
@@ -5286,7 +5286,7 @@ 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, 0, 0,
+ rnmode = get_best_mode (end_bit - first_bit, first_bit,
TYPE_ALIGN (TREE_TYPE (lr_inner)), word_mode,
volatilep);
if (rnmode == VOIDmode)
Index: testsuite/c-c++-common/cxxbitfields-6.c
===================================================================
--- testsuite/c-c++-common/cxxbitfields-6.c (revision 0)
+++ testsuite/c-c++-common/cxxbitfields-6.c (revision 0)
@@ -0,0 +1,19 @@
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 --param allow-store-data-races=0" } */
+
+struct bits
+{
+ char a;
+ int b:7;
+ int :0;
+ volatile int c:7;
+ unsigned char d;
+} x;
+
+/* Store into <c> should not clobber <d>. */
+void update_c(struct bits *p, int val)
+{
+ p -> c = val;
+}
+
+/* { dg-final { scan-assembler "movb" } } */
Index: testsuite/c-c++-common/cxxbitfields-8.c
===================================================================
--- testsuite/c-c++-common/cxxbitfields-8.c (revision 0)
+++ testsuite/c-c++-common/cxxbitfields-8.c (revision 0)
@@ -0,0 +1,29 @@
+/* { dg-do compile { target x86_64-*-* } } */
+/* { dg-options "-O --param allow-store-data-races=0" } */
+
+struct bits {
+ /* Make sure the bit position of the bitfield is larger than what
+ can be represented in an unsigned HOST_WIDE_INT, to force
+ get_inner_reference() to return something in POFFSET. */
+
+ struct {
+ int some_padding[1<<30];
+ char more_padding;
+ } pad[1<<29];
+
+ struct {
+ volatile char bitfield :1;
+ } x;
+ char b;
+};
+
+struct bits *p;
+
+/* Test that the store into <bitfield> is not done with something
+ wider than a byte move. */
+void foo()
+{
+ p->x.bitfield = 1;
+}
+
+/* { dg-final { scan-assembler "movb" } } */
Index: testsuite/c-c++-common/cxxbitfields-7.c
===================================================================
--- testsuite/c-c++-common/cxxbitfields-7.c (revision 0)
+++ testsuite/c-c++-common/cxxbitfields-7.c (revision 0)
@@ -0,0 +1,19 @@
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 --param allow-store-data-races=0" } */
+
+struct bits
+{
+ int some_padding;
+ struct {
+ volatile char bitfield :1;
+ } x;
+ char b;
+};
+
+/* Store into <bitfield> should not clobber <b>. */
+void update(struct bits *p)
+{
+ p->x.bitfield = 1;
+}
+
+/* { dg-final { scan-assembler "movb" } } */
Index: expr.c
===================================================================
--- expr.c (revision 176891)
+++ expr.c (working copy)
@@ -145,7 +145,7 @@ static void store_constructor_field (rtx
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,
- unsigned HOST_WIDE_INT, unsigned HOST_WIDE_INT,
+ tree, HOST_WIDE_INT,
enum machine_mode,
tree, tree, alias_set_type, bool);
@@ -2077,7 +2077,8 @@ 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,
- 0, 0, mode, tmps[i]);
+ integer_zero_node, MAX_FIXED_MODE_SIZE,
+ mode, tmps[i]);
}
/* Copy from the pseudo into the (probable) hard reg. */
@@ -2171,7 +2172,8 @@ 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, 0, 0, copy_mode,
+ store_bit_field (dst, bitsize, bitpos % BITS_PER_WORD,
+ integer_zero_node, MAX_FIXED_MODE_SIZE, copy_mode,
extract_bit_field (src, bitsize,
xbitpos % BITS_PER_WORD, 1, false,
NULL_RTX, copy_mode, copy_mode));
@@ -2808,7 +2810,8 @@ 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, 0, 0, imode, val);
+ store_bit_field (cplx, ibitsize, imag_p ? ibitsize : 0,
+ integer_zero_node, MAX_FIXED_MODE_SIZE, imode, val);
}
/* Extract one of the components of the complex value CPLX. Extract the
@@ -3943,8 +3946,8 @@ get_subtarget (rtx x)
static bool
optimize_bitfield_assignment_op (unsigned HOST_WIDE_INT bitsize,
unsigned HOST_WIDE_INT bitpos,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
+ tree bitregion_offset ATTRIBUTE_UNUSED,
+ HOST_WIDE_INT bitregion_maxbits,
enum machine_mode mode1, rtx str_rtx,
tree to, tree src)
{
@@ -4005,8 +4008,9 @@ optimize_bitfield_assignment_op (unsigne
if (str_bitsize == 0 || str_bitsize > BITS_PER_WORD)
str_mode = word_mode;
+ if (bitregion_maxbits < GET_MODE_BITSIZE (str_mode))
+ str_mode = smallest_mode_for_size (bitregion_maxbits, MODE_INT);
str_mode = get_best_mode (bitsize, bitpos,
- bitregion_start, bitregion_end,
MEM_ALIGN (str_rtx), str_mode, 0);
if (str_mode == VOIDmode)
return false;
@@ -4118,18 +4122,31 @@ optimize_bitfield_assignment_op (unsigne
/* 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.
