re PR tree-optimization/57051 (Optimization regression in 4.8.0 from 4.7.2)

	PR tree-optimization/57051
	* fold-const.c (const_binop) <case VEC_LSHIFT_EXPR,
	case VEC_RSHIFT_EXPR>: Fix BYTES_BIG_ENDIAN handling.

From-SVN: r199002

gcc/ChangeLog

+2013-05-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/57051
+	* fold-const.c (const_binop) <case VEC_LSHIFT_EXPR,
+	case VEC_RSHIFT_EXPR>: Fix BYTES_BIG_ENDIAN handling.
+
 2013-05-16  Nick Clifton  <nickc@redhat.com>
 
 	* config/rl78/rl78.c (rl78_attribute_table): Add naked.

gcc/fold-const.c

@@ -1393,7 +1393,11 @@ const_binop (enum tree_code code, tree arg1, tree arg2)
 	  if (shiftc >= outerc || (shiftc % innerc) != 0)
 	    return NULL_TREE;
 	  int offset = shiftc / innerc;
-	  if (code == VEC_LSHIFT_EXPR)
+	  /* The direction of VEC_[LR]SHIFT_EXPR is endian dependent.
+	     For reductions, compiler emits VEC_RSHIFT_EXPR always,
+	     for !BYTES_BIG_ENDIAN picks first vector element, but
+	     for BYTES_BIG_ENDIAN last element from the vector.  */
+	  if ((code == VEC_RSHIFT_EXPR) ^ (!BYTES_BIG_ENDIAN))
 	    offset = -offset;
 	  tree zero = build_zero_cst (TREE_TYPE (type));
 	  for (i = 0; i < count; i++)