c++: Adjust mangling of __alignof__ [PR88115]

r11-4926 made __alignof__ get mangled differently from alignof,
encoding __alignof__ as a vendor extended operator.  But this
mangling is problematic for the reasons mentioned in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115#c6.

This patch changes our mangling of __alignof__ to instead use the
new "vendor extended expression" syntax that's proposed in
https://github.com/itanium-cxx-abi/cxx-abi/issues/112.  Clang does
the same thing already, so after this patch Clang and GCC agree
about the mangling of __alignof__(type) and __alignof__(expr).

gcc/cp/ChangeLog:

	PR c++/88115
	* mangle.c (write_expression): Adjust the mangling of
	__alignof__.

include/ChangeLog:

	PR c++/88115
	* demangle.h (enum demangle_component_type): Add
	DEMANGLE_COMPONENT_VENDOR_EXPR.

libiberty/ChangeLog:

	PR c++/88115
	* cp-demangle.c (d_dump, d_make_comp, d_expression_1)
	(d_count_templates_scopes): Handle DEMANGLE_COMPONENT_VENDOR_EXPR.
	(d_print_comp_inner): Likewise.
	<case DEMANGLE_COMPONENT_EXTENDED_OPERATOR>: Revert r11-4926
	change.
	<case DEMANGLE_COMPONENT_UNARY>: Likewise.
	* testsuite/demangle-expected: Adjust __alignof__ tests.

gcc/testsuite/ChangeLog:

	PR c++/88115
	* g++.dg/cpp0x/alignof7.C: Adjust expected mangling.

5 files changed, 37 insertions, 29 deletions

diff --git a/gcc/cp/mangle.c b/gcc/cp/mangle.c
index 0a9e5aa79a0..57ce9a6710f 100644
--- a/gcc/cp/mangle.c
+++ b/gcc/cp/mangle.c
@@ -3124,11 +3124,9 @@ write_expression (tree expr)
 	  if (abi_version_at_least (15))
 	    {
 	      /* We used to mangle __alignof__ like alignof.  */
-	      write_string ("v111__alignof__");
-	      if (TYPE_P (TREE_OPERAND (expr, 0)))
-		write_type (TREE_OPERAND (expr, 0));
-	      else
-		write_expression (TREE_OPERAND (expr, 0));
+	      write_string ("u11__alignof__");
+	      write_template_arg (TREE_OPERAND (expr, 0));
+	      write_char ('E');
 	      return;
 	    }
 	}
diff --git a/gcc/testsuite/g++.dg/cpp0x/alignof7.C b/gcc/testsuite/g++.dg/cpp0x/alignof7.C
index a4d7f24a4d7..2369b879392 100644
--- a/gcc/testsuite/g++.dg/cpp0x/alignof7.C
+++ b/gcc/testsuite/g++.dg/cpp0x/alignof7.C
@@ -18,5 +18,5 @@ template void f4<int>(std::size_t);
 
 // { dg-final { scan-assembler "_Z2f1IiEvDTatT_E" } }
 // { dg-final { scan-assembler "_Z2f2IiEvDTaztlT_EE" } }
-// { dg-final { scan-assembler "_Z2f3IiEvDTv111__alignof__T_E" } }
-// { dg-final { scan-assembler "_Z2f4IiEvDTv111__alignof__tlT_EE" } }
+// { dg-final { scan-assembler "_Z2f3IiEvDTu11__alignof__T_EE" } }
+// { dg-final { scan-assembler "_Z2f4IiEvDTu11__alignof__XtlT_EEEE" } }
diff --git a/include/demangle.h b/include/demangle.h
index 23b47265d94..295d58cb454 100644
--- a/include/demangle.h
+++ b/include/demangle.h
@@ -408,6 +408,9 @@ enum demangle_component_type
      number which involves neither modifying the mangled string nor
      allocating a new copy of the literal in memory.  */
   DEMANGLE_COMPONENT_LITERAL_NEG,
+  /* A vendor's builtin expression.  The left subtree holds the
+     expression's name, and the right subtree is a argument list.  */
+  DEMANGLE_COMPONENT_VENDOR_EXPR,
   /* A libgcj compiled resource.  The left subtree is the name of the
      resource.  */
   DEMANGLE_COMPONENT_JAVA_RESOURCE,
diff --git a/libiberty/cp-demangle.c b/libiberty/cp-demangle.c
index d3e798455cc..33490f60285 100644
--- a/libiberty/cp-demangle.c
+++ b/libiberty/cp-demangle.c
@@ -815,6 +815,9 @@ d_dump (struct demangle_component *dc, int indent)
     case DEMANGLE_COMPONENT_LITERAL_NEG:
       printf ("negative literal\n");
       break;
+    case DEMANGLE_COMPONENT_VENDOR_EXPR:
+      printf ("vendor expression\n");
+      break;
     case DEMANGLE_COMPONENT_JAVA_RESOURCE:
       printf ("java resource\n");
       break;
@@ -976,6 +979,7 @@ d_make_comp (struct d_info *di, enum demangle_component_type type,
     case DEMANGLE_COMPONENT_TRINARY_ARG1:
     case DEMANGLE_COMPONENT_LITERAL:
     case DEMANGLE_COMPONENT_LITERAL_NEG:
+    case DEMANGLE_COMPONENT_VENDOR_EXPR:
     case DEMANGLE_COMPONENT_COMPOUND_NAME:
     case DEMANGLE_COMPONENT_VECTOR_TYPE:
     case DEMANGLE_COMPONENT_CLONE:
@@ -3344,6 +3348,7 @@ d_unresolved_name (struct d_info *di)
 		::= cl <expression>+ E
                 ::= st <type>
                 ::= <template-param>
+		::= u <source-name> <template-arg>* E # vendor extended expression
 		::= <unresolved-name>
                 ::= <expr-primary>
 
