vlib

i got answer.
Here's the mapping:

.x64P == .out ("x" stands for "executable")
.l64P == .a64P == .lib ("l" stands for "library", "a" for "library archive" which is the same thing)
.o64P == .obj

"64P" means "DaVinci DSP architecture".

So a .x64P file is nothing more or less than a DSP .out -- executable -- file with its extension renamed; ".l64P" or ".a64P" is nothing more or less than a DSP library files with its extension renamed; and .o64P... you get the idea. For example, you can load myprog.x64P on the DSP via Code Composer Studio and CCS will treat the file and its symbols just like an ordinary .out file, because that's what it is.