Move DecodedInstruction into MIR.

Change-Id: I188dc7fef4f4033361c78daf2015b869242191c6
diff --git a/compiler/optimizing/builder.cc b/compiler/optimizing/builder.cc
index 1efdd38..b0aa63b 100644
--- a/compiler/optimizing/builder.cc
+++ b/compiler/optimizing/builder.cc
@@ -409,7 +409,7 @@
       uint32_t method_idx = instruction.VRegB_35c();
       uint32_t number_of_vreg_arguments = instruction.VRegA_35c();
       uint32_t args[5];
-      instruction.GetArgs(args);
+      instruction.GetVarArgs(args);
       if (!BuildInvoke(instruction, dex_offset, method_idx, number_of_vreg_arguments, false, args, -1)) {
         return false;
       }