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llvm-project/clang/lib/Serialization/InMemoryModuleCache.cpp

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Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
//===- InMemoryModuleCache.cpp - Cache for loaded memory buffers ----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "clang/Serialization/InMemoryModuleCache.h"
#include "llvm/Support/MemoryBuffer.h"
using namespace clang;
llvm::MemoryBuffer &
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
InMemoryModuleCache::addPCM(llvm::StringRef Filename,
std::unique_ptr<llvm::MemoryBuffer> Buffer) {
auto Insertion = PCMs.insert(std::make_pair(Filename, std::move(Buffer)));
assert(Insertion.second && "Already has a PCM");
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
return *Insertion.first->second.Buffer;
}
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
llvm::MemoryBuffer &
[modules] Do not cache invalid state for modules that we attempted to load. Partially reverts 0a2be46cfdb698fefcc860a56b47dde0884d5335 as it turned out to cause redundant module rebuilds in multi-process incremental builds. When a module was getting out of date, all compilation processes started at the same time were marking it as `ToBuild`. So each process was building the same module instead of checking if it was built by someone else and using that result. In addition to the work duplication, contention on the same .pcm file wasn't making builds faster. Note that for a single-process build this change would cause redundant module reads and validations. But reading a module is faster than building it and multi-process builds are more common than single-process. So I'm willing to make such a trade-off. rdar://problem/54395127 Reviewed By: dexonsmith Differential Revision: https://reviews.llvm.org/D72860
2020-01-17 09:12:41 +08:00
InMemoryModuleCache::addFinalPCM(llvm::StringRef Filename,
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
std::unique_ptr<llvm::MemoryBuffer> Buffer) {
auto &PCM = PCMs[Filename];
assert(!PCM.IsFinal && "Trying to override finalized PCM?");
[modules] Do not cache invalid state for modules that we attempted to load. Partially reverts 0a2be46cfdb698fefcc860a56b47dde0884d5335 as it turned out to cause redundant module rebuilds in multi-process incremental builds. When a module was getting out of date, all compilation processes started at the same time were marking it as `ToBuild`. So each process was building the same module instead of checking if it was built by someone else and using that result. In addition to the work duplication, contention on the same .pcm file wasn't making builds faster. Note that for a single-process build this change would cause redundant module reads and validations. But reading a module is faster than building it and multi-process builds are more common than single-process. So I'm willing to make such a trade-off. rdar://problem/54395127 Reviewed By: dexonsmith Differential Revision: https://reviews.llvm.org/D72860
2020-01-17 09:12:41 +08:00
assert(!PCM.Buffer && "Already has a non-final PCM");
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
PCM.Buffer = std::move(Buffer);
PCM.IsFinal = true;
return *PCM.Buffer;
}
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
llvm::MemoryBuffer *
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
InMemoryModuleCache::lookupPCM(llvm::StringRef Filename) const {
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
auto I = PCMs.find(Filename);
if (I == PCMs.end())
return nullptr;
return I->second.Buffer.get();
}
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
bool InMemoryModuleCache::isPCMFinal(llvm::StringRef Filename) const {
[modules] Do not cache invalid state for modules that we attempted to load. Partially reverts 0a2be46cfdb698fefcc860a56b47dde0884d5335 as it turned out to cause redundant module rebuilds in multi-process incremental builds. When a module was getting out of date, all compilation processes started at the same time were marking it as `ToBuild`. So each process was building the same module instead of checking if it was built by someone else and using that result. In addition to the work duplication, contention on the same .pcm file wasn't making builds faster. Note that for a single-process build this change would cause redundant module reads and validations. But reading a module is faster than building it and multi-process builds are more common than single-process. So I'm willing to make such a trade-off. rdar://problem/54395127 Reviewed By: dexonsmith Differential Revision: https://reviews.llvm.org/D72860
2020-01-17 09:12:41 +08:00
auto I = PCMs.find(Filename);
if (I == PCMs.end())
return false;
return I->second.IsFinal;
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
}
[modules] Do not cache invalid state for modules that we attempted to load. Partially reverts 0a2be46cfdb698fefcc860a56b47dde0884d5335 as it turned out to cause redundant module rebuilds in multi-process incremental builds. When a module was getting out of date, all compilation processes started at the same time were marking it as `ToBuild`. So each process was building the same module instead of checking if it was built by someone else and using that result. In addition to the work duplication, contention on the same .pcm file wasn't making builds faster. Note that for a single-process build this change would cause redundant module reads and validations. But reading a module is faster than building it and multi-process builds are more common than single-process. So I'm willing to make such a trade-off. rdar://problem/54395127 Reviewed By: dexonsmith Differential Revision: https://reviews.llvm.org/D72860
