Hi,
fold_ctor_reference attempts to use a recursive local processing in order to
call native_encode_expr on the leaf nodes of the constructor, before falling
back to calling native_encode_initializer if this fails. There are a couple
of issues related to endianness present in it:
1) it does not specifically handle integral bit-fields; now these are left
justified on big-endian platforms so cannot be treated like ordinary fields.
2) it does not check that the constructor uses the native storage order.
Proposed fix attached, tested on x86-64/Linux and SPARC/Solaris, OK for the
mainline and some branches?
2023-06-30 Eric Botcazou
* gimple-fold.cc (fold_array_ctor_reference): Fix head comment.
(fold_nonarray_ctor_reference): Likewise. Specifically deal
with integral bit-fields.
(fold_ctor_reference): Check that the constructor uses the
native storage order.
2023-06-30 Eric Botcazou
* gcc.c-torture/execute/20230630-1.c: New test.
* gcc.c-torture/execute/20230630-2.c: Likewise.
--
Eric Botcazoudiff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 3d46b76edeb..e80a72dfa22 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -7849,12 +7849,11 @@ get_base_constructor (tree base, poly_int64_pod *bit_offset,
}
}
-/* CTOR is CONSTRUCTOR of an array type. Fold a reference of SIZE bits
- to the memory at bit OFFSET. When non-null, TYPE is the expected
- type of the reference; otherwise the type of the referenced element
- is used instead. When SIZE is zero, attempt to fold a reference to
- the entire element which OFFSET refers to. Increment *SUBOFF by
- the bit offset of the accessed element. */
+/* CTOR is a CONSTRUCTOR of an array or vector type. Fold a reference of SIZE
+ bits to the memory at bit OFFSET. If non-null, TYPE is the expected type of
+ the reference; otherwise the type of the referenced element is used instead.
+ When SIZE is zero, attempt to fold a reference to the entire element OFFSET
+ refers to. Increment *SUBOFF by the bit offset of the accessed element. */
static tree
fold_array_ctor_reference (tree type, tree ctor,
@@ -8019,13 +8018,11 @@ fold_array_ctor_reference (tree type, tree ctor,
return type ? build_zero_cst (type) : NULL_TREE;
}
-/* CTOR is CONSTRUCTOR of an aggregate or vector. Fold a reference
- of SIZE bits to the memory at bit OFFSET. When non-null, TYPE
- is the expected type of the reference; otherwise the type of
- the referenced member is used instead. When SIZE is zero,
- attempt to fold a reference to the entire member which OFFSET
- refers to; in this case. Increment *SUBOFF by the bit offset
- of the accessed member. */
+/* CTOR is a CONSTRUCTOR of a record or union type. Fold a reference of SIZE
+ bits to the memory at bit OFFSET. If non-null, TYPE is the expected type of
+ the reference; otherwise the type of the referenced member is used instead.
+ When SIZE is zero, attempt to fold a reference to the entire member OFFSET
+ refers to. Increment *SUBOFF by the bit offset of the accessed member. */
static tree
fold_nonarray_ctor_reference (tree type, tree ctor,
@@ -8037,8 +8034,7 @@ fold_nonarray_ctor_reference (tree type, tree ctor,
unsigned HOST_WIDE_INT cnt;
tree cfield, cval;
- FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield,
- cval)
+ FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
{
tree byte_offset = DECL_FIELD_OFFSET (cfield);
tree field_offset = DECL_FIELD_BIT_OFFSET (cfield);
@@ -8110,6 +8106,19 @@ fold_nonarray_ctor_reference (tree type, tree ctor,
return NULL_TREE;
offset_int inner_offset = offset_int (offset) - bitoffset;
+
+ /* Integral bit-fields are left-justified on big-endian targets, so
+ we must arrange for native_encode_int to look at the MSB. */
+ if (DECL_BIT_FIELD (cfield) && INTEGRAL_TYPE_P (TREE_TYPE (cfield)))
+ {
+ if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN)
+ return NULL_TREE;
+ const unsigned int encoding_size
+ = GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE (TREE_TYPE (cfield)));
+ if (BYTES_BIG_ENDIAN)
+ inner_offset += encoding_size - wi::to_offset (field_size);
+ }
+
return fold_ctor_reference (type, cval,
inner_offset.to_uhwi (), size,
from_decl, suboff);
@@ -8122,7 +8131,7 @@ fold_nonarray_ctor_reference (tree type, tree ctor,
return build_zero_cst (type);
}
-/* CTOR is value initializing memory. Fold a reference of TYPE and
+/* CTOR is a value initializing memory. Fold a reference of TYPE and
bit size POLY_SIZE to the memory at bit POLY_OFFSET. When POLY_SIZE
is zero, attempt to fold a reference to the entire subobject
which OFFSET refers to. This is used when folding accesses to
@@ -8163,7 +8172,8 @@ fold_ctor_reference (tree type, tree ctor, const poly_uint64 _offset,
}
return ret;
