[clang][modules] Introduce new `ModuleCache` interface (#131193)

This PR adds new `ModuleCache` interface to Clang's implicitly-built
modules machinery. The main motivation for this change is to create a
second implementation that uses a more efficient kind of
`llvm::AdvisoryLock` during dependency scanning.

In addition to the lock abstraction, the `ModuleCache` interface also
manages the existing `InMemoryModuleCache` instance. I found that
compared to keeping these separate/independent, the code is a bit
simpler now, since these are two tightly coupled concepts. I can
envision a more efficient implementation of the `InMemoryModuleCache`
for the single-process case too, which will be much easier to implement
with the current setup.

This is not intended to be a functional change.

1 files changed, 5 insertions, 2 deletions

diff --git a/clang/unittests/Frontend/FrontendActionTest.cpp b/clang/unittests/Frontend/FrontendActionTest.cpp
index 75e1667..a6bb767 100644
--- a/clang/unittests/Frontend/FrontendActionTest.cpp
+++ b/clang/unittests/Frontend/FrontendActionTest.cpp
@@ -18,6 +18,7 @@
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Sema/Sema.h"
 #include "clang/Serialization/InMemoryModuleCache.h"
+#include "clang/Serialization/ModuleCache.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include "llvm/Support/VirtualFileSystem.h"
@@ -287,10 +288,12 @@ TEST(GeneratePCHFrontendAction, CacheGeneratedPCH) {
     // Check whether the PCH was cached.
     if (ShouldCache)
       EXPECT_EQ(InMemoryModuleCache::Final,
-                Compiler.getModuleCache().getPCMState(PCHFilename));
+                Compiler.getModuleCache().getInMemoryModuleCache().getPCMState(
+                    PCHFilename));
     else
       EXPECT_EQ(InMemoryModuleCache::Unknown,
-                Compiler.getModuleCache().getPCMState(PCHFilename));
+                Compiler.getModuleCache().getInMemoryModuleCache().getPCMState(
+                    PCHFilename));
   }
 }