Index: include/llvm/CodeGen/Passes.h
===================================================================
--- include/llvm/CodeGen/Passes.h
+++ include/llvm/CodeGen/Passes.h
@@ -340,7 +340,7 @@
 
   /// createDwarfEHPass - This pass mulches exception handling code into a form
   /// adapted to code generation.  Required if using dwarf exception handling.
-  FunctionPass *createDwarfEHPass();
+  FunctionPass *createDwarfEHPass(bool PruneUnreachableResumes);
 
   /// createWinEHPass - Prepares personality functions used by MSVC on Windows,
   /// in addition to the Itanium LSDA based personalities.
Index: lib/CodeGen/DwarfEHPrepare.cpp
===================================================================
--- lib/CodeGen/DwarfEHPrepare.cpp
+++ lib/CodeGen/DwarfEHPrepare.cpp
@@ -48,6 +48,7 @@
     // RewindFunction - _Unwind_Resume or the target equivalent.
     FunctionCallee RewindFunction = nullptr;
 
+    bool PruneUnreachableResumes;
     DominatorTree *DT = nullptr;
     const TargetLowering *TLI = nullptr;
 
@@ -61,7 +62,8 @@
   public:
     static char ID; // Pass identification, replacement for typeid.
 
-    DwarfEHPrepare() : FunctionPass(ID) {}
+    DwarfEHPrepare(bool PruneUnreachableResumes = true)
+      : FunctionPass(ID), PruneUnreachableResumes(PruneUnreachableResumes) {}
 
     bool runOnFunction(Function &Fn) override;
 
@@ -89,12 +91,15 @@
 INITIALIZE_PASS_END(DwarfEHPrepare, DEBUG_TYPE,
                     "Prepare DWARF exceptions", false, false)
 
-FunctionPass *llvm::createDwarfEHPass() { return new DwarfEHPrepare(); }
+FunctionPass *llvm::createDwarfEHPass(bool PruneUnreachableResumes) {
+  return new DwarfEHPrepare(PruneUnreachableResumes);
+}
 
 void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<TargetPassConfig>();
   AU.addRequired<TargetTransformInfoWrapperPass>();
-  AU.addRequired<DominatorTreeWrapperPass>();
+  if (PruneUnreachableResumes)
+    AU.addRequired<DominatorTreeWrapperPass>();
 }
 
 /// GetExceptionObject - Return the exception object from the value passed into
@@ -142,6 +147,9 @@
 size_t DwarfEHPrepare::pruneUnreachableResumes(
     Function &Fn, SmallVectorImpl<ResumeInst *> &Resumes,
     SmallVectorImpl<LandingPadInst *> &CleanupLPads) {
+  if (!PruneUnreachableResumes)
+    return Resumes.size();
+
   BitVector ResumeReachable(Resumes.size());
   size_t ResumeIndex = 0;
   for (auto *RI : Resumes) {
@@ -259,7 +267,8 @@
 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
   const TargetMachine &TM =
       getAnalysis<TargetPassConfig>().getTM<TargetMachine>();
-  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+  auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
+  DT = DTWP ? &DTWP->getDomTree() : nullptr;
   TLI = TM.getSubtargetImpl(Fn)->getTargetLowering();
   bool Changed = InsertUnwindResumeCalls(Fn);
   DT = nullptr;
Index: lib/CodeGen/TargetPassConfig.cpp
===================================================================
--- lib/CodeGen/TargetPassConfig.cpp
+++ lib/CodeGen/TargetPassConfig.cpp
@@ -729,14 +729,16 @@
     LLVM_FALLTHROUGH;
   case ExceptionHandling::DwarfCFI:
   case ExceptionHandling::ARM:
-    addPass(createDwarfEHPass());
+    addPass(createDwarfEHPass(
+        /* PruneUnreachableResumes */ getOptLevel() != CodeGenOpt::None));
     break;
   case ExceptionHandling::WinEH:
     // We support using both GCC-style and MSVC-style exceptions on Windows, so
     // add both preparation passes. Each pass will only actually run if it
     // recognizes the personality function.
     addPass(createWinEHPass());
-    addPass(createDwarfEHPass());
+    addPass(createDwarfEHPass(
+        /* PruneUnreachableResumes */ getOptLevel() != CodeGenOpt::None));
     break;
   case ExceptionHandling::Wasm:
     // Wasm EH uses Windows EH instructions, but it does not need to demote PHIs
Index: test/CodeGen/AArch64/O0-pipeline.ll
===================================================================
--- test/CodeGen/AArch64/O0-pipeline.ll
+++ test/CodeGen/AArch64/O0-pipeline.ll
@@ -27,7 +27,6 @@
 ; CHECK-NEXT:       AArch64 Stack Tagging
 ; CHECK-NEXT:     Rewrite Symbols
 ; CHECK-NEXT:     FunctionPass Manager
-; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Exception handling preparation
 ; CHECK-NEXT:       Safe Stack instrumentation pass
 ; CHECK-NEXT:       Insert stack protectors
Index: test/CodeGen/X86/O0-pipeline.ll
===================================================================
--- test/CodeGen/X86/O0-pipeline.ll
+++ test/CodeGen/X86/O0-pipeline.ll
@@ -29,7 +29,6 @@
 ; CHECK-NEXT:       Expand indirectbr instructions
 ; CHECK-NEXT:     Rewrite Symbols
 ; CHECK-NEXT:     FunctionPass Manager
-; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Exception handling preparation
 ; CHECK-NEXT:       Safe Stack instrumentation pass
 ; CHECK-NEXT:       Insert stack protectors