A software mechanism for enabling a programmer to embed selected machine instructions into program source code in a convenient fashion, and optionally restricting the re-ordering of such instructions by the compiler without making any significant modifications to the compiler processing. Using a table-driven approach, the mechanism parses the embedded machine instruction constructs and verifies syntax and semantic correctness. The mechanism then translates the constructs into low-level compiler internal representations that may be integrated into other compiler code with minimal compiler changes. When also supported by a robust underlying inter-module optimization framework, library routines containing embedded machine instructions according to the present invention can be inlined into applications. When those applications invoke such library routines, the present invention enables the routines to be optimized more effectively, thereby improving run-time application performance. A mechanism is also disclosed using a "_fpreg" data type to enable floating-point arithmetic to be programmed from a source level where the programmer gains access to the full width of the floating-point register representation of the underlying processor.