Modifying the ISA

This section is incomplete. Older manuals did have it, but the information got outdated. If you want to do this, send an email to S.D.Cotofana@tudelft.nl, also to get the compiler source code files.

If you choose to modify the instruction set of the processor you're building, you will also need to change the compiler for it. Otherwise, the new instructions you add will not be used by the compiler, or if you remove instructions, the compiler will still happily generate them.

To do this, we provide the source of the MIPS cross compiler: mips-pdp-elf-...., as well as tools to build this cross compiler itself (crosstool-NG).

The required compiler modifications should be made in the form of patches which should be placed in the folder toolchain-ctng/ctng-bin/lib/crosstool-ng-1.22.0/patches/my_patches.

The source packages used to build the cross-compiler are available in the folder toolchain-ctng/ctng_toolchain_src. It is advisable not to overwrite the original compiler, but to run

ct−ng menuconfig