re PR middle-end/17894 (div/compare folding incorrect)

	PR middle-end/17894
	* fold-const.c (fold_div_compare): When optimizing X/C1 op C2, the
	relational comparison operator op needs to be swapped/reversed when
	C1 is negative.  i.e. X/-10 < 1 becomes X >= -9, not X < -9.

	* gcc.c-torture/execute/divcmp-4.c: New test case.

From-SVN: r88818

4 files changed, 217 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8f9daf8..5d968b1 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2004-10-09  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/17894
+	* fold-const.c (fold_div_compare): When optimizing X/C1 op C2, the
+	relational comparison operator op needs to be swapped/reversed when
+	C1 is negative.  i.e. X/-10 < 1 becomes X >= -9, not X < -9.
+
 2004-10-08  Andrew Pinski  <pinskia@physics.uc.edu>
 
 	PR tree-opt/17902
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 7de102f..41feda3 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -5720,6 +5720,9 @@ fold_div_compare (enum tree_code code, tree type, tree arg0, tree arg1)
     }
   else
     {
+      /* A negative divisor reverses the relational operators.  */
+      code = swap_tree_comparison (code);
+
       tmp = int_const_binop (PLUS_EXPR, arg01, integer_one_node, 0);
       switch (tree_int_cst_sgn (arg1))
 	{
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0ac5e9b..28d0a11 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2004-10-09  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/17894
+	* gcc.c-torture/execute/divcmp-4.c: New test case.
+
 2004-10-08  Andrew Pinski  <pinskia@physics.uc.edu>
 
 	PR tree-opt/17902
diff --git a/gcc/testsuite/gcc.c-torture/execute/divcmp-4.c b/gcc/testsuite/gcc.c-torture/execute/divcmp-4.c
new file mode 100644
index 0000000..ebc09a1
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/divcmp-4.c
@@ -0,0 +1,202 @@
+/* PR middle-end/17894 */
+
+extern void abort(void);
+
+int test1(int x)
+{
+  return x/-10 == 2;
+}
+
+int test2(int x)
+{
+  return x/-10 == 0;
+}
+
+int test3(int x)
+{
+  return x/-10 != 2;
+}
+
+int test4(int x)
+{
+  return x/-10 != 0;
+}
+
+int test5(int x)
+{
+  return x/-10 < 2;
+}
+
+int test6(int x)
+{
+  return x/-10 < 0;
+}
+
+int test7(int x)
+{
+  return x/-10  <= 2;
+}
+
+int test8(int x)
+{
+  return x/-10 <= 0;
+}
+
+int test9(int x)
+{
+  return x/-10 > 2;
+}
+
+int test10(int x)
+{
+  return x/-10 > 0;
+}
+
+int test11(int x)
+{
+  return x/-10 >= 2;
+}
+
+int test12(int x)
+{
+  return x/-10 >= 0;
+}
+
+
+int main()
+{
+  if (test1(-30) != 0)
+    abort ();
+  if (test1(-29) != 1)
+    abort ();
+  if (test1(-20) != 1)
+    abort ();
+  if (test1(-19) != 0)
+    abort ();
+
+  if (test2(0) != 1)
+    abort ();
+  if (test2(9) != 1)
+    abort ();
+  if (test2(10) != 0)
+    abort ();
+  if (test2(-1) != 1)
+    abort ();
+  if (test2(-9) != 1)
+    abort ();
+  if (test2(-10) != 0)
+    abort ();
+
+  if (test3(-30) != 1)
+    abort ();
+  if (test3(-29) != 0)
+    abort ();
+  if (test3(-20) != 0)
+    abort ();
+  if (test3(-19) != 1)
+    abort ();
+
+  if (test4(0) != 0)
+    abort ();
+  if (test4(9) != 0)
+    abort ();
+  if (test4(10) != 1)
+    abort ();
+  if (test4(-1) != 0)
+    abort ();
+  if (test4(-9) != 0)
+    abort ();
+  if (test4(-10) != 1)
+    abort ();
+
+  if (test5(-30) != 0)
+    abort ();
+  if (test5(-29) != 0)
+    abort ();
+  if (test5(-20) != 0)
+    abort ();
+  if (test5(-19) != 1)
+    abort ();
+
+  if (test6(0) != 0)
+    abort ();
+  if (test6(9) != 0)
+    abort ();
+  if (test6(10) != 1)
+    abort ();
+  if (test6(-1) != 0)
+    abort ();
+  if (test6(-9) != 0)
+    abort ();
+  if (test6(-10) != 0)
+    abort ();
+
+  if (test7(-30) != 0)
+    abort ();
+  if (test7(-29) != 1)
+    abort ();
+  if (test7(-20) != 1)
+    abort ();
+  if (test7(-19) != 1)
+    abort ();
+
+  if (test8(0) != 1)
+    abort ();
+  if (test8(9) != 1)
+    abort ();
+  if (test8(10) != 1)
+    abort ();
+  if (test8(-1) != 1)
+    abort ();
+  if (test8(-9) != 1)
+    abort ();
+  if (test8(-10) != 0)
+    abort ();
+
+  if (test9(-30) != 1)
+    abort ();
+  if (test9(-29) != 0)
+    abort ();
+  if (test9(-20) != 0)
+    abort ();
+  if (test9(-19) != 0)
+    abort ();
+
+  if (test10(0) != 0)
+    abort ();
+  if (test10(9) != 0)
+    abort ();
+  if (test10(10) != 0)
+    abort ();
+  if (test10(-1) != 0)
+    abort ();
+  if (test10(-9) != 0)
+    abort ();
+  if (test10(-10) != 1)
+    abort ();
+
+  if (test11(-30) != 1)
+    abort ();
+  if (test11(-29) != 1)
+    abort ();
+  if (test11(-20) != 1)
+    abort ();
+  if (test11(-19) != 0)
+    abort ();
+
+  if (test12(0) != 1)
+    abort ();
+  if (test12(9) != 1)
+    abort ();
+  if (test12(10) != 0)
+    abort ();
+  if (test12(-1) != 1)
+    abort ();
+  if (test12(-9) != 1)
+    abort ();
+  if (test12(-10) != 1)
+    abort ();
+
+  return 0;
+}
+