[PATCH] c++, debug: Treat -std=c++20 -gdwarf-5 like C++14 rather than C++98

[Jakub Jelinek via Gcc-patches]

Hi!

I have noticed that while we use DW_LANG_C_plus_plus_14 for -std=c++17 
-gdwarf-5,
we use DW_LANG_C_plus_plus (aka C++98) for -std=c++20 -gdwarf-5.  The
following patch makes those two match.

Ok for trunk if it passes bootstrap/regtest?

2020-11-30  Jakub Jelinek  <ja...@redhat.com>

        * dwarf2out.c (gen_compile_unit_die): Treat GNU C++20
        like C++14 for -gdwarf-5.

        * g++.dg/debug/dwarf2/lang-cpp17.C: New test.
        * g++.dg/debug/dwarf2/lang-cpp20.C: New test.

--- gcc/dwarf2out.c.jj  2020-11-26 16:22:29.111352844 +0100
+++ gcc/dwarf2out.c     2020-11-30 15:05:52.601317310 +0100
@@ -24646,7 +24646,8 @@ gen_compile_unit_die (const char *filena
            language = DW_LANG_C_plus_plus_11;
          else if (strcmp (language_string, "GNU C++14") == 0)
            language = DW_LANG_C_plus_plus_14;
-         else if (strcmp (language_string, "GNU C++17") == 0)
+         else if (strcmp (language_string, "GNU C++17") == 0
+                  || strcmp (language_string, "GNU C++20") == 0)
            /* For now.  */
            language = DW_LANG_C_plus_plus_14;
        }
--- gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp17.C.jj   2020-11-30 
15:06:35.631836747 +0100
+++ gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp17.C      2020-11-30 
15:07:19.160350623 +0100
@@ -0,0 +1,7 @@
+// { dg-do compile }
+// { dg-options "-O -std=c++17 -gdwarf-5 -dA" }
+// For -gdwarf-6 hopefully DW_LANG_C_plus_plus_17
+// DW_LANG_C_plus_plus_14 = 0x0021
+// { dg-final { scan-assembler "0x21\[^\n\r]* DW_AT_language" } } */
+
+int version;
--- gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp20.C.jj   2020-11-30 
15:07:27.436258201 +0100
+++ gcc/testsuite/g++.dg/debug/dwarf2/lang-cpp20.C      2020-11-30 
15:07:37.801142442 +0100
@@ -0,0 +1,7 @@
+// { dg-do compile }
+// { dg-options "-O -std=c++20 -gdwarf-5 -dA" }
+// For -gdwarf-6 hopefully DW_LANG_C_plus_plus_20
+// DW_LANG_C_plus_plus_14 = 0x0021
+// { dg-final { scan-assembler "0x21\[^\n\r]* DW_AT_language" } } */
+
+int version;

        Jakub