Hi Matthias, 2017-04-22 4:55 GMT+09:00 Matthias Kaehlcke <mka@xxxxxxxxxxxx>: > Hi Masahiro, > > El Fri, Apr 21, 2017 at 02:02:46PM +0900 Masahiro Yamada ha dit: > >> 2017-04-05 2:27 GMT+09:00 Matthias Kaehlcke <mka@xxxxxxxxxxxx>: >> > From: Vinícius Tinti <viniciustinti@xxxxxxxxx> >> > >> > Add rules to kbuild in order to generate LLVM bitcode files with the .ll >> > extension when using clang. >> >> >> First, I'd like to be sure about the terminology "LLVM bitcode" >> because "bitcode" sounds like human-unreadable binary. >> >> >> For example, 'man llvm-as' says: >> llvm-as is the LLVM assembler. It reads a file containing >> human-readable LLVM assembly language, translates it to LLVM >> bitcode, and writes the result into a file or to standard output. >> >> >> As far as I understood: >> >> *.ll - LLVM assembly (human readable file) >> *.bc - LLVM bitcode (binary file) >> >> Is this correct? > > Yes, the terminology should be changed to talk about 'LLVM assembly'. > >> > # from c code >> > CC=clang make kernel/pid.ll >> >> This does not work because CC is overridden in the top-level Makefile. >> It should be >> make CC=clang kernel/pid.ll > > Will change > >> > # from asm code >> > CC=clang make arch/x86/kernel/preempt.ll >> >> arch/x86/kernel/preempt.* does not exist >> (at least in the latest tree). >> >> >> >> >> > + >> > +quiet_cmd_as_ll_S = CPP $(quiet_modtag) $@ >> > + cmd_as_ll_S = $(CPP) $(a_flags) -o $@ $< >> > + >> > +$(obj)/%.ll: $(src)/%.S FORCE >> > + $(call if_changed_dep,as_ll_S) >> > + >> >> I could not understand how this rule can convert >> architecture-specific assembly to LLVM intermediate expression. >> >> This is just pre-processing *.S file. >> >> >> Actually, this is completely the same as the rule *.S -> *.s >> >> quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@ >> cmd_cpp_s_S = $(CPP) $(a_flags) -o $@ $< >> >> $(obj)/%.s: $(src)/%.S FORCE >> $(call if_changed_dep,cpp_s_S) > > Indeed, unsurprisingly the content of a .ll file generated from a .S > is the same as the corresponding .s. > > Besides the Makefile rules it isn't clear to me how assembly would be > converted to LLVM IR. I suggest to remove the rules for assembly. > I agree. This rule should be removed. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
