> -----Original Message-----
> From: Andrew Pinski (QUIC) <quic_apin...@quicinc.com>
> Sent: Tuesday, February 20, 2024 7:06 PM
> To: gcc-patches@gcc.gnu.org
> Cc: Andrew Pinski (QUIC) <quic_apin...@quicinc.com>
> Subject: [PATCH] c++/c-common: Fix convert_vector_to_array_for_subscript
> for qualified vector types [PR89224]
>
> After r7-987-gf17a223de829cb, the access for the elements of a vector type
> would lose the qualifiers.
> So if we had `constvector[0]`, the type of the element of the array would not
> have const on it.
> This was due to a missing build_qualified_type for the inner type of the
> vector
> when building the array type.
> We need to add back the call to build_qualified_type and now the access has
> the correct qualifiers. So the overloads and even if it is a lvalue or rvalue
> is
> correctly done.
>
> Note we correctly now reject the testcase gcc.dg/pr83415.c which was
> incorrectly accepted after r7-987-gf17a223de829cb.
Ping?
>
> Built and tested for aarch64-linux-gnu.
>
> PR c++/89224
>
> gcc/c-family/ChangeLog:
>
> * c-common.cc (convert_vector_to_array_for_subscript): Call
> build_qualified_type
> for the inner type.
>
> gcc/cp/ChangeLog:
>
> * constexpr.cc (cxx_eval_array_reference): Compare main variants
> for the vector/array types instead of the types directly.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/torture/vector-subaccess-1.C: New test.
> * gcc.dg/pr83415.c: Change warning to error.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> gcc/c-family/c-common.cc | 7 +++++-
> gcc/cp/constexpr.cc | 3 ++-
> .../g++.dg/torture/vector-subaccess-1.C | 23 +++++++++++++++++++
> gcc/testsuite/gcc.dg/pr83415.c | 2 +-
> 4 files changed, 32 insertions(+), 3 deletions(-) create mode 100644
> gcc/testsuite/g++.dg/torture/vector-subaccess-1.C
>
> diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc index
> e15eff698df..884dd9043f9 100644
> --- a/gcc/c-family/c-common.cc
> +++ b/gcc/c-family/c-common.cc
> @@ -8936,6 +8936,7 @@ convert_vector_to_array_for_subscript (location_t
> loc,
> if (gnu_vector_type_p (TREE_TYPE (*vecp)))
> {
> tree type = TREE_TYPE (*vecp);
> + tree newitype;
>
> ret = !lvalue_p (*vecp);
>
> @@ -8950,8 +8951,12 @@ convert_vector_to_array_for_subscript
> (location_t loc,
> for function parameters. */
> c_common_mark_addressable_vec (*vecp);
>
> + /* Make sure qualifiers are copied from the vector type to the new
> element
> + of the array type. */
> + newitype = build_qualified_type (TREE_TYPE (type), TYPE_QUALS
> +(type));
> +
> *vecp = build1 (VIEW_CONVERT_EXPR,
> - build_array_type_nelts (TREE_TYPE (type),
> + build_array_type_nelts (newitype,
> TYPE_VECTOR_SUBPARTS (type)),
> *vecp);
> }
> diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index
> fa346fe01c9..1fe91d16e8e 100644
> --- a/gcc/cp/constexpr.cc
> +++ b/gcc/cp/constexpr.cc
> @@ -4421,7 +4421,8 @@ cxx_eval_array_reference (const constexpr_ctx
> *ctx, tree t,
> if (!lval
> && TREE_CODE (ary) == VIEW_CONVERT_EXPR
> && VECTOR_TYPE_P (TREE_TYPE (TREE_OPERAND (ary, 0)))
> - && TREE_TYPE (t) == TREE_TYPE (TREE_TYPE (TREE_OPERAND (ary, 0))))
> + && TYPE_MAIN_VARIANT (TREE_TYPE (t))
> + == TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (TREE_OPERAND
> (ary,
> +0)))))
> ary = TREE_OPERAND (ary, 0);
>
> tree oldidx = TREE_OPERAND (t, 1);
> diff --git a/gcc/testsuite/g++.dg/torture/vector-subaccess-1.C
> b/gcc/testsuite/g++.dg/torture/vector-subaccess-1.C
> new file mode 100644
> index 00000000000..0c8958a4e03
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/torture/vector-subaccess-1.C
> @@ -0,0 +1,23 @@
> +/* PR c++/89224 */
> +
> +/* The access of `vector[i]` has the same qualifiers as the original
> + vector which was missing. */
> +
> +typedef __attribute__((vector_size(16))) unsigned char Int8x8_t;
> +
> +template <class T>
> +void g(T &x) {
> + __builtin_abort();
> +}
> +template <class T>
> +void g(const T &x) {
> + __builtin_exit(0);
> +}
> +void f(const Int8x8_t x) {
> + g(x[0]);
> +}
> +int main(void)
> +{
> + Int8x8_t x ={};
> + f(x);
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr83415.c b/gcc/testsuite/gcc.dg/pr83415.c
> index 5934c16d97c..2fc85031505 100644
> --- a/gcc/testsuite/gcc.dg/pr83415.c
> +++ b/gcc/testsuite/gcc.dg/pr83415.c
> @@ -7,6 +7,6 @@ int
> main (int argc, short *argv[])
> {
> int i = argc;
> - y[i] = 7 - i; /* { dg-warning "read-only" } */
> + y[i] = 7 - i; /* { dg-error "read-only" } */
> return 0;
> }
> --
> 2.43.0
