Index: llvm/include/llvm/IR/Instructions.h
===================================================================
--- llvm/include/llvm/IR/Instructions.h
+++ llvm/include/llvm/IR/Instructions.h
@@ -3468,7 +3468,7 @@
   /// This action invalidates iterators for all cases following the one removed,
   /// including the case_end() iterator. It returns an iterator for the next
   /// case.
-  CaseIt removeCase(CaseIt I);
+  CaseIt removeCase(CaseIt I, bool DropPerfMetadata = false);
 
   unsigned getNumSuccessors() const { return getNumOperands()/2; }
   BasicBlock *getSuccessor(unsigned idx) const {
Index: llvm/lib/IR/Instructions.cpp
===================================================================
--- llvm/lib/IR/Instructions.cpp
+++ llvm/lib/IR/Instructions.cpp
@@ -28,6 +28,7 @@
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
@@ -3767,9 +3768,22 @@
   SubclassOptionalData = SI.SubclassOptionalData;
 }
 
+static MDNode *getProfBranchWeightsMD(const SwitchInst *SI) {
+  if (MDNode *ProfileData = SI->getMetadata(LLVMContext::MD_prof))
+    if (auto *MDName = dyn_cast<MDString>(ProfileData->getOperand(0)))
+      if (MDName->getString() == "branch_weights")
+        return ProfileData;
+  return nullptr;
+}
+
 /// addCase - Add an entry to the switch instruction...
 ///
 void SwitchInst::addCase(ConstantInt *OnVal, BasicBlock *Dest) {
+  // Drop metdadata.
+  if (MDNode *ProfileData = getProfBranchWeightsMD(this))
+    if (ProfileData->getNumOperands() == getNumSuccessors() + 1)
+      setMetadata(LLVMContext::MD_prof, nullptr);
+
   unsigned NewCaseIdx = getNumCases();
   unsigned OpNo = getNumOperands();
   if (OpNo+2 > ReservedSpace)
@@ -3784,11 +3798,36 @@
 
 /// removeCase - This method removes the specified case and its successor
 /// from the switch instruction.
-SwitchInst::CaseIt SwitchInst::removeCase(CaseIt I) {
+SwitchInst::CaseIt SwitchInst::removeCase(CaseIt I, bool DropPerfMetadata) {
   unsigned idx = I->getCaseIndex();
 
   assert(2 + idx*2 < getNumOperands() && "Case index out of range!!!");
 
+  if (MDNode *ProfileData = getProfBranchWeightsMD(this))
+    if (ProfileData->getNumOperands() == getNumSuccessors() + 1) {
+      if (DropPerfMetadata) {
+        setMetadata(LLVMContext::MD_prof, nullptr);
+      } else {
+        SmallVector<uint32_t, 8> Weights;
+        uint64_t SW = 0;
+        for (unsigned CI = 0, CE = getNumSuccessors() - 1; CI < CE; ++CI) {
+          // At the removed position we put the end of the list.
+          unsigned WI = (CI == idx + 1 ? CE : CI) + 1;
+          ConstantInt *C =
+              mdconst::extract<ConstantInt>(ProfileData->getOperand(WI));
+          uint32_t CW = C->getValue().getZExtValue();
+          SW += CW;
+          Weights.push_back(CW);
+        }
+        assert(Weights.size() == getNumSuccessors() - 1);
+        auto *NewProfileData = !SW || Weights.size() < 2
+                                   ? nullptr
+                                   : MDBuilder(getParent()->getContext())
+                                         .createBranchWeights(Weights);
+        setMetadata(LLVMContext::MD_prof, NewProfileData);
+      }
+    }
+
   unsigned NumOps = getNumOperands();
   Use *OL = getOperandList();
 
Index: llvm/lib/IR/Verifier.cpp
===================================================================
--- llvm/lib/IR/Verifier.cpp
+++ llvm/lib/IR/Verifier.cpp
@@ -2440,6 +2440,20 @@
            "Duplicate integer as switch case", &SI, Case.getCaseValue());
   }
 
+  // Check consistency of !prof branch_weights metadata if any.
+  auto *ProfileData = SI.getMetadata(LLVMContext::MD_prof);
+  if (ProfileData != nullptr && ProfileData->getNumOperands() > 0) {
+    if (auto *ProfDataName = dyn_cast<MDString>(ProfileData->getOperand(0)))
+      if (ProfDataName->getString().equals("branch_weights")) {
+        Assert(ProfileData->getNumOperands() == SI.getNumSuccessors() + 1,
+               "Number of !prof brunch_weights operands differ from number of "
+               "successors");
+        for (unsigned i = 1; i < ProfileData->getNumOperands(); ++i)
+          Assert(mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(i)),
+                 "!prof brunch_weights operand is not a const int");
+      }
+  }
+
   visitTerminator(SI);
 }
 
