[patch mingw]: Fix PR/51726 - LTO and attribute 'selectany'

[Kai Tietz <ktietz70@googlemail.com>]

Hello,

This patch fixes the reported LTO issue, which is caused by not
implemented case of uniinitialized variables with selectany-attribute
(as common), as such variables couldn't be placed into
linkonce-section for pe-coff.

I adjusted existing testcase to reflect now supported case of
selectany-attribute on uninitialized variables, too.

ChangeLog

2015-10-01  Kai Tietz  <ktietz70@googlemail.com>

    PR target/51726
    * config/i386/winnt.c (ix86_handle_selectany_attribute): Handle
    selectany within this function without need to keep attribute.
    (i386_pe_encode_section_info): Remove selectany-code.

I regression-tested this patch for i686 and x86_64 mingw &
cygwin-targets. will apply this patch tomorrow, if there are no
objections.

Kai

Index: winnt.c
===================================================================
--- winnt.c    (Revision 228280)
+++ winnt.c    (Arbeitskopie)
@@ -89,17 +89,23 @@ tree
 ix86_handle_selectany_attribute (tree *node, tree name, tree, int,
                  bool *no_add_attrs)
 {
+  tree decl = *node;
   /* The attribute applies only to objects that are initialized and have
      external linkage.  However, we may not know about initialization
-     until the language frontend has processed the decl. We'll check for
-     initialization later in encode_section_info.  */
-  if (TREE_CODE (*node) != VAR_DECL || !TREE_PUBLIC (*node))
-    {
-      error ("%qE attribute applies only to initialized variables"
-                " with external linkage", name);
-      *no_add_attrs = true;
+     until the language frontend has processed the decl.   Therefore
+     we make sure that variable isn't initialized as common.  */
+  if (TREE_CODE (decl) != VAR_DECL || !TREE_PUBLIC (decl))
+    error ("%qE attribute applies only to initialized variables"
+              " with external linkage", name);
+  else
+    {
+      make_decl_one_only (decl, DECL_ASSEMBLER_NAME (decl));
+      /* A variable with attribute selectany never can be common.  */
+      DECL_COMMON (decl) = 0;
     }

+  /* We don't need to keep attribute itself.  */
+  *no_add_attrs = true;
   return NULL_TREE;
 }

@@ -320,23 +326,7 @@ i386_pe_encode_section_info (tree decl, rtx rtl, i
   switch (TREE_CODE (decl))
     {
     case FUNCTION_DECL:
-      break;
-
     case VAR_DECL:
-      if (lookup_attribute ("selectany", DECL_ATTRIBUTES (decl)))
-    {
-      if (DECL_INITIAL (decl)
-          /* If an object is initialized with a ctor, the static
-         initialization and destruction code for it is present in
-         each unit defining the object.  The code that calls the
-         ctor is protected by a link-once guard variable, so that
-         the object still has link-once semantics,  */
-          || TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (decl)))
-        make_decl_one_only (decl, DECL_ASSEMBLER_NAME (decl));
-      else
-        error ("%q+D:'selectany' attribute applies only to "
-           "initialized objects", decl);
-    }
       break;

     default:

ChangeLog

2015-10-01  Kai Tietz  <ktietz70@googlemail.com>

    PR target/51726
    * g++.dg/ext/sectany2.C: Allow uninitialized variable case.

Index: g++.dg/ext/selectany2.C
===================================================================
--- g++.dg/ext/selectany2.C    (Revision 228347)
+++ g++.dg/ext/selectany2.C    (Arbeitskopie)
@@ -18,7 +18,7 @@ struct  f
 };
 __declspec (selectany) struct f  F= {1}; // OK

-__declspec (selectany) int boo;    //{ dg-error "selectany" }
+__declspec (selectany) int boo;    //  OK

 __declspec (selectany) static int bar = 1; // { dg-error "selectany" }
 int use_bar = bar;  //  Avoid defined but not used warning.