diff mbox series

[1/4] kbuild: remove LLVM=1 test from HAS_LTO_CLANG

Message ID 20210303183333.46543-1-masahiroy@kernel.org (mailing list archive)
State New
Headers show
Series [1/4] kbuild: remove LLVM=1 test from HAS_LTO_CLANG | expand

Commit Message

Masahiro Yamada March 3, 2021, 6:33 p.m. UTC
This guarding is wrong. As Documentation/kbuild/llvm.rst notes, LLVM=1
switches the default of tools, but you can still override CC, LD, etc.
individually.

BTW, LLVM is not 1/0 flag. If LLVM is not passed in, it is empty.

Non-zero return code is all treated as failure anyway.

So, $(success,test $(LLVM) -eq 1) and $(success,test "$(LLVM)" = 1)
works equivalently in the sense that both are expanded to 'n' if LLVM
is not given. The difference is that the former internally fails due
to syntax error.

  $ test ${LLVM} -eq 1
  bash: test: -eq: unary operator expected
  $ echo $?
  2

  $ test "${LLVM}" -eq 1
  bash: test: : integer expression expected
  $ echo $?
  2

  $ test "${LLVM}" = 1
  echo $?
  1

  $ test -n "${LLVM}"
  $ echo $?
  1

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 arch/Kconfig | 1 -
 1 file changed, 1 deletion(-)

Comments

Nick Desaulniers March 3, 2021, 8:47 p.m. UTC | #1
+ Sami

On Wed, Mar 3, 2021 at 10:34 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> This guarding is wrong. As Documentation/kbuild/llvm.rst notes, LLVM=1
> switches the default of tools, but you can still override CC, LD, etc.
> individually.
>
> BTW, LLVM is not 1/0 flag. If LLVM is not passed in, it is empty.

Do we have the same problem with LLVM_IAS?  LGTM otherwise, but wanted
to check that before signing off.

(Also, the rest of the patches in this series seem more related to
DWARFv5 cleanups; this patch seems orthogonal while those are a
visible progression).

>
> Non-zero return code is all treated as failure anyway.
>
> So, $(success,test $(LLVM) -eq 1) and $(success,test "$(LLVM)" = 1)
> works equivalently in the sense that both are expanded to 'n' if LLVM
> is not given. The difference is that the former internally fails due
> to syntax error.
>
>   $ test ${LLVM} -eq 1
>   bash: test: -eq: unary operator expected
>   $ echo $?
>   2
>
>   $ test "${LLVM}" -eq 1
>   bash: test: : integer expression expected
>   $ echo $?
>   2
>
>   $ test "${LLVM}" = 1
>   echo $?
>   1
>
>   $ test -n "${LLVM}"
>   $ echo $?
>   1
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
>  arch/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 2bb30673d8e6..2af10ebe5ed0 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -632,7 +632,6 @@ config HAS_LTO_CLANG
>         def_bool y
>         # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
>         depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
> -       depends on $(success,test $(LLVM) -eq 1)

IIRC, we needed some other LLVM utilities like llvm-nm and llvm-ar,
which are checked below. So I guess we can still support CC=clang
AR=llvm-ar NM=llvm-nm, and this check is redundant.

>         depends on $(success,test $(LLVM_IAS) -eq 1)
>         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
>         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
> --
> 2.27.0
>


--
Thanks,
~Nick Desaulniers
Nathan Chancellor March 3, 2021, 11:37 p.m. UTC | #2
On Thu, Mar 04, 2021 at 03:33:30AM +0900, Masahiro Yamada wrote:
> This guarding is wrong. As Documentation/kbuild/llvm.rst notes, LLVM=1
> switches the default of tools, but you can still override CC, LD, etc.
> individually.
> 
> BTW, LLVM is not 1/0 flag. If LLVM is not passed in, it is empty.
> 
> Non-zero return code is all treated as failure anyway.
> 
> So, $(success,test $(LLVM) -eq 1) and $(success,test "$(LLVM)" = 1)
> works equivalently in the sense that both are expanded to 'n' if LLVM
> is not given. The difference is that the former internally fails due
> to syntax error.
> 
>   $ test ${LLVM} -eq 1
>   bash: test: -eq: unary operator expected
>   $ echo $?
>   2
> 
>   $ test "${LLVM}" -eq 1
>   bash: test: : integer expression expected
>   $ echo $?
>   2
> 
>   $ test "${LLVM}" = 1
>   echo $?
>   1
> 
>   $ test -n "${LLVM}"
>   $ echo $?
>   1
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Yes, there is not too much point of checking if $(LLVM) is set or not
because we already check for the other tools.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
> 
>  arch/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 2bb30673d8e6..2af10ebe5ed0 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -632,7 +632,6 @@ config HAS_LTO_CLANG
>  	def_bool y
>  	# Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
>  	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
> -	depends on $(success,test $(LLVM) -eq 1)
>  	depends on $(success,test $(LLVM_IAS) -eq 1)
>  	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
>  	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
> -- 
> 2.27.0
>
Masahiro Yamada March 5, 2021, 6:06 a.m. UTC | #3
On Thu, Mar 4, 2021 at 5:47 AM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> + Sami
>
> On Wed, Mar 3, 2021 at 10:34 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > This guarding is wrong. As Documentation/kbuild/llvm.rst notes, LLVM=1
> > switches the default of tools, but you can still override CC, LD, etc.
> > individually.
> >
> > BTW, LLVM is not 1/0 flag. If LLVM is not passed in, it is empty.
>
> Do we have the same problem with LLVM_IAS?  LGTM otherwise, but wanted
> to check that before signing off.

