diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -54,6 +54,7 @@
 CODEGENOPT(EnableAIXExtendedAltivecABI, 1, 0) ///< Set for -mabi=vec-extabi. Enables the extended Altivec ABI on AIX.
 ENUM_CODEGENOPT(FramePointer, FramePointerKind, 2, FramePointerKind::None) /// frame-pointer: all,non-leaf,none
 
+CODEGENOPT(ClearASTBeforeBackend , 1, 0) ///< Free the AST before running backend code generation. Only works with -disable-free.
 CODEGENOPT(DisableFree       , 1, 0) ///< Don't free memory.
 CODEGENOPT(DiscardValueNames , 1, 0) ///< Discard Value Names from the IR (LLVMContext flag)
 CODEGENOPT(DisableLLVMPasses , 1, 0) ///< Don't run any LLVM IR passes to get
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5297,6 +5297,9 @@
 def disable_free : Flag<["-"], "disable-free">,
   HelpText<"Disable freeing of memory on exit">,
   MarshallingInfoFlag<FrontendOpts<"DisableFree">>;
+def clear_ast_before_backend : Flag<["-"], "clear-ast-before-backend">,
+  HelpText<"Clear the Clang AST before running backend code generation">,
+  MarshallingInfoFlag<CodeGenOpts<"ClearASTBeforeBackend">>;
 def enable_noundef_analysis : Flag<["-"], "enable-noundef-analysis">, Group<f_Group>,
   HelpText<"Enable analyzing function argument and return types for mandatory definedness">,
   MarshallingInfoFlag<CodeGenOpts<"EnableNoundefAttrs">>;
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -351,6 +351,11 @@
         }
       }
 
+      // FIXME: Fix cleanup issues with clearing the AST when we properly free
+      // things.
+      if (CodeGenOpts.DisableFree && CodeGenOpts.ClearASTBeforeBackend)
+        C.getAllocator().Reset();
+
       EmbedBitcode(getModule(), CodeGenOpts, llvm::MemoryBufferRef());
 
       EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
diff --git a/clang/test/Misc/clear-ast-before-backend.c b/clang/test/Misc/clear-ast-before-backend.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Misc/clear-ast-before-backend.c
@@ -0,0 +1,3 @@
+// RUN: %clang_cc1 -clear-ast-before-backend %s -emit-obj -o /dev/null -O1
+
+void f() {}