diff --git a/llvm/lib/Target/ARM/README-Thumb.txt b/llvm/lib/Target/ARM/README-Thumb.txt
index 4d3200b445c1..ecef58a32da3 100644
--- a/llvm/lib/Target/ARM/README-Thumb.txt
+++ b/llvm/lib/Target/ARM/README-Thumb.txt
@@ -226,3 +226,9 @@ etc. Almost all Thumb instructions clobber condition code.
 //===---------------------------------------------------------------------===//
 
 Add ldmia, stmia support.
+
+//===---------------------------------------------------------------------===//
+
+Thumb load / store address mode offsets are scaled. The values kept in the
+instruction operands are pre-scale values. This probably ought to be changed
+to avoid extra work when we convert Thumb2 instructions to Thumb1 instructions.