* fold-const.c (fold_unary) <CASE_CONVERT>: Add ??? comment.

From-SVN: r136200

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index aeff771692be73cabd97fdfbe78cacfd983d4ebd..82d24789424a46437cc15fcbc009890541d93a1d 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2008-05-30  Eric Botcazou  <ebotcazou@adacore.com>
+
+       * fold-const.c (fold_unary) <CASE_CONVERT>: Add ??? comment.
+
 2008-05-30  Danny Smith  <dannysmith@users.sourceforge.net>
 
        * incpath.c: Use HOST_LACKS_INODE_NUMBERS conditional

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 25756bbb9c93d2b963e35f1b189ef56ade3c7c1a..4a9d55ff238cc55a2c40fa12b21000ab02773037 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -7866,7 +7866,10 @@ fold_unary (enum tree_code code, tree type, tree op0)
 
       /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
         constants (if x has signed type, the sign bit cannot be set
-        in c).  This folds extension into the BIT_AND_EXPR.  */
+        in c).  This folds extension into the BIT_AND_EXPR.
+        ??? We don't do it for BOOLEAN_TYPE or ENUMERAL_TYPE because they
+        very likely don't have maximal range for their precision and this
+        transformation effectively doesn't preserve non-maximal ranges.  */
       if (TREE_CODE (type) == INTEGER_TYPE
          && TREE_CODE (op0) == BIT_AND_EXPR
          && TREE_CODE (TREE_OPERAND (op0, 1)) == INTEGER_CST)