Fwd: Many questions

[Dale Johannesen <dalej at apple dot com>]

> To: Solra Bizna <sbizna@tejat.net>

This address bounced.

On Sunday, October 26, 2003, at 05:15  PM, Solra Bizna wrote:
> I have been assigned to find or create a C compiler, assembler, 
> linker, etc. for the TCS architecture. Rather than writing my own 
> compiler (something I do not look forward to trying) I would like to 
> add TCS support to GCC (and binutils) if possible. However, I have 
> several questions:
>
> * Odd calling conventions
> TCS function parameters and variables are stored in registers when 
> possible. The TCS has 16 general-purpose registers, all are 64-bit 
> integers. RE and RF are reserved for the frame pointer and stack 
> pointer, respectively, and R0 is reserved for function return values. 
> That leaves 13 registers for parameters and variables. Only the first 
> 13 parameters are stored in registers, however, after that all are 
> pushed onto the stack.
> Varargs functions' parameters are loaded up to the last "static" 
> argument, then pushed left-to-right.
> Variables go after parameters in registers.
> Now, these calling conventions cause problems. For example, what 
> happens if the number of static arguments and variables exceeds 13? 
> They should be swapped onto the stack, but GCC may have to be modified 
> to compensate. Where would I perform the modifications allowing for 
> these weird calling conventions?

This is not that odd, Sparc and rs6000 are similar.  Take a look at 
those ports.

> * Odd immediates
> TCS instructions are 32 bits long. The low 16 bits (second in memory) 
> store the instruction opcode, the high 16-bits store its operands. 
> Each operand is 4-bit, allowing for instructions of the type
> MA R2,R2,R4,R3 ; Multiply Add word
> to be stored without trouble. Unfortunately, that limits immediates to 
> either 4 or 12 bits (depending on the instruction). As a consequence, 
> immediates must be embedded with code similiar to:

Most ports have limits to how big an immediate field can be in some 
instructions.
See, e.g., the I constraint on Sparc.

> * Compiling 64-bit on 32-bit
> Can GCC compile for 64-bit architectures on a 32-bit one? 
> (specifically: powerpc-linux-gnu or powerpc-apple-darwin)

Yes.

> * Machine descriptions
> I can no longer seem to find the machine description documentation. 
> How do I write machine descriptions?

It's in the manual, which you find here:
http://gcc.gnu.org/onlinedocs/
Please read it, questions that are answered in the manual are not well 
received.