The Mitsubishi D10V version of as uses the following machine dependent option.

The D10V syntax is based on the syntax in the Mitsubishi document, D10V Architecture: A VLIW Mediaprocessor for Multimedia Applications (Mitsubishi Electric Corporation, version 1.00; October 24, 1996). The differences are detailed in the following discussions.

The D10V version of as uses the instruction names in the Mitsubishi document, D10V Architecture: A VLIW Mediaprocessor for Multimedia Applications (Mitsubishi Electric Corporation, version 1.00; October 24, 1996). However, the names in the documentation are sometimes ambiguous. There are instruction names that can assemble to a short or long form opcode. How does the assembler pick the correct form? as will always pick the smallest form if it can. When dealing with a symbol that is not defined yet when a line is being assembled, it will always use the long form. If you need to force the assembler to use either the short or long form of the instruction, you can append either .s (short) or .l (long) to it. For example, if you are writing an assembly program and you want to do a branch to a symbol that is defined later in your program, you can write bra.s foo. objdump and GDB will always append .s or .l to instructions which have both short and long forms.

The D10V assembler takes as input a series of instructions, either one-per-line, or in the special two-per-line format described in the next section. Some of these instructions will be short-form or sub-instructions. These sub-instructions can be packed into a single instruction. The assembler will do this automatically. It will also detect when it should not pack instructions. For example, when a label is defined, the next instruction will never be packaged with the previous one. Whenever a branch and link instruction is called, it will not be packaged with the next instruction so the return address will be valid. Nops are automatically inserted when necessary.
 

; and # are the line comment characters. Sub-instructions may be executed in order, in reverse-order, or in parallel. Instructions listed in the standard one-per-line format will be executed sequentially. To specify the executing order, use the following symbols.

You can use the predefined symbols r0' through r15 to refer to the D10V registers. You can also use sp as an alias for r15. The accumulators are a0 and a1. There are special register-pair names that may optionally be used in opcodes that require even-numbered registers. Register names are not case sensitive.

as understands the following addressing modes for the D10V. Rn in the following documentation refers to any of the numbered registers, but not the control registers.

Any symbol followed by @word will be replaced by the symbol's value shifted right by 2. This is used in situations such as loading a register with the address of a function (or any other code fragment). For example, if you want to load a register with the location of the function, main, then jump to that function, you could do it as follows.

The D10V has no hardware floating point, but the .float and .double directives generates IEEE floating-point numbers for compatibility with other development tools.

For detailed information on the D10V machine instruction set, see the Mitsubishi document, D10V Architecture: A VLIW Mediaprocessor for Multimedia Applications (published by Mitsubishi Electric Corporation, version 1.00; October 24, 1996); as implements all the standard D10V opcodes found there. The only changes are those described in the section on size modifiers.