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

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.

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" } }
-- 
2.55.0.481.ga97fcc37c2