linux-kernel - Re: [PATCH 1/2] perf build: Autodetect minimum required llvm-dev version

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Message-ID: <b60928c6-19c5-473c-8f13-532ed3fd3b3a@kernel.org>
Date: Tue, 10 Sep 2024 17:53:16 +0100
From: Quentin Monnet <qmo@...nel.org>
To: James Clark <james.clark@...aro.org>, linux-perf-users@...r.kernel.org,
 sesse@...gle.com, acme@...nel.org
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
 Changbin Du <changbin.du@...wei.com>, Guilherme Amadio <amadio@...too.org>,
 Leo Yan <leo.yan@....com>, Manu Bretelle <chantr4@...il.com>,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 1/2] perf build: Autodetect minimum required llvm-dev
 version

2024-09-10 16:11 UTC+0100 ~ James Clark <james.clark@...aro.org>
> 
> 
> On 9/10/24 15:27, Quentin Monnet wrote:
>> 2024-09-10 15:04 UTC+0100 ~ James Clark <james.clark@...aro.org>
>>> The new LLVM addr2line feature requires a minimum version of 13 to
>>> compile. Add a feature check for the version so that NO_LLVM=1 doesn't
>>> need to be explicitly added. Leave the existing llvm feature check
>>> intact because it's used by tools other than Perf.
>>>
>>> This fixes the following compilation error when the llvm-dev version
>>> doesn't match:
>>>
>>>    util/llvm-c-helpers.cpp: In function 'char* 
>>> llvm_name_for_code(dso*, const char*, u64)':
>>>    util/llvm-c-helpers.cpp:178:21: error: 
>>> 'std::remove_reference_t<llvm::DILineInfo>' {aka 'struct 
>>> llvm::DILineInfo'} has no member named 'StartAddress'
>>>      178 |   addr, res_or_err->StartAddress ? *res_or_err- 
>>> >StartAddress : 0);
>>>
>>> Fixes: c3f8644c21df ("perf report: Support LLVM for addr2line()")
>>> Signed-off-by: James Clark <james.clark@...aro.org>
>>> ---
>>>   tools/build/Makefile.feature           |  2 +-
>>>   tools/build/feature/Makefile           |  9 +++++++++
>>>   tools/build/feature/test-llvm-perf.cpp | 14 ++++++++++++++
>>>   tools/perf/Makefile.config             |  6 +++---
>>>   4 files changed, 27 insertions(+), 4 deletions(-)
>>>   create mode 100644 tools/build/feature/test-llvm-perf.cpp
>>>
>>> diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
>>> index 0717e96d6a0e..427a9389e26c 100644
>>> --- a/tools/build/Makefile.feature
>>> +++ b/tools/build/Makefile.feature
>>> @@ -136,7 +136,7 @@ FEATURE_DISPLAY ?=              \
>>>            libunwind              \
>>>            libdw-dwarf-unwind     \
>>>            libcapstone            \
>>> -         llvm                   \
>>> +         llvm-perf              \
>>
>> Hi! Just a quick question, why remove "llvm" from the list, here?
>>
>> Quentin
> 
> Just because with respect to the linked fixes: commit, it wasn't 
> actually there before. It was added just for addr2line so it should 
> probably be llvm-perf rather than the generic one.
> 
> But yes we can add llvm output if it's useful, but could probably be a 
> separate commit.
> 


It wasn't there before, but you're not removing the rest of the "llvm" 
feature, so I'd expect that part to stay as well? But I don't mind much. 
We use the "llvm" feature in bpftool, but beyond that, I don't 
personally need it to be displayed in tools/build/Makefile.feature, so 
no need to respin for that :)

Thanks,
Quentin