Index: llvm/include/llvm/CodeGen/MachineBasicBlock.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -1086,6 +1086,11 @@
     IrrLoopHeaderWeight = Weight;
   }
 
+  /// Return probability of the edge from this block to MBB. This method should
+  /// NOT be called directly, but by using getEdgeProbability method from
+  /// MachineBranchProbabilityInfo class.
+  BranchProbability getSuccProbability(const_succ_iterator Succ) const;
+
 private:
   /// Return probability iterator corresponding to the I successor iterator.
   probability_iterator getProbabilityIterator(succ_iterator I);
@@ -1095,11 +1100,6 @@
   friend class MachineBranchProbabilityInfo;
   friend class MIPrinter;
 
-  /// Return probability of the edge from this block to MBB. This method should
-  /// NOT be called directly, but by using getEdgeProbability method from
-  /// MachineBranchProbabilityInfo class.
-  BranchProbability getSuccProbability(const_succ_iterator Succ) const;
-
   // Methods used to maintain doubly linked list of blocks...
   friend struct ilist_callback_traits<MachineBasicBlock>;
 
Index: llvm/test/tools/llvm-reduce/mir/preserve-block-info.mir
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-reduce/mir/preserve-block-info.mir
@@ -0,0 +1,72 @@
+# REQUIRES: amdgpu-registered-target
+# RUN: llvm-reduce -simplify-mir -mtriple=amdgcn-amd-amdhsa --test FileCheck --test-arg --check-prefix=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t 2> %t.log
+# RUN: FileCheck --match-full-lines --check-prefix=RESULT %s < %t
+
+# CHECK-INTERESTINGNESS: V_MOV_B32
+
+
+# RESULT: bb.0.entry:
+# RESULT: %{{[0-9]+}}:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
+
+# RESULT: bb.1 (address-taken, align 8):
+# RESULT: bb.2 (landing-pad, align 16):
+# RESULT: bb.3 (inlineasm-br-indirect-target):
+# RESULT: bb.4 (ehfunclet-entry):
+# RESULT: bb.5 (bbsections 1):
+# RESULT: bb.6 (bbsections 2):
+# RESULT: bb.7 (bbsections 3):
+# RESULT: bb.8:
+# RESULT-NEXT: successors: %bb.9(0x66666666), %bb.10(0x1999999a)
+# RESULT: bb.9:
+# RESULT: bb.10.exitblock:
+
+--- |
+  define void @func(i32 %size)  {
+  entry:
+    br label %exitblock
+
+  exitblock:
+    ret void
+  }
+
+...
+
+---
+name: func
+alignment:       32
+exposesReturnsTwice: true
+legalized:       true
+regBankSelected: true
+selected:        true
+failedISel:      true
+tracksRegLiveness: true
+hasWinCFI:       true
+failsVerification: true
+tracksDebugUserValues: true
+body:             |
+  bb.0.entry:
+    S_NOP 0
+    %0:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
+
+  bb.1 (address-taken, align 8):
+
+  bb.2 (landing-pad, align 16):
+
+  bb.3 (inlineasm-br-indirect-target):
+
+  bb.4 (ehfunclet-entry):
+
+  bb.5 (bbsections 1):
+  bb.6 (bbsections 2):
+  bb.7 (bbsections 3):
+
+  bb.8:
+    successors: %bb.9(4), %bb.10(1)
+    S_CBRANCH_SCC1 %bb.10, implicit undef $scc
+    S_BRANCH %bb.9
+
+  bb.9:
+
+  bb.10.exitblock:
+    S_ENDPGM 0, implicit %0
+...
Index: llvm/tools/llvm-reduce/ReducerWorkItem.cpp
===================================================================
--- llvm/tools/llvm-reduce/ReducerWorkItem.cpp
+++ llvm/tools/llvm-reduce/ReducerWorkItem.cpp
@@ -127,8 +127,41 @@
   auto *DstMRI = &DstMF->getRegInfo();
 
