Subject: Re: [PATCH 2/4] samples/bpf: Use llc in PATH, rather than a hardcoded value

From: Alexei Starovoitov <[email-masked]>
Date: Thu, 31 Mar 2016 10:46:37 -0700

On 3/31/16 4:25 AM, Naveen N. Rao wrote:
> While at it, fix some typos in the comment.
>
> Cc: Alexei Starovoitov <[email-masked]>
> Cc: David S. Miller <[email-masked]>
> Cc: Ananth N Mavinakayanahalli <[email-masked]>
> Cc: Michael Ellerman <[email-masked]>
> Signed-off-by: Naveen N. Rao <[email-masked]>
> ---
>   samples/bpf/Makefile | 11 ++++-------
>   1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 502c9fc..88bc5a0 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -76,16 +76,13 @@ HOSTLOADLIBES_offwaketime += -lelf
>   HOSTLOADLIBES_spintest += -lelf
>   HOSTLOADLIBES_map_perf_test += -lelf -lrt
>
> -# point this to your LLVM backend with bpf support
> -LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
> -
> -# asm/sysreg.h inline assmbly used by it is incompatible with llvm.
> -# But, ehere is not easy way to fix it, so just exclude it since it is
> +# asm/sysreg.h - inline assembly used by it is incompatible with llvm.
> +# But, there is no easy way to fix it, so just exclude it since it is
>   # useless for BPF samples.
>   $(obj)/%.o: $(src)/%.c
>   	clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
>   		-D__KERNEL__ -D__ASM_SYSREG_H -Wno-unused-value -Wno-pointer-sign \
> -		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@
> +		-O2 -emit-llvm -c $< -o -| llc -march=bpf -filetype=obj -o $@
>   	clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
>   		-D__KERNEL__ -D__ASM_SYSREG_H -Wno-unused-value -Wno-pointer-sign \
> -		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=asm -o $@.s
> +		-O2 -emit-llvm -c $< -o -| llc -march=bpf -filetype=asm -o $@.s

that was a workaround when clang/llvm didn't have bpf support.
Now clang 3.7 and 3.8 have bpf built-in, so make sense to remove
manual calls to llc completely.
Just use 'clang -target bpf -O2 -D... -c $< -o $@'