+ Given a COMPONENT_REF, this function calculates the byte offset of
+ the beginning of the memory location containing bit field being
+ referenced. The byte offset is returned in *OFFSET and is the byte
+ offset from the beginning of the containing object (INNERDECL).
+
+ The largest mode that can be used to write into the bit field will
+ be returned in *LARGEST_MODE.
+
+ For example, in the following structure, the bit region starts in
+ byte 4. In an architecture where the size of BITS gets padded to
+ 32-bits, SImode will be returned in *LARGEST_MODE.
+
+ struct bits {
+ int some_padding;
+ struct {
+ volatile char bitfield :1;
+ } bits;
+ char b;
+ };
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...
+ Examples.
+
+ While storing into FOO.A here...
struct {
BIT 0:
@@ -4140,67 +4157,99 @@ optimize_bitfield_assignment_op (unsigne
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). */
+ ...we are not allowed to store past <b>, so for the layout above,
+ *OFFSET will be byte 0, and *LARGEST_MODE will be QImode.
+
+ Here we have 3 distinct memory locations because of the zero-sized
+ bit-field separating the bits:
+
+ struct bits
+ {
+ char a;
+ int b:7;
+ int :0;
+ int c:7;
+ } foo;
+
+ Here we also have 3 distinct memory locations because
+ structure/union boundaries will separate contiguous bit-field
+ sequences:
+
+ struct {
+ char a:3;
+ struct { char b:4; } x;
+ char c:5;
+ } foo; */
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)
+get_bit_range (tree exp, tree *offset, HOST_WIDE_INT *maxbits)
{
tree field, record_type, fld;
bool found_field = false;
bool prev_field_is_bitfield;
+ tree start_offset, end_offset, maxbits_tree;
+ tree start_bitpos_direct_parent = NULL_TREE;
+ HOST_WIDE_INT start_bitpos, end_bitpos;
+ HOST_WIDE_INT cumulative_bitsize = 0;
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)
- && (DECL_THREAD_LOCAL_P (innerdecl)
- || !TREE_STATIC (innerdecl))))
- {
- *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;
+ start_offset = size_zero_node;
+ start_bitpos = 0;
+ prev_field_is_bitfield = false;
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 we have a bit-field with a bitsize > 0... */
+ if (DECL_BIT_FIELD_TYPE (fld)
+ && (!host_integerp (DECL_SIZE (fld), 1)
+ || tree_low_cst (DECL_SIZE (fld), 1) > 0))
{
+ /* Start of a new bit region. */
if (prev_field_is_bitfield == false)
{
- *bitstart = bitpos;
+ HOST_WIDE_INT bitsize;
+ enum machine_mode mode;
+ int unsignedp, volatilep;
+
+ /* Save starting bitpos and offset. */
+ get_inner_reference (build3 (COMPONENT_REF,
+ TREE_TYPE (exp),
+ TREE_OPERAND (exp, 0),
+ fld, NULL_TREE),
+ &bitsize, &start_bitpos, &start_offset,
+ &mode, &unsignedp, &volatilep, true);
+ /* Save the bit offset of the current structure. */
+ start_bitpos_direct_parent = DECL_FIELD_BIT_OFFSET (fld);
prev_field_is_bitfield = true;
+ cumulative_bitsize = 0;
+ }
+
+ cumulative_bitsize += tree_low_cst (DECL_SIZE (fld), 1);
+
+ /* Short-circuit out if we have the max bits allowed. */
+ /* ?? Is this even worth it. ?? */
+ if (cumulative_bitsize >= MAX_FIXED_MODE_SIZE)
+ {
+ *maxbits = MAX_FIXED_MODE_SIZE;
+ /* Calculate byte offset to the beginning of the bit region. */
+ gcc_assert (start_bitpos % BITS_PER_UNIT == 0);
+ *offset = fold_build2 (PLUS_EXPR, TREE_TYPE (start_offset),
+ start_offset,
+ build_int_cst (integer_type_node,
