diff --git a/lib/CodeGen/MIRCanonicalizerPass.cpp b/lib/CodeGen/MIRCanonicalizerPass.cpp
index 7a57cd6890d..5ef907b8831 100644
--- a/lib/CodeGen/MIRCanonicalizerPass.cpp
+++ b/lib/CodeGen/MIRCanonicalizerPass.cpp
@@ -49,10 +49,6 @@ static cl::opt<unsigned>
                                cl::value_desc("N"),
                                cl::desc("Function number to canonicalize."));
 
-static cl::opt<unsigned> CanonicalizeBasicBlockNumber(
-    "canon-nth-basicblock", cl::Hidden, cl::init(~0u), cl::value_desc("N"),
-    cl::desc("BasicBlock number to canonicalize."));
-
 namespace {
 
 class MIRCanonicalizer : public MachineFunctionPass {
@@ -374,24 +370,7 @@ static bool doDefKillClear(MachineBasicBlock *MBB) {
 }
 
 static bool runOnBasicBlock(MachineBasicBlock *MBB,
-                            std::vector<StringRef> &bbNames,
-                            unsigned &basicBlockNum, VRegRenamer &Renamer) {
-
-  if (CanonicalizeBasicBlockNumber != ~0U) {
-    if (CanonicalizeBasicBlockNumber != basicBlockNum++)
-      return false;
-    LLVM_DEBUG(dbgs() << "\n Canonicalizing BasicBlock " << MBB->getName()
-                      << "\n";);
-  }
-
-  if (llvm::find(bbNames, MBB->getName()) != bbNames.end()) {
-    LLVM_DEBUG({
-      dbgs() << "Found potentially duplicate BasicBlocks: " << MBB->getName()
-             << "\n";
-    });
-    return false;
-  }
-
+                            unsigned BasicBlockNum, VRegRenamer &Renamer) {
   LLVM_DEBUG({
     dbgs() << "\n\n  NEW BASIC BLOCK: " << MBB->getName() << "  \n\n";
     dbgs() << "\n\n================================================\n\n";
@@ -399,7 +378,6 @@ static bool runOnBasicBlock(MachineBasicBlock *MBB,
 
   bool Changed = false;
 
-  bbNames.push_back(MBB->getName());
   LLVM_DEBUG(dbgs() << "\n\n NEW BASIC BLOCK: " << MBB->getName() << "\n\n";);
 
   LLVM_DEBUG(dbgs() << "MBB Before Canonical Copy Propagation:\n";
@@ -412,8 +390,10 @@ static bool runOnBasicBlock(MachineBasicBlock *MBB,
   Changed |= rescheduleCanonically(IdempotentInstCount, MBB);
   LLVM_DEBUG(dbgs() << "MBB After Scheduling:\n"; MBB->dump(););
 
-  Changed |= Renamer.renameVRegs(MBB);
+  Changed |= Renamer.renameVRegs(MBB, BasicBlockNum);
 
+  // TODO: Consider dropping this. Dropping kill defs is probably not
+  // semantically sound.
   Changed |= doDefKillClear(MBB);
 
   LLVM_DEBUG(dbgs() << "Updated MachineBasicBlock:\n"; MBB->dump();
@@ -445,16 +425,12 @@ bool MIRCanonicalizer::runOnMachineFunction(MachineFunction &MF) {
            : RPOList) { dbgs() << MBB->getName() << "\n"; } dbgs()
       << "\n\n================================================\n\n";);
 
-  std::vector<StringRef> BBNames;
-
   unsigned BBNum = 0;
-
   bool Changed = false;
-
   MachineRegisterInfo &MRI = MF.getRegInfo();
   VRegRenamer Renamer(MRI);
   for (auto MBB : RPOList)
-    Changed |= runOnBasicBlock(MBB, BBNames, BBNum, Renamer);
+    Changed |= runOnBasicBlock(MBB, BBNum++, Renamer);
 
   return Changed;
 }
diff --git a/lib/CodeGen/MIRNamerPass.cpp b/lib/CodeGen/MIRNamerPass.cpp
index 62d0f2e52c7..9f61dd9ef24 100644
--- a/lib/CodeGen/MIRNamerPass.cpp
+++ b/lib/CodeGen/MIRNamerPass.cpp
@@ -57,9 +57,10 @@ public:
 
     VRegRenamer Renamer(MF.getRegInfo());
 
