[gcc/devel/c++-modules] IPA symver: allow multiple symvers for a definition

[gcc/devel/c++-modules] IPA symver: allow multiple symvers for a definition

[Nathan Sidwell]

https://gcc.gnu.org/g:363080bb8bd2cca81dd9e2e774910a8c8226f430

commit 363080bb8bd2cca81dd9e2e774910a8c8226f430
Author: Martin Liska <mliska@suse.cz>
Date:   Mon Aug 24 13:21:10 2020 +0200

    IPA symver: allow multiple symvers for a definition
    
    gcc/ChangeLog:
    
            * cgraphunit.c (process_symver_attribute): Allow multiple
            symver attributes for one symbol.
            * doc/extend.texi: Document the change.
    
    gcc/testsuite/ChangeLog:
    
            * lib/target-supports-dg.exp: Add dg-require-symver.
            * lib/target-supports.exp: Likewise.
            * gcc.dg/ipa/symver1.c: New test.

Diff:
---
 gcc/cgraphunit.c                         | 143 ++++++++++++++++---------------
 gcc/doc/extend.texi                      |  16 ++--
 gcc/testsuite/gcc.dg/ipa/symver1.c       |  11 +++
 gcc/testsuite/lib/target-supports-dg.exp |  10 +++
 gcc/testsuite/lib/target-supports.exp    |  12 +++
 5 files changed, 116 insertions(+), 76 deletions(-)

diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index 0b1009d0dea..fa3aec79a48 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -720,80 +720,81 @@ process_symver_attribute (symtab_node *n)
 {
   tree value = lookup_attribute ("symver", DECL_ATTRIBUTES (n->decl));
 
-  if (!value)
-    return;
-  if (lookup_attribute ("symver", TREE_CHAIN (value)))
+  for (; value != NULL; value = TREE_CHAIN (value))
     {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"multiple versions for one symbol");
-      return;
-    }
-  tree symver = get_identifier_with_length
-		  (TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (value))),
-		   TREE_STRING_LENGTH (TREE_VALUE (TREE_VALUE (value))));
-  symtab_node *def = symtab_node::get_for_asmname (symver);
+      /* Starting from bintuils 2.35 gas supports:
+	  # Assign foo to bar@V1 and baz@V2.
+	  .symver foo, bar@V1
+	  .symver foo, baz@V2
+      */
+
+      tree symver = get_identifier_with_length
+	(TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (value))),
+	 TREE_STRING_LENGTH (TREE_VALUE (TREE_VALUE (value))));
+      symtab_node *def = symtab_node::get_for_asmname (symver);
+
+      if (def)
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "duplicate definition of a symbol version");
+	  inform (DECL_SOURCE_LOCATION (def->decl),
+		  "same version was previously defined here");
+	  return;
+	}
+      if (!n->definition)
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "symbol needs to be defined to have a version");
+	  return;
+	}
+      if (DECL_COMMON (n->decl))
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "common symbol cannot be versioned");
+	  return;
+	}
+      if (DECL_COMDAT (n->decl))
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "comdat symbol cannot be versioned");
+	  return;
+	}
+      if (n->weakref)
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "%<weakref%> cannot be versioned");
+	  return;
+	}
+      if (!TREE_PUBLIC (n->decl))
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "versioned symbol must be public");
+	  return;
+	}
+      if (DECL_VISIBILITY (n->decl) != VISIBILITY_DEFAULT)
+	{
+	  error_at (DECL_SOURCE_LOCATION (n->decl),
+		    "versioned symbol must have default visibility");
+	  return;
+	}
 
-  if (def)
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"duplicate definition of a symbol version");
-      inform (DECL_SOURCE_LOCATION (def->decl),
-	      "same version was previously defined here");
-      return;
-    }
-  if (!n->definition)
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"symbol needs to be defined to have a version");
-      return;
-    }
-  if (DECL_COMMON (n->decl))
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"common symbol cannot be versioned");
-      return;
-    }
-  if (DECL_COMDAT (n->decl))
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"comdat symbol cannot be versioned");
-      return;
-    }
-  if (n->weakref)
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"%<weakref%> cannot be versioned");
-      return;
+      /* Create new symbol table entry representing the version.  */
+      tree new_decl = copy_node (n->decl);
+
+      DECL_INITIAL (new_decl) = NULL_TREE;
+      if (TREE_CODE (new_decl) == FUNCTION_DECL)
+	DECL_STRUCT_FUNCTION (new_decl) = NULL;
+      SET_DECL_ASSEMBLER_NAME (new_decl, symver);
+      TREE_PUBLIC (new_decl) = 1;
+      DECL_ATTRIBUTES (new_decl) = NULL;
+
+      symtab_node *symver_node = symtab_node::get_create (new_decl);
+      symver_node->alias = true;
+      symver_node->definition = true;
+      symver_node->symver = true;
+      symver_node->create_reference (n, IPA_REF_ALIAS, NULL);
+      symver_node->analyzed = true;
     }
-  if (!TREE_PUBLIC (n->decl))
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"versioned symbol must be public");
-      return;
-    }
-  if (DECL_VISIBILITY (n->decl) != VISIBILITY_DEFAULT)
-    {
-      error_at (DECL_SOURCE_LOCATION (n->decl),
-		"versioned symbol must have default visibility");
-      return;
-    }
-
-  /* Create new symbol table entry representing the version.  */
-  tree new_decl = copy_node (n->decl);
-
-  DECL_INITIAL (new_decl) = NULL_TREE;
-  if (TREE_CODE (new_decl) == FUNCTION_DECL)
-    DECL_STRUCT_FUNCTION (new_decl) = NULL;
-  SET_DECL_ASSEMBLER_NAME (new_decl, symver);
-  TREE_PUBLIC (new_decl) = 1;
-  DECL_ATTRIBUTES (new_decl) = NULL;
-
-  symtab_node *symver_node = symtab_node::get_create (new_decl);
-  symver_node->alias = true;
-  symver_node->definition = true;
-  symver_node->symver = true;
-  symver_node->create_reference (n, IPA_REF_ALIAS, NULL);
-  symver_node->analyzed = true;
 }
 
 /* Process attributes common for vars and functions.  */
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 2bb9b2f72f5..3b37aba5795 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3742,13 +3742,19 @@ foo_v1 (void)
 Will produce a @code{.symver foo_v1, foo@@VERS_1} directive in the assembler
 output. 
 
-It's an error to define multiple version of a given symbol.  In such case
-an alias can be used.
+One can also define multiple version for a given symbol.
 
 @smallexample
-__attribute__ ((__symver__ ("foo@@VERS_2")))
-__attribute__ ((alias ("foo_v1")))
-int symver_foo_v1 (void);
+__attribute__ ((__symver__ ("foo@@VERS_2"), ("foo@@VERS_3")))
+int symver_foo_v1 (void)
+@{
+@}
+
+__attribute__ ((__symver__ ("bar@@VERS_2"))))
+__attribute__ ((__symver__ ("bar@@VERS_3"))))
+int symver_bar_v1 (void)
+@{
+@}
 @end smallexample
 
 This example creates an alias of @code{foo_v1} with symbol name
diff --git a/gcc/testsuite/gcc.dg/ipa/symver1.c b/gcc/testsuite/gcc.dg/ipa/symver1.c
new file mode 100644
index 00000000000..645de7ea259
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/symver1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+
+__attribute__ ((__symver__ ("foo@VER_2")))
+__attribute__ ((__symver__ ("foo@VER_3")))
+int foo()
+{
+  return 2;
+}
+
+/* { dg-final { scan-assembler ".symver.*foo, foo@VER_2" } } */
+/* { dg-final { scan-assembler ".symver.*foo, foo@VER_3" } } */
diff --git a/gcc/testsuite/lib/target-supports-dg.exp b/gcc/testsuite/lib/target-supports-dg.exp
index 5bb99f4e8f9..4a03eaae9ce 100644
--- a/gcc/testsuite/lib/target-supports-dg.exp
+++ b/gcc/testsuite/lib/target-supports-dg.exp
@@ -665,3 +665,13 @@ if { [info procs saved-dg-process-target] == [list] } {
 	return [dg-process-target-1 $selector]
     }
 }
+
+# If this target does not support the "symver" attribute, skip this
+# test.
+
+proc dg-require-symver { args } {
+    if { ![ check_symver_available ] } {
+	upvar dg-do-what dg-do-what
+	set dg-do-what [list [lindex ${dg-do-what} 0] "N" "P"]
+    }
+}
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index c24330a27ab..f3fc5b80aea 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -10445,3 +10445,15 @@ proc check_effective_target_large_initializer { } {
 
     return 1
 }
+# Returns 1 if the target toolchain supports extended
+# syntax of .symver directive, 0 otherwise.
+
+proc check_symver_available { } {
+    return [check_no_compiler_messages symver_available object {
+	    int foo(void) { return 0; }
+	    int main (void) {
+		asm volatile (".symver foo,foo@VER_1, local");
+		return 0;
+	    }
+	}]
+}