[llvm-dev] Generating object files more efficiently

[J S via llvm-dev]

How can we pass compiler options to clang? I'm trying to pass this option -mcpu=mycpu but it's not taking it.
When I print the Opts->CPU string in TargetInfo::CreateTargetInfo(), I get an empty string.

clang --target=XYZ -mcpu=mycpu x.c -o foo.elf
________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of J S via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Saturday, March 23, 2019 3:18 PM
To: Craig Topper
Cc: via llvm-dev
Subject: Re: [llvm-dev] Generating object files more efficiently

Thanks, Craig,

FYI, I also had to update clang/lib/Basic/CMakeLists.txt
________________________________
From: Craig Topper <craig.topper at gmail.com>
Sent: Saturday, March 23, 2019 2:10 PM
To: Doerfert, Johannes
Cc: J S; via llvm-dev
Subject: Re: [llvm-dev] Generating object files more efficiently

In order for clang to support a new target you need to add support in lib/Basic/Targets.cpp in the AllocateTarget function and add new files to the lib/Basic/Targets/ directory.

~Craig


On Sat, Mar 23, 2019 at 2:06 PM Craig Topper <craig.topper at gmail.com<mailto:craig.topper at gmail.com>> wrote:
-march for clang and -march for llc do different things unfortunately. -march for clang at least on x86 is the same as -mcpu in llc. Which is an artifact of gcc compatibility.

~Craig


On Sat, Mar 23, 2019 at 1:40 PM Doerfert, Johannes via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:

Oh, my bad.


Idk why llc seems to know that architecture but clang does not.

Doesn't make sense to me, sorry.

________________________________
From: J S <mm92126 at hotmail.com<mailto:mm92126 at hotmail.com>>
Sent: Saturday, March 23, 2019 3:32:03 PM
To: Doerfert, Johannes
Cc: via llvm-dev
Subject: Re: [llvm-dev] Generating object files more efficiently

It is my actual target architecture
________________________________
From: Doerfert, Johannes <jdoerfert at anl.gov<mailto:jdoerfert at anl.gov>>
Sent: Saturday, March 23, 2019 1:30 PM
To: J S
Cc: via llvm-dev
Subject: Re: [llvm-dev] Generating object files more efficiently


I copied "-march=XYZ" from your original email,

you have to replace it with your actual target architecture or simply drop it.

________________________________
From: J S <mm92126 at hotmail.com<mailto:mm92126 at hotmail.com>>
Sent: Saturday, March 23, 2019 3:26:59 PM
To: Doerfert, Johannes
Cc: via llvm-dev
Subject: Re: [llvm-dev] Generating object files more efficiently



Johannes,


I tried the last one and it gave me this:


error: unknown target CPU 'XYZ'
note: valid target CPU values are: nocona, core2, penryn, bonnell, atom,
      silvermont, slm, goldmont, goldmont-plus, tremont, nehalem, corei7,
      westmere, sandybridge, corei7-avx, ivybridge, core-avx-i, haswell,
      core-avx2, broadwell, skylake, skylake-avx512, skx, cascadelake,
      cannonlake, icelake-client, icelake-server, knl, knm, k8, athlon64,
      athlon-fx, opteron, k8-sse3, athlon64-sse3, opteron-sse3, amdfam10,
      barcelona, btver1, btver2, bdver1, bdver2, bdver3, bdver4, znver1, znver2,
      x86-64


________________________________
From: Doerfert, Johannes <jdoerfert at anl.gov<mailto:jdoerfert at anl.gov>>
Sent: Saturday, March 23, 2019 1:15 PM
To: J S
Cc: via llvm-dev
Subject: Re: [llvm-dev] Generating object files more efficiently

I would have guessed:

object:
clang -c foo.c -o foo.o -march=XYZ

shared library:
clang -shared foo.c -o foo.so -march=XYZ

executable:
clang foo.c -o foo -march=XYZ


On 03/23, J S via llvm-dev wrote:
> Currently I compile my C code in 2 steps in order to generate .o files
>
> clang -emit-llvm -c foo.c -o foo.bc
> llc -march=XYZ foo.bc -filetype=obj
>
> Is there a way to generate either .o or .elf files in just 1 command?
>
> Thanks.
>

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--

Johannes Doerfert
Researcher

Argonne National Laboratory
Lemont, IL 60439, USA

jdoerfert at anl.gov<mailto:jdoerfert at anl.gov>
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