[offload] Allow liboffload cuda plugin to accept PTX binaries as input

[RossBrunton]

Currently users of liboffload have to manually build and link any input PTX files into CUBIN files. For example (from Unified Runtime):

ur_result_t ProgramCreateCudaWorkaround(ur_context_handle_t hContext,
                                        const uint8_t *Binary, size_t Length,
                                        ur_program_handle_t hProgram) {
  uint8_t *RealBinary;
  size_t RealLength;
  CUlinkState State;
  cuLinkCreate(0, nullptr, nullptr, &State);

  cuLinkAddData(State, CU_JIT_INPUT_PTX, (char *)(Binary), Length, nullptr, 0,
                nullptr, nullptr);

  void *CuBin = nullptr;
  size_t CuBinSize = 0;
  cuLinkComplete(State, &CuBin, &CuBinSize);
  RealBinary = (uint8_t *)CuBin;
  RealLength = CuBinSize;

  auto Res = olCreateProgram(hContext->Device->OffloadDevice, RealBinary,
                             RealLength, &hProgram->OffloadProgram);

  // Program owns the linked module now
  cuLinkDestroy(State);

  return offloadResultToUR(Res);
}

It makes sense for this format to be detected, built and linked in liboffload itself to save users from having to duplicate this logic and link against libcudadrv.

[llvmbot]

@llvm/issue-subscribers-offload

Author: Ross Brunton (RossBrunton)

Currently users of liboffload have to manually build and link any input PTX files into CUBIN files. For example (from Unified Runtime):

ur_result_t ProgramCreateCudaWorkaround(ur_context_handle_t hContext,
                                        const uint8_t *Binary, size_t Length,
                                        ur_program_handle_t hProgram) {
  uint8_t *RealBinary;
  size_t RealLength;
  CUlinkState State;
  cuLinkCreate(0, nullptr, nullptr, &State);

  cuLinkAddData(State, CU_JIT_INPUT_PTX, (char *)(Binary), Length, nullptr, 0,
                nullptr, nullptr);

  void *CuBin = nullptr;
  size_t CuBinSize = 0;
  cuLinkComplete(State, &CuBin, &CuBinSize);
  RealBinary = (uint8_t *)CuBin;
  RealLength = CuBinSize;

  auto Res = olCreateProgram(hContext->Device->OffloadDevice, RealBinary,
                             RealLength, &hProgram->OffloadProgram);

  // Program owns the linked module now
  cuLinkDestroy(State);

  return offloadResultToUR(Res);
}

It makes sense for this format to be detected, built and linked in liboffload itself to save users from having to duplicate this logic and link against libcudadrv.

[jhuber6]

We already do this kind of stuff in the JIT engine, the main annoyance is detecting it since PTX is a textual format. Beyond that, should be pretty easy to slot it next to where we discern between ELF and IR.