[5.3] Lazily Associate a SILRemarkStreamer with an LLVMContext #31221
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Corrects a mistake introduced in swiftlang#31106 I was under the impression that the LLVMContext for an instance of llvm::remarks::RemarkStreamer was somehow just scratch-space. It turns out the ASMPrinters don't gather remarks data from modules, they gather it from the remark streamer associated with the module's context. Thus, we cannot have the module's context be distinct from whatever context the streamer is eventually associated with. In order to bring these two systems back into harmony, introduce a simple ownership contract to SILRemarkStreamer. That is, it starts owned by a SILModule, in which case the SILRemarkStreamer holds onto the underlying LLVM object as the optimizer emits remarks. When it comes time to IRGen the module, then and only then do we install the streamer on the module's context. This tranfers ownership of the underlying LLVM streamer to LLVM itself, so it acts as a consuming operation. When we are about to perform IR Generation, the SILModule will be expiring anyways, so the streamer was already about to be destroyed. We're just putting it to better use doing its job.
Destroying the SIL remark streamer after transferring ownership to LLVM is frought. For one, the streamer holds the remark file's stream open. Destroying it early doesn't accomodate sil-opt, which transfers control to LLVM before running passes that emit remarks. Instead, just take a reference to the context that the streamer gets parented onto. If the remarks streamer infrastructure could just hold the file stream open for us, we wouldn't have to do any of this.
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@swift-ci test and merge |
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Builder died @swift-ci test macOS |
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AnthonyLatsis
added
swift 5.3
🍒 release cherry pick
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Cherry-pick #31167 to 5.3 because the refactoring that broke this went in before the branch date.