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
This reverts commit r298185, effectively reapplying r298165, after fixing the
new unit tests (PR32338). The memory buffer generator doesn't null-terminate
the MemoryBuffer it creates; this version of the commit informs getMemBuffer
about that to avoid the assert.
Original commit message follows:
----
Clang's internal build system for implicit modules uses lock files to
ensure that after a process writes a PCM it will read the same one back
in (without contention from other -cc1 commands). Since PCMs are read
from disk repeatedly while invalidating, building, and importing, the
lock is not released quickly. Furthermore, the LockFileManager is not
robust in every environment. Other -cc1 commands can stall until
timeout (after about eight minutes).
This commit changes the lock file from being necessary for correctness
to a (possibly dubious) performance hack. The remaining benefit is to
reduce duplicate work in competing -cc1 commands which depend on the
same module. Follow-up commits will change the internal build system to
continue after a timeout, and reduce the timeout. Perhaps we should
reconsider blocking at all.
This also fixes a use-after-free, when one part of a compilation
validates a PCM and starts using it, and another tries to swap out the
PCM for something new.
The PCMCache is a new type called MemoryBufferCache, which saves memory
buffers based on their filename. Its ownership is shared by the
CompilerInstance and ModuleManager.
- The ModuleManager stores PCMs there that it loads from disk, never
touching the disk if the cache is hot.
- When modules fail to validate, they're removed from the cache.
- When a CompilerInstance is spawned to build a new module, each
already-loaded PCM is assumed to be valid, and is frozen to avoid
the use-after-free.
- Any newly-built module is written directly to the cache to avoid the
round-trip to the filesystem, making lock files unnecessary for
correctness.
Original patch by Manman Ren; most testcases by Adrian Prantl!
llvm-svn: 298278
Clang's internal build system for implicit modules uses lock files to
ensure that after a process writes a PCM it will read the same one back
in (without contention from other -cc1 commands). Since PCMs are read
from disk repeatedly while invalidating, building, and importing, the
lock is not released quickly. Furthermore, the LockFileManager is not
robust in every environment. Other -cc1 commands can stall until
timeout (after about eight minutes).
This commit changes the lock file from being necessary for correctness
to a (possibly dubious) performance hack. The remaining benefit is to
reduce duplicate work in competing -cc1 commands which depend on the
same module. Follow-up commits will change the internal build system to
continue after a timeout, and reduce the timeout. Perhaps we should
reconsider blocking at all.
This also fixes a use-after-free, when one part of a compilation
validates a PCM and starts using it, and another tries to swap out the
PCM for something new.
The PCMCache is a new type called MemoryBufferCache, which saves memory
buffers based on their filename. Its ownership is shared by the
CompilerInstance and ModuleManager.
- The ModuleManager stores PCMs there that it loads from disk, never
touching the disk if the cache is hot.
- When modules fail to validate, they're removed from the cache.
- When a CompilerInstance is spawned to build a new module, each
already-loaded PCM is assumed to be valid, and is frozen to avoid
the use-after-free.
- Any newly-built module is written directly to the cache to avoid the
round-trip to the filesystem, making lock files unnecessary for
correctness.
Original patch by Manman Ren; most testcases by Adrian Prantl!
llvm-svn: 298165
Duncan P. N. Exon Smith