3/4 will replace this LLVM_IAS check with AS_IS_LLVM.

We do not need to add a noise change.




>
> (Also, the rest of the patches in this series seem more related to
> DWARFv5 cleanups; this patch seems orthogonal while those are a
> visible progression).

Kind of orthogonal, but I am touching the same code hunk,
which would cause a merge conflict.


> >
> > Non-zero return code is all treated as failure anyway.
> >
> > So, $(success,test $(LLVM) -eq 1) and $(success,test "$(LLVM)" = 1)
> > works equivalently in the sense that both are expanded to 'n' if LLVM
> > is not given. The difference is that the former internally fails due
> > to syntax error.
> >
> >   $ test ${LLVM} -eq 1
> >   bash: test: -eq: unary operator expected
> >   $ echo $?
> >   2
> >
> >   $ test "${LLVM}" -eq 1
> >   bash: test: : integer expression expected
> >   $ echo $?
> >   2
> >
> >   $ test "${LLVM}" = 1
> >   echo $?
> >   1
> >
> >   $ test -n "${LLVM}"
> >   $ echo $?
> >   1
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> >  arch/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 2bb30673d8e6..2af10ebe5ed0 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -632,7 +632,6 @@ config HAS_LTO_CLANG
> >         def_bool y
> >         # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
> >         depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
> > -       depends on $(success,test $(LLVM) -eq 1)
>
> IIRC, we needed some other LLVM utilities like llvm-nm and llvm-ar,
> which are checked below. So I guess we can still support CC=clang
> AR=llvm-ar NM=llvm-nm, and this check is redundant.

Yes, I think so.


>
> >         depends on $(success,test $(LLVM_IAS) -eq 1)
> >         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
> >         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
> > --
> > 2.27.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
>
> --
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Sami Tolvanen March 8, 2021, 7:11 p.m. UTC | #4
On Wed, Mar 3, 2021 at 12:47 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> + Sami
>
> On Wed, Mar 3, 2021 at 10:34 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > This guarding is wrong. As Documentation/kbuild/llvm.rst notes, LLVM=1
> > switches the default of tools, but you can still override CC, LD, etc.
> > individually.
> >
> > BTW, LLVM is not 1/0 flag. If LLVM is not passed in, it is empty.
>
> Do we have the same problem with LLVM_IAS?  LGTM otherwise, but wanted
> to check that before signing off.
>
> (Also, the rest of the patches in this series seem more related to
> DWARFv5 cleanups; this patch seems orthogonal while those are a
> visible progression).
>
> >
> > Non-zero return code is all treated as failure anyway.
> >
> > So, $(success,test $(LLVM) -eq 1) and $(success,test "$(LLVM)" = 1)
> > works equivalently in the sense that both are expanded to 'n' if LLVM
> > is not given. The difference is that the former internally fails due
> > to syntax error.
> >
> >   $ test ${LLVM} -eq 1
> >   bash: test: -eq: unary operator expected
> >   $ echo $?
> >   2
> >
> >   $ test "${LLVM}" -eq 1
> >   bash: test: : integer expression expected
> >   $ echo $?
> >   2
> >
> >   $ test "${LLVM}" = 1
> >   echo $?
> >   1
> >
> >   $ test -n "${LLVM}"
> >   $ echo $?
> >   1
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> >  arch/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 2bb30673d8e6..2af10ebe5ed0 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -632,7 +632,6 @@ config HAS_LTO_CLANG
> >         def_bool y
> >         # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
> >         depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
> > -       depends on $(success,test $(LLVM) -eq 1)
>
> IIRC, we needed some other LLVM utilities like llvm-nm and llvm-ar,
> which are checked below. So I guess we can still support CC=clang
> AR=llvm-ar NM=llvm-nm, and this check is redundant.

I'm fine with removing the check, but the idea here was to just make
it slightly harder for people to accidentally use a mismatched
toolchain, even though checking for LLVM=1 doesn't stop them from
doing so anyway. But yes, the only LLVM tools required in addition to
the compiler and the linker are llvm-ar and llvm-nm.

Sami
diff mbox series

Patch

diff --git a/arch/Kconfig b/arch/Kconfig
index 2bb30673d8e6..2af10ebe5ed0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -632,7 +632,6 @@  config HAS_LTO_CLANG
 	def_bool y
 	# Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
 	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
-	depends on $(success,test $(LLVM) -eq 1)
 	depends on $(success,test $(LLVM_IAS) -eq 1)
 	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)