llvm dev - Dec 2014 - [LLVMdev] [Compiler-rt] -march=aarch64 flag in gcc/clang

On 10 December 2014 at 16:06, Renato Golin <renato.golin at linaro.org>
wrote:
> Hi Sumanth,
>
> Christophe (cc'd) is seeing the same problems on his build. It seems
> that r181130 (by Tim) has something to do with it, but I'm not sure.
>
> I remember trying to build compiler-rt on AArch64 natively in
> February, and even running the test-suite with it, so I'm sure it
> should work (modulo regressions).
>
Removing compiler-rt from projects sources enables cmake step to succeed.
The error message is:
[...]
CMake Error at projects/compiler-rt/cmake/config-ix.cmake:87 (message):
  Cannot compile for aarch64:
[...]
  Building CXX object CMakeFiles/cmTryCompileExec4274316732.dir/simple.cc.o

  /usr/bin/c++ -fPIC -fvisibility-inlines-hidden -Wall -W
  -Wno-unused-parameter -Wwrite-strings -Wcast-qual
  -Wno-missing-field-initializers -pedantic -Wno-long-long
  -Wno-maybe-uninitialized -Wno-comment -std=c++11 -ffunction-sections
  -fdata-sections -march=aarch64 -o
  CMakeFiles/cmTryCompileExec4274316732.dir/simple.cc.o -c
  /home/christophe.lyon/LLVM-sanitizers/build-cmake/CMakeFiles/simple.cc


  /home/christophe.lyon/LLVM-sanitizers/build-cmake/CMakeFiles/simple.cc:1:0:
  error: unknown value 'aarch64' for -march

Not sure what r181130 is supposed to do, though, since it introduces a
buggy option.
> We desperately need a full buildbot on AArch64, but we also need to
> common up all docs, especially the one in the sanitizer's page, since
> they're not following what the rest of the LLVM community is doing,
> ie. building all in one tree.
>
I should also mention that the doc at
http://clang.llvm.org/get_started.html
should be updated since it seems that configure is deprecated in favor of cmake.

Christophe.
> cheers,
> --renato
>
> On 1 December 2014 at 22:42, Gundapaneni, Sumanth <sgundapa at
quicinc.com> wrote:
>> Hi,
>>
>>       I wonder if this is a valid flag in either clang/gcc.
>>
>> The flag in question is “-march=aarch64”. I verified with latest tip
and
>> neither clang nor gcc fail to recognize this flag.
>>
>> This piece of code is in cmake/config-ix.cmake in compiler-rt repo.
>>
>>
>>
>> +  elseif("${COMPILER_RT_TEST_TARGET_ARCH}" MATCHES
"aarch64")
>>
>> +    test_target_arch(aarch64 "-march=aarch64")
>>
>>
>>
>> Anyone have any thoughts or any suggestions ? Currently this is
blocking my
>> compiler-rt build for aarch64-linux.
>>
>>
>>
>> --Sumanth G

> Not sure what r181130 is supposed to do, though, since it introduces a
> buggy option.
I didn't even have compiler-rt checked out when I was doing that; I
was just trying to get the base check-all working. As I recall that
option filtered through to some llvm-lit config files. Though it might
have been a .inc header.

Cheers.

Tim.

The point here is, if you are not building for Android.
You will hit this patch with cmake configuration
-DCOMPILER_RT_TEST_TRIPLE=aarch64-linux-gnu

+  elseif("${COMPILER_RT_TEST_TARGET_ARCH}" MATCHES
"aarch64")
+    test_target_arch(aarch64 "-march=aarch64")

I don't see "-march=aarch64" is a valid flag on either LLVM or
GCC.
Should we replace this with a flag which is valid for only aarch64 and works for
both LLVM and GCC ?

If the compiler-rt build works for others, I would like to see their cmake
recipe ?

--Sumanth G
-----Original Message-----
From: Tim Northover [mailto:t.p.northover at gmail.com] 
Sent: Wednesday, December 10, 2014 8:02 AM
To: Christophe Lyon
Cc: Renato Golin; Gundapaneni, Sumanth; llvmdev at cs.uiuc.edu; Kostya
Serebryany
Subject: Re: [Compiler-rt] -march=aarch64 flag in gcc/clang
> Not sure what r181130 is supposed to do, though, since it introduces a 
> buggy option.
I didn't even have compiler-rt checked out when I was doing that; I was just
trying to get the base check-all working. As I recall that option filtered
through to some llvm-lit config files. Though it might have been a .inc header.

Cheers.

Tim.