On Fri, 30 Jan 2015, Markos Chandras wrote: > When we configure the toolchain, we can set the default > ISA level to be used when none is set in the command line. > This, however, has some undesired consequences when the parameters > used in the command line are incompatible with the built-in ISA > level of the toolchain. In order to minimize such problems, we set > a good default ISA level if the Makefile hasn't set one for the > selected processor. Agreed, but does it happen for any actual configuration? If so, then the configuration is broken and your proposal papers over it, an explicit `-march=' option is supposed to be there for all the possible CPU_foo settings. At first look it seems to be the case in arch/mips/Makefile, but maybe I'm missing something. Besides, a default of `-march=mips32' or whatever may not really be adequate for the CPU selected. > diff --git a/arch/mips/Makefile b/arch/mips/Makefile > index 0608ec524d3d..a244fb311a37 100644 > --- a/arch/mips/Makefile > +++ b/arch/mips/Makefile > @@ -226,6 +226,15 @@ cflags-y += -I$(srctree)/arch/mips/include/asm/mach-generic > drivers-$(CONFIG_PCI) += arch/mips/pci/ > > # > +# Don't trust the toolchain defaults. Use a sensible -march > +# option but only if we don't have one already. > +# > +ifeq (,$(findstring march=, $(cflags-y))) > +cflags-$(CONFIG_32BIT) += -march=mips32 > +cflags-$(CONFIG_64BIT) += -march=mips64 > +endif So I'd rather see some form of diagnostics instead, e.g.: ifeq (,$(filter -march=% -mips%, $(cflags-y))) $(error Configuration bug, no `-march=' option set for the CPU selected!) endif or suchlike (`-mips%' for the legacy stuff; we should probably drop it sometime). WDYT? Maciej