   // Clone blocks.
-  for (auto &SrcMBB : *SrcMF)
-    Src2DstMBB[&SrcMBB] = DstMF->CreateMachineBasicBlock();
+  for (auto &SrcMBB : *SrcMF) {
+    MachineBasicBlock *DstMBB =
+        DstMF->CreateMachineBasicBlock(SrcMBB.getBasicBlock());
+    Src2DstMBB[&SrcMBB] = DstMBB;
+
+    if (SrcMBB.hasAddressTaken())
+      DstMBB->setHasAddressTaken();
+
+    // FIXME: This is not serialized
+    if (SrcMBB.hasLabelMustBeEmitted())
+      DstMBB->setLabelMustBeEmitted();
+
+    DstMBB->setAlignment(SrcMBB.getAlignment());
+
+    // FIXME: This is not serialized
+    DstMBB->setMaxBytesForAlignment(SrcMBB.getMaxBytesForAlignment());
+
+    DstMBB->setIsEHPad(SrcMBB.isEHPad());
+    DstMBB->setIsEHScopeEntry(SrcMBB.isEHScopeEntry());
+    DstMBB->setIsEHCatchretTarget(SrcMBB.isEHCatchretTarget());
+    DstMBB->setIsEHFuncletEntry(SrcMBB.isEHFuncletEntry());
+
+    // FIXME: These are not serialized
+    DstMBB->setIsCleanupFuncletEntry(SrcMBB.isCleanupFuncletEntry());
+    DstMBB->setIsBeginSection(SrcMBB.isBeginSection());
+    DstMBB->setIsEndSection(SrcMBB.isEndSection());
+
+    DstMBB->setSectionID(SrcMBB.getSectionID());
+    DstMBB->setIsInlineAsmBrIndirectTarget(
+        SrcMBB.isInlineAsmBrIndirectTarget());
+
+    // FIXME: This is not serialized
+    if (Optional<uint64_t> Weight = SrcMBB.getIrrLoopHeaderWeight())
+      DstMBB->setIrrLoopHeaderWeight(*Weight);
+  }
 
   const MachineFrameInfo &SrcMFI = SrcMF->getFrameInfo();
   MachineFrameInfo &DstMFI = DstMF->getFrameInfo();
@@ -189,25 +222,36 @@
     }
   }
 
+  const TargetSubtargetInfo &STI = DstMF->getSubtarget();
+  const TargetInstrInfo *TII = STI.getInstrInfo();
+  const TargetRegisterInfo *TRI = STI.getRegisterInfo();
+
   // Link blocks.
   for (auto &SrcMBB : *SrcMF) {
     auto *DstMBB = Src2DstMBB[&SrcMBB];
     DstMF->push_back(DstMBB);
+
     for (auto It = SrcMBB.succ_begin(), IterEnd = SrcMBB.succ_end();
          It != IterEnd; ++It) {
       auto *SrcSuccMBB = *It;
       auto *DstSuccMBB = Src2DstMBB[SrcSuccMBB];
-      DstMBB->addSuccessor(DstSuccMBB);
+      DstMBB->addSuccessor(DstSuccMBB, SrcMBB.getSuccProbability(It));
     }
     for (auto &LI : SrcMBB.liveins())
       DstMBB->addLiveIn(LI);
+
+    // Make sure MRI knows about registers clobbered by unwinder.
+    if (DstMBB->isEHPad()) {
+      if (auto *RegMask = TRI->getCustomEHPadPreservedMask(*DstMF))
+        DstMRI->addPhysRegsUsedFromRegMask(RegMask);
+    }
   }
+
   // Clone instructions.
   for (auto &SrcMBB : *SrcMF) {
     auto *DstMBB = Src2DstMBB[&SrcMBB];
     for (auto &SrcMI : SrcMBB) {
-      const auto &MCID =
-          DstMF->getSubtarget().getInstrInfo()->get(SrcMI.getOpcode());
+      const auto &MCID = TII->get(SrcMI.getOpcode());
       auto *DstMI = DstMF->CreateMachineInstr(MCID, SrcMI.getDebugLoc(),
                                               /*NoImplicit=*/true);
       DstMBB->push_back(DstMI);