I am trying to implement power management for an embedded device using a NEC VR4120 CPU core, which has the special instructions "standby", "suspend" and "hibernate". I use a toolchain based on binutils 2.12.90.0.1 and gcc 2.95.4-debian. To use that instructions I have to pass -march=vr4100 to the assembler. Unfortunately, -march and -mcpu cannot be used together, so first I changed arch/mips/Makefile from GCCFLAGS += -mcpu=r4600 -mips2 -Wa,--trap to GCCFLAGS += -Wa,-march=vr4100 -mips2 -Wa,--trap This works, but I am unshure what the effects of the missing -mcpu switch are wrt the code generated by gcc. AFAICS the kernel still works, but is the generated code slower or subtly incorrect? Then I the tried to compile the kernel with the standard GCCFLAGS, setting -march=vr4100 only for the one file which contains the standby/suspend/hibernate instructions. This fails a link time with: mips-linux-ld: power.o: uses different e_flags (0x1100) fields than previous modules (0x1000) Bad value: failed to merge target specific data of file power.o I looked at an old arch/mips/Makefile from http://sourceforge.net/projects/linux-vr/, which has: CFLAGS += -mcpu=r4600 -mips2 -Wa,-m4100,--trap This does not work with my toolchain. So I think I need either: - make gas accept -march=vr4100 along with -mcpu=r4600 (or -mcpu=r4100?) - or have a ".set vr4100" directive to enable the vr41xx specific instructions where needed, without changing the flags in the ELF header - or make the linker link modules with different (but compatible) e_flags - or is "GCCFLAGS += -Wa,-march=vr4100 -mips2 -Wa,--trap" perfect? Please, does anybody have suggestions how to solve this issue? Regards, Johannes
