Re: [PATCH 1/2] c++: testsuite: Add some opt/is_constant_evaluated3.C variants

On 8/6/26 10:59 AM, Patrick Palka wrote:
> r13-6422 added opt/is_constant_evaluated3.C to verify that we constant
> fold copy-init such as a1.  (Later, r14-6506 enabled constant folding of
> a2-a5 initializers.)  r13-6422 turned out to cause PR c++/126483, a bug
> in our folding of copy-init inside a lambda scope.
> 
> The new 3a.C demonstrates however that we still don't constant
> fold a1's copy-init when inside a constexpr function scope.  3b.C
> demonstrates that we do fold it when inside a (maybe-constexpr) lambda
> scope.

OK.
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/opt/is_constant_evaluated3a.C: New test.
> 	* g++.dg/opt/is_constant_evaluated3b.C: New test.
> ---
>   .../g++.dg/opt/is_constant_evaluated3a.C      | 24 +++++++++++++++++++
>   .../g++.dg/opt/is_constant_evaluated3b.C      | 24 +++++++++++++++++++
>   2 files changed, 48 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C
>   create mode 100644 gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C
> 
> diff --git a/gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C
> new file mode 100644
> index 000000000000..4ec3ecdf7b5d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C
> @@ -0,0 +1,24 @@
> +// A version of is_constant_evaluated3.C where the containing function is
> +// constexpr.
> +// { dg-do compile { target c++14 } }
> +// { dg-additional-options "-O -fdump-tree-original" }
> +
> +struct A {
> +  constexpr A(int n) : n(n), m(__builtin_is_constant_evaluated()) { }
> +  constexpr A() : A(42) { }
> +  int n, m;
> +};
> +
> +constexpr void f() {
> +  A a1 = {42};
> +  A a2{42};
> +  A a3(42);
> +  A a4;
> +  A a5{};
> +}
> +
> +// { dg-final { scan-tree-dump "a1 = {\\.n=42, \\.m=0}" "original" { xfail *-*-* } } }
> +// { dg-final { scan-tree-dump "a2 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a3 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a4 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a5 = {\\.n=42, \\.m=0}" "original" } }
> diff --git a/gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C
> new file mode 100644
> index 000000000000..ff708e23832b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C
> @@ -0,0 +1,24 @@
> +// A version of is_constant_evaluated3.C where the containing function is
> +// a (maybe-constexpr) lambda.
> +// { dg-do compile { target c++17 } }
> +// { dg-additional-options "-O -fdump-tree-original" }
> +
> +struct A {
> +  constexpr A(int n) : n(n), m(__builtin_is_constant_evaluated()) { }
> +  constexpr A() : A(42) { }
> +  int n, m;
> +};
> +
> +auto f = [] {
> +  A a1 = {42};
> +  A a2{42};
> +  A a3(42);
> +  A a4;
> +  A a5{};
> +};
> +
> +// { dg-final { scan-tree-dump "a1 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a2 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a3 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a4 = {\\.n=42, \\.m=0}" "original" } }
> +// { dg-final { scan-tree-dump "a5 = {\\.n=42, \\.m=0}" "original" } }