patch: vector_size attribute

[Aldy Hernandez <aldyh at redhat dot com>]

as per, the altivec discussion, here is a patch to add a vector_size
attribute-- complete with documentation and a test case.  and waddaya
know, it actually works...

bootstrapped on x86.

is this ok?

-- 
Aldy Hernandez			E-mail: aldyh@redhat.com
Professional Gypsy
Red Hat, Inc.

2001-12-04  Aldy Hernandez  <aldyh@redhat.com>

        * extend.texi (Variable Attributes): Document vector_size.

        * gcc.dg/altivec-2.c: New.

        * attribs.c (c_common_attribute_table): Add vector_size.
        (handle_vector_size_attribute): New.

Index: doc/extend.texi
===================================================================
RCS file: /cvs/uberbaum/gcc/doc/extend.texi,v
retrieving revision 1.37
diff -c -p -r1.37 extend.texi
*** extend.texi	2001/11/18 03:30:55	1.37
--- extend.texi	2001/12/04 20:42:08
*************** This attribute, attached to a variable, 
*** 3035,3040 ****
--- 3035,3055 ----
  to be possibly unused.  GCC will not produce a warning for this
  variable.
  
+ @item vector_size (@var{bytes})
+ This attribute specifies the vector size for the variable, measured in
+ bytes.  For example, the declaration:
+ 
+ @smallexample
+ int foo __attribute__ ((vector_size (16)));
+ @end smallexample
+ 
+ @noindent
+ causes the compiler to set the mode for @code{foo}, to be 16 bytes,
+ divided into @code{int} sized units.  Assuming a 32 bit int (a vector of
+ 4 units of 4 bytes), the corresponding mode of @code{foo} will be V4SI.
+ 
+ This attribute is only applicable to integral and float scalars.
+ 
  @item weak
  The @code{weak} attribute is described in @xref{Function Attributes}.
  
Index: testsuite/gcc.dg/altivec-2.c
===================================================================
RCS file: altivec-2.c
diff -N altivec-2.c
*** /dev/null	Tue May  5 13:32:27 1998
--- altivec-2.c	Tue Dec  4 12:42:08 2001
***************
*** 0 ****
--- 1,7 ----
+ /* { dg-do compile { target powerpc-*-* } } */
+ /* { dg-options "-maltivec" } */
+ 
+ /* Program to test the vector_size attribute.  This needs to run on a
+    target that has vectors, so use AltiVec.  */
+ 
+ __attribute__((vector_size(16))) int foobar;
Index: attribs.c
===================================================================
RCS file: /cvs/uberbaum/gcc/attribs.c,v
retrieving revision 1.4
diff -c -p -r1.4 attribs.c
*** attribs.c	2001/11/04 02:51:21	1.4
--- attribs.c	2001/12/04 20:42:08
*************** static tree handle_no_limit_stack_attrib
*** 84,89 ****
--- 84,91 ----
  						     bool *));
  static tree handle_pure_attribute	PARAMS ((tree *, tree, tree, int,
  						 bool *));
+ static tree handle_vector_size_attribute PARAMS ((tree *, tree, tree, int,
+ 						  bool *));
  
  /* Table of machine-independent attributes common to all C-like languages.  */
  static const struct attribute_spec c_common_attribute_table[] =
*************** static const struct attribute_spec c_com
*** 139,144 ****
--- 141,148 ----
  			      handle_no_limit_stack_attribute },
    { "pure",                   0, 0, true,  false, false,
  			      handle_pure_attribute },
+   { "vector_size",	      1, 1, true, false, false,
+ 			      handle_vector_size_attribute },
    { NULL,                     0, 0, false, false, false, NULL }
  };
  
*************** handle_pure_attribute (node, name, args,
*** 1153,1158 ****
--- 1157,1233 ----
        *no_add_attrs = true;
      }
  
+   return NULL_TREE;
+ }
+ 
+ /* Handle a "vector_size" attribute; arguments as in
+    struct attribute_spec.handler.  */
+ 
+ static tree
+ handle_vector_size_attribute (node, name, args, flags, no_add_attrs)
+      tree *node;
+      tree name;
+      tree args;
+      int flags ATTRIBUTE_UNUSED;
+      bool *no_add_attrs;
+ {
+   unsigned int vecsize, nunits;
+   enum machine_mode mode, orig_mode, new_mode;
+   tree decl = *node;
+   tree type = TREE_TYPE (decl);
+ 
+   if (TREE_CODE (TREE_VALUE (args)) != INTEGER_CST)
+     {
+       warning ("`%s' attribute ignored", IDENTIFIER_POINTER (name));
+       return NULL_TREE;
+     }
+ 
+   /* Get the vector size (in bytes).  */
+   vecsize = TREE_INT_CST_LOW (TREE_VALUE (args));
+ 
+   /* Calculate how many units fit in the vector.  */
+   nunits = vecsize / (TYPE_PRECISION (TREE_TYPE (*node)) / 8);
+ 
+   /* Get the mode of the type being modified.  */
+   orig_mode = TYPE_MODE (TREE_TYPE (*node));
+ 
+   if (GET_MODE_CLASS (orig_mode) != MODE_FLOAT
+       && GET_MODE_CLASS (orig_mode) != MODE_INT)
+     {
+       error ("invalid vector type for attribute `%s'",
+ 	     IDENTIFIER_POINTER (name));
+       return NULL_TREE;
+     }
+ 
+   /* Find a suitably sized vector.  */
+   new_mode = VOIDmode;
+   for (mode = GET_CLASS_NARROWEST_MODE (GET_MODE_CLASS (orig_mode) == MODE_INT
+ 					? MODE_VECTOR_INT
+ 					: MODE_VECTOR_FLOAT);
+        mode != VOIDmode;
+        mode = GET_MODE_WIDER_MODE (mode))
+     if (vecsize == GET_MODE_SIZE (mode)	&& nunits == GET_MODE_NUNITS (mode))
+       {
+ 	new_mode = mode;
+ 	break;
+       }
+ 
+   if (new_mode == VOIDmode)
+     error ("No relevant vector mode found");
+   else
+     {
+       type = type_for_mode (new_mode, TREE_UNSIGNED (type));
+       if (!type)
+ 	error ("No data type for mode `%s'", GET_MODE_NAME (new_mode));
+       else
+ 	{
+ 	  TREE_TYPE (decl) = type;
+ 	  DECL_SIZE (decl) = DECL_SIZE_UNIT (decl) = 0;
+ 	  if (TREE_CODE (decl) != FIELD_DECL)
+ 	    layout_decl (decl, 0);
+ 	}
+     }
+     
    return NULL_TREE;
  }