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. Cheers Matthias -- 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
