[cfarm-users] Enable one ISA for my code, and another ISA for GCC code?

[Jeffrey Walton]

I'm catching a SIGILL on POWER7 ppc64-le machine. I compiled the
source with -mcpu=power8 so I could enable some builtins I may need.
Use of the builtins is guarded at runtime. (This is the classic distro
model, where most source code is compiled for a minimum machine but
higher ISAs are guarded at runtime).

GCC converted some C code into POWER8 code. The SIGILL is happening in
the function prologue due to use of mtfprwz. Apparently mtfprwz is a
ISA 2.07B/POWER8 instruction.

My question is, how do I tell GCC to use a different ISA than I am using?

Jeff