Index: lib/LTO/LTO.cpp =================================================================== --- lib/LTO/LTO.cpp +++ lib/LTO/LTO.cpp @@ -542,8 +542,12 @@ }; auto ModuleID = MBRef.getBufferIdentifier(); - if (!Cache || !CombinedIndex.modulePaths().count(ModuleID)) - // Cache disabled or no entry for this module in the combined index + + if (!Cache || !CombinedIndex.modulePaths().count(ModuleID) || + all_of(CombinedIndex.getModuleHash(ModuleID), + [](uint32_t V) { return V == 0; })) + // Cache disabled or no entry for this module in the combined index or + // no module hash. return RunThinBackend(AddStream); SmallString<40> Key; Index: lib/LTO/ThinLTOCodeGenerator.cpp =================================================================== --- lib/LTO/ThinLTOCodeGenerator.cpp +++ lib/LTO/ThinLTOCodeGenerator.cpp @@ -243,6 +243,13 @@ // export list, the hash for every single module in the import list, the // list of ResolvedODR for the module, and the list of preserved symbols. + // Include the hash for the current module + auto ModHash = Index.getModuleHash(ModuleID); + + if (all_of(ModHash, [](uint32_t V) { return V == 0; })) + // No hash entry, no caching! + return; + SHA1 Hasher; // Start with the compiler revision @@ -251,8 +258,6 @@ Hasher.update(LLVM_REVISION); #endif - // Include the hash for the current module - auto ModHash = Index.getModuleHash(ModuleID); Hasher.update(ArrayRef((uint8_t *)&ModHash[0], sizeof(ModHash))); for (auto F : ExportList) // The export list can impact the internalization, be conservative here Index: test/ThinLTO/X86/cache.ll =================================================================== --- test/ThinLTO/X86/cache.ll +++ test/ThinLTO/X86/cache.ll @@ -1,6 +1,28 @@ +; Verify first that *without* hash, we don't use the cache. + ; RUN: opt -module-summary %s -o %t.bc ; RUN: opt -module-summary %p/Inputs/cache.ll -o %t2.bc +; Verify that enabling caching is ignoring module without hash +; RUN: rm -Rf %t.cache && mkdir %t.cache +; RUN: llvm-lto -thinlto-action=run -exported-symbol=globalfunc %t2.bc %t.bc -thinlto-cache-dir %t.cache +; RUN: ls %t.cache/llvmcache.timestamp +; RUN: ls %t.cache | count 1 + +; Verify that enabling caching is ignoring module without hash with llvm-lto2 +; RUN: rm -Rf %t.cache && mkdir %t.cache +; RUN: llvm-lto2 -o %t.o %t2.bc %t.bc -cache-dir %t.cache \ +; RUN: -r=%t2.bc,_main,plx \ +; RUN: -r=%t2.bc,_globalfunc,lx \ +; RUN: -r=%t.bc,_globalfunc,plx +; RUN: ls %t.cache | count 0 + + +; Repeat again, *with* hash this time. + +; RUN: opt -module-hash -module-summary %s -o %t.bc +; RUN: opt -module-hash -module-summary %p/Inputs/cache.ll -o %t2.bc + ; Verify that enabling caching is working ; RUN: rm -Rf %t.cache && mkdir %t.cache ; RUN: llvm-lto -thinlto-action=run -exported-symbol=globalfunc %t2.bc %t.bc -thinlto-cache-dir %t.cache