Author: pluto Date: Tue May 2 21:00:43 2006 GMT
Module: SOURCES Tag: GCC_4_1
---- Log message:
- fix detection of overflow from multiply expressions.
---- Files affected:
SOURCES:
gcc-pr27364.patch (NONE -> 1.1.2.1) (NEW)
---- Diffs:
================================================================
Index: SOURCES/gcc-pr27364.patch
diff -u /dev/null SOURCES/gcc-pr27364.patch:1.1.2.1
--- /dev/null Tue May 2 23:00:43 2006
+++ SOURCES/gcc-pr27364.patch Tue May 2 23:00:38 2006
@@ -0,0 +1,47 @@
+ PR tree-optimization/27364
+ * tree-vrp.c (vrp_int_const_binop): Fix detection of overflow from
+ multiply expressions.
+
+--- gcc-4_1-branch/gcc/tree-vrp.c.orig 2006-02-10 09:46:43.000000000 +0100
++++ gcc-4_1-branch/gcc/tree-vrp.c 2006-05-02 22:59:17.000000000 +0200
+@@ -1101,17 +1101,39 @@
+ if (TYPE_UNSIGNED (TREE_TYPE (val1)))
+ {
+ int checkz = compare_values (res, val1);
++ bool overflow = false;
+
+ /* Ensure that res = val1 [+*] val2 >= val1
+ or that res = val1 - val2 <= val1. */
+- if (((code == PLUS_EXPR || code == MULT_EXPR)
++ if ((code == PLUS_EXPR
+ && !(checkz == 1 || checkz == 0))
+ || (code == MINUS_EXPR
+ && !(checkz == 0 || checkz == -1)))
+ {
++ overflow = true;
++ }
++ /* Checking for multiplication overflow is done by dividing the
++ output of the multiplication by the first input of the
++ multiplication. If the result of that division operation is
++ not equal to the second input of the multiplication, then the
++ multiplication overflowed. */
++ else if (code == MULT_EXPR && !integer_zerop (val1))
++ {
++ tree tmp = int_const_binop (TRUNC_DIV_EXPR,
++ TYPE_MAX_VALUE (TREE_TYPE (val1)),
++ val1, 0);
++ int check = compare_values (tmp, val2);
++
++ if (check != 0)
++ overflow = true;
++ }
++
++ if (overflow)
++ {
+ res = copy_node (res);
+ TREE_OVERFLOW (res) = 1;
+ }
++
+ }
+ else if (TREE_OVERFLOW (res)
+ && !TREE_OVERFLOW (val1)
================================================================
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