i. You may be using Alchemy decompile. but, Project "Alchemy" is now the Flash C++ Compiler (FlasCC). Adobe Forum, refer to information about it.
Alchemy is a research project from Adobe Systems that allows compiling C and C++ code to ActionScript Virtual Machine (AVM2), so that it can be run on Flash Player or Adobe AIR. This is achieved by compiling C/C++ code to LLVM bytecode and then translating LLVM to ActionScript 3 with inlined AVM2 bytecode, which is then compiled with a specialized ActionScript compiler. The resulting SWF/SWC is considerably faster than normal ActionScript code, but up to 2x - 10x slower than native C++ code.
Alchemy site: Alchemy
FlasCC Documents: FlasCC
ii. Another way is to use a free swf decompiler.