[clang] [clang] Add optional pass to remove UBSAN traps using PGO (PR #84214)

[Arthur Eubanks via cfe-commits]

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@@ -744,6 +750,21 @@ static void addSanitizers(const Triple &TargetTriple,
     // LastEP does not need GlobalsAA.
     PB.registerOptimizerLastEPCallback(SanitizersCallback);
   }
+
+  if (ClRemoveTraps) {
+    // We can optimize after inliner, and PGO profile matching. The hook below
+    // is called from `buildModuleOptimizationPipeline` just after profile use,
+    // and inliner is a part of `buildModuleSimplificationPipeline`, which is
+    // before `buildModuleOptimizationPipeline`.
+    PB.registerOptimizerEarlyEPCallback([&](ModulePassManager &MPM,
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aeubanks wrote:

I think this can go at the end of the function simplification pipeline (and there's already a SimplifyCFG run right after) with `registerScalarOptimizerLateEPCallback`. The function should already have been mostly simplified at that point.

https://github.com/llvm/llvm-project/pull/84214