tree 95766c5ecf03c233b6ce106477563d855aa50656
parent 4e042cfed52ce252223872c26e5930e76724f800
author QuarticCat <QuarticCat@pm.me> 1694023097 +0000
committer PyTorch MergeBot <pytorchmergebot@users.noreply.github.com> 1694023101 +0000

Fix extension rebuilding on Linux (#108613)

On Linux, CUDA header dependencies are not correctly tracked. After you modify a CUDA header, affected CUDA files won't be rebuilt. This PR will fix this problem.

```console
$ ninja -t deps
rep_penalty.o: #deps 2, deps mtime 1693956351892493247 (VALID)
    /home/qc/Workspace/NotMe/exllama/exllama_ext/cpu_func/rep_penalty.cpp
    /home/qc/Workspace/NotMe/exllama/exllama_ext/cpu_func/rep_penalty.h

rms_norm.cuda.o: #deps 0, deps mtime 1693961188871054130 (VALID)

rope.cuda.o: #deps 0, deps mtime 1693961188954388632 (VALID)

cuda_buffers.cuda.o: #deps 0, deps mtime 1693961188797719768 (VALID)

...
```

Historically, this line of code has been changed twice. It was first implemented in #49344 and there's no `if IS_WINDOWS`, just like now. Then in #56015 someone added `if IS_WINDOWS` for unknown reason. That PR has no description so I don't know what bug he encountered. I don't think there's any bug with these flags on Linux, at least for today. CMake generates exactly the same flags for CUDA.

```ninja
#############################################
# Rule for compiling CUDA files.

rule CUDA_COMPILER__cpp_cuda_unscanned_Debug
  depfile = $DEP_FILE
  deps = gcc
  command = ${LAUNCHER}${CODE_CHECK}/opt/cuda/bin/nvcc -forward-unknown-to-host-compiler $DEFINES $INCLUDES $FLAGS -MD -MT $out -MF $DEP_FILE -x cu -c $in -o $out
  description = Building CUDA object $out
```

where `-MD` is short for `--generate-dependencies-with-compile` and `-MF` is short for `--dependency-output`. My words can be verified by `nvcc --help`.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/108613
Approved by: https://github.com/ezyang