diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fea2d33d41f..373cbdd23e3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2002-03-15  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR target/5170
+	* arm.md (split pattern for thumb shiftable immediates): Add comment
+	explaining non-obvious test.
+
 2002-03-15  Richard Earnshaw  <rearnsha@arm.com>
 
 	PR target/5712
diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index cb59ece2cd4..1db601a4d60 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -4124,6 +4124,7 @@
       if ((val & (mask << i)) == val)
         break;
 
+    /* Shouldn't happen, but we don't want to split if the shift is zero.  */
     if (i == 0)
       FAIL;