(extract_muldiv): When constructing a multiplier/divisor, do not expect

const_binop to correctly determine if overflow has occured, so check explicitly.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@34135 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b874d9f..d3f281e 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2000-05-24  Nick Clifton  <nickc@cygnus.com>
+
+       * fold-const.c (extract_muldiv): When constructing a
+       multiplier/divisor, do not expect const_binop to correctly
+       determine if overflow has occured, so check explicitly.
+
 2000-05-24  Alexandre Oliva  <aoliva@cygnus.com>
 
        * c-decl.c (build_enumerator): Don't modify the value's type,

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 12a8d1a..eec3bc4 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -4451,6 +4451,10 @@ extract_muldiv (t, c, code, wide_type)
         or floor division, by a power of two, so we can treat it that
         way unless the multiplier or divisor overflows.  */
       if (TREE_CODE (op1) == INTEGER_CST
+         /* const_binop may not detect overflow correctly,
+            so check for it explicitly here.  */
+         && TYPE_PRECISION (TREE_TYPE (size_one_node)) > TREE_INT_CST_LOW (op1)
+         && TREE_INT_CST_HIGH (op1) == 0
          && 0 != (t1 = convert (ctype,
                                 const_binop (LSHIFT_EXPR, size_one_node,
                                              op1, 0)))