port gcc for c51 step by step

... snip ...

I suggest the OP would be better off starting from a recursive descent compiler, such as SmallC. He can maintain the C parsing unchanged, and only alter the code generation area. To do that he will have to understand the destination architecture intimately, and build whatever run time assistance and standard library components are needed.

Most 8051 C compilers do not implement a stack in software but instead rely on passing parameters via registers and avoid stack manipulation altogether. Most also include profilers that help optimise register usage. AFAIK gcc is unable to work this way without changes to its core functionality. You *could* use a software stack but it is incredibly inefficient on an 8051.

Anything is possible and you could create a unique fork of gcc that supported the 8051 in the same way that there are special ports of other micros not supported by the gcc core team. However, I do not think the 8051 will ever be supported by the gcc core.

Ian

IIRC, the one I'm remembering (Archimedes?) would do things either way. It would use registers or static locations by default, but if you told it you wanted re-entrant code, it would do a software stack.

It's been done, and I know projects where it was used successfully.

Yup. I use one of them every day.

I don't think so either. It would be too much work for what I think would be pretty lousy results.

I don't recall that one - is it still available? Common ones available now are Keil, Renaissance and Tasking, all of which I believe operate as I described. A software stack is of course feasible but very messy and slow on an 8051.

Ian

Hmm. It's looking doubtful. That was probably 10+ years ago. I found a link at

We also had the Franklin compiler, so I might be mixing them up. Their web site looks a bit out-of-date as well:

# State-of-the-art integrated Windows 3.1, WIN95, and Windows NT compliant software tools

How do they generate re-entrant code if they don't implement a stack in softwate?

lcc is simple (while being full ANSI C) and strictly divided into architecture independent and dependent parts (and reasonably well documented, including the book*); it is designed for easy retargetability. Other compilers may have particular advantages for tiny architectures though. Things get tricky with lcc on architectures < 32 bits (and few registers).

• formatting link

They have a special directive to declare a function reentrant, which then builds a software stack for that function e.g. Keil uses:

void myfunc(void) reentrant { ... }

Ian

You may find it in the IAR product line. Archimedes used to resell IAR compilers under its own name.

Wasn't Renaissance sold as Archimedes in the USA at one time ?

Regards Anton Erasmus

Dunno. That was probably almost 15 years ago.

It's *very* easy to use with gcc -- the official Microchip tool chain for the PIC30 is based on gcc.

-- Dave Tweed

Thanks all for your time !!! This is over this subjekt. I have solve c51 & gcc problem.

Best regards Pawel_O

I'm sorry for my poor english... ;)

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