Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1627969 > unrolled thread

Re: [PATCH v3] kbuild: Add support to generate LLVM bitcode files

Started byMasahiro Yamada <yamada.masahiro@socionext.com>
First post2017-04-21 07:10 +0200
Last post2017-04-24 04:30 +0200
Articles 4 — 2 participants

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH v3] kbuild: Add support to generate LLVM bitcode files Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-04-21 07:10 +0200
    Re: [PATCH v3] kbuild: Add support to generate LLVM bitcode files Matthias Kaehlcke <mka@chromium.org> - 2017-04-21 22:00 +0200
      Re: [PATCH v3] kbuild: Add support to generate LLVM bitcode files Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-04-23 09:00 +0200
      Re: [PATCH v3] kbuild: Add support to generate LLVM bitcode files Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-04-24 04:30 +0200

#1627969 — Re: [PATCH v3] kbuild: Add support to generate LLVM bitcode files

FromMasahiro Yamada <yamada.masahiro@socionext.com>
Date2017-04-21 07:10 +0200
SubjectRe: [PATCH v3] kbuild: Add support to generate LLVM bitcode files
Message-ID<tyyZt-1MT-43@gated-at.bofh.it>
Hi Matthias,


2017-04-05 2:27 GMT+09:00 Matthias Kaehlcke <mka@chromium.org>:
> From: Vinícius Tinti <viniciustinti@gmail.com>
>
> 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?






>   # 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




>   # 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)





-- 
Best Regards
Masahiro Yamada

[toc] | [next] | [standalone]

#1628567

FromMatthias Kaehlcke <mka@chromium.org>
Date2017-04-21 22:00 +0200
Message-ID<tyMSK-1qO-23@gated-at.bofh.it>
In reply to#1627969
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@chromium.org>:
> > From: Vinícius Tinti <viniciustinti@gmail.com>
> >
> > 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

[toc] | [prev] | [next] | [standalone]

#1628911

FromMasahiro Yamada <yamada.masahiro@socionext.com>
Date2017-04-23 09:00 +0200
Message-ID<tzjEZ-53L-1@gated-at.bofh.it>
In reply to#1628567
Hi Matthias,




2017-04-22 4:55 GMT+09:00 Matthias Kaehlcke <mka@chromium.org>:
> 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@chromium.org>:
>> > From: Vinícius Tinti <viniciustinti@gmail.com>
>> >
>> > 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

[toc] | [prev] | [next] | [standalone]

#1629126

FromMasahiro Yamada <yamada.masahiro@socionext.com>
Date2017-04-24 04:30 +0200
Message-ID<tzBVf-A4-3@gated-at.bofh.it>
In reply to#1628567
Hi Matthias,



2017-04-22 4:55 GMT+09:00 Matthias Kaehlcke <mka@chromium.org>:
> 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@chromium.org>:
>> > From: Vinícius Tinti <viniciustinti@gmail.com>
>> >
>> > 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.
>>


One more thing:

Please add '*.ll' pattern to the following clean target.


clean: $(clean-dirs)
        $(call cmd,rmdirs)
        $(call cmd,rmfiles)
        @find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
                \( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \
                -o -name '*.ko.*' \
                -o -name '*.dwo'  \
                -o -name '*.su'  \
                -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
                -o -name '*.symtypes' -o -name 'modules.order' \
                -o -name modules.builtin -o -name '.tmp_*.o.*' \
                -o -name '*.c.[012]*.*' \
                -o -name '*.gcno' \) -type f -print | xargs rm -f





-- 
Best Regards
Masahiro Yamada

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web