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[mlir] Remove the Identifier ThreadLocalCache from MLIRContext

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This used to be important for reducing lock contention when accessing identifiers, but
the cost of the cache can be quite large if parsing in a multi-threaded context. After
D104167, the win of keeping a cache is not worth the cost.

Differential Revision: https://reviews.llvm.org/D104737
This commit is contained in:
River Riddle 2021-06-22 19:13:57 +00:00
parent e4e31e19bb
commit 87e59e47e9
1 changed files with 3 additions and 16 deletions
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19
mlir/lib/IR/MLIRContext.cpp
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@ -24,7 +24,6 @@
#include "mlir/IR/OpImplementation.h"
#include "mlir/IR/Types.h"
#include "mlir/Support/DebugAction.h"
#include "mlir/Support/ThreadLocalCache.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SetVector.h"
@ -275,10 +274,6 @@ public:
llvm::StringMap<PointerUnion<Dialect *, MLIRContext *>,
llvm::BumpPtrAllocator &>
identifiers;
/// A thread local cache of identifiers to reduce lock contention.
ThreadLocalCache<llvm::StringMap<
llvm::StringMapEntry<PointerUnion<Dialect *, MLIRContext *>> *>>
localIdentifierCache;
/// An allocator used for AbstractAttribute and AbstractType objects.
llvm::BumpPtrAllocator abstractDialectSymbolAllocator;
@ -811,26 +806,18 @@ Identifier Identifier::get(const Twine &string, MLIRContext *context) {
return Identifier(&*insertedIt.first);
}
// Check for an existing instance in the local cache.
auto *&localEntry = (*impl.localIdentifierCache)[str];
if (localEntry)
return Identifier(localEntry);
// Check for an existing identifier in read-only mode.
{
llvm::sys::SmartScopedReader<true> contextLock(impl.identifierMutex);
auto it = impl.identifiers.find(str);
if (it != impl.identifiers.end()) {
localEntry = &*it;
return Identifier(localEntry);
}
if (it != impl.identifiers.end())
return Identifier(&*it);
}
// Acquire a writer-lock so that we can safely create the new instance.
llvm::sys::SmartScopedWriter<true> contextLock(impl.identifierMutex);
auto it = impl.identifiers.insert({str, getDialectOrContext()}).first;
localEntry = &*it;
return Identifier(localEntry);
return Identifier(&*it);
}
Dialect *Identifier::getDialect() {