+ start_bitpos /
BITS_PER_UNIT));
+ return;
}
}
else
@@ -4212,17 +4261,58 @@ get_bit_range (unsigned HOST_WIDE_INT *b
}
gcc_assert (found_field);
+ /* Calculate byte offset to the beginning of the bit region. */
+ /* OFFSET = START_OFFSET + (START_BITPOS / BITS_PER_UNIT) */
+ gcc_assert (start_bitpos % BITS_PER_UNIT == 0);
+ if (!start_offset)
+ start_offset = size_zero_node;
+ *offset = fold_build2 (PLUS_EXPR, TREE_TYPE (start_offset),
+ start_offset,
+ build_int_cst (integer_type_node,
+ start_bitpos / BITS_PER_UNIT));
if (fld)
{
+ HOST_WIDE_INT bitsize;
+ enum machine_mode mode;
+ int unsignedp, volatilep;
+
/* We found the end of the bit field sequence. Include the
- padding up to the next field and be done. */
- *bitend = bitpos - 1;
+ padding up to the next field. */
+
+ /* Calculate bitpos and offset of the next field. */
+ get_inner_reference (build3 (COMPONENT_REF,
+ TREE_TYPE (exp),
+ TREE_OPERAND (exp, 0),
+ fld, NULL_TREE),
+ &bitsize, &end_bitpos, &end_offset,
+ &mode, &unsignedp, &volatilep, true);
+ gcc_assert (end_bitpos % BITS_PER_UNIT == 0);
+
+ if (end_offset)
+ {
+ tree type = TREE_TYPE (end_offset), end;
+
+ /* Calculate byte offset to the end of the bit region. */
+ end = fold_build2 (PLUS_EXPR, type,
+ end_offset,
+ build_int_cst (type,
+ end_bitpos / BITS_PER_UNIT));
+ maxbits_tree = fold_build2 (MINUS_EXPR, type, end, *offset);
+ }
+ else
+ maxbits_tree = build_int_cst (integer_type_node,
+ end_bitpos - start_bitpos);
+
+ /* ?? Can we get a variable-lengthened offset here ?? */
+ gcc_assert (host_integerp (maxbits_tree, 1));
+ *maxbits = TREE_INT_CST_LOW (maxbits_tree);
}
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;
+ *maxbits = TREE_INT_CST_LOW (TYPE_SIZE (record_type))
+ - TREE_INT_CST_LOW (start_bitpos_direct_parent);
}
}
@@ -4324,8 +4414,8 @@ expand_assignment (tree to, tree from, b
{
enum machine_mode mode1;
HOST_WIDE_INT bitsize, bitpos;
- unsigned HOST_WIDE_INT bitregion_start = 0;
- unsigned HOST_WIDE_INT bitregion_end = 0;
+ tree bitregion_offset = size_zero_node;
+ HOST_WIDE_INT bitregion_maxbits = MAX_FIXED_MODE_SIZE;
tree offset;
int unsignedp;
int volatilep = 0;
@@ -4337,8 +4427,23 @@ expand_assignment (tree to, tree from, b
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);
+ {
+ /* If other threads can't see this value, no need to
+ restrict stores. */
+ if (ALLOW_STORE_DATA_RACES
+ || ((TREE_CODE (tem) == MEM_REF
+ || TREE_CODE (tem) == TARGET_MEM_REF)
+ && !ptr_deref_may_alias_global_p (TREE_OPERAND (tem, 0)))
+ || (DECL_P (tem)
+ && (DECL_THREAD_LOCAL_P (tem)
+ || !TREE_STATIC (tem))))
+ {
+ bitregion_offset = size_zero_node;
+ bitregion_maxbits = MAX_FIXED_MODE_SIZE;
+ }
+ else
+ get_bit_range (to, &bitregion_offset, &bitregion_maxbits);
+ }
/* If we are going to use store_bit_field and extract_bit_field,
make sure to_rtx will be safe for multiple use. */
@@ -4388,12 +4493,19 @@ expand_assignment (tree to, tree from, b
&& MEM_ALIGN (to_rtx) == GET_MODE_ALIGNMENT (mode1))
{
to_rtx = adjust_address (to_rtx, mode1, bitpos / BITS_PER_UNIT);
+ bitregion_offset = fold_build2 (MINUS_EXPR, integer_type_node,
+ bitregion_offset,
+ build_int_cst (integer_type_node,
+ bitpos /
BITS_PER_UNIT));
bitpos = 0;
}
to_rtx = offset_address (to_rtx, offset_rtx,
highest_pow2_factor_for_target (to,
offset));
+ bitregion_offset = fold_build2 (MINUS_EXPR, integer_type_node,
