re PR rtl-optimization/24899 (loop.c miscompiles libgnomecanvas)

	PR rtl-optimization/24899
	* loop.c (strength_reduce): Don't reduce giv that is not always
	computable and where add_val or mult_val can trap.

	* gcc.c-torture/execute/20051215-1.c: New test.

From-SVN: r108642

gcc/ChangeLog

 2005-12-16  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/24899
+	* loop.c (strength_reduce): Don't reduce giv that is not always
+	computable and where add_val or mult_val can trap.
+
 	* doc/invoke.texi (-fdump-tree-*): Remove note about C/C++ only.
 
 2005-12-16  Nathan Sidwell  <nathan@codesourcery.com>

gcc/loop.c

@@ -6486,6 +6486,17 @@ strength_reduce (struct loop *loop, int flags)
 	      v->ignore = 1;
 	      bl->all_reduced = 0;
 	    }
+	  else if (!v->always_computable
+		   && (may_trap_or_fault_p (v->add_val)
+		       || may_trap_or_fault_p (v->mult_val)))
+	    {
+	      if (loop_dump_stream)
+		fprintf (loop_dump_stream,
+			 "giv of insn %d: not always computable.\n",
+			 INSN_UID (v->insn));
+	      v->ignore = 1;
+	      bl->all_reduced = 0;
+	    }
 	  else
 	    {
 	      /* Check that we can increment the reduced giv without a

gcc/testsuite/ChangeLog

+2005-12-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/24899
+	* gcc.c-torture/execute/20051215-1.c: New test.
+
 2005-12-16  Andreas Krebbel  <krebbel1@de.ibm.com>
 
 	PR 24823

gcc/testsuite/gcc.c-torture/execute/20051215-1.c

+/* PR rtl-optimization/24899 */
+
+extern void abort (void);
+
+__attribute__ ((noinline)) int
+foo (int x, int y, int *z)
+{
+  int a, b, c, d;
+
+  a = b = 0;
+  for (d = 0; d < y; d++)
+    {
+      if (z)
+	b = d * *z;
+      for (c = 0; c < x; c++)
+	a += b;
+    }
+
+  return a;
+}
+
+int
+main (void)
+{
+  if (foo (3, 2, 0) != 0)
+    abort ();
+  return 0;
+}