jansvoboda11 created this revision.
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This patch makes use of the infrastructure established in D157046
<https://reviews.llvm.org/D157046> to speed up computation of the canonical
context hash in the dependency scanner. This is somewhat hot code, since it's
ran for all modules in the dependency graph of every TU.
I also tried an alternative approach that tried to avoid allocations as much as
possible (essentially doing `HashBuilder.add(Arg.toStringRef(ArgVec))`), but
that turned out to be slower than approach in this patch.
Note that this is not problematic in the same way command-line hashing used to
be prior D143027 <https://reviews.llvm.org/D143027>. The lambda is now being
called even for constant strings.
Depends on D157046 <https://reviews.llvm.org/D157046>.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D157052
Files:
clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
Index: clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
===================================================================
--- clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -269,12 +269,13 @@
HashBuilder.add(serialization::VERSION_MAJOR, serialization::VERSION_MINOR);
// Hash the BuildInvocation without any input files.
- SmallVector<const char *, 32> Args;
- llvm::BumpPtrAllocator Alloc;
- llvm::StringSaver Saver(Alloc);
- CI.generateCC1CommandLine(
- Args, [&](const Twine &Arg) { return Saver.save(Arg).data(); });
- HashBuilder.addRange(Args);
+ SmallString<0> ArgVec;
+ ArgVec.reserve(4096);
+ CI.generateCC1CommandLine([&](const Twine &Arg) {
+ Arg.toVector(ArgVec);
+ ArgVec.push_back('\0');
+ });
+ HashBuilder.add(ArgVec);
// Hash the module dependencies. These paths may differ even if the
invocation
// is identical if they depend on the contents of the files in the TU -- for
Index: clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
===================================================================
--- clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -269,12 +269,13 @@
HashBuilder.add(serialization::VERSION_MAJOR, serialization::VERSION_MINOR);
// Hash the BuildInvocation without any input files.
- SmallVector<const char *, 32> Args;
- llvm::BumpPtrAllocator Alloc;
- llvm::StringSaver Saver(Alloc);
- CI.generateCC1CommandLine(
- Args, [&](const Twine &Arg) { return Saver.save(Arg).data(); });
- HashBuilder.addRange(Args);
+ SmallString<0> ArgVec;
+ ArgVec.reserve(4096);
+ CI.generateCC1CommandLine([&](const Twine &Arg) {
+ Arg.toVector(ArgVec);
+ ArgVec.push_back('\0');
+ });
+ HashBuilder.add(ArgVec);
// Hash the module dependencies. These paths may differ even if the invocation
// is identical if they depend on the contents of the files in the TU -- for
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