[clang-cl, PCH] Implement support for MS-style PCH through headers

Implement support for MS-style PCH through headers.

This enables support for /Yc and /Yu where the through header is either
on the command line or included in the source. It replaces the current
support the requires the header also be specified with /FI.

This change adds a -cc1 option -pch-through-header that is used to either
start or stop compilation during PCH create or use.

When creating a PCH, the compilation ends after compilation of the through
header.

When using a PCH, tokens are skipped until after the through header is seen.

Patch By: mikerice
Differential Revision: https://reviews.llvm.org/D46652

llvm-svn: 336379

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index f56afeb8923..84286ca3808 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -704,6 +704,17 @@ static bool checkPreprocessorOptions(const PreprocessorOptions &PPOpts,
   // Compute the #include and #include_macros lines we need.
   for (unsigned I = 0, N = ExistingPPOpts.Includes.size(); I != N; ++I) {
     StringRef File = ExistingPPOpts.Includes[I];
+
+    if (!ExistingPPOpts.ImplicitPCHInclude.empty() &&
+        !ExistingPPOpts.PCHThroughHeader.empty()) {
+      // In case the through header is an include, we must add all the includes
+      // to the predefines so the start point can be determined.
+      SuggestedPredefines += "#include \"";
+      SuggestedPredefines += File;
+      SuggestedPredefines += "\"\n";
+      continue;
+    }
+
     if (File == ExistingPPOpts.ImplicitPCHInclude)
       continue;