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re PR c++/49136 ([C++0x][constexpr] Incorrect constexpr c'tor evaluation with bitfields)

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PR c++/49136
	* semantics.c (cxx_eval_bit_field_ref): Handle the
	case when BIT_FIELD_REF doesn't cover only a single field.

	* g++.dg/cpp0x/constexpr-bitfield2.C: New test.
	* g++.dg/cpp0x/constexpr-bitfield3.C: New test.

From-SVN: r174168
This commit is contained in:
Jakub Jelinek 2011-05-25 09:00:01 +02:00 committed by Jakub Jelinek
parent 349ea8e855
commit 9893368980
5 changed files with 104 additions and 2 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2011-05-25 Jakub Jelinek <jakub@redhat.com>
PR c++/49136
* semantics.c (cxx_eval_bit_field_ref): Handle the
case when BIT_FIELD_REF doesn't cover only a single field.
2011-05-24 Jason Merrill <jason@redhat.com>
PR c++/49042

42
gcc/cp/semantics.c
View File

@ -6449,6 +6449,9 @@ cxx_eval_bit_field_ref (const constexpr_call *call, tree t,
bool *non_constant_p)
{
tree orig_whole = TREE_OPERAND (t, 0);
tree retval, fldval, utype, mask;
bool fld_seen = false;
HOST_WIDE_INT istart, isize;
tree whole = cxx_eval_constant_expression (call, orig_whole,
allow_non_constant, addr,
non_constant_p);
@ -6469,12 +6472,47 @@ cxx_eval_bit_field_ref (const constexpr_call *call, tree t,
return t;
start = TREE_OPERAND (t, 2);
istart = tree_low_cst (start, 0);
isize = tree_low_cst (TREE_OPERAND (t, 1), 0);
utype = TREE_TYPE (t);
if (!TYPE_UNSIGNED (utype))
utype = build_nonstandard_integer_type (TYPE_PRECISION (utype), 1);
retval = build_int_cst (utype, 0);
FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (whole), i, field, value)
{
if (bit_position (field) == start)
tree bitpos = bit_position (field);
if (bitpos == start && DECL_SIZE (field) == TREE_OPERAND (t, 1))
return value;
if (TREE_CODE (TREE_TYPE (field)) == INTEGER_TYPE
&& TREE_CODE (value) == INTEGER_CST
&& host_integerp (bitpos, 0)
&& host_integerp (DECL_SIZE (field), 0))
{
HOST_WIDE_INT bit = tree_low_cst (bitpos, 0);
HOST_WIDE_INT sz = tree_low_cst (DECL_SIZE (field), 0);
HOST_WIDE_INT shift;
if (bit >= istart && bit + sz <= istart + isize)
{
fldval = fold_convert (utype, value);
mask = build_int_cst_type (utype, -1);
mask = fold_build2 (LSHIFT_EXPR, utype, mask,
size_int (TYPE_PRECISION (utype) - sz));
mask = fold_build2 (RSHIFT_EXPR, utype, mask,
size_int (TYPE_PRECISION (utype) - sz));
fldval = fold_build2 (BIT_AND_EXPR, utype, fldval, mask);
shift = bit - istart;
if (BYTES_BIG_ENDIAN)
shift = TYPE_PRECISION (utype) - shift - sz;
fldval = fold_build2 (LSHIFT_EXPR, utype, fldval,
size_int (shift));
retval = fold_build2 (BIT_IOR_EXPR, utype, retval, fldval);
fld_seen = true;
}
}
}
gcc_unreachable();
if (fld_seen)
return fold_convert (TREE_TYPE (t), retval);
gcc_unreachable ();
return error_mark_node;
}

6
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,9 @@
2011-05-25 Jakub Jelinek <jakub@redhat.com>
PR c++/49136
* g++.dg/cpp0x/constexpr-bitfield2.C: New test.
* g++.dg/cpp0x/constexpr-bitfield3.C: New test.
2011-05-24 Vladimir Makarov <vmakarov@redhat.com>
PR rtl-optimization/48757

19
gcc/testsuite/g++.dg/cpp0x/constexpr-bitfield2.C Normal file
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@ -0,0 +1,19 @@
// PR c++/49136
// { dg-do compile }
// { dg-options "-std=c++0x" }
struct day
{
unsigned d : 5;
unsigned n : 3;
constexpr explicit day (int dd) : d(dd), n(7) {}
};
struct date {
int d;
constexpr date (day dd) : d(dd.n != 7 ? 7 : dd.d) {}
};
constexpr day d(0);
constexpr date dt(d);
static_assert (dt.d == 0, "Error");

33
gcc/testsuite/g++.dg/cpp0x/constexpr-bitfield3.C Normal file
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@ -0,0 +1,33 @@
// PR c++/49136
// { dg-do compile }
// { dg-options "-std=c++0x" }
struct S
{
unsigned : 1; unsigned s : 27; unsigned : 4;
constexpr S (unsigned int x) : s(x) {}
};
template <typename S>
struct T
{
unsigned int t;
constexpr T (S s) : t(s.s != 7 ? 0 : s.s) {}
constexpr T (S s, S s2) : t(s.s != s2.s ? 0 : s.s) {}
};
constexpr S s (7), s2 (7);
constexpr T<S> t (s), t2 (s, s2);
static_assert (t.t == 7, "Error");
static_assert (t2.t == 7, "Error");
struct U
{
int a : 1; int s : 1;
constexpr U (int x, int y) : a (x), s (y) {}
};
constexpr U u (0, -1), u2 (-1, -1);
constexpr T<U> t3 (u), t4 (u, u2);
static_assert (t3.t == 0, "Error");
static_assert (t4.t == -1, "Error");