c++: make source_location follow DECL_RAMP_FN

This fixes the value of current_function in compiler generated coroutine
code.

PR c++/110855 - std::source_location doesn't work with C++20 coroutine

gcc/cp/ChangeLog:

	PR c++/110855
	* cp-gimplify.cc (fold_builtin_source_location): Use the name of
	the DECL_RAMP_FN of the current function if present.

gcc/testsuite/ChangeLog:

	PR c++/110855
	* g++.dg/coroutines/pr110855.C: New test.

2 files changed, 69 insertions, 1 deletions

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 6a5e4cf..b88c3b7 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -3933,7 +3933,14 @@ fold_builtin_source_location (const_tree t)
 	      const char *name = "";
 
 	      if (current_function_decl)
-		name = cxx_printable_name (current_function_decl, 2);
+		{
+		  /* If this is a coroutine, we should get the name of the user
+		     function rather than the actor we generate.  */
+		  if (tree ramp = DECL_RAMP_FN (current_function_decl))
+		    name = cxx_printable_name (ramp, 2);
+		  else
+		    name = cxx_printable_name (current_function_decl, 2);
+		}
 
 	      val = build_string_literal (name);
 	    }
diff --git a/gcc/testsuite/g++.dg/coroutines/pr110855.C b/gcc/testsuite/g++.dg/coroutines/pr110855.C
new file mode 100644
index 0000000..6b5c014
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/pr110855.C
@@ -0,0 +1,61 @@
+// { dg-do run }
+// { dg-output {^} }
+// { dg-output {ReturnObject bar\(int, char, bool\)(\n|\r\n|\r)} }
+// { dg-output {ReturnObject bar\(int, char, bool\)(\n|\r\n|\r)} }
+// { dg-output {ReturnObject bar\(int, char, bool\)(\n|\r\n|\r)} }
+// { dg-output {ReturnObject bar\(int, char, bool\)(\n|\r\n|\r)} }
+// { dg-output {ReturnObject bar\(int, char, bool\)(\n|\r\n|\r)} }
+// { dg-output {$} }
+// https://gcc.gnu.org/PR110855
+#include <coroutine>
+#include <source_location>
+
+struct ReturnObject {
+  struct promise_type {
+    auto
+    initial_suspend(const std::source_location location =
+                    std::source_location::current()) {
+      __builtin_puts (location.function_name ());
+      return std::suspend_never{};
+    }
+    auto
+    final_suspend(const std::source_location location =
+                  std::source_location::current()) noexcept {
+      __builtin_puts (location.function_name ());
+      return std::suspend_never{};
+    }
+    auto
+    get_return_object(const std::source_location location =
+                      std::source_location::current()) {
+      __builtin_puts (location.function_name ());
+      return ReturnObject{std::coroutine_handle<promise_type>::from_promise(*this)};
+    }
+    auto
+    unhandled_exception() { }
+    auto return_void(const std::source_location location =
+                     std::source_location::current()) {
+      __builtin_puts (location.function_name ());
+    }
+  };
+  std::coroutine_handle<> handle;
+};
+
+struct awaitable : std::suspend_never
+{
+  void await_resume(const std::source_location location =
+                     std::source_location::current())
+  {
+      __builtin_puts (location.function_name ());
+  }
+};
+
+ReturnObject
+bar(int, char, bool) {
+  co_await awaitable{};
+  co_return;
+}
+
+int
+main() {
+  bar(1, 'a', false);
+}