+ bitregion_offset,
+ offset);
}
/* No action is needed if the target is not a memory and the field
@@ -4421,13 +4533,13 @@ expand_assignment (tree to, tree from, b
nontemporal);
else if (bitpos + bitsize <= mode_bitsize / 2)
result = store_field (XEXP (to_rtx, 0), bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_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,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
mode1, from,
TREE_TYPE (tem), get_alias_set (to),
nontemporal);
@@ -4450,7 +4562,7 @@ expand_assignment (tree to, tree from, b
write_complex_part (temp, XEXP (to_rtx, 0), false);
write_complex_part (temp, XEXP (to_rtx, 1), true);
result = store_field (temp, bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
mode1, from,
TREE_TYPE (tem), get_alias_set (to),
nontemporal);
@@ -4477,13 +4589,14 @@ expand_assignment (tree to, tree from, b
}
if (optimize_bitfield_assignment_op (bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset,
+ bitregion_maxbits,
mode1,
to_rtx, to, from))
result = NULL;
else
result = store_field (to_rtx, bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
mode1, from,
TREE_TYPE (tem), get_alias_set (to),
nontemporal);
@@ -5917,10 +6030,10 @@ 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.
- BITREGION_START is bitpos of the first bitfield in this region.
- BITREGION_END is the bitpos of the ending bitfield in this region.
- These two fields are 0, if the C++ memory model does not apply,
- or we are not interested in keeping track of bitfield regions.
+ BITREGION_OFFSET is the byte offset from the beginning of the
+ containing object to the start of the bit region.
+ BITREGION_MAXBITS is the size in bits of the largest mode that can
+ be used to set the bit-field in question.
Always return const0_rtx unless we have something particular to
return.
@@ -5935,8 +6048,8 @@ store_constructor (tree exp, rtx target,
static rtx
store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
+ tree bitregion_offset,
+ HOST_WIDE_INT bitregion_maxbits,
enum machine_mode mode, tree exp, tree type,
alias_set_type alias_set, bool nontemporal)
{
@@ -5970,7 +6083,7 @@ store_field (rtx target, HOST_WIDE_INT b
emit_move_insn (object, target);
store_field (blk_object, bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
mode, exp, type, alias_set, nontemporal);
emit_move_insn (target, object);
@@ -6086,7 +6199,7 @@ store_field (rtx target, HOST_WIDE_INT b
/* Store the value in the bitfield. */
store_bit_field (target, bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
mode, temp);
return const0_rtx;
Index: expr.h
===================================================================
--- expr.h (revision 176891)
+++ expr.h (working copy)
@@ -666,8 +666,8 @@ mode_for_extraction (enum extraction_pat
extern void store_bit_field (rtx, unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
+ tree,
+ HOST_WIDE_INT,
enum machine_mode, rtx);
extern rtx extract_bit_field (rtx, unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT, int, bool, rtx,
Index: stor-layout.c
===================================================================
--- stor-layout.c (revision 176891)
+++ stor-layout.c (working copy)
@@ -2361,13 +2361,6 @@ fixup_unsigned_type (tree type)
/* Find the best machine mode to use when referencing a bit field of length
BITSIZE bits starting at BITPOS.