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -884,7 +884,7 @@
           Weights.pop_back();
         }
         i->getCaseSuccessor()->removePredecessor(TI->getParent());
-        SI->removeCase(i);
+        SI->removeCase(i, true);
       }
     }
     if (HasWeight && Weights.size() >= 2)
@@ -4461,7 +4461,7 @@
 
     // Prune unused values from PHI nodes.
     CaseI->getCaseSuccessor()->removePredecessor(SI->getParent());
-    SI->removeCase(CaseI);
+    SI->removeCase(CaseI, true);
   }
   if (HasWeight && Weights.size() >= 2) {
     SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
Index: llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
===================================================================
--- llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
+++ llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
@@ -152,7 +152,7 @@
 ; CHECK-NEXT:    switch i32 [[S]], label [[OUT]] [
 ; CHECK-NEXT:    i32 -2, label [[NEXT:%.*]]
 ; CHECK-NEXT:    i32 -1, label [[NEXT]]
-; CHECK-NEXT:    ]
+; CHECK-NEXT:    !prof ![[MD0:[0-9]+]]
 ; CHECK:       out:
 ; CHECK-NEXT:    [[P:%.*]] = phi i32 [ 1, [[ENTRY:%.*]] ], [ -1, [[NEGATIVE]] ]
 ; CHECK-NEXT:    ret i32 [[P]]
@@ -171,7 +171,7 @@
   i32 -2, label %next
   i32 2, label %out
   i32 3, label %out
-  ]
+  ], !prof !{!"branch_weights", i32 99, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6}
 
 out:
   %p = phi i32 [ 1, %entry ], [ -1, %negative ], [ -1, %negative ], [ -1, %negative ], [ -1, %negative ], [ -1, %negative ]
@@ -723,3 +723,5 @@
 exit:
   ret i1 %cmp
 }
+
+; CHECK: ![[MD0]] = !{!"branch_weights", i32 99, i32 4, i32 3}
Index: llvm/test/Transforms/SimpleLoopUnswitch/basictest.ll
===================================================================
--- llvm/test/Transforms/SimpleLoopUnswitch/basictest.ll
+++ llvm/test/Transforms/SimpleLoopUnswitch/basictest.ll
@@ -41,6 +41,8 @@
 
   br label %loop_begin
 
+; CHECK: loop_begin:
+; CHECK: !prof ![[MD0:[0-9]+]]
 loop_begin:
 
   %var_val = load i32, i32* %var
@@ -48,7 +50,7 @@
   switch i32 %c, label %default [
       i32 1, label %inc
       i32 2, label %dec
-  ]
+  ], !prof !{!"branch_weights", i32 1, i32 1, i32 1}
 
 inc:
   call void @incf() noreturn nounwind
@@ -183,3 +185,5 @@
 declare void @incf() noreturn
 declare void @decf() noreturn
 declare void @conv() convergent
+
+; CHECK: ![[MD0]] = !{!"branch_weights", i32 1, i32 1}
Index: llvm/test/Transforms/SimpleLoopUnswitch/trivial-unswitch.ll
===================================================================
--- llvm/test/Transforms/SimpleLoopUnswitch/trivial-unswitch.ll
+++ llvm/test/Transforms/SimpleLoopUnswitch/trivial-unswitch.ll
@@ -135,13 +135,13 @@
     i32 13, label %loop_exit1
     i32 2, label %loop2
     i32 42, label %loop_exit3
-  ]
+  ], !prof !{!"branch_weights", i32 1, i32 1, i32 1, i32 1, i32 1, i32 1}
 ; CHECK:       loop_begin:
 ; CHECK-NEXT:    load
 ; CHECK-NEXT:    switch i32 %cond2, label %loop2 [
 ; CHECK-NEXT:      i32 0, label %loop0
 ; CHECK-NEXT:      i32 1, label %loop1
-; CHECK-NEXT:    ]
+; CHECK-NEXT:    ], !prof ![[MD0:[0-9]+]]
 
 loop0:
   call void @some_func() noreturn nounwind
@@ -1243,3 +1243,5 @@
 ; CHECK:       loopexit:
 ; CHECK-NEXT:    ret
 }
+
+; CHECK: ![[MD0]] = !{!"branch_weights", i32 1, i32 1, i32 1}