The PSP's calling convention ("MIPS EABI", not to be confused with ARM EABI) is simple, the executable format ("PRX" - basically ELF with some extra sections) i

The PSP's calling convention ("MIPS EABI", not to be confused with ARM EABI) is simple, the executable format ("PRX" - basically ELF with some extra sections) is converted from ELFs by a PSPSDK tool, and the dynamic linker uses a funny table of 32-bit virtual pointers ("NIBs") correlating with the first 32 bits of the SHA-1 of a method name, which, once the method name is known, makes things pretty straightforward to set up. Basically any compiler supporting MIPS-EABI-ELF can be made to generate PSP executables with the use of the ELF-to-PRX tools from the open-source PSP toolchain. The PSP does support some special instructions (a VFPU and some "allegrex extensions") but they aren't necessary to make working binaries - just for performance.