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class.c (layout_class_type): Restructure overlong-bitfield tpe search.

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* class.c (layout_class_type): Restructure overlong-bitfield tpe
	search.

From-SVN: r248971
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Nathan Sidwell 2017-06-07 13:41:20 +00:00 committed by Nathan Sidwell
parent 2f8d29a497
commit a6d31e8499
2 changed files with 33 additions and 30 deletions
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5
gcc/cp/ChangeLog
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@ -1,3 +1,8 @@
2017-06-07 Nathan Sidwell <nathan@acm.org>
* class.c (layout_class_type): Restructure overlong-bitfield tpe
search.
2017-06-07 Jonathan Wakely <jwakely@redhat.com>
PR c++/80990

58
gcc/cp/class.c
View File

@ -6426,41 +6426,39 @@ layout_class_type (tree t, tree *virtuals_p)
if (DECL_C_BIT_FIELD (field)
&& tree_int_cst_lt (TYPE_SIZE (type), DECL_SIZE (field)))
{
unsigned int itk;
tree integer_type;
bool was_unnamed_p = false;
/* We must allocate the bits as if suitably aligned for the
longest integer type that fits in this many bits. type
of the field. Then, we are supposed to use the left over
bits as additional padding. */
for (itk = itk_char; itk != itk_none; ++itk)
if (integer_types[itk] != NULL_TREE
&& (tree_int_cst_lt (size_int (MAX_FIXED_MODE_SIZE),
TYPE_SIZE (integer_types[itk]))
|| tree_int_cst_lt (DECL_SIZE (field),
TYPE_SIZE (integer_types[itk]))))
break;
longest integer type that fits in this many bits. Then,
we are supposed to use the left over bits as additional
padding. */
/* ITK now indicates a type that is too large for the
field. We have to back up by one to find the largest
type that fits. */
do
{
--itk;
integer_type = integer_types[itk];
} while (itk > 0 && integer_type == NULL_TREE);
/* Do not pick a type bigger than MAX_FIXED_MODE_SIZE. */
tree limit = size_int (MAX_FIXED_MODE_SIZE);
if (tree_int_cst_lt (DECL_SIZE (field), limit))
limit = DECL_SIZE (field);
tree integer_type = integer_types[itk_char];
for (unsigned itk = itk_char; itk != itk_none; itk++)
if (tree next = integer_types[itk])
{
if (tree_int_cst_lt (limit, TYPE_SIZE (next)))
/* Too big, so our current guess is what we want. */
break;
/* Not bigger than limit, ok */
integer_type = next;
}
/* Figure out how much additional padding is required. */
if (tree_int_cst_lt (TYPE_SIZE (integer_type), DECL_SIZE (field)))
{
if (TREE_CODE (t) == UNION_TYPE)
/* In a union, the padding field must have the full width
of the bit-field; all fields start at offset zero. */
padding = DECL_SIZE (field);
else
padding = size_binop (MINUS_EXPR, DECL_SIZE (field),
TYPE_SIZE (integer_type));
}
if (TREE_CODE (t) == UNION_TYPE)
/* In a union, the padding field must have the full width
of the bit-field; all fields start at offset zero. */
padding = DECL_SIZE (field);
else
padding = size_binop (MINUS_EXPR, DECL_SIZE (field),
TYPE_SIZE (integer_type));
if (integer_zerop (padding))
padding = NULL_TREE;
/* An unnamed bitfield does not normally affect the
alignment of the containing class on a target where