combine.c (try_combine): Set subst_low_luid to i0.

2010-09-06  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>

	* combine.c (try_combine): Set subst_low_luid to i0.

2010-09-06  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>

	* gcc.dg/20100906-1.c: New testcase.

From-SVN: r163917

gcc/ChangeLog

+2010-09-06  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
+
+	* combine.c (try_combine): Set subst_low_luid to i0.
+
 2010-09-06  Richard Guenther  <rguenther@suse.de>
 
 	* tree.def (MISALIGNED_INDIRECT_REF): Remove.

gcc/combine.c

@@ -3138,7 +3138,7 @@ try_combine (rtx i3, rtx i2, rtx i1, rtx i0, int *new_direct_jump_p)
 	}
 
       n_occurrences = 0;
-      subst_low_luid = DF_INSN_LUID (i1);
+      subst_low_luid = DF_INSN_LUID (i0);
       newpat = subst (newpat, i0dest, i0src, 0,
 		      i0_feeds_i1_n && i0dest_in_i0src);
       substed_i0 = 1;

gcc/testsuite/ChangeLog

+2010-09-06  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
+
+	* gcc.dg/20100906-1.c: New testcase.
+
 2010-09-06  Jakub Jelinek  <jakub@redhat.com>
 
 	PR testsuite/45543

gcc/testsuite/gcc.dg/20100906-1.c

+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+/* This testcase got misoptimized by combine due to a wrong setting of
+   subst_low_luid in try_combine.  */
+
+enum rtx_code {
+  A, B
+};
+
+void abort (void);
+
+struct rtx_def {
+  __extension__ enum rtx_code code:16;
+};
+typedef struct rtx_def *rtx;
+
+void __attribute__((noinline))
+add_constraint (unsigned char is_a)
+{
+  if (is_a)
+    abort ();
+}
+
+void __attribute__((noinline))
+foo (rtx defn)
+{
+  switch (defn->code)
+    {
+    case A:
+    case B:
+      add_constraint (defn->code == A);
+      break;
+    default:
+      break;
+    }
+}
+
+int
+main ()
+{
+  struct rtx_def r;
+
+  r.code = B;
+
+  foo (&r);
+  return 0;
+}