The machine instruction sets are (almost by definition) different on each machine where as runs. Floating point representations vary as well, and as often supports a few additional directives or command-line options for compatibility with other assemblers on a particular platform. Finally, some versions of as support special pseudo-instructions for branch optimization. For details on particular architectures, see the hardware manufacturer’s manual.
The
following documentation discusses the assembler directives and machine
dependent features regarding the following supported architectures.