[gcc r12-3216] libiberty: Add support for demangling local D template declarations

[gcc r12-3216] libiberty: Add support for demangling local D template declarations

[Iain Buclaw]

https://gcc.gnu.org/g:392e141079a198c93b19bfcd1fe2bd5df456c999

commit r12-3216-g392e141079a198c93b19bfcd1fe2bd5df456c999
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Sun Aug 29 20:26:06 2021 +0200

    libiberty: Add support for demangling local D template declarations
    
    The D language now allows multiple different template declarations in
    the same function that have the same mangled name.  To make the mangled
    names unique, a fake parent in the form `__Sddd' is added to the symbol.
    This information is not important for the user, so the demangler now
    handles and ignores it.
    
    libiberty/ChangeLog:
    
            * d-demangle.c (dlang_identifier): Skip over fake parent manglings.
            * testsuite/d-demangle-expected: Add tests.

Diff:
---
 libiberty/d-demangle.c                  | 19 +++++++++++++++++++
 libiberty/testsuite/d-demangle-expected | 24 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/libiberty/d-demangle.c b/libiberty/d-demangle.c
index d74cf47b1a9..a2152cc6551 100644
--- a/libiberty/d-demangle.c
+++ b/libiberty/d-demangle.c
@@ -1044,6 +1044,25 @@ dlang_identifier (string *decl, const char *mangled, struct dlang_info *info)
       && (mangled[2] == 'T' || mangled[2] == 'U'))
     return dlang_parse_template (decl, mangled, info, len);
 
+  /* There can be multiple different declarations in the same function that have
+     the same mangled name.  To make the mangled names unique, a fake parent in
+     the form `__Sddd' is added to the symbol.  */
+  if (len >= 4 && mangled[0] == '_' && mangled[1] == '_' && mangled[2] == 'S')
+    {
+      const char *numptr = mangled + 3;
+      while (numptr < (mangled + len) && ISDIGIT (*numptr))
+	numptr++;
+
+      if (mangled + len == numptr)
+	{
+	  /* Skip over the fake parent.  */
+	  mangled += len;
+	  return dlang_identifier (decl, mangled, info);
+	}
+
+      /* else demangle it as a plain identifier.  */
+    }
+
   return dlang_lname (decl, mangled, len);
 }
 
diff --git a/libiberty/testsuite/d-demangle-expected b/libiberty/testsuite/d-demangle-expected
index 87ed8d330a8..c35185c3e1e 100644
--- a/libiberty/testsuite/d-demangle-expected
+++ b/libiberty/testsuite/d-demangle-expected
@@ -1420,5 +1420,29 @@ _D3std3uni__T6toCaseS_DQvQt12toLowerIndexFNaNbNiNewZtVii1043S_DQCjQCi10toLowerTa
 std.uni.toCase!(std.uni.toLowerIndex(dchar), 1043, std.uni.toLowerTab(ulong), std.ascii.toLower, immutable(char)[]).toCase(immutable(char)[]).__foreachbody2(ref ulong, ref dchar).__foreachbody3(ref dchar)
 #
 --format=dlang
+_D8demangle4mainFZ1xi
+demangle.main().x
+#
+--format=dlang
+_D8demangle4mainFZ4__S11xi
+demangle.main().x
+#
+--format=dlang
+_D8demangle4mainFZ1fMFNaNbNiNfZv
+demangle.main().f()
+#
+--format=dlang
+_D8demangle4mainFZ4__S11fMFNaNbNiNfZv
+demangle.main().f()
+#
+--format=dlang
+_D3mod4funcFZ__T6nestedTiZQkMFNaNbNiNfZi
+mod.func().nested!(int).nested()
+#
+--format=dlang
+_D3mod4funcFZ__T6nestedTiZ4__S1QpMFNaNbNiNfZi
+mod.func().nested!(int).nested()
+#
+--format=dlang
 _D6mangle__T8fun21753VSQv6S21753S1f_DQBj10__lambda71MFNaNbNiNfZvZQCbQp
 mangle.fun21753!(mangle.S21753(mangle.__lambda71())).fun21753