[gcc r13-4631] Use DW_ATE_UTF for the Rust 'char' type

[Arthur Cohen <cohenarthur@gcc.gnu.org>]

https://gcc.gnu.org/g:dd950cbbb97ff5ebc203cba6c2112edd322b6f35

commit r13-4631-gdd950cbbb97ff5ebc203cba6c2112edd322b6f35
Author: Tom Tromey <tom@tromey.com>
Date:   Tue Aug 23 15:47:13 2022 +0100

    Use DW_ATE_UTF for the Rust 'char' type
    
    The Rust 'char' type should use the DWARF DW_ATE_UTF encoding.
    
            gcc/
            * dwarf2out.cc (is_rust): New.
            (base_type_die): Use DW_ATE_UTF for the Rust 'char' type.
            (gen_compile_unit_die): Handle "GNU Rust".
    
    Co-authored-by: Mark Wielaard <mark@klomp.org>
    Co-authored-by: Marc Poulhiès <dkm@kataplop.net>

Diff:
---
 gcc/dwarf2out.cc | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index e81044b8c48..ed06707a7b4 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -5600,6 +5600,17 @@ is_fortran (const_tree decl)
   return is_fortran ();
 }
 
+/* Return TRUE if the language is Rust.
+   Note, returns FALSE for dwarf_version < 5 && dwarf_strict. */
+
+static inline bool
+is_rust ()
+{
+  unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
+
+  return lang == DW_LANG_Rust;
+}
+
 /* Return TRUE if the language is Ada.  */
 
 static inline bool
@@ -13232,7 +13243,11 @@ base_type_die (tree type, bool reverse)
 	}
       if (TYPE_STRING_FLAG (type))
 	{
-	  if (TYPE_UNSIGNED (type))
+	  if ((dwarf_version >= 4 || !dwarf_strict)
+	      && is_rust ()
+	      && int_size_in_bytes (type) == 4)
+	    encoding = DW_ATE_UTF;
+	  else if (TYPE_UNSIGNED (type))
 	    encoding = DW_ATE_unsigned_char;
 	  else
 	    encoding = DW_ATE_signed_char;
@@ -25231,6 +25246,8 @@ gen_compile_unit_die (const char *filename)
 	{
 	  if (strcmp (language_string, "GNU Go") == 0)
 	    language = DW_LANG_Go;
+	  else if (strcmp (language_string, "GNU Rust") == 0)
+	    language = DW_LANG_Rust;
 	}
     }
   /* Use a degraded Fortran setting in strict DWARF2 so is_fortran works.  */