Re: [RFC PATCH v6 24/32] perf record: Compile scriptlets if pass '.c' to --event

[Alexei Starovoitov <ast@plumgrid.com>]

On 6/8/15 10:50 PM, Wang Nan wrote:
> +struct bpf_param bpf_param = {
> +	.clang_path = "clang",
> +	.llc_path = "llc",
> +	.clang_opt = "",
> +	.llc_opt = "",
> +};

the defaults are ok-ish, but llc is never in PATH.
So most likely it won't work out of the box.
I think the cleanest option is too wait a little bit
until we finish clang integration.
(hopefully few more days)

we've quite been busy on llvm side
and I'm excited to announce that BPF backend finally
graduated from experimental.
So now anyone can just pull the latest llvm and
bpf will be present by default.
No more cmake -DLLVM_EXPERIMENTAL...

Once clang integration is complete. One can pull
upsteam llvm and clang and just use 'clang -O2 -c -march=bpf file.c'

> +	err = WEXITSTATUS(pclose(file));
> +	if (err || read_sz <= 0) {
> +		err = -EINVAL;
> +		pr_err("Error:\tsomething went wrong when compiling %s\n",
> +		       filename);
> +		pr_err("Hint:\tTry manually run following command and check:\n");
> +		pr_err("  # " CMD_FMT "\n\n",
> +		       clang_path, bpf_param.clang_opt, filename,
> +		       llc_path, bpf_param.llc_opt, "/dev/null");

not terribly informative hint.
I think would be good to point to some readme or at least mention
that only the latest clang/llvm support bpf.
Either svn/git trunk or upcoming 3.7
May be a link to llvm.org?