Hi!
I thought this wouldn't be necessary because RAW_DATA_CST can only appear
inside of (array) CONSTRUCTORs within DECL_INITIAL of TREE_STATIC vars,
so there shouldn't be a need to expand it. Except that we have an
optimization when reading ARRAY_REF from such a CONSTRUCTOR which will
try to expand the constructor if it either can be stored by pieces
(I think that is just fine) or if it is mostly zeros (which is at least
75% of the initializer zeros). Now the second case is I think in some
cases desirable (say 256MB initializer and just 20 elements out of that
non-zero, so clear everything and store 20 elements must be fastest and
short), but could be really bad as well (say 40GB initializer with
10GB non-zero in it, especially if it doesn't result in the original
variable being optimized away). Maybe it would help if expand_constructor
and store_constructor* etc. had some optional argument with addresses into
the original VAR_DECL so that it could be copying larger amounts of data
like larger RAW_DATA_CSTs from there instead of pushing those into new
.rodata again. And another problem is that we apparently expand the
initializes twice, expand_constructor in store_constructor can expand
the stores one and if expand_constructor returns non-NULL, we then
expand_expr the CONSTRUCTOR again. to the same location.
This patch doesn't address either of those issues, just adds RAW_DATA_CST
support to store_constructor for now. For the can_store_by_pieces
cases it stores those by pieces using a new callback very similar to
string_cst_read_str, for the rest (unfortunately) forces it into a memory
and copies from there.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/15
branch?
2025-09-10 Jakub Jelinek <ja...@redhat.com>
PR middle-end/121831
* expr.cc (raw_data_cst_read_str): New function.
(store_constructor) <case ARRAY_TYPE>: Handle RAW_DATA_CST.
* g++.dg/lto/pr121831_0.C: New test.
* g++.dg/lto/pr121831_1.C: New test.
--- gcc/expr.cc.jj 2025-08-05 12:57:06.719031397 +0200
+++ gcc/expr.cc 2025-09-09 08:52:39.246507748 +0200
@@ -6533,6 +6533,31 @@ string_cst_read_str (void *data, void *,
return c_readstr (TREE_STRING_POINTER (str) + offset, mode, false);
}
+/* Helper function for store_expr storing of RAW_DATA_CST. */
+
+static rtx
+raw_data_cst_read_str (void *data, void *, HOST_WIDE_INT offset,
+ fixed_size_mode mode)
+{
+ tree cst = (tree) data;
+
+ gcc_assert (offset >= 0);
+ if (offset >= RAW_DATA_LENGTH (cst))
+ return const0_rtx;
+
+ if ((unsigned HOST_WIDE_INT) offset + GET_MODE_SIZE (mode)
+ > (unsigned HOST_WIDE_INT) RAW_DATA_LENGTH (cst))
+ {
+ char *p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
+ size_t l = RAW_DATA_LENGTH (cst) - offset;
+ memcpy (p, RAW_DATA_POINTER (cst) + offset, l);
+ memset (p + l, '\0', GET_MODE_SIZE (mode) - l);
+ return c_readstr (p, mode, false);
+ }
+
+ return c_readstr (RAW_DATA_POINTER (cst) + offset, mode, false);
+}
+
/* Generate code for computing expression EXP,
and storing the value into TARGET.
@@ -7630,7 +7655,7 @@ store_constructor (tree exp, rtx target,
case ARRAY_TYPE:
{
tree value, index;
- unsigned HOST_WIDE_INT i;
+ unsigned HOST_WIDE_INT i, j = 0;
bool need_to_clear;
tree domain;
tree elttype = TREE_TYPE (type);
@@ -7692,6 +7717,8 @@ store_constructor (tree exp, rtx target,
this_node_count = (tree_to_uhwi (hi_index)
- tree_to_uhwi (lo_index) + 1);
}
+ else if (TREE_CODE (value) == RAW_DATA_CST)
+ this_node_count = RAW_DATA_LENGTH (value);
else
this_node_count = 1;
@@ -7734,7 +7761,11 @@ store_constructor (tree exp, rtx target,
rtx xtarget = target;
if (cleared && initializer_zerop (value))
- continue;
+ {
+ if (TREE_CODE (value) == RAW_DATA_CST)
+ j += RAW_DATA_LENGTH (value) - 1;
+ continue;
+ }
mode = TYPE_MODE (elttype);
if (mode != BLKmode)
@@ -7750,6 +7781,8 @@ store_constructor (tree exp, rtx target,
unsigned HOST_WIDE_INT lo, hi, count;
tree offset;
+ gcc_assert (TREE_CODE (value) != RAW_DATA_CST);
+
/* If the range is constant and "small", unroll the loop. */
if (const_bounds_p
&& tree_fits_uhwi_p (lo_index)
@@ -7846,13 +7879,14 @@ store_constructor (tree exp, rtx target,
{
tree offset;
+ gcc_assert (TREE_CODE (value) != RAW_DATA_CST);
if (index)
offset = fold_build2 (MINUS_EXPR,
TREE_TYPE (index),
index,
TYPE_MIN_VALUE (domain));
else
- offset = size_int (i);
+ offset = size_int (i + j);
offset = size_binop (MULT_EXPR,
fold_convert (sizetype, offset),
@@ -7869,7 +7903,7 @@ store_constructor (tree exp, rtx target,
bitpos = ((tree_to_uhwi (index) - minelt)
* tree_to_uhwi (TYPE_SIZE (elttype)));
else
- bitpos = (i * tree_to_uhwi (TYPE_SIZE (elttype)));
+ bitpos = ((i + j) * tree_to_uhwi (TYPE_SIZE (elttype)));
