Fix off-by-one error.

(low two bits always zero, so off by one bit of encoded value).

llvm-svn: 134247
diff --git a/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp b/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
index 692189c..c741a6e 100644
--- a/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
+++ b/llvm/lib/Target/ARM/Thumb2SizeReduction.cpp
@@ -491,7 +491,7 @@
     // The immediate must be in range, the destination register must be a low
     // reg, the predicate must be "always" and the condition flags must not
     // be being set.
-    if (Imm & 3 || Imm > 1024)
+    if (Imm & 3 || Imm > 1020)
       return false;
     if (!isARMLowRegister(MI->getOperand(0).getReg()))
       return false;