llvm-xray doesn't print logs on apple m1

[csmoe]

llvm version: 17.0.0-rc3

code:

#include <cstdio>

[[clang::xray_always_instrument]] void foo() {
  printf("foo() is always instrumented!");
}

int main() {
  foo();
}

clang++ commands:

 llvm/bin/clang++ -fxray-instrument -fxray-instruction-threshold=1 -std=c++17 -isysroot $(xcrun --show-sdk-path) -L llvm/lib/clang/17/lib/darwin test.cc -o test 

execute with xray options:

 XRAY_OPTIONS="xray_naive_log=true patch_premain=true xray_mode=basic verbosity=1" ./test

expected the output on Linux:

==72477==XRay: Log file in 'xray-log.test.7CSV51'
==72477==Cleaned up log for TID: 72477
foo() is always instrumented!
...

actual output(no xray log):

foo() is always instrumented!

[csmoe]

Btw,objdump -h -j xray_instr_map test prints:

test:      file format mach-o arm64

Sections:
Idx Name           Size     VMA              Type
  5 xray_instr_map 00000080 0000000100008000 DATA

while it prints on linux:

test:     file format elf64-x86-64

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
 16 xray_instr_map 00000080  0000000000028116  0000000000028116  00028116  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA

[MaskRay]

The actual issue is that the runtime does not work for macOS yet. There is also a CMake problem that the x86_64 version instead of aarch64 version is built on Apple m1 (https://maskray.me/blog/2023-06-18-port-llvm-xray-to-apple-systems#runtime-library-issues).

[MaskRay]

Btw,objdump -h -j xray_instr_map test prints:

This is just object file format differences. To the best of my knowledge, the metadata sections are correct after my fixes, but of course I am not 100% sure as the runtime does not work...
Since CMake doesn't work, it makes me less motivated so investigate the issue.

[csmulhern]

I'd also be interested in helping push forward llvm-xray support on darwin-aarch64. I had looked into this myself earlier this year (and am responsible for the comment on the linked blog post).

@MaskRay is there any documentation around what the remaining work is? I have not really contributed to LLVM before, and so might need occasional help along the way, if you know someone who might be able to assist in that capacity.

[MaskRay]

I'd also be interested in helping push forward llvm-xray support on darwin-aarch64. I had looked into this myself earlier this year (and am responsible for the comment on the linked blog post).

@MaskRay is there any documentation around what the remaining work is? I have not really contributed to LLVM before, and so might need occasional help along the way, if you know someone who might be able to assist in that capacity.

There is no roadmap doc. There are many tests under compiler-rt/test/xray/ that "document" the features...

Our primary problem right now is that compiler-rt/lib/xray/CMakeLists.txt doesn't build libraries correctly on macOS, so further investigation is difficult.