Here you can find patches for binutils and gcc. These patches enable the resulting hc12-gcc to generate code for Motorolas 68HC12 microcontroller.
The gcc part is merely copied from the website of Stephane Carrez, who wrote an HC11 patch. I adapted it in one case to match my preferred assembler syntax. Here's the patch: hc12-gcc-2.95.1-0.0a.tar.gz (533687 Bytes).
The binutils patch is completely rewritten, here it is: hc12-binutils-2.9.1-0.0a.tar.gz (152729 Bytes).
And here's an example that should work: hello_port_a.tar.gz (1704 Bytes).
These patches are no longer supported, maybe you can use them as an example on patching gcc for other architectures. If you really want to use it as an HC12 compiler, then try the webpage of Stephane Carrez.