- BITREGION_START is the bit position of the first bit in this
- sequence of bit fields. BITREGION_END is the last bit in this
- sequence. If these two fields are non-zero, we should restrict the
- memory access to a maximum sized chunk of
- BITREGION_END - BITREGION_START + 1. Otherwise, we are allowed to touch
- any adjacent non bit-fields.
-
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).
@@ -2386,20 +2379,11 @@ fixup_unsigned_type (tree type)
enum machine_mode
get_best_mode (int bitsize, int bitpos,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
unsigned int align,
enum machine_mode largest_mode, int volatilep)
{
enum machine_mode mode;
unsigned int unit = 0;
- unsigned HOST_WIDE_INT maxbits;
-
- /* If unset, no restriction. */
- if (!bitregion_end)
- maxbits = MAX_FIXED_MODE_SIZE;
- else
- maxbits = (bitregion_end - bitregion_start) % align + 1;
/* Find the narrowest integer mode that contains the bit field. */
for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
@@ -2436,7 +2420,6 @@ get_best_mode (int bitsize, int bitpos,
&& bitpos / unit == (bitpos + bitsize - 1) / unit
&& unit <= BITS_PER_WORD
&& unit <= MIN (align, BIGGEST_ALIGNMENT)
- && unit <= maxbits
&& (largest_mode == VOIDmode
|| unit <= GET_MODE_BITSIZE (largest_mode)))
wide_mode = tmode;
Index: expmed.c
===================================================================
--- expmed.c (revision 176891)
+++ expmed.c (working copy)
@@ -48,13 +48,11 @@ 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,
- unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
+ tree, HOST_WIDE_INT,
rtx);
static void store_split_bit_field (rtx, unsigned HOST_WIDE_INT,
unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
- unsigned HOST_WIDE_INT,
+ tree, HOST_WIDE_INT,
rtx);
static rtx extract_fixed_bit_field (enum machine_mode, rtx,
unsigned HOST_WIDE_INT,
@@ -340,8 +338,8 @@ 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,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
+ tree bitregion_offset,
+ HOST_WIDE_INT bitregion_maxbits,
enum machine_mode fieldmode,
rtx value, bool fallback_p)
{
@@ -558,7 +556,7 @@ 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,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
word_mode,
value_word, fallback_p))
{
@@ -722,10 +720,6 @@ store_bit_field_1 (rtx str_rtx, unsigned
if (HAVE_insv && MEM_P (op0))
{
enum machine_mode bestmode;
- unsigned HOST_WIDE_INT maxbits = MAX_FIXED_MODE_SIZE;
-
- if (bitregion_end)
- maxbits = bitregion_end - bitregion_start + 1;
/* Get the mode to use for inserting into this field. If OP0 is
BLKmode, get the smallest mode consistent with the alignment. If
@@ -733,15 +727,18 @@ store_bit_field_1 (rtx str_rtx, unsigned
mode. Otherwise, use the smallest mode containing the field. */
if (GET_MODE (op0) == BLKmode
- || GET_MODE_BITSIZE (GET_MODE (op0)) > maxbits
+ || GET_MODE_BITSIZE (GET_MODE (op0)) > bitregion_maxbits
|| (op_mode != MAX_MACHINE_MODE
&& GET_MODE_SIZE (GET_MODE (op0)) > GET_MODE_SIZE (op_mode)))
- bestmode = get_best_mode (bitsize, bitnum,
- bitregion_start, bitregion_end,
- MEM_ALIGN (op0),
- (op_mode == MAX_MACHINE_MODE
- ? VOIDmode : op_mode),
- MEM_VOLATILE_P (op0));
+ {
+ bestmode = (op_mode == MAX_MACHINE_MODE ? VOIDmode : op_mode);
+ if (bitregion_maxbits < GET_MODE_SIZE (op_mode))
+ bestmode = smallest_mode_for_size (bitregion_maxbits, MODE_INT);
+ bestmode = get_best_mode (bitsize, bitnum,
+ MEM_ALIGN (op0),
+ bestmode,
+ MEM_VOLATILE_P (op0));
+ }
else
bestmode = GET_MODE (op0);
@@ -767,7 +764,8 @@ store_bit_field_1 (rtx str_rtx, unsigned
the unit. */
tempreg = copy_to_reg (xop0);
if (store_bit_field_1 (tempreg, bitsize, xbitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset,
+ bitregion_maxbits - xoffset * BITS_PER_UNIT,
fieldmode, orig_value, false))
{
emit_move_insn (xop0, tempreg);
@@ -780,8 +778,9 @@ store_bit_field_1 (rtx str_rtx, unsigned
if (!fallback_p)
return false;
+ bitregion_maxbits -= offset * BITS_PER_UNIT;
store_fixed_bit_field (op0, offset, bitsize, bitpos,
- bitregion_start, bitregion_end, value);
+ bitregion_offset, bitregion_maxbits, value);
return true;
}
@@ -789,18 +788,17 @@ store_bit_field_1 (rtx str_rtx, unsigned
into a bit-field within structure STR_RTX
containing BITSIZE bits starting at bit BITNUM.
