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

From-SVN: r136200

* fold-const.c (fold_unary) <CASE_CONVERT>: Add ??? comment.
From-SVN: r136200
bfab40f8 · Eric Botcazou · Eric Botcazou · c100de59 · bfab40f8 · bfab40f8
Commit bfab40f8 authored May 30, 2008 by Eric Botcazou Committed by Eric Botcazou May 30, 2008
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gcc/ChangeLog
+4 -0

gcc/fold-const.c
+4 -1

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--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
+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

--- 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)