re PR rtl-optimization/11536 ([strength-reduce] -O2 optimalization produces wrong code)

PR optimization/11536
	* unroll.c (loop_iterations): Do not replace a register holding
	the final value by its equivalent before the loop if it is not
	invariant.

        PR optimization/11536
	* gcc.dg/20030721-1.c: New test.

From-SVN: r69635

gcc/ChangeLog

@@ -1,3 +1,10 @@
+2003-07-17  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+        PR optimization/11536
+	* unroll.c (loop_iterations): Do not replace a register holding
+	the final value by its equivalent before the loop if it is not
+	invariant.
+
 2003-07-21  Dave Fluri  <dave.fluri@onlink.net>
 
 	* doc/extend.texi: Fixes to spelling, grammar, and diction.

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2003-07-21  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+        PR optimization/11536
+	* gcc.dg/20030721-1.c: New test.
+
 2003-07-19  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/11546

gcc/testsuite/gcc.dg/20030721-1.c

@@ -0,0 +1,41 @@
+/* { dg-options "-O2" } */
+/* PR optimization/11536 */
+/* Origin: samal@kam.mff.cuni.cz <samal@kam.mff.cuni.cz> */
+/* Testcase by Andrew Pinski <pinskia@physics.uc.edu> */
+
+/* Verify that the loop optimizer doesn't use moving targets
+   to calculate the number of iterations of a loop.  */
+
+extern void abort(void);
+
+void foo(int) __attribute__((__noinline__));
+
+void foo(int i)
+{
+  abort();
+}
+
+int main()
+{
+  int i;
+  int first= 0;
+  int last= 0;
+
+  while (last<3) {
+    last = first;
+
+    while (first<=last) {
+      first++;
+
+      for (i=0;i<3;i++)
+        last++;
+
+      if (last>10)
+        return 0;
+    }
+    
+    foo(first);
+  }
+
+  return 0;
+}

gcc/unroll.c

@@ -3618,7 +3618,7 @@ loop_iterations (struct loop *loop)
 
 	  if (find_common_reg_term (temp, reg2))
 	    initial_value = temp;
-	  else
+	  else if (loop_invariant_p (loop, reg2))
 	    {
 	      /* Find what reg2 is equivalent to.  Hopefully it will
 		 either be reg1 or reg1 plus a constant.  Let's ignore