- BITREGION_START is bitpos of the first bitfield in this region.
- BITREGION_END is the bitpos of the ending bitfield in this region.
- These two fields are 0, if the C++ memory model does not apply,
- or we are not interested in keeping track of bitfield regions.
+ BITREGION_OFFSET is the byte offset STR_RTX to the start of the bit
+ region. BITREGION_MAXBITS is the number of bits of the largest
+ mode that can be used to set the bit-field in question.
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,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
+ tree bitregion_offset,
+ HOST_WIDE_INT bitregion_maxbits,
enum machine_mode fieldmode,
rtx value)
{
@@ -808,30 +806,23 @@ store_bit_field (rtx str_rtx, unsigned H
bit region. Adjust the address to start at the beginning of the
bit region. */
if (MEM_P (str_rtx)
- && bitregion_start > 0)
+ && bitregion_maxbits < MAX_FIXED_MODE_SIZE)
{
- enum machine_mode bestmode;
- enum machine_mode op_mode;
- unsigned HOST_WIDE_INT offset;
+ HOST_WIDE_INT offset;
- op_mode = mode_for_extraction (EP_insv, 3);
- if (op_mode == MAX_MACHINE_MODE)
- op_mode = VOIDmode;
-
- offset = bitregion_start / BITS_PER_UNIT;
- bitnum -= bitregion_start;
- bitregion_end -= bitregion_start;
- bitregion_start = 0;
- bestmode = get_best_mode (bitsize, bitnum,
- bitregion_start, bitregion_end,
- MEM_ALIGN (str_rtx),
- op_mode,
- MEM_VOLATILE_P (str_rtx));
- str_rtx = adjust_address (str_rtx, bestmode, offset);
+ /* ?? Can we get a variable length offset here ?? */
+ gcc_assert (host_integerp (bitregion_offset, 1));
+ offset = tree_low_cst (bitregion_offset, 1);
+
+ /* Adjust the bit position accordingly. */
+ bitnum -= offset * BITS_PER_UNIT;
+ bitregion_offset = integer_zero_node;
+ /* Adjust the actual address. */
+ str_rtx = adjust_address (str_rtx, GET_MODE (str_rtx), offset);
}
if (!store_bit_field_1 (str_rtx, bitsize, bitnum,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
fieldmode, value, true))
gcc_unreachable ();
}
@@ -849,8 +840,8 @@ static void
store_fixed_bit_field (rtx op0, unsigned HOST_WIDE_INT offset,
unsigned HOST_WIDE_INT bitsize,
unsigned HOST_WIDE_INT bitpos,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
+ tree bitregion_offset,
+ HOST_WIDE_INT bitregion_maxbits,
rtx value)
{
enum machine_mode mode;
@@ -873,17 +864,14 @@ store_fixed_bit_field (rtx op0, unsigned
if (bitsize + bitpos > BITS_PER_WORD)
{
store_split_bit_field (op0, bitsize, bitpos,
- bitregion_start, bitregion_end,
+ bitregion_offset, bitregion_maxbits,
value);
return;
}
}
else
{
- unsigned HOST_WIDE_INT maxbits = MAX_FIXED_MODE_SIZE;
-
- if (bitregion_end)
- maxbits = bitregion_end - bitregion_start + 1;
+ HOST_WIDE_INT maxbits = bitregion_maxbits;
