SDCC is a Free ware , retargettable, optimizing ANSI-C compiler. The current 
version targets Intel 8051 based MCUs, it can be retargetted for other 8 bit 
MCUs or PICs. The entire source code for the compiler is distributed under 
GPL. SDCC used ASXXXX & ASLINK a Free ware, retargettable assembler & linker.

HTML docs are in work/*/doc.

Note I added a patch from sailer@ife.ee.ethz.ch "asxxxx.diff" for making
firmware for the Anchor EZUSB chips.