[clang] Add option to disable -clear-ast-before-backend

Some downstream users have plugins that -clear-ast-before-backend may
affect. Add an option to opt out.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D112100

1 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 881e30a..52c54d3 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -52,6 +52,8 @@
 using namespace clang;
 using namespace llvm;
 
+#define DEBUG_TYPE "codegenaction"
+
 namespace clang {
   class BackendConsumer;
   class ClangDiagnosticHandler final : public DiagnosticHandler {
@@ -352,6 +354,7 @@ namespace clang {
       }
 
       if (CodeGenOpts.ClearASTBeforeBackend) {
+        LLVM_DEBUG(llvm::dbgs() << "Clearing AST...\n");
         // Access to the AST is no longer available after this.
         // Other things that the ASTContext manages are still available, e.g.
         // the SourceManager. It'd be nice if we could separate out all the