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(ClearASTBeforeCodeGen , 1, 1) ///< Free the AST before running 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/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -120,6 +120,7 @@
     bool IRGenFinished = false;
 
     bool TimerIsEnabled = false;
+    bool ASTCleared = false;
 
     std::unique_ptr<CodeGenerator> Gen;
 
@@ -329,6 +330,13 @@
       if (LinkInModules())
         return;
 
+      // FIXME: Fix cleanup issues with clearing the AST when we properly free
+      // things.
+      if (CodeGenOpts.DisableFree && CodeGenOpts.ClearASTBeforeCodeGen) {
+        Context->getAllocator().Reset();
+        ASTCleared = true;
+      }
+
       EmbedBitcode(getModule(), CodeGenOpts, llvm::MemoryBufferRef());
 
       EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
@@ -568,6 +576,7 @@
     // We do not know how to format other severities.
     return false;
 
+  // FIXME
   if (const Decl *ND = Gen->GetDeclForMangledName(D.getFunction().getName())) {
     // FIXME: Shouldn't need to truncate to uint32_t
     Diags.Report(ND->getASTContext().getFullLoc(ND->getLocation()),
@@ -607,7 +616,7 @@
   // function definition. We use the definition's right brace to differentiate
   // from diagnostics that genuinely relate to the function itself.
   FullSourceLoc Loc(DILoc, SourceMgr);
-  if (Loc.isInvalid())
+  if (Loc.isInvalid() && !ASTCleared)
     if (const Decl *FD = Gen->GetDeclForMangledName(D.getFunction().getName()))
       Loc = FD->getASTContext().getFullLoc(FD->getLocation());
 
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -182,6 +182,7 @@
 llvm::Expected<std::unique_ptr<Interpreter>>
 Interpreter::create(std::unique_ptr<CompilerInstance> CI) {
   llvm::Error Err = llvm::Error::success();
+  CI->getCodeGenOpts().ClearASTBeforeCodeGen = false;
   auto Interp =
       std::unique_ptr<Interpreter>(new Interpreter(std::move(CI), Err));
   if (Err)
diff --git a/clang/test/Frontend/optimization-remark-analysis.c b/clang/test/Frontend/optimization-remark-analysis.c
--- a/clang/test/Frontend/optimization-remark-analysis.c
+++ b/clang/test/Frontend/optimization-remark-analysis.c
@@ -1,8 +1,8 @@
-// RUN: %clang -O1 -fvectorize -target x86_64-unknown-unknown -emit-llvm -Rpass-analysis -S %s -o - 2>&1 | FileCheck %s --check-prefix=RPASS
-// RUN: %clang -O1 -fvectorize -target x86_64-unknown-unknown -emit-llvm -S %s -o - 2>&1 | FileCheck %s
+// RUN: %clang -O1 -g2 -fvectorize -target x86_64-unknown-unknown -emit-llvm -Rpass-analysis -S %s -o - 2>&1 | FileCheck %s --check-prefix=RPASS
+// RUN: %clang -O1 -g2 -fvectorize -target x86_64-unknown-unknown -emit-llvm -S %s -o - 2>&1 | FileCheck %s
 
-// RPASS: {{.*}}:7:8: remark: loop not vectorized: loop contains a switch statement
-// CHECK-NOT: {{.*}}:7:8: remark: loop not vectorized: loop contains a switch statement
+// RPASS: {{.*}}:12:5: remark: loop not vectorized: loop contains a switch statement
+// CHECK-NOT: {{.*}}:12:5: remark: loop not vectorized: loop contains a switch statement
 
 double foo(int N, int *Array) {
   double v = 0.0;
diff --git a/clang/test/Misc/backend-stack-frame-diagnostics.cpp b/clang/test/Misc/backend-stack-frame-diagnostics.cpp
--- a/clang/test/Misc/backend-stack-frame-diagnostics.cpp
+++ b/clang/test/Misc/backend-stack-frame-diagnostics.cpp
@@ -1,3 +1,5 @@
+// FIXME
+
 // REQUIRES: x86-registered-target
 // RUN: %clang -target i386-apple-darwin -std=c++11 -fblocks -Wframe-larger-than=70 -Wno-stdlibcxx-not-found -Xclang -verify -o /dev/null -c %s
 // RUN: %clang -target i386-apple-darwin -std=c++11 -fblocks -Wframe-larger-than=70 -Wno-stdlibcxx-not-found -Xclang -verify -o /dev/null -c %s -DIS_SYSHEADER