README.md

My helpers for debugging AMD GPU issues:

• amdgpu_trace.py

  Sometimes you run into a corrupted value in a register, but it has been produced by a series of other instructions. Instead of debugging every instruction one by one you can use this script. For a given function, on every instruction it will save the values in registers of a single GPU lane. It works by getting function disassembly from gdb and scanning it for instructions offsets and then registers used by the instruction. Keep in mind some things:

  • It's meant to work with only a single wavefront running (for some reason $_streq($_dispatch_pos,"(X,Y,Z)/W") does not work in conditional breakpoints)
  • There's a limitation in rocgdb (or a bug?) where it can't set breakpoints with offsets before GPU function is broken into, so the pattern of use is:

    b foobar
    c
    # once foobar is broken into
    amdgpu_trace foobar ...
    

  • It is extremally slow

  Load it like this:

  source <PATH_TO_REPO>/amdgpu_trace.py
  

  and check the usage with

  help amdgpu_trace
  

• .gdbinit

  Function amdgpu_reg_dump to print the content of every vector register. Useful if you are suspecting a function is miscompiled (fill/spill mismatch, unbalanced stack, signature mismatch, etc). Print the regsters before and after and compare. Add it to your .gdbinit like this:

  source <PATH_TO_REPO>/.gdbinit
  

• split_llvm_print.py

  When using Clang with -mllvm -print-after-all or -mllvm -print-before-all Clang will output all the passes in one big vomit to console. This script takes this (piped to file) output and splits it into separate files by passes