/* Get the proper mode to use for this field. We want a mode that
includes the entire field. If such a mode would be larger than
@@ -901,16 +889,19 @@ store_fixed_bit_field (rtx op0, unsigned
&& flag_strict_volatile_bitfields > 0)
mode = GET_MODE (op0);
else
- mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT,
- bitregion_start, bitregion_end,
- MEM_ALIGN (op0), mode, MEM_VOLATILE_P (op0));
+ {
+ if (bitregion_maxbits < GET_MODE_BITSIZE (mode))
+ mode = smallest_mode_for_size (bitregion_maxbits, MODE_INT);
+ mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT,
+ MEM_ALIGN (op0), mode, MEM_VOLATILE_P (op0));
+ }
if (mode == VOIDmode)
{
/* The only way this should occur is if the field spans word
boundaries. */
store_split_bit_field (op0, bitsize, bitpos + offset * BITS_PER_UNIT,
- bitregion_start, bitregion_end, value);
+ bitregion_offset, bitregion_maxbits, value);
return;
}
@@ -1031,8 +1022,8 @@ 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,
- unsigned HOST_WIDE_INT bitregion_start,
- unsigned HOST_WIDE_INT bitregion_end,
+ tree bitregion_offset,
+ HOST_WIDE_INT bitregion_maxbits,
rtx value)
{
unsigned int unit;
@@ -1148,7 +1139,8 @@ 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, bitregion_start, bitregion_end, part);
+ thispos, bitregion_offset, bitregion_maxbits,
+ part);
bitsdone += thissize;
}
}
@@ -1588,7 +1580,7 @@ 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, 0, 0, MEM_ALIGN (op0),
+ bestmode = get_best_mode (bitsize, bitnum, MEM_ALIGN (op0),
(ext_mode == MAX_MACHINE_MODE
? VOIDmode : ext_mode),
MEM_VOLATILE_P (op0));
@@ -1714,7 +1706,7 @@ extract_fixed_bit_field (enum machine_mo
mode = tmode;
}
else
- mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT, 0, 0,
+ mode = get_best_mode (bitsize, bitpos + offset * BITS_PER_UNIT,
MEM_ALIGN (op0), word_mode, MEM_VOLATILE_P (op0));
if (mode == VOIDmode)
/* In the C++ memory model, consecutive bit fields in a structure are
considered one memory location.
Given a COMPONENT_REF, this function calculates the byte offset of
the beginning of the memory location containing bit field being
referenced. The byte offset is returned in *OFFSET and is the byte
offset from the beginning of the containing object (INNERDECL).
The largest mode that can be used to write into the bit field will
be returned in *LARGEST_MODE.
For example, in the following structure, the bit region starts in
byte 4. In an architecture where the size of BITS gets padded to
32-bits, SImode will be returned in *LARGEST_MODE.
struct bits {
int some_padding;
struct {
volatile char bitfield :1;
} bits;
char b;
};
EXP is the COMPONENT_REF.
Examples.
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,
*OFFSET will be byte 0, and *LARGEST_MODE will be QImode.
