[clang dependency scanning] C APIs for Current Working Directory Optimization #10146
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I'm concerned about making the change to default optimizations in this downstream branch. Can you say more about why we think this optimization is okay by default for upstream but not here? I can see how informing the build system that the CWD can be canonicalized or ignored would be helpful to the build system, but I'm not clear why it's necessary to have this handshake about whether the optimization is enabled or not. |
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I think upstream it should be disabled by default too. Most build systems care about the working directory, and so the build system needs to know to look at that field. The non-libclang parts of this should also go upstream. It's necessary because if the dep scanner collides names that the build system thinks are different due to WD, it can create problems. Although exactly what happens depends on the build system and how it's used. Best case it's just non-deterministic which WD gets used, but you can also get multiple different jobs targeting the same file path, or the build system may just error out. |
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Thanks for the comment @benlangmuir and @Bigcheese. llvm#129809 is posted to change the default behavior upstream. I will modify this PR to exclude the default behavior change. |
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llvm#129809 has landed. I will land this PR once llvm#129809 is in |
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| int clang_experimental_DepGraphModule_isCWDIgnored(CXDepGraphModule); |
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Is there precedent for "CWD" in the C API layer? Maybe we should spell it out as "WorkingDirectory".
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I tried doing this but clang_experimental_DependencyScannerServiceOptions_setCurrentWorkingDirOptimization got too long (83 chars), and I don't want to rename one API but not the other. In this case I think I slightly prefer keeping the names as they are. But I am all ears for better/consistent names.
…pstream llvm." This reverts commit 1399861.
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…mization (#10146) This PR implements two new C APIs so the build system can communicate with the dependency scanner about current working directory optimization. Two new functions are added: 1. `void clang_experimental_DependencyScannerServiceOptions_setCWDOptimization(CXDependencyScannerServiceOptions Opts, int)`: the caller can use this function to set `Opts` to indicate that it can support current working directory optimization. 2. `int clang_experimental_DepGraphModule_isCWDIgnored(CXDepGraphModule)`: this function can retrieve the module info from the scanner, indicating if the current working directory is ignored for this module's context hash. As an example usage, the user of the APIs (e.g. a build system) can use them to set reasonable debug working directories for each `pcm`s. rdar://145860213 (cherry picked from commit b9c8668) Conflicts: clang/test/ClangScanDeps/cas-fs-multiple-commands.c clang/test/ClangScanDeps/include-tree-multiple-commands.c clang/tools/libclang/libclang.map
Adopt new libclang API which the scanner uses to notify the build system when it is ok to compile a module using an arbitrary current working directory to facilitate increased module sharing. The relevant API was introduced in swiftlang/llvm-project#10146. rdar://145991369
Adopt new libclang API which the scanner uses to notify the build system when it is ok to compile a module using an arbitrary current working directory to facilitate increased module sharing. The relevant API was introduced in swiftlang/llvm-project#10146. rdar://145991369
This PR implements two new C APIs so the build system can communicate with the dependency scanner about current working directory optimization.
Two new functions are added:
void clang_experimental_DependencyScannerServiceOptions_setCWDOptimization(CXDependencyScannerServiceOptions Opts, int): the caller can use this function to setOptsto indicate that it can support current working directory optimization.int clang_experimental_DepGraphModule_isCWDIgnored(CXDepGraphModule): this function can retrieve the module info from the scanner, indicating if the current working directory is ignored for this module's context hash.As an example usage, the user of the APIs (e.g. a build system) can use them to set reasonable debug working directories for each
pcms.rdar://145860213