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https://github.com/vercel-labs/scriptc.git
synced 2026-10-25 06:24:27 +08:00
Chris Tate
3ea231d70d
Large executables were simplified and inlined as one module before the optimizer split them, so most of a release build ran on a single core, and any edit recompiled the whole program. The LLVM helper now divides the program before optimization. It splits the emitter's assembly text directly, so partitions also parse concurrently, and falls back to LLVM's module splitter for any input outside the emitter's grammar. Internal functions referenced by a single function stay with that function, and globals stay with their first user. Optimized partitions follow the ThinLTO model: each is simplified and summarized on its own thread, a thin link imports small functions across partitions for inlining and returns unexported hidden definitions to internal linkage, then each partition is optimized and compiled on its own thread. Unoptimized partitions compile independently, so dev builds of large programs are parallel too. A private per-helper cache directory stores simplified partitions under the hash of their source and objects under the hash of the module after importing, so a rebuild recompiles only the partitions an edit can affect. To keep unchanged partitions identical across edits, each partition numbers its metadata in first-use order, lists only the debug compile units it uses, and orders declarations by name, and interned string constants are named by their content rather than first-use order. Partition counts are powers of two that depend only on the module size, up to 64, so output stays the same on every host and functions keep their partition across ordinary edits. LLVM text that arrives in parts is written in large batches and handed to the helper in place instead of being written a second time.
39 lines
1.3 KiB
C++
39 lines
1.3 KiB
C++
#pragma once
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include <memory>
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#include <string>
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namespace scriptc {
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// Hex SHA-256 of length-prefixed parts, so distinct part lists never collide
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// by concatenation.
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std::string hashParts(llvm::ArrayRef<llvm::StringRef> Parts);
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// A content-addressed store of partition artifacts in a private directory
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// owned by the caller. Each entry carries a trailing SHA-256 of its contents
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// and is published by rename, so a reader observes either a complete,
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// verified entry or a miss. Lookups refresh the entry's modification time so
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// the caller's least-recently-used pruning keeps artifacts still in use.
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class ArtifactCache {
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public:
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explicit ArtifactCache(std::string Directory)
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: Directory(std::move(Directory)) {}
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bool enabled() const { return !Directory.empty(); }
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std::unique_ptr<llvm::MemoryBuffer> lookup(llvm::StringRef Key,
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llvm::StringRef Kind) const;
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// Best effort: a full or read-only cache never fails the build.
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void store(llvm::StringRef Key, llvm::StringRef Kind,
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llvm::StringRef Contents) const;
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private:
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std::string path(llvm::StringRef Key, llvm::StringRef Kind) const;
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std::string Directory;
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};
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} // namespace scriptc
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