https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71216
--- Comment #9 from Rin Okuyama <rin at NetBSD dot org> --- Hi Segher, Thank you for your kind reply. I committed your fix to NetBSD's local tree of GCC 5.4. > > However, I have a question on this fix. How about the case where > > "-Wa,-mXXX" option is given without "-mcpu=YYY" option specified? > > That might or might not work; the user had better know what he is > doing if he uses an assembler option. Hmm, I understand. Is this documented explicitly anywhere? > > This may sound pedantic to you. However, this is dangerous because > > some special mnemonics in inline assembler codes can be misassembled. > > In addition, for example, "-mcpu=e500" is forbidden whereas "-Wa,-me500" > > is possible; the user cannot use instructions for e500 in inline > > assembler codes. > > GCC does not support -me500, right. You need to configure your compiler > for a powerpc-*-eabispe* target as far as I know (I'm no expert on this). We use -Wa,-me500 option to compile kernel on some machines. As they share userland with other machines, we cannot configure GCC for a powerpc-*-eabispe* target. Instead, I found a workaround to specify -mcpu=powerpc option. It passes -mppc option to assembler, but as it is preceding to -me500, the latter is prior to the former.
