diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index 7bd1f18004580..fe1ceb74429c9 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -391,7 +391,8 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   /// likely simplifications post-inlining. The most important aspect we track
   /// is CFG altering simplifications -- when we prove a basic block dead, that
   /// can cause dramatic shifts in the cost of inlining a function.
-  DenseMap<Value *, Constant *> SimplifiedValues;
+  /// Note: The simplified Value may be owned by the caller function.
+  DenseMap<Value *, Value *> SimplifiedValues;
 
   /// Keep track of the values which map back (through function arguments) to
   /// allocas on the caller stack which could be simplified through SROA.
@@ -432,7 +433,7 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   template <typename T> T *getDirectOrSimplifiedValue(Value *V) const {
     if (auto *Direct = dyn_cast<T>(V))
       return Direct;
-    return dyn_cast_if_present<T>(SimplifiedValues.lookup(V));
+    return getSimplifiedValue<T>(V);
   }
 
   // Custom simplification helper routines.
@@ -525,11 +526,33 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
 
   InlineResult analyze();
 
-  std::optional<Constant *> getSimplifiedValue(Instruction *I) {
-    auto It = SimplifiedValues.find(I);
-    if (It != SimplifiedValues.end())
-      return It->second;
-    return std::nullopt;
+  /// Lookup simplified Value. May return a value owned by the caller.
+  Value *getSimplifiedValueUnchecked(Value *V) const {
+    return SimplifiedValues.lookup(V);
+  }
+
+  /// Lookup simplified Value, but return nullptr if the simplified value is
+  /// owned by the caller.
+  template <typename T> T *getSimplifiedValue(Value *V) const {
+    Value *SimpleV = SimplifiedValues.lookup(V);
+    if (!SimpleV)
+      return nullptr;
+
+    // Skip checks if we know T is a global. This has a small, but measurable
+    // impact on compile-time.
+    if constexpr (std::is_base_of_v<Constant, T>)
+      return dyn_cast<T>(SimpleV);
+
+    // Make sure the simplified Value is owned by this function
+    if (auto *I = dyn_cast<Instruction>(SimpleV)) {
+      if (I->getFunction() != &F)
+        return nullptr;
+    } else if (auto *Arg = dyn_cast<Argument>(SimpleV)) {
+      if (Arg->getParent() != &F)
+        return nullptr;
+    } else if (!isa<Constant>(SimpleV))
+      return nullptr;
+    return dyn_cast<T>(SimpleV);
   }
 
   // Keep a bunch of stats about the cost savings found so we can print them
@@ -921,12 +944,11 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
         if (BranchInst *BI = dyn_cast<BranchInst>(&I)) {
           // Count a conditional branch as savings if it becomes unconditional.
           if (BI->isConditional() &&
-              isa_and_nonnull<ConstantInt>(
-                  SimplifiedValues.lookup(BI->getCondition()))) {
+              getSimplifiedValue<ConstantInt>(BI->getCondition())) {
             CurrentSavings += InstrCost;
           }
         } else if (SwitchInst *SI = dyn_cast<SwitchInst>(&I)) {
-          if (isa_and_present<ConstantInt>(SimplifiedValues.lookup(SI->getCondition())))
+          if (getSimplifiedValue<ConstantInt>(SI->getCondition()))
             CurrentSavings += InstrCost;
         } else if (Value *V = dyn_cast<Value>(&I)) {
           // Count an instruction as savings if we can fold it.
@@ -1423,10 +1445,17 @@ void InlineCostAnnotationWriter::emitInstructionAnnot(
     if (Record->hasThresholdChanged())
       OS << ", threshold delta = " << Record->getThresholdDelta();
   }
-  auto C = ICCA->getSimplifiedValue(const_cast<Instruction *>(I));
-  if (C) {
+  auto *V = ICCA->getSimplifiedValueUnchecked(const_cast<Instruction *>(I));
+  if (V) {
     OS << ", simplified to ";
-    (*C)->print(OS, true);
+    V->print(OS, true);
+    if (auto *VI = dyn_cast<Instruction>(V)) {
+      if (VI->getFunction() != I->getFunction())
+        OS << " (caller instruction)";
+    } else if (auto *VArg = dyn_cast<Argument>(V)) {
+      if (VArg->getParent() != I->getFunction())
+        OS << " (caller argument)";
+    }
   }
   OS << "\n";
 }
@@ -1483,7 +1512,7 @@ bool CallAnalyzer::isGEPFree(GetElementPtrInst &GEP) {
   SmallVector<Value *, 4> Operands;
   Operands.push_back(GEP.getOperand(0));
   for (const Use &Op : GEP.indices())
-    if (Constant *SimpleOp = SimplifiedValues.lookup(Op))
+    if (Constant *SimpleOp = getSimplifiedValue<Constant>(Op))
       Operands.push_back(SimpleOp);
     else
       Operands.push_back(Op);
@@ -1498,7 +1527,7 @@ bool CallAnalyzer::visitAlloca(AllocaInst &I) {
   // Check whether inlining will turn a dynamic alloca into a static
   // alloca and handle that case.
   if (I.isArrayAllocation()) {
-    Constant *Size = SimplifiedValues.lookup(I.getArraySize());
+    Constant *Size = getSimplifiedValue<Constant>(I.getArraySize());
     if (auto *AllocSize = dyn_cast_or_null<ConstantInt>(Size)) {
       // Sometimes a dynamic alloca could be converted into a static alloca
       // after this constant prop, and become a huge static alloca on an
@@ -2388,7 +2417,7 @@ bool CallAnalyzer::visitCallBase(CallBase &Call) {
     // Check if this happens to be an indirect function call to a known function
     // in this inline context. If not, we've done all we can.
     Value *Callee = Call.getCalledOperand();
-    F = dyn_cast_or_null<Function>(SimplifiedValues.lookup(Callee));
+    F = getSimplifiedValue<Function>(Callee);
     if (!F || F->getFunctionType() != Call.getFunctionType()) {
       onCallArgumentSetup(Call);
 
@@ -2483,8 +2512,7 @@ bool CallAnalyzer::visitSelectInst(SelectInst &SI) {
 
   Constant *TrueC = getDirectOrSimplifiedValue<Constant>(TrueVal);
   Constant *FalseC = getDirectOrSimplifiedValue<Constant>(FalseVal);
-  Constant *CondC =
-      dyn_cast_or_null<Constant>(SimplifiedValues.lookup(SI.getCondition()));
+  Constant *CondC = getSimplifiedValue<Constant>(SI.getCondition());
 
   if (!CondC) {
     // Select C, X, X => X
@@ -2833,8 +2861,9 @@ InlineResult CallAnalyzer::analyze() {
   auto CAI = CandidateCall.arg_begin();
   for (Argument &FAI : F.args()) {
     assert(CAI != CandidateCall.arg_end());
-    if (Constant *C = dyn_cast<Constant>(CAI))
-      SimplifiedValues[&FAI] = C;
+    SimplifiedValues[&FAI] = *CAI;
+    if (isa<Constant>(*CAI))
+      ++NumConstantArgs;
 
     Value *PtrArg = *CAI;
     if (ConstantInt *C = stripAndComputeInBoundsConstantOffsets(PtrArg)) {
@@ -2849,7 +2878,6 @@ InlineResult CallAnalyzer::analyze() {
     }
     ++CAI;
   }
-  NumConstantArgs = SimplifiedValues.size();
   NumConstantOffsetPtrArgs = ConstantOffsetPtrs.size();
   NumