* tree-vrp.c (vrp_int_const_binop): Handle PLUS_EXPR and

	the *_DIV_EXPR codes correctly with overflow infinities.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@122820 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1bdc306..d26d9be 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2007-03-11  Ian Lance Taylor  <iant@google.com>
+
+       * tree-vrp.c (vrp_int_const_binop): Handle PLUS_EXPR and
+       the *_DIV_EXPR codes correctly with overflow infinities.
+
 2007-03-11  Ira Rosen  <irar@il.ibm.com>
 
        * tree-data-ref.c (analyze_offset): Add a return value (bool) to 

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index dcb5f6a..d3fd911 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -1519,15 +1519,26 @@ vrp_int_const_binop (enum tree_code code, tree val1, tree val2)
          && !supports_overflow_infinity (TREE_TYPE (res)))
        return NULL_TREE;
 
-      /* We have to punt on subtracting infinities of the same sign,
-        since we can't tell what the sign of the result should
-        be.  */
-      if (code == MINUS_EXPR
-         && sgn1 == sgn2
+      /* We have to punt on adding infinities of different signs,
+        since we can't tell what the sign of the result should be.
+        Likewise for subtracting infinities of the same sign.  */
+      if (((code == PLUS_EXPR && sgn1 != sgn2)
+          || (code == MINUS_EXPR && sgn1 == sgn2))
          && is_overflow_infinity (val1)
          && is_overflow_infinity (val2))
        return NULL_TREE;
 
+      /* Don't try to handle division or shifting of infinities.  */
+      if ((code == TRUNC_DIV_EXPR
+          || code == FLOOR_DIV_EXPR
+          || code == CEIL_DIV_EXPR
+          || code == EXACT_DIV_EXPR
+          || code == ROUND_DIV_EXPR
+          || code == RSHIFT_EXPR)
+         && (is_overflow_infinity (val1)
+             || is_overflow_infinity (val2)))
+       return NULL_TREE;
+
       /* Notice that we only need to handle the restricted set of
         operations handled by extract_range_from_binary_expr.
         Among them, only multiplication, addition and subtraction
@@ -1541,8 +1552,12 @@ vrp_int_const_binop (enum tree_code code, tree val1, tree val2)
       if ((code == MULT_EXPR && sgn1 == sgn2)
           /* For addition, the operands must be of the same sign
             to yield an overflow.  Its sign is therefore that
-            of one of the operands, for example the first.  */
-         || (code == PLUS_EXPR && sgn1 > 0)
+            of one of the operands, for example the first.  For
+            infinite operands X + -INF is negative, not positive.  */
+         || (code == PLUS_EXPR
+             && (sgn1 >= 0
+                 ? !is_negative_overflow_infinity (val2)
+                 : is_positive_overflow_infinity (val2)))
          /* For subtraction, non-infinite operands must be of
             different signs to yield an overflow.  Its sign is
             therefore that of the first operand or the opposite of