[clang][rtsan] Reland realtime sanitizer codegen and driver (#102622)

This reverts commit a1e9b7e646b76bf844e8a9a101ebd27de11992ff
This relands commit d010ec6af8162a8ae4e42d2cac5282f83db0ce07

No modifications from the original patch. It was determined that the
ubsan build failure was happening even after the revert, some examples:

https://lab.llvm.org/buildbot/#/builders/159/builds/4477 
https://lab.llvm.org/buildbot/#/builders/159/builds/4478 
https://lab.llvm.org/buildbot/#/builders/159/builds/4479

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index fdd89ed..026f164 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -78,6 +78,7 @@
 #include "llvm/Transforms/Instrumentation/MemorySanitizer.h"
 #include "llvm/Transforms/Instrumentation/NumericalStabilitySanitizer.h"
 #include "llvm/Transforms/Instrumentation/PGOInstrumentation.h"
+#include "llvm/Transforms/Instrumentation/RealtimeSanitizer.h"
 #include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h"
 #include "llvm/Transforms/Instrumentation/SanitizerCoverage.h"
 #include "llvm/Transforms/Instrumentation/ThreadSanitizer.h"
@@ -990,6 +991,13 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
             FPM.addPass(BoundsCheckingPass());
           });
 
+    if (LangOpts.Sanitize.has(SanitizerKind::Realtime))
+      PB.registerScalarOptimizerLateEPCallback(
+          [](FunctionPassManager &FPM, OptimizationLevel Level) {
+            RealtimeSanitizerOptions Opts;
+            FPM.addPass(RealtimeSanitizerPass(Opts));
+          });
+
     // Don't add sanitizers if we are here from ThinLTO PostLink. That already
     // done on PreLink stage.
     if (!IsThinLTOPostLink) {