re PR middle-end/17055 (ICE while folding int/float vectors)

	PR middle-end/17055
	* fold-const.c (build_zero_vector): New function to construct a
	vector (either floating point or integer) of zeros.
	(fold_convert): Internally, enable conversions of integer zero
	to arbitrary vector types, using the new build_zero_vector.

	* gcc.dg/pr17055-1.c: New test case.

From-SVN: r87272

gcc/ChangeLog

 2004-09-09  Roger Sayle  <roger@eyesopen.com>
 
+	PR middle-end/17055
+	* fold-const.c (build_zero_vector): New function to construct a
+	vector (either floating point or integer) of zeros.
+	(fold_convert): Internally, enable conversions of integer zero
+	to arbitrary vector types, using the new build_zero_vector.
+
+2004-09-09  Roger Sayle  <roger@eyesopen.com>
+
 	* config/i386/i386.c (ix86_expand_ashlsi3_const): New function to
 	expand a left shift by an immediate constant as either an ashl or
 	a sequence of additions.

gcc/fold-const.c

@@ -89,6 +89,7 @@ static tree negate_expr (tree);
 static tree split_tree (tree, enum tree_code, tree *, tree *, tree *, int);
 static tree associate_trees (tree, tree, enum tree_code, tree);
 static tree const_binop (enum tree_code, tree, tree, int);
+static tree build_zero_vector (tree);
 static tree fold_convert_const (enum tree_code, tree, tree);
 static enum tree_code invert_tree_comparison (enum tree_code, bool);
 static enum comparison_code comparison_to_compcode (enum tree_code);
@@ -1677,6 +1678,23 @@ size_diffop (tree arg0, tree arg1)
 							arg1, arg0)));
 }
 
+/* Construct a vector of zero elements of vector type TYPE.  */
+
+static tree
+build_zero_vector (tree type)
+{
+  tree elem, list;
+  int i, units;
+
+  elem = fold_convert_const (NOP_EXPR, TREE_TYPE (type), integer_zero_node);
+  units = TYPE_VECTOR_SUBPARTS (type);
+
+  list = NULL_TREE;
+  for (i = 0; i < units; i++)
+    list = tree_cons (NULL_TREE, elem, list);
+  return build_vector (type, list);
+}
+
 
 /* Attempt to fold type conversion operation CODE of expression ARG1 to
    type TYPE.  If no simplification can be done return NULL_TREE.  */
@@ -1940,6 +1958,8 @@ fold_convert (tree type, tree arg)
 	}
       
     case VECTOR_TYPE:
+      if (integer_zerop (arg))
+	return build_zero_vector (type);
       gcc_assert (tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (orig)));
       gcc_assert (INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig)
 		  || TREE_CODE (orig) == VECTOR_TYPE);

gcc/testsuite/ChangeLog

+2004-09-09  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/17055
+	* gcc.dg/pr17055-1.c: New test case.
+
 2004-09-09  Hans-Peter Nilsson  <hp@axis.com>
 
 	PR target/17377

gcc/testsuite/gcc.dg/pr17055-1.c

+/* PR middle-end/17055.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ffast-math" } */
+
+/* This test used to abort, beacuse we do an "integer" fold to zero, i.e.
+   x - x = (T)0 where T is the type of x.  Unfortunately, fold_convert
+   was unable to convert integer_zero_node to the appropriate vector type.  */
+
+typedef float v4sf __attribute__((vector_size(16)));
+typedef int v4si __attribute__((vector_size(16)));
+
+v4sf ivf, ovf;
+v4si ivi, ovi;
+
+void testf (void)
+{
+  ovf = ivf - ivf;
+}
+
+void testi (void)
+{
+  ovi = ivi - ivi;
+}
+