Thumb assembly parsing and encoding for LDM instruction.

Fix base register type and canonicallize to the "ldm" spelling rather than
"ldmia." Add diagnostics for incorrect writeback token and out-of-range
registers.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137986 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
index 961b057..1999ee7 100644
--- a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
+++ b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
@@ -155,9 +155,9 @@
     }
 
     if (Opcode == ARM::tLDMIA)
-      O << "\tldmia";
+      O << "\tldm";
     else if (Opcode == ARM::tSTMIA)
-      O << "\tstmia";
+      O << "\tstm";
     else
       llvm_unreachable("Unknown opcode!");