SASM is an abstract assembly language. The operations performed and the registers and other storage manipulated by those operations are all represented symbolically.
Consider the following example instruction:
(assign (reg operand) (op load-array) (label $scmglobal-char-Eq?) (const 0))
This is an assignment instruction. The target of the assignment
(left-hand side) is an abstract register, named operand. The source
of the assignment (right-hand side) is an operation, named
load-array which references memory. A label is used for the base
pointer of the load-array operation, and a 0-word offset is specified.
This is an exact instruction emitted by the Scheme frontend for referencing a global variable. When we run this instruction through the SASM "optimizer" tool, sasm-opt.exe, it is translated into a more specific form of SASM instruction:
(assign (reg ebx) (op load-array) (label $scmglobal-char-Eq?) (const 0))
In this form of the instruction, the symbolic operand register is
replaced with a real, physical x86 register ebx. The remainder of
the instruction is still exactly the same. In this case, there is a
static mapping of the operand register to ebx, however the
sasm-opt.exe tool is capable of performing register allocation and
transforming other storage such as (temp my-variable) and (local 1) into actual register references.
Lastly, we run this instruction through the sasm.exe tool, and it is translated into an actual x86 instruction that is recognized by NASM.
mov ebx, [___Doscmglobal_char_Eq__Qu]
The base syntax for SASM is a Scheme or LISP style s-exp, although supporting other syntaxes is planned work.
The SASM language was heavily influenced by Wizard Book's 5th chapter, Computing With Register Machines.