Here we have 3 distinct memory locations because of the zero-sized
bit-field separating the bits:
struct bits
{
char a;
int b:7;
int :0;
int c:7;
} foo;
Here we also have 3 distinct memory locations because
structure/union boundaries will separate contiguous bit-field
sequences:
struct {
char a:3;
struct { char b:4; } x;
char c:5;
} foo; */
static void
get_bit_range (tree exp, tree *offset, HOST_WIDE_INT *maxbits)
{
tree field, record_type, fld;
bool found_field = false;
bool prev_field_is_bitfield;
tree start_offset, end_offset, maxbits_tree;
tree start_bitpos_direct_parent = NULL_TREE;
HOST_WIDE_INT start_bitpos, end_bitpos;
HOST_WIDE_INT cumulative_bitsize = 0;
gcc_assert (TREE_CODE (exp) == COMPONENT_REF);
/* 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. */
start_offset = size_zero_node;
start_bitpos = 0;
prev_field_is_bitfield = false;
for (fld = TYPE_FIELDS (record_type); fld; fld = DECL_CHAIN (fld))
{
if (TREE_CODE (fld) != FIELD_DECL)
continue;
if (field == fld)
found_field = true;
/* If we have a bit-field with a bitsize > 0... */
if (DECL_BIT_FIELD_TYPE (fld)
&& (!host_integerp (DECL_SIZE (fld), 1)
|| tree_low_cst (DECL_SIZE (fld), 1) > 0))
{
/* Start of a new bit region. */
if (prev_field_is_bitfield == false)
{
HOST_WIDE_INT bitsize;
enum machine_mode mode;
int unsignedp, volatilep;
/* Save starting bitpos and offset. */
get_inner_reference (build3 (COMPONENT_REF,
TREE_TYPE (exp),
TREE_OPERAND (exp, 0),
fld, NULL_TREE),
&bitsize, &start_bitpos, &start_offset,
&mode, &unsignedp, &volatilep, true);
/* Save the bit offset of the current structure. */
start_bitpos_direct_parent = DECL_FIELD_BIT_OFFSET (fld);
prev_field_is_bitfield = true;
cumulative_bitsize = 0;
}
cumulative_bitsize += tree_low_cst (DECL_SIZE (fld), 1);
/* Short-circuit out if we have the max bits allowed. */
/* ?? Is this even worth it. ?? */
if (cumulative_bitsize >= MAX_FIXED_MODE_SIZE)
{
*maxbits = MAX_FIXED_MODE_SIZE;
/* Calculate byte offset to the beginning of the bit region. */
gcc_assert (start_bitpos % BITS_PER_UNIT == 0);
*offset = fold_build2 (PLUS_EXPR, TREE_TYPE (start_offset),
start_offset,
build_int_cst (integer_type_node,
start_bitpos /
BITS_PER_UNIT));
return;
}
}
else
{
prev_field_is_bitfield = false;
if (found_field)
break;
}
}
gcc_assert (found_field);
/* Calculate byte offset to the beginning of the bit region. */
/* OFFSET = START_OFFSET + (START_BITPOS / BITS_PER_UNIT) */
gcc_assert (start_bitpos % BITS_PER_UNIT == 0);
if (!start_offset)
start_offset = size_zero_node;
*offset = fold_build2 (PLUS_EXPR, TREE_TYPE (start_offset),
start_offset,
build_int_cst (integer_type_node,
start_bitpos / BITS_PER_UNIT));
if (fld)
{
HOST_WIDE_INT bitsize;
enum machine_mode mode;
int unsignedp, volatilep;
/* We found the end of the bit field sequence. Include the
padding up to the next field. */
/* Calculate bitpos and offset of the next field. */
get_inner_reference (build3 (COMPONENT_REF,
TREE_TYPE (exp),
TREE_OPERAND (exp, 0),
fld, NULL_TREE),
&bitsize, &end_bitpos, &end_offset,
&mode, &unsignedp, &volatilep, true);
gcc_assert (end_bitpos % BITS_PER_UNIT == 0);
if (end_offset)
{
tree type = TREE_TYPE (end_offset), end;
/* Calculate byte offset to the end of the bit region. */
end = fold_build2 (PLUS_EXPR, type,
end_offset,
build_int_cst (type,
end_bitpos / BITS_PER_UNIT));
maxbits_tree = fold_build2 (MINUS_EXPR, type, end, *offset);
}
else
maxbits_tree = build_int_cst (integer_type_node,
end_bitpos - start_bitpos);
/* ?? Can we get a variable-lengthened offset here ?? */
gcc_assert (host_integerp (maxbits_tree, 1));
*maxbits = TREE_INT_CST_LOW (maxbits_tree);
}
else
{
/* If this is the last element in the structure, include the padding
at the end of structure. */
*maxbits = TREE_INT_CST_LOW (TYPE_SIZE (record_type))
- TREE_INT_CST_LOW (start_bitpos_direct_parent);
}
}
