[libclang] Allow to suspend a translation unit.

A suspended translation unit uses significantly less memory but on the
other side does not support any other calls than
clang_reparseTranslationUnit to resume it or
clang_disposeTranslationUnit to dispose it completely.

This helps IDEs to reduce the memory footprint. The data that is freed
by a call to clang_suspendTranslationUnit will be re-generated on the
next (re)parse anyway. Used with a preamble, this allows pretty fast
resumption of the translation unit for further use (compared to disposal
of the translation unit and a parse from scratch).

Patch by Nikolai Kosjar!

llvm-svn: 304212

3 files changed, 17 insertions, 0 deletions

diff --git a/clang/tools/c-index-test/c-index-test.c b/clang/tools/c-index-test/c-index-test.c
index 1f5d6044319..31ad828a2f1 100644
--- a/clang/tools/c-index-test/c-index-test.c
+++ b/clang/tools/c-index-test/c-index-test.c
@@ -1742,6 +1742,8 @@ int perform_test_load_source(int argc, const char **argv,
       return -1;
 
     if (Repeats > 1) {
+      clang_suspendTranslationUnit(TU);
+
       Err = clang_reparseTranslationUnit(TU, num_unsaved_files, unsaved_files,
                                          clang_defaultReparseOptions(TU));
       if (Err != CXError_Success) {
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index 394ee0ec439..2d92de19d99 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -3918,6 +3918,20 @@ void clang_disposeTranslationUnit(CXTranslationUnit CTUnit) {
   }
 }
 
+unsigned clang_suspendTranslationUnit(CXTranslationUnit CTUnit) {
+  if (CTUnit) {
+    ASTUnit *Unit = cxtu::getASTUnit(CTUnit);
+
+    if (Unit && Unit->isUnsafeToFree())
+      return false;
+
+    Unit->ResetForParse();
+    return true;
+  }
+
+  return false;
+}
+
 unsigned clang_defaultReparseOptions(CXTranslationUnit TU) {
   return CXReparse_None;
 }
diff --git a/clang/tools/libclang/libclang.exports b/clang/tools/libclang/libclang.exports
index d9a406e5741..f3758469cb6 100644
--- a/clang/tools/libclang/libclang.exports
+++ b/clang/tools/libclang/libclang.exports
@@ -305,6 +305,7 @@ clang_remap_getFilenames
 clang_remap_getNumFiles
 clang_reparseTranslationUnit
 clang_saveTranslationUnit
+clang_suspendTranslationUnit
 clang_sortCodeCompletionResults
 clang_toggleCrashRecovery
 clang_tokenize