mirror of https://github.com/llvm/torch-mlir
28bb866260
This patch, by itself, doesn't fix caching on Windows, but once a new release of ccache is available, caching for Windows builds should start working again (validated by building ccache from source and using it with LLVM builds). Ccache rejects caching when either the `/Zi` or `/ZI` flags are used during compilation on Windows, since these flags tell the compiler to embed debug information in a PDB file (separate from the object file produced by the compiler). In particular, our CI builds add the `/Zi` flag, making ccache mark these compiler invocations as uncacheable. But what caused our CI to add debug flags, especially when we specified `-DCMAKE_BUILD_TYPE=Release`? On Windows, unless we specify the `--config Release` flag during the CMake build step, CMake assumes a debug build. So all this while, we had been producing debug builds of torch-mlir for every PR! No doubt it took so long to build the Windows binaries. The reason for having to specify the configuration during the _build_ step (as opposed to the _configure_ step) of CMake on Windows is that CMake's Visual Studio generators will produce _both_ Release and Debug profiles during the CMake configure step (thus requiring a build-time value that tells CMake whether to build in Release or Debug mode). Luckily, on Linux and macOS, the `--config` flag seems to be simply ignored, instead of causing build errors. Strangely, based on cursory tests, it seems like on Windows we need to specify the Relase configuration as both `-DCMAKE_BUILD_TYPE=Release` as well as `--config Release`. Dropping either made my build switch to a Debug configuration. Additionally, there is a bug in ccache v4.8 (although this is addressed in trunk) that causes ccache to reject caching if the compiler invocation includes any flag that starts with `/Z`, including /`Zc`, which is added by LLVM's HandleLLVMOptions.cmake and which isn't related to debug info or PDB files. The next release of ccache should include the fix, which is to reject caching only for `/Zi` and `/ZI` flags and not all flags that start with `/Z`. As a side note, debugging this problem was possible because of ccache's log file, which is enabled by: `ccache --set-config="log_file=log.txt"`. |
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| .. | ||
| docker | ||
| python_deploy | ||
| autogen_ltc_backend.py | ||
| autogen_ltc_backend.yaml | ||
| build_libtorch.sh | ||
| build_python_wheels.sh | ||
| build_standalone.sh | ||
| scrape_releases.py | ||
| update_abstract_interp_lib.sh | ||
| update_torch_ods.sh | ||
| write_env_file.sh | ||