re PR middle-end/21085 (Virtual memory exhausted with g++)

2005-04-18  James A. Morrison  <phython@gcc.gnu.org>

        PR tree-optimization/21085
        * fold-const (fold_binary): Don't change X % -C to X % C if C has
        overflowed.

From-SVN: r98365

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2005-04-18  James A. Morrison  <phython@gcc.gnu.org>
+
+	PR tree-optimization/21085
+	* fold-const (fold_binary): Don't change X % -C to X % C if C has
+	overflowed.
+
 2005-04-19  Ben Elliston  <bje@au.ibm.com>
 
 	* doc/invoke.texi (Optimize Options): Refer to the correct

gcc/fold-const.c

@@ -8504,6 +8504,7 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
       if (code == TRUNC_MOD_EXPR
 	  && !TYPE_UNSIGNED (type)
 	  && TREE_CODE (arg1) == INTEGER_CST
+	  && !TREE_CONSTANT_OVERFLOW (arg1)
 	  && TREE_INT_CST_HIGH (arg1) < 0
 	  && !flag_trapv
 	  /* Avoid this transformation if C is INT_MIN, i.e. C == -C.  */

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2005-04-18  James A. Morrison  <phython@gcc.gnu.org>
+
+	* gcc.dg/pr21085.c: New test.
+
 2005-04-18  Richard Sandiford  <rsandifo@redhat.com>
 
 	* gcc.target/mips/mips.exp: Minor formatting.  Call setup_mips_tests.

gcc/testsuite/gcc.dg/pr21085.c

@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* This used to cause excessive use, or a stack overflow, depending on which
+   came first.  */
+void foo (void)
+{
+  int maxstringlen = 1;
+  int limit = 0, maxblock = 0, maxblockrem = 0;
+  maxblockrem = (maxstringlen) % (2147483647 + 1); /* { dg-warning "overflow" } */
+}