Error when running llvm-goc

[Kavindu Gimhan Zoysa]

Hi all,

I have build the gollvm and now I am trying to run it. So I run follwing command against a simple go source code. I am getting below error. Really appreciate your input to solve this issue. 

command : 

./bin/llvm-goc test.go

error:

llvm-goc: /home/kavindu/GIT/llvm-project/llvm/tools/gollvm/driver/Action.cpp:51: const char* gollvm::driver::Action::resultFileSuffix() const: Assertion `false' failed.

../bin/llvm-goc(+0x2c46a3f)[0x55a113e42a3f]

../bin/llvm-goc(+0x2c46ad6)[0x55a113e42ad6]

../bin/llvm-goc(+0x2c44829)[0x55a113e40829]

../bin/llvm-goc(+0x2c46387)[0x55a113e42387]

/lib/x86_64-linux-gnu/libpthread.so.0(+0x153c0)[0x7f67e0aad3c0]

/lib/x86_64-linux-gnu/libc.so.6(gsignal+0xcb)[0x7f67e056818b]

/lib/x86_64-linux-gnu/libc.so.6(abort+0x12b)[0x7f67e0547859]

/lib/x86_64-linux-gnu/libc.so.6(+0x25729)[0x7f67e0547729]

/lib/x86_64-linux-gnu/libc.so.6(+0x36f36)[0x7f67e0558f36]

../bin/llvm-goc(+0x827e69)[0x55a111a23e69]

../bin/llvm-goc(+0x8167d5)[0x55a111a127d5]

../bin/llvm-goc(+0x81db02)[0x55a111a19b02]

../bin/llvm-goc(+0x81ddfb)[0x55a111a19dfb]

../bin/llvm-goc(+0x811cb9)[0x55a111a0dcb9]

/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x7f67e05490b3]

../bin/llvm-goc(+0x81112e)[0x55a111a0d12e]

PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.

Stack dump:

0. Program arguments: ../bin/llvm-goc test.go 

Aborted (core dumped)

I have build gollvm using exact commits as shown here.

https://groups.google.com/g/golang-nuts/c/E770QGuKkpU/m/sJFuarbrBQAJ

Thank you,

Kavindu

[Kavindu Gimhan Zoysa]

Hi all,

Still, I was unable to figure out the reason for the above error. Really appreciate your help.

Thank you,

Kavindu

[Than McIntosh]

Could you please post the complete "go build" command?

Thanks, Than

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[Kavindu Gimhan Zoysa]

I did not use any go build command. Sorry if I missed anything. These are the steps I followed.

1. Build gollvm referring to the official documentation. I followed the steps until https://go.googlesource.com/gollvm/#cmakeninja. 

2. I was able to see the llvm-goc in the bin folder.  I export the path using 'export LD_LIBRARY_PATH=<HOME>/build-debug/libgo/x86_64-unknown-linux-gnu' command.

3. Then I tried to dump the llvm IR using '../bin/llvm-goc -S test.go -dump-ir', and it was successful.

4. Then I ran this command './bin/llvm-goc test.go'. I got the above error.

Did i miss anything?

Thank you,

Kavindu

[Than McIntosh]

Hello again,

Couple of things. 

First, it is important to keep in mind that the "llvm-goc" binary is not intended to be used as a top level go compiler, in the same way that the "gcc" or "clang" commands are used as top-level C/C++ compilers. The normal use case is to use "go build" as opposed to invoking llvm-goc directly.  Just to recap: build the 'install-gollvm' ninja target (as described in https://go.googlesource.com/gollvm/#installing), prepend the install dir "bin" directory in your path, and then run "go build".

It's also problematic to run llvm-goc directly out of the build area instead of doing and install and using the copy in the install dir. For example, if I do a build of llvm-goc in my LLVM build area, then invoke it directly on a small Go program, this is what I see:

$ ./bin/llvm-goc smallmain.go
/usr/bin/ld.gold: error: cannot find -lgobegin
/usr/bin/ld.gold: error: cannot find -lgo
/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crt1.o:function _start: error: undefined reference to 'main'
<built-in>:1: error: undefined reference to 'runtime.registerTypeDescriptors'
smallmain.go:4: error: undefined reference to 'runtime.printlock'
smallmain.go:4: error: undefined reference to 'runtime.printint'
smallmain.go:4: error: undefined reference to 'runtime.printnl'
smallmain.go:4: error: undefined reference to 'runtime.printunlock'
$ 

Here the compiler is unable to find the right runtime libraries. I'll see if I can update the documentation to make this a little clearer.

Regarding the crash you're seeing when building from 

 LLVM: 43ff75f2c3feef64f9d73328230d34dac8832a91

gollvm: 44a7a475cfd3b871b7a5a0941b8ab1ea9d489adc
gofrontend: be0d2cc2df9f98d967c242594838f86362dae2e7
libbacktrace: 5a99ff7fed66b8ea8f09c9805c138524a7035ece
libffi: 737d4faa00d681b4c758057f67e1a02d813d01c2

Sorry, but I can't reproduce your crash (I did another build using the config above and it seems to work ok). What is the exact cmake command you're using to set up your build area?

You might also try this: in your LLVM build area, run "ninja llvm-symbolizer" and then set

export LLVM_SYMBOLIZER=${HERE}/bin/llvm-symbolizer

then rerun the failing "llvm-goc" invocation, that might give you a better stack trace.

Thanks, Than

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[Kavindu Gimhan Zoysa]

Hi,

Thank you for your detailed explanation. I will try your suggestions and let you know. 

I used this cmake command.

`cmake -DCMAKE_INSTALL_PREFIX=/my/install/dir -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_LINKER=gold -G Ninja ../llvm-project/llvm`

Then I used, `ninja gollvm`, and it was successful.

Also, I used, `ninja install-gollvm`, but nothing happens.

I have a couple of unclear points. As I know, llvm-goc is a tool that generates llvm IR for a go source code. 
If I run `go build test.go`, when does llvm-goc executable start to run?  Does go build command replace its' existing compiler with llvm-goc? 

Thank you,

Kavindu

[Than McIntosh]

You wrote:

>If I run `go build test.go`, when does llvm-goc executable start to run?  Does go build command replace its' existing compiler with llvm-goc?

The "go" command, the program that orchestrates the building of Go programs, runs 'llvm-goc' at each point where it needs to compile a Go package, and then at the point where it needs to do a final link step to create an executable.

You can learn more about how the compiler is invoked by the Go command (what is happening "under the hood" so to speak) by using the "-x" option with go build. E.g.

  $ go clean -cache
  $ go build -x myprogram.go 1> transcript.txt 2>&1
  $

then inspect "transcript.txt" to see how the compiler is being invoked.

If your program "myprogram.go" imports packages P1 and P2, then in the transcript you would expect to see (at minimum) an invocation of llvm-goc for P1, for P2, then for the main package,  and for the final link.

Also:

>Does go build command replace its' existing compiler with llvm-goc?

More or less. The set of command line flags supported by the two compilers is completely different (and there are many other implementation differences), so there will be some differences in the build steps.

Than

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