Initial ARM/Thumb disassembler check-in. It consists of a tablgen backend

(RISCDisassemblerEmitter) which emits the decoder functions for ARM and Thumb,
and the disassembler core which invokes the decoder function and builds up the
MCInst based on the decoded Opcode.

Added sub-formats to the NeonI/NeonXI instructions to further refine the NEONFrm
instructions to help disassembly.

We also changed the output of the addressing modes to omit the '+' from the
assembler syntax #+/-<imm> or +/-<Rm>.  See, for example, A8.6.57/58/60.

And modified test cases to not expect '+' in +reg or #+num.  For example,

; CHECK:       ldr.w	r9, [r7, #28]


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98637 91177308-0d34-0410-b5e6-96231b3b80d8

utils/TableGen/DisassemblerEmitter.cpp

@@ -12,6 +12,8 @@
 #include "Record.h"
 #include "X86DisassemblerTables.h"
 #include "X86RecognizableInstr.h"
+#include "RISCDisassemblerEmitter.h"
+
 using namespace llvm;
 using namespace llvm::X86Disassembler;
 
@@ -124,6 +126,12 @@ void DisassemblerEmitter::run(raw_ostream &OS) {
     return;
   }
 
+  // Fixed-instruction-length targets use a common disassembler.
+  if (Target.getName() == "ARM") {
+    RISCDisassemblerEmitter(Records).run(OS);
+    return;
+  }  
+
   throw TGError(Target.getTargetRecord()->getLoc(),
                 "Unable to generate disassembler for this target");
 }