Revamp the SourceManager to separate the representation of parsed

source locations from source locations loaded from an AST/PCH file.

Previously, loading an AST/PCH file involved carefully pre-allocating
space at the beginning of the source manager for the source locations
and FileIDs that correspond to the prefix, and then appending the
source locations/FileIDs used for parsing the remaining translation
unit. This design forced us into loading PCH files early, as a prefix,
whic has become a rather significant limitation.

This patch splits the SourceManager space into two parts: for source
location "addresses", the lower values (growing upward) are used to
describe parsed code, while upper values (growing downward) are used
for source locations loaded from AST/PCH files. Similarly, positive
FileIDs are used to describe parsed code while negative FileIDs are
used to file/macro locations loaded from AST/PCH files. As a result,
we can load PCH/AST files even during parsing, making various
improvemnts in the future possible, e.g., teaching #include <foo.h> to
look for and load <foo.h.gch> if it happens to be already available.

This patch was originally written by Sebastian Redl, then brought
forward to the modern age by Jonathan Turner, and finally
polished/finished by me to be committed.

llvm-svn: 135484

1 files changed, 2 insertions, 3 deletions

diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 0128d6ee053..344c85627fb 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -224,9 +224,8 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
     } else if (!CI.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
       // Use PCH.
       assert(hasPCHSupport() && "This action does not have PCH support!");
-      ASTDeserializationListener *DeserialListener
-          = CI.getInvocation().getFrontendOpts().ChainedPCH ?
-                  Consumer->GetASTDeserializationListener() : 0;
+      ASTDeserializationListener *DeserialListener =
+          Consumer->GetASTDeserializationListener();
       if (CI.getPreprocessorOpts().DumpDeserializedPCHDecls)
         DeserialListener = new DeserializedDeclsDumper(DeserialListener);
       if (!CI.getPreprocessorOpts().DeserializedPCHDeclsToErrorOn.empty())