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fold-const: Fix up native_encode_initializer missing field handling [PR98193]

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When native_encode_initializer is called with non-NULL mask (i.e. ATM
bit_cast only), it checks if the current index in the CONSTRUCTOR (if any)
is the next initializable FIELD_DECL, and if not, decrements cnt and
performs the iteration with that FIELD_DECL as field and val of zero
(so that it computes mask properly).  As the testcase shows, I forgot to
set pos to the byte position of the field though (like it is done
for e.g. index referenced FIELD_DECLs in the constructor.

2020-12-09  Jakub Jelinek  <jakub@redhat.com>

	PR c++/98193
	* fold-const.c (native_encode_initializer): Set pos to field's
	byte position if iterating over a field with missing initializer.

	* g++.dg/cpp2a/bit-cast7.C: New test.
This commit is contained in:
Jakub Jelinek 2020-12-09 09:34:51 +01:00
parent c3a63fb385
commit 4164e58bfd
2 changed files with 40 additions and 0 deletions
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1
gcc/fold-const.c
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@ -8256,6 +8256,7 @@ native_encode_initializer (tree init, unsigned char *ptr, int len,
{
cnt--;
field = fld;
pos = int_byte_position (field);
val = build_zero_cst (TREE_TYPE (fld));
if (TREE_CODE (val) == CONSTRUCTOR)
to_free = val;

39
gcc/testsuite/g++.dg/cpp2a/bit-cast7.C Normal file
View File

@ -0,0 +1,39 @@
// PR c++/98193
// { dg-do compile { target c++20 } }
template <typename To, typename From>
constexpr To
bit_cast (const From &from)
{
return __builtin_bit_cast (To, from);
}
struct J
{
long int a, b : 11, h;
};
struct K
{
long int a, b : 11, c;
constexpr bool operator == (const K &x)
{
return a == x.a && b == x.b && c == x.c;
}
};
struct L
{
long long int a, b : 11, h;
};
struct M
{
long long int a, b : 11, c;
constexpr bool operator == (const M &x)
{
return a == x.a && b == x.b && c == x.c;
}
};
static_assert (bit_cast <K> (J{}) == K{}, "");
static_assert (bit_cast <M> (L{0x0feedbacdeadbeefLL}) == M{0x0feedbacdeadbeefLL}, "");