@@ -3425,6 +3430,15 @@ d_expression_1 (struct d_info *di)
       return d_make_comp (di, DEMANGLE_COMPONENT_INITIALIZER_LIST,
 			  type, d_exprlist (di, 'E'));
     }
+  else if (peek == 'u')
+    {
+      /* A vendor extended expression.  */
+      struct demangle_component *name, *args;
+      d_advance (di, 1);
+      name = d_source_name (di);
+      args = d_template_args_1 (di);
+      return d_make_comp (di, DEMANGLE_COMPONENT_VENDOR_EXPR, name, args);
+    }
   else
     {
       struct demangle_component *op;
@@ -4229,6 +4243,7 @@ d_count_templates_scopes (struct d_print_info *dpi,
     case DEMANGLE_COMPONENT_TRINARY_ARG2:
     case DEMANGLE_COMPONENT_LITERAL:
     case DEMANGLE_COMPONENT_LITERAL_NEG:
+    case DEMANGLE_COMPONENT_VENDOR_EXPR:
     case DEMANGLE_COMPONENT_JAVA_RESOURCE:
     case DEMANGLE_COMPONENT_COMPOUND_NAME:
     case DEMANGLE_COMPONENT_DECLTYPE:
@@ -5509,18 +5524,9 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
       }
 
     case DEMANGLE_COMPONENT_EXTENDED_OPERATOR:
-      {
-	struct demangle_component *name = dc->u.s_extended_operator.name;
-	if (name->type == DEMANGLE_COMPONENT_NAME
-	    && !strncmp (name->u.s_name.s, "__alignof__", name->u.s_name.len))
-	  d_print_comp (dpi, options, dc->u.s_extended_operator.name);
-	else
-	  {
-	    d_append_string (dpi, "operator ");
-	    d_print_comp (dpi, options, dc->u.s_extended_operator.name);
-	  }
-	return;
-      }
+      d_append_string (dpi, "operator ");
+      d_print_comp (dpi, options, dc->u.s_extended_operator.name);
+      return;
 
     case DEMANGLE_COMPONENT_CONVERSION:
       d_append_string (dpi, "operator ");
@@ -5585,14 +5591,8 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
 	if (code && !strcmp (code, "gs"))
 	  /* Avoid parens after '::'.  */
 	  d_print_comp (dpi, options, operand);
-	else if ((code && !strcmp (code, "st"))
-		 || (op->type == DEMANGLE_COMPONENT_EXTENDED_OPERATOR
-		     && (op->u.s_extended_operator.name->type
-			 == DEMANGLE_COMPONENT_NAME)
-		     && !strncmp (op->u.s_extended_operator.name->u.s_name.s,
-				  "__alignof__",
-				  op->u.s_extended_operator.name->u.s_name.len)))
-	  /* Always print parens for sizeof (type) and __alignof__.  */
+	else if (code && !strcmp (code, "st"))
+	  /* Always print parens for sizeof (type).  */
 	  {
 	    d_append_char (dpi, '(');
 	    d_print_comp (dpi, options, operand);
@@ -5805,6 +5805,13 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
       }
       return;
 
+    case DEMANGLE_COMPONENT_VENDOR_EXPR:
+      d_print_comp (dpi, options, d_left (dc));
+      d_append_char (dpi, '(');
+      d_print_comp (dpi, options, d_right (dc));
+      d_append_char (dpi, ')');
+      return;
+
     case DEMANGLE_COMPONENT_NUMBER:
       d_append_num (dpi, dc->u.s_number.number);
       return;
diff --git a/libiberty/testsuite/demangle-expected b/libiberty/testsuite/demangle-expected
index e6b5b64b9a9..19a0d621bc0 100644
--- a/libiberty/testsuite/demangle-expected
+++ b/libiberty/testsuite/demangle-expected
@@ -1471,10 +1471,10 @@ _Z2F2IZ1FvEUlvE_EN1AIT_E1XES2_
 A<F()::{lambda()#1}>::X F2<F()::{lambda()#1}>(F()::{lambda()#1})
 
 # PR 88115
-_Z1fIiEvDTv111__alignof__T_E
+_Z1fIiEvDTu11__alignof__T_EE
 void f<int>(decltype (__alignof__(int)))
 
-_Z1fIiEvDTv111__alignof__tlT_EE
+_Z1fIiEvDTu11__alignof__XtlT_EEEE
 void f<int>(decltype (__alignof__(int{})))
 
 _Z1gI1AEv1SIXadsrT_oncviEE