expr.c (do_store_flag): Expand vector comparison by building an appropriate VEC_COND_EXPR.

2011-09-29  Artjoms Sinkarovs <artyom.shinkaroff@gmail.com>

	* expr.c (do_store_flag): Expand vector comparison by
	building an appropriate VEC_COND_EXPR.
	* c-typeck.c (build_binary_op): Typecheck vector comparisons.
	(c_objc_common_truthvalue_conversion): Adjust.
	* tree-vect-generic.c (do_compare): Helper function.
	(expand_vector_comparison): Check if hardware supports
	vector comparison of the given type or expand vector
	piecewise.
	(expand_vector_operation): Treat comparison as binary
	operation of vector type.
	(expand_vector_operations_1): Adjust.

	* gcc.c-torture/execute/vector-compare-1.c: New testcase.
	* gcc.c-torture/execute/vector-compare-2.c: Likewise.
	* gcc.dg/vector-compare-1.c: Likewise.
	* gcc.dg/vector-compare-2.c: Likewise.

From-SVN: r179342

1 files changed, 23 insertions, 0 deletions

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index f59333c..e8a777d 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -6561,6 +6561,29 @@ invoke undefined behavior at runtime.  Warnings for out of bound
 accesses for vector subscription can be enabled with
 @option{-Warray-bounds}.
 
+In GNU C vector comparison is supported within standard comparison
+operators: @code{==, !=, <, <=, >, >=}. Comparison operands can be
+vector expressions of integer-type or real-type. Comparison between
+integer-type vectors and real-type vectors are not supported.  The
+result of the comparison is a vector of the same width and number of
+elements as the comparison operands with a signed integral element
+type.
+
+Vectors are compared element-wise producing 0 when comparison is false
+and -1 (constant of the appropriate type where all bits are set)
+otherwise. Consider the following example.
+
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+
+v4si a = @{1,2,3,4@};
+v4si b = @{3,2,1,4@};
+v4si c;
+
+c = a >  b;     /* The result would be @{0, 0,-1, 0@}  */
+c = a == b;     /* The result would be @{0,-1, 0,-1@}  */
+@end smallexample
+
 You can declare variables and use them in function calls and returns, as
 well as in assignments and some casts.  You can specify a vector type as
 a return type for a function.  Vector types can also be used as function