2020-01-17 09:12:41 +08:00
bool InMemoryModuleCache::tryToRemovePCM(llvm::StringRef Filename) {
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
auto I = PCMs.find(Filename);
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
assert(I != PCMs.end() && "PCM to remove is unknown...");
auto &PCM = I->second;
if (PCM.IsFinal)
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
return true;
[modules] Do not cache invalid state for modules that we attempted to load. Partially reverts 0a2be46cfdb698fefcc860a56b47dde0884d5335 as it turned out to cause redundant module rebuilds in multi-process incremental builds. When a module was getting out of date, all compilation processes started at the same time were marking it as `ToBuild`. So each process was building the same module instead of checking if it was built by someone else and using that result. In addition to the work duplication, contention on the same .pcm file wasn't making builds faster. Note that for a single-process build this change would cause redundant module reads and validations. But reading a module is faster than building it and multi-process builds are more common than single-process. So I'm willing to make such a trade-off. rdar://problem/54395127 Reviewed By: dexonsmith Differential Revision: https://reviews.llvm.org/D72860
2020-01-17 09:12:41 +08:00
PCMs.erase(I);
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
return false;
}
Modules: Invalidate out-of-date PCMs as they're discovered Leverage the InMemoryModuleCache to invalidate a module the first time it fails to import (and to lock a module as soon as it's built or imported successfully). For implicit module builds, this optimizes importing deep graphs where the leaf module is out-of-date; see example near the end of the commit message. Previously the cache finalized ("locked in") all modules imported so far when starting a new module build. This was sufficient to prevent loading two versions of the same module, but was somewhat arbitrary and hard to reason about. Now the cache explicitly tracks module state, where each module must be one of: - Unknown: module not in the cache (yet). - Tentative: module in the cache, but not yet fully imported. - ToBuild: module found on disk could not be imported; need to build. - Final: module in the cache has been successfully built or imported. Preventing repeated failed imports avoids variation in builds based on shifting filesystem state. Now it's guaranteed that a module is loaded from disk exactly once. It now seems safe to remove FileManager::invalidateCache, but I'm leaving that for a later commit. The new, precise logic uncovered a pre-existing problem in the cache: the map key is the module filename, and different contexts use different filenames for the same PCM file. (In particular, the test Modules/relative-import-path.c does not build without this commit. r223577 started using a relative path to describe a module's base directory when importing it within another module. As a result, the module cache sees an absolute path when (a) building the module or importing it at the top-level, and a relative path when (b) importing the module underneath another one.) The "obvious" fix is to resolve paths using FileManager::getVirtualFile and change the map key for the cache to a FileEntry, but some contexts (particularly related to ASTUnit) have a shorter lifetime for their FileManager than the InMemoryModuleCache. This is worth pursuing further in a later commit; perhaps by tying together the FileManager and InMemoryModuleCache lifetime, or moving the in-memory PCM storage into a VFS layer. For now, use the PCM's base directory as-written for constructing the filename to check the ModuleCache. Example ======= To understand the build optimization, first consider the build of a module graph TU -> A -> B -> C -> D with an empty cache: TU builds A' A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' If we build TU again, where A, B, C, and D are in the cache and D is out-of-date, we would previously get this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' A' imports B imports C imports D (out-of-date) builds B' B' imports C imports D (out-of-date) builds C' C' imports D (out-of-date) builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' After this commit, we'll immediateley invalidate A, B, C, and D when we first observe that D is out-of-date, giving this build: TU imports A imports B imports C imports D (out-of-date) TU builds A' // The same graph as an empty cache. A' builds B' B' builds C' C' builds D' imports D' B' imports C' imports D' A' imports B' imports C' imports D' TU imports A' imports B' imports C' imports D' The new build matches what we'd naively expect, pretty closely matching the original build with the empty cache. rdar://problem/48545366 llvm-svn: 355778
2019-03-10 01:44:01 +08:00
void InMemoryModuleCache::finalizePCM(llvm::StringRef Filename) {
auto I = PCMs.find(Filename);
assert(I != PCMs.end() && "PCM to finalize is unknown...");
auto &PCM = I->second;
assert(PCM.Buffer && "Trying to finalize a dropped PCM...");
PCM.IsFinal = true;
Modules: Rename MemoryBufferCache to InMemoryModuleCache Change MemoryBufferCache to InMemoryModuleCache, moving it from Basic to Serialization. Another patch will start using it to manage module build more explicitly, but this is split out because it's mostly mechanical. Because of the move to Serialization we can no longer abuse the Preprocessor to forward it to the ASTReader. Besides the rename and file move, that means Preprocessor::Preprocessor has one fewer parameter and ASTReader::ASTReader has one more. llvm-svn: 355777
2019-03-10 01:33:56 +08:00
}