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* [gcc r13-8626] fold-const: Handle NON_LVALUE_EXPR in native_encode_initializer [PR114537]
@ 2024-04-21 4:08 Jakub Jelinek
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From: Jakub Jelinek @ 2024-04-21 4:08 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:a297f9bbb9611414fe48f6d61a8829bf5808bd2c
commit r13-8626-ga297f9bbb9611414fe48f6d61a8829bf5808bd2c
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Apr 4 10:47:52 2024 +0200
fold-const: Handle NON_LVALUE_EXPR in native_encode_initializer [PR114537]
The following testcase is incorrectly rejected. The problem is that
for bit-fields native_encode_initializer expects the corresponding
CONSTRUCTOR elt value must be INTEGER_CST, but that isn't the case
here, it is wrapped into NON_LVALUE_EXPR by maybe_wrap_with_location.
We could STRIP_ANY_LOCATION_WRAPPER as well, but as all we are looking for
is INTEGER_CST inside, just looking through NON_LVALUE_EXPR seems easier.
2024-04-04 Jakub Jelinek <jakub@redhat.com>
PR c++/114537
* fold-const.cc (native_encode_initializer): Look through
NON_LVALUE_EXPR if val is INTEGER_CST.
* g++.dg/cpp2a/bit-cast16.C: New test.
(cherry picked from commit 1baec8deb014b8a7da58879a407a4c00cdeb5a09)
Diff:
---
gcc/fold-const.cc | 2 ++
gcc/testsuite/g++.dg/cpp2a/bit-cast16.C | 16 ++++++++++++++++
2 files changed, 18 insertions(+)
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 31ae6cebbe6..25dd7c1094e 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -8485,6 +8485,8 @@ native_encode_initializer (tree init, unsigned char *ptr, int len,
if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN)
return 0;
+ if (TREE_CODE (val) == NON_LVALUE_EXPR)
+ val = TREE_OPERAND (val, 0);
if (TREE_CODE (val) != INTEGER_CST)
return 0;
diff --git a/gcc/testsuite/g++.dg/cpp2a/bit-cast16.C b/gcc/testsuite/g++.dg/cpp2a/bit-cast16.C
new file mode 100644
index 00000000000..d298af67ef2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/bit-cast16.C
@@ -0,0 +1,16 @@
+// PR c++/114537
+// { dg-do compile { target c++20 } }
+
+namespace std {
+template<typename T, typename F>
+constexpr T
+bit_cast (const F& f) noexcept
+{
+ return __builtin_bit_cast (T, f);
+}
+}
+
+struct A { signed char b : 1 = 0; signed char c : 7 = 0; };
+struct D { unsigned char e; };
+constexpr unsigned char f = std::bit_cast<D> (A{}).e;
+static_assert (f == 0);
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