diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 047bcef4ba2..7412c201f7c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2010-12-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/46771
+	* reginfo.c (init_subregs_of_mode): Don't call find_subregs_of_mode
+	on DEBUG_INSNs.
+
 	PR rtl-optimization/46777
 	* cfglayout.c (duplicate_insn_chain): Avoid duplicating
 	also barrier after tablejump.
diff --git a/gcc/reginfo.c b/gcc/reginfo.c
index aaf062ed135..7c1209fe4b4 100644
--- a/gcc/reginfo.c
+++ b/gcc/reginfo.c
@@ -1330,7 +1330,7 @@ init_subregs_of_mode (void)
 
   FOR_EACH_BB (bb)
     FOR_BB_INSNS (bb, insn)
-    if (INSN_P (insn))
+    if (NONDEBUG_INSN_P (insn))
       find_subregs_of_mode (PATTERN (insn));
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3c5c43e1696..f64afd42572 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2010-12-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/46771
+	* gcc.dg/pr46771.c: New test.
+
 	PR rtl-optimization/46777
 	* gcc.dg/pr46777.c: New test.
 
diff --git a/gcc/testsuite/gcc.dg/pr46771.c b/gcc/testsuite/gcc.dg/pr46771.c
new file mode 100644
index 00000000000..b44dfd466ab
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr46771.c
@@ -0,0 +1,18 @@
+/* PR debug/46771 */
+/* { dg-do compile } */
+/* { dg-options "-O -ftree-vectorize -fcompare-debug" } */
+
+unsigned char v[1600];
+
+unsigned char
+foo (unsigned char x)
+{
+  int i;
+  unsigned char a = x;
+  unsigned char b = x;
+  for (i = 0; i < 1600; i++)
+    a = a < v[i] ? v[i] : a;
+  for (i = 0; i < 1600; i++)
+    b = b > v[i] ? v[i] : b;
+  return a - b;
+}