diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a9720018fae..c8e74f5c58a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2008-02-27  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/34971
+	* expr.c (expand_expr_real_1): Assert on rotates that operate
+	on partial modes.
+	* fold-const.c (fold_binary): Use the types precision, not the
+	bitsize of the mode if folding rotate expressions.  Build rotates
+	only for full modes.
+
 2008-02-27  Jakub Jelinek  <jakub@redhat.com>
 
 	* c-ppoutput.c (scan_translation_unit): Handle CPP_PRAGMA
diff --git a/gcc/expr.c b/gcc/expr.c
index 36741918fb3..79a039a529f 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -8898,10 +8898,16 @@ expand_expr_real_1 (tree exp, rtx target, enum machine_mode tmode,
     case BIT_XOR_EXPR:
       goto binop;
 
-    case LSHIFT_EXPR:
-    case RSHIFT_EXPR:
     case LROTATE_EXPR:
     case RROTATE_EXPR:
+      /* The expansion code only handles expansion of mode precision
+	 rotates.  */
+      gcc_assert (GET_MODE_PRECISION (TYPE_MODE (type))
+		  == TYPE_PRECISION (type));
+
+      /* Falltrough.  */
+    case LSHIFT_EXPR:
+    case RSHIFT_EXPR:
       /* If this is a fixed-point operation, then we cannot use the code
 	 below because "expand_shift" doesn't support sat/no-sat fixed-point
          shifts.   */
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 1ecd2255e4a..f6a73efe9ad 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -9886,13 +9886,18 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	 is a rotate of A by B bits.  */
       {
 	enum tree_code code0, code1;
+	tree rtype;
 	code0 = TREE_CODE (arg0);
 	code1 = TREE_CODE (arg1);
 	if (((code0 == RSHIFT_EXPR && code1 == LSHIFT_EXPR)
 	     || (code1 == RSHIFT_EXPR && code0 == LSHIFT_EXPR))
 	    && operand_equal_p (TREE_OPERAND (arg0, 0),
 			        TREE_OPERAND (arg1, 0), 0)
-	    && TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg0, 0))))
+	    && (rtype = TREE_TYPE (TREE_OPERAND (arg0, 0)),
+	        TYPE_UNSIGNED (rtype))
+	    /* Only create rotates in complete modes.  Other cases are not
+	       expanded properly.  */
+	    && TYPE_PRECISION (rtype) == GET_MODE_PRECISION (TYPE_MODE (rtype)))
 	  {
 	    tree tree01, tree11;
 	    enum tree_code code01, code11;
@@ -11636,7 +11641,7 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
       if (code == LROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST)
 	{
 	  tree tem = build_int_cst (TREE_TYPE (arg1),
-				    GET_MODE_BITSIZE (TYPE_MODE (type)));
+				    TYPE_PRECISION (type));
 	  tem = const_binop (MINUS_EXPR, tem, arg1, 0);
 	  return fold_build2 (RROTATE_EXPR, type, op0, tem);
 	}
@@ -11655,8 +11660,8 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 			    fold_build2 (code, type,
 					 TREE_OPERAND (arg0, 1), arg1));
 
-      /* Two consecutive rotates adding up to the width of the mode can
-	 be ignored.  */
+      /* Two consecutive rotates adding up to the precision of the
+	 type can be ignored.  */
       if (code == RROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST
 	  && TREE_CODE (arg0) == RROTATE_EXPR
 	  && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
@@ -11664,7 +11669,7 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	  && TREE_INT_CST_HIGH (TREE_OPERAND (arg0, 1)) == 0
 	  && ((TREE_INT_CST_LOW (arg1)
 	       + TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)))
-	      == (unsigned int) GET_MODE_BITSIZE (TYPE_MODE (type))))
+	      == (unsigned int) TYPE_PRECISION (type)))
 	return TREE_OPERAND (arg0, 0);
 
       /* Fold (X & C2) << C1 into (X << C1) & (C2 << C1)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8f652d21218..3435b5bfb42 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2008-02-27  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/34971
+	* gcc.c-torture/execute/pr34971.c: New testcase.
+
 2008-02-27  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.dg/gomp/preprocess-1.c: New test.
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr34971.c b/gcc/testsuite/gcc.c-torture/execute/pr34971.c
new file mode 100644
index 00000000000..3299aee22c9
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr34971.c
@@ -0,0 +1,22 @@
+struct foo
+{
+  unsigned long long b:40;
+} x;
+
+extern void abort (void);
+
+void test1(unsigned long long res)
+{
+  /* Build a rotate expression on a 40 bit argument.  */
+  if ((x.b<<8) + (x.b>>32) != res)
+    abort ();
+}
+
+int main()
+{
+  x.b = 0x0100000001;
+  test1(0x0000000101);
+  x.b = 0x0100000000;
+  test1(0x0000000001);
+  return 0;
+}