https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65837
--- Comment #22 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> --- (In reply to prathamesh3492 from comment #18) > Created attachment 35420 [details] > patch to override default options by options in object file > > Hi, > > The following untested patch gives preference to option value in object file. > In run_gcc(), > options from COLLECT_GCC_OPTIONS which are taken from command line are > stored in decoded_options. > options from object file are stored in fdecoded_options. > so override the option in decoded_options if it is present in > fdecoded_options. > > With the patch this works: > arm-linux-gnueabihf-gcc test.c -mfpu=neon -flto -c > arm-linux-gnueabihf-gcc test.o -flto > only passes -mfpu=neon to lto1 > > However the patch doesn't work when same option is passed different values > at compile and link-time: > arm-linux-gnuebihf-gcc test.c -mfpu=neon -flto -c > arm-linux-gnueabihf-gcc test.o -mfpu=vfpv3-d16 -flto > > In this case, -mfpu=neon is still passed to lto1, since the patch prefers > option value from object file. > Without the patch, the option from the command line was given preference. > > for both the following cases: > arm-linux-gnueabihf-gcc test.o -flto > arm-linux-gnueabihf-gcc test.o -flto -mfpu=vfpv3-d16 > > COLLECT_GCC_OPTIONS contains "-mfpu=vfpv3-d16", however in the first case it > isn't explictly passed by user, so passing -mfpu=neon > would be correct. In the second case, since -mfpu=vfpv3-d16 is passed > intentionally by user, should it be considered > as an error - "conflicting options" ? No, otherwise users will have to rebuild their compilers for different defaults, thus defeating the whole purpose of having command line options ! > > Unfortunately, it looks like there is no way to distinguish between options > defined by default and explicitly passed options from COLLECT_GCC_OPTIONS > and that's the only way command line options are passed to lto-wrapper from > the driver. One way would be to modify COLLECT_GCC_OPTIONS in the driver to > indicate which options were explicitly passed from command line. > For instance, additionally COLLECT_GCC_OPTIONS would contain > "-mfpu=vfpv3-d16-explicit" to indiciate that -mfpu=vfpv3-d16 was > passed from command line and not set by default. In lto-wrapper the options > could be parsed to check if they have "explicit" suffix and thus distinguish > between explicit and defualt defined options. > Does that sound reasonable ? I would be grateful for suggestions. > > Thank you, > Prathamesh
