c-decl.c (finish_decl): Don't set DECL_C_HARD_REGISTER for non-register variables.

	* c-decl.c (finish_decl): Don't set DECL_C_HARD_REGISTER for
	non-register variables.
	* extend.texi: Document that asm-specifications do not make sense
	for non-static local variables.

From-SVN: r42403

gcc/ChangeLog

+2001-05-21  Mark Mitchell  <mark@codesourcery.com>
+
+	* c-decl.c (finish_decl): Don't set DECL_C_HARD_REGISTER for
+	non-register variables.
+	* extend.texi: Document that asm-specifications do not make sense
+	for non-static local variables.
+
 2001-05-21  Jason Merrill  <jason_merrill@redhat.com>
 
 	* dbxout.c (MINIMAL_DEBUG, flag_minimal_debug): Lose.

gcc/c-decl.c

@@ -3616,11 +3616,30 @@ finish_decl (decl, init, asmspec_tree)
 	}
       else
 	{
+	  /* This is a local variable.  If there is an ASMSPEC, the
+	     user has requested that we handle it specially.  */
 	  if (asmspec)
 	    {
-	      SET_DECL_ASSEMBLER_NAME (decl, get_identifier (asmspec));
-	      DECL_C_HARD_REGISTER (decl) = 1;
+	      /* In conjunction with an ASMSPEC, the `register'
+		 keyword indicates that we should place the variable
+		 in a particular register.  */
+	      if (DECL_REGISTER (decl))
+		DECL_C_HARD_REGISTER (decl) = 1;
+
+	      /* If this is not a static variable, issue a warning.
+		 It doesn't make any sense to give an ASMSPEC for an
+		 ordinary, non-register local variable.  Historically,
+		 GCC has accepted -- but ignored -- the ASMSPEC in
+		 this case.  */
+	      if (TREE_CODE (decl) == VAR_DECL 
+		  && !DECL_REGISTER (decl)
+		  && !TREE_STATIC (decl))
+		warning_with_decl (decl,
+				   "ignoring asm-specifier for non-static local variable `%s'");
+	      else
+		SET_DECL_ASSEMBLER_NAME (decl, get_identifier (asmspec));
 	    }
+
 	  add_decl_stmt (decl);
 	}
 

gcc/extend.texi

@@ -3290,6 +3290,13 @@ On systems where an underscore is normally prepended to the name of a C
 function or variable, this feature allows you to define names for the
 linker that do not start with an underscore.
 
+It does not make sense to use this feature with a non-static local
+variable since such variables do not have assembler names.  If you are
+trying to put the variable in a particular register, see @ref{Explicit
+Reg Vars}.  GCC presently accepts such code with a warning, but will
+probably be changed to issue an error, rather than a warning, in the
+future.
+
 You cannot use @code{asm} in this way in a function @emph{definition}; but
 you can get the same effect by writing a declaration for the function
 before its definition and putting @code{asm} there, like this:

gcc/testsuite/gcc.dg/20010520-1.c

+/* { dg-do compile { target i?86-*-* } } */
+/* { dg-options "-w" } */
+
+void f ()
+{
+  int i __asm__ ("%eax");
+  __asm__ volatile ("" : "=a" (i));
+}
+
+