Modules: Use hash of PCM content for SIGNATURE

Change ASTFileSignature from a random 32-bit number to the hash of the
PCM content.

  - Move definition ASTFileSignature to Basic/Module.h so Module and
    ASTSourceDescriptor can use it.

  - Change the signature from uint64_t to std::array<uint32_t,5>.

  - Stop using (saving/reading) the size and modification time of PCM
    files when there is a valid SIGNATURE.

  - Add UNHASHED_CONTROL_BLOCK, and use it to store the SIGNATURE record
    and other records that shouldn't affect the hash.  Because implicit
    modules reuses the same file for multiple levels of -Werror, this
    includes DIAGNOSTIC_OPTIONS and DIAG_PRAGMA_MAPPINGS.

This helps to solve a PCH + implicit Modules dependency issue: PCH files
are handled by the external build system, whereas implicit modules are
handled by internal compiler build system.  This prevents invalidating a
PCH when the compiler overwrites a PCM file with the same content
(modulo the diagnostic differences).

Design and original patch by Manman Ren!

llvm-svn: 297655

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 39fe7771a6f..a0e81f01f9b 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1029,7 +1029,7 @@ static bool compileModuleImpl(CompilerInstance &ImportingInstance,
 
   // Remove any macro definitions that are explicitly ignored by the module.
   // They aren't supposed to affect how the module is built anyway.
-  const HeaderSearchOptions &HSOpts = Invocation->getHeaderSearchOpts();
+  HeaderSearchOptions &HSOpts = Invocation->getHeaderSearchOpts();
   PPOpts.Macros.erase(
       std::remove_if(PPOpts.Macros.begin(), PPOpts.Macros.end(),
                      [&HSOpts](const std::pair<std::string, bool> &def) {
@@ -1060,6 +1060,8 @@ static bool compileModuleImpl(CompilerInstance &ImportingInstance,
   FrontendOpts.DisableFree = false;
   FrontendOpts.GenerateGlobalModuleIndex = false;
   FrontendOpts.BuildingImplicitModule = true;
+  // Force implicitly-built modules to hash the content of the module file.
+  HSOpts.ModulesHashContent = true;
   FrontendOpts.Inputs.clear();
   InputKind IK = getSourceInputKindFromOptions(*Invocation->getLangOpts());