| Message ID | Zg5YdwFVIn7hjt+q@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | fold-const: Handle NON_LVALUE_EXPR in native_encode_initializer [PR114537] | expand |
On Thu, 4 Apr 2024, Jakub Jelinek wrote: > Hi! > > 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. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? OK. Richard. > 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. > > --- gcc/fold-const.cc.jj 2024-03-26 11:21:31.996860739 +0100 > +++ gcc/fold-const.cc 2024-04-03 16:59:05.747297410 +0200 > @@ -8601,6 +8601,8 @@ native_encode_initializer (tree init, un > 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; > > --- gcc/testsuite/g++.dg/cpp2a/bit-cast16.C.jj 2024-04-03 17:06:46.720974426 +0200 > +++ gcc/testsuite/g++.dg/cpp2a/bit-cast16.C 2024-04-03 17:06:40.233063410 +0200 > @@ -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); > > Jakub > >
--- gcc/fold-const.cc.jj 2024-03-26 11:21:31.996860739 +0100 +++ gcc/fold-const.cc 2024-04-03 16:59:05.747297410 +0200 @@ -8601,6 +8601,8 @@ native_encode_initializer (tree init, un 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; --- gcc/testsuite/g++.dg/cpp2a/bit-cast16.C.jj 2024-04-03 17:06:46.720974426 +0200 +++ gcc/testsuite/g++.dg/cpp2a/bit-cast16.C 2024-04-03 17:06:40.233063410 +0200 @@ -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);