if (MEM_P (target) && !MEM_KEEP_ALIAS_SET_P (target)
&& TREE_CODE (type) == ARRAY_TYPE
@@ -7878,10 +7912,50 @@ store_constructor (tree exp, rtx target,
target = copy_rtx (target);
MEM_KEEP_ALIAS_SET_P (target) = 1;
}
- store_constructor_field (target, bitsize, bitpos, 0,
- bitregion_end, mode, value,
- cleared, get_alias_set (elttype),
- reverse);
+ if (TREE_CODE (value) != RAW_DATA_CST)
+ store_constructor_field (target, bitsize, bitpos, 0,
+ bitregion_end, mode, value,
+ cleared, get_alias_set (elttype),
+ reverse);
+ else
+ {
+ j += RAW_DATA_LENGTH (value) - 1;
+ gcc_assert (known_eq (bitsize, BITS_PER_UNIT));
+ rtx to_rtx = adjust_address (target, mode,
+ bitpos / BITS_PER_UNIT);
+
+ if (to_rtx == target)
+ to_rtx = copy_rtx (to_rtx);
+
+ if (!MEM_KEEP_ALIAS_SET_P (to_rtx)
+ && MEM_ALIAS_SET (to_rtx) != 0)
+ set_mem_alias_set (to_rtx, get_alias_set (elttype));
+
+ if (can_store_by_pieces (RAW_DATA_LENGTH (value),
+ raw_data_cst_read_str,
+ (void *) value,
+ MEM_ALIGN (target), false))
+ {
+ store_by_pieces (target, RAW_DATA_LENGTH (value),
+ raw_data_cst_read_str, (void *) value,
+ MEM_ALIGN (target), false,
+ RETURN_BEGIN);
+ continue;
+ }
+
+ elttype
+ = build_array_type_nelts (TREE_TYPE (value),
+ RAW_DATA_LENGTH (value));
+ tree ctor = build_constructor_single (elttype, NULL_TREE,
+ value);
+ ctor = tree_output_constant_def (ctor);
+ mode = TYPE_MODE (type);
+ store_constructor_field (target,
+ bitsize * RAW_DATA_LENGTH (value),
+ bitpos, 0, bitregion_end, mode,
+ ctor, cleared,
+ get_alias_set (elttype), reverse);
+ }
}
}
break;
--- gcc/testsuite/g++.dg/lto/pr121831_0.C.jj 2025-09-09 09:16:55.204603044
+0200
+++ gcc/testsuite/g++.dg/lto/pr121831_0.C 2025-09-09 08:40:48.196226782
+0200
@@ -0,0 +1,17 @@
+/* PR middle-end/121831 */
+/* { dg-lto-do run } */
+/* { dg-lto-options { { -O2 -flto } } } */
+
+struct S { unsigned char s[256]; };
+S a;
+extern const S b[1];
+struct T { unsigned char t[2048]; };
+T c;
+extern const T d[1];
+
+__attribute__((noipa)) void
+foo ()
+{
+ a = b[0];
+ c = d[0];
+}
--- gcc/testsuite/g++.dg/lto/pr121831_1.C.jj 2025-09-09 09:16:58.582556614
+0200
+++ gcc/testsuite/g++.dg/lto/pr121831_1.C 2025-09-09 08:48:27.849935692
+0200
@@ -0,0 +1,64 @@
+struct S { unsigned char s[256]; };
+extern S a;
+struct T { unsigned char t[2048]; };
+extern T c;
+extern const T d[1];
+extern void foo ();
+
+extern const S b[1] {
+ { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+ 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+ 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
+ 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
+ 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
+ 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112,
+ 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
128,
+ 129, 0 }
+};
+extern const T d[1] {
+ { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+ 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+ 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
+ 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
+ 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
+ 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112,
+ 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
128,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+ 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+ 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
+ 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
+ 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
+ 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112,
+ 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
128,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+ 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+ 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
+ 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
+ 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
+ 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112,
+ 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
128,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+ 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+ 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
+ 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
+ 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
+ 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112,
+ 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
128 }
+};
+
+int
+main ()
+{
+ foo ();
+ for (int i = 0; i < 256; ++i)
+ if (a.s[i] != (i < 129 ? i + 1 : 0))
+ __builtin_abort ();
+ for (int i = 0; i < 2048; ++i)
+ if (c.t[i] != (i < 512 ? (i & 127) + 1 : 0))
+ __builtin_abort ();
+}
Jakub
