* fold-const.c (fold): Fold some comparisons of bit operations.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@70009 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 923f25e..caa596b 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2003-07-31  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
+
+       * fold-const.c (fold): Fold some comparisons of bit operations.
+
 Thu Jul 31 19:49:53 CEST 2003  Jan Hubicka  <jh@suse.cz>
 
        * cgraph.c (create_edge): Fix typo.

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 58cec23..aea392f 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -7182,6 +7182,34 @@ fold (tree expr)
       if (tem)
        return tem;
 
+      /* If we have (A & C) == D where D & ~C != 0, convert this into 0.
+        Similarly for NE_EXPR.  */
+      if ((code == EQ_EXPR || code == NE_EXPR)
+         && TREE_CODE (arg0) == BIT_AND_EXPR
+         && TREE_CODE (arg1) == INTEGER_CST
+         && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
+       {
+         tree dandnotc = fold (build (BIT_ANDTC_EXPR, TREE_TYPE (arg0),
+                                      arg1, TREE_OPERAND (arg0, 1)));
+         tree rslt = code == EQ_EXPR ? integer_zero_node : integer_one_node;
+         if (!integer_zerop (dandnotc))
+           return omit_one_operand (type, rslt, arg0);
+       }
+
+      /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
+        Similarly for NE_EXPR.  */
+      if ((code == EQ_EXPR || code == NE_EXPR)
+         && TREE_CODE (arg0) == BIT_IOR_EXPR
+         && TREE_CODE (arg1) == INTEGER_CST
+         && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
+       {
+         tree candnotd = fold (build (BIT_ANDTC_EXPR, TREE_TYPE (arg0),
+                                      TREE_OPERAND (arg0, 1), arg1));
+         tree rslt = code == EQ_EXPR ? integer_zero_node : integer_one_node;
+         if (!integer_zerop (candnotd))
+           return omit_one_operand (type, rslt, arg0);
+       }
+
       /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
         and similarly for >= into !=.  */
       if ((code == LT_EXPR || code == GE_EXPR)