(Binary Analysis) Fixed problems with PPC instruction decoding

* Create "unknown" instructions instead of throwing an exception when
  decoding an invalid PPC machine instruction.

* Fixed the MULLDO instruction so it works for both 32- and 64-bit
  instruction sets.

Issue #215

src/Rose/BinaryAnalysis/Disassembler/Powerpc.C

@@ -102,10 +102,15 @@ Powerpc::disassembleOne(const MemoryMap::Ptr &map, rose_addr_t start_va, Address
         c = ByteOrder::swapBytes(c);
 
     // Disassemble the instruction
-    State state;
-    startInstruction(state, start_va, c);
-    SgAsmPowerpcInstruction *insn = disassemble(state);      // throws an exception on error
-    ASSERT_not_null(insn);
+    SgAsmPowerpcInstruction *insn = nullptr;
+    try {
+        State state;
+        startInstruction(state, start_va, c);
+        insn = disassemble(state);                      // throws an exception on error, but we want to return an unknown insn
+        ASSERT_not_null(insn);
+    } catch (const ExceptionPowerpc &e) {
+        return makeUnknownInstruction(e);
+    }
 
     // Note successors if necessary
     if (successors) {

src/Rose/BinaryAnalysis/InstructionSemantics/DispatcherPowerpc.C

@@ -1349,10 +1349,10 @@ struct IP_mulldo: P {
     explicit IP_mulldo(UpdateCr::Flag updateCr): updateCr(updateCr) {}
     void p(D d, Ops ops, I insn, A args) {
         assert_args(insn, args, 3);
-        BaseSemantics::SValue::Ptr a = d->read(args[1], 32);
-        BaseSemantics::SValue::Ptr b = d->read(args[2], 32);
+        BaseSemantics::SValue::Ptr a = d->read(args[1]);
+        BaseSemantics::SValue::Ptr b = d->read(args[2]);
         BaseSemantics::SValue::Ptr product = ops->signedMultiply(a, b);
-        BaseSemantics::SValue::Ptr result = ops->extract(product, 0, 32);
+        BaseSemantics::SValue::Ptr result = ops->extract(product, 0, args[0]->get_type()->get_nBits());
         d->write(args[0], result);
         d->setXerOverflow(ops->invert(ops->equalToZero(ops->extract(result, 32, 64))));
         if (UpdateCr::YES == updateCr)