+    unsigned BBIndex = 0;
     ReversePostOrderTraversal<MachineBasicBlock *> RPOT(&*MF.begin());
     for (auto &MBB : RPOT)
-      Changed |= Renamer.renameVRegs(MBB);
+      Changed |= Renamer.renameVRegs(MBB, BBIndex++);
 
     return Changed;
   }
diff --git a/lib/CodeGen/MIRVRegNamerUtils.h b/lib/CodeGen/MIRVRegNamerUtils.h
index ebe309757f2..8e76bfa2bbd 100644
--- a/lib/CodeGen/MIRVRegNamerUtils.h
+++ b/lib/CodeGen/MIRVRegNamerUtils.h
@@ -84,7 +84,7 @@ public:
 
   /// Same as the above, but sets a BBNum depending on BB traversal that
   /// will be used as prefix for the vreg names.
-  bool renameVRegs(MachineBasicBlock *MBB, unsigned BBNum = 0);
+  bool renameVRegs(MachineBasicBlock *MBB, unsigned BBNum);
 
   unsigned getCurrentBBNumber() const { return CurrentBBNumber; }
 };
diff --git a/test/CodeGen/MIR/X86/mir-canon-hash-bb.mir b/test/CodeGen/MIR/X86/mir-canon-hash-bb.mir
new file mode 100644
index 00000000000..94c69f1be36
--- /dev/null
+++ b/test/CodeGen/MIR/X86/mir-canon-hash-bb.mir
@@ -0,0 +1,61 @@
+# RUN: llc  -run-pass mir-namer -x mir -verify-machineinstrs %s -o - | FileCheck %s
+# RUN: llc  -run-pass mir-canonicalizer -x mir -verify-machineinstrs %s -o - | FileCheck %s
+--- |
+  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-unknown-linux-gnu"
+  define i32 @_Z1fi(i32 %arg) {
+    %tmp = alloca i32, align 4
+    %tmp1 = alloca i32, align 4
+    ret i32 %arg
+  }
+
+...
+---
+name:            _Z1fi
+registers:
+  - { id: 0, class: _, preferred-register: '' }
+  - { id: 1, class: _, preferred-register: '' }
+  - { id: 2, class: _, preferred-register: '' }
+  - { id: 3, class: _, preferred-register: '' }
+  - { id: 4, class: _, preferred-register: '' }
+  - { id: 5, class: _, preferred-register: '' }
+  - { id: 6, class: _, preferred-register: '' }
+  - { id: 7, class: _, preferred-register: '' }
+  - { id: 8, class: _, preferred-register: '' }
+stack:
+  - { id: 0, name: tmp, type: default, offset: 0, size: 4, alignment: 4  }
+  - { id: 1, name: tmp1, type: default, offset: 0, size: 4, alignment: 4 }
+body:             |
+  bb.0:
+    %tmp0:_(s32) = COPY $edi
+    %tmp1:_(s32) = G_CONSTANT i32 0
+    %tmp5:_(p0) = G_FRAME_INDEX %stack.0.tmp
+    %tmp6:_(p0) = G_FRAME_INDEX %stack.1.tmp1
+    G_STORE %tmp0(s32), %tmp5(p0) :: (store 4 into %ir.tmp)
+    %tmp7:_(s32) = G_LOAD %tmp5(p0) :: (load 4 from %ir.tmp)
+    %tmp8:_(s1) = G_ICMP intpred(ne), %tmp7(s32), %tmp1
+    G_BRCOND %tmp8(s1), %bb.1
+    G_BR %bb.2
+
+  ; CHECK: bb.1:
+  ; CHECK: %bb2_{{[0-9]+}}__1:_(s32) = G_CONSTANT
+  bb.1:
+    %tmp4:_(s32) = G_CONSTANT i32 1
+    G_STORE %tmp4(s32), %tmp6(p0) :: (store 4 into %ir.tmp1)
+    G_BR %bb.3
+
+
+  ; CHECK: bb.2:
+  ; CHECK: %bb1_{{[0-9]+}}__1:_(s32) = G_CONSTANT
+  bb.2:
+    %tmp3:_(s32) = G_CONSTANT i32 2
+    G_STORE %tmp3(s32), %tmp6(p0) :: (store 4 into %ir.tmp1)
+
+  ; CHECK: bb.3:
+  ; CHECK: %bb3_{{[0-9]+}}__1:_(s32) =  G_LOAD
+  bb.3:
+    %tmp9:_(s32) = G_LOAD %tmp6(p0) :: (load 4 from %ir.tmp1)
+    $eax = COPY %tmp9(s32)
+    RET 0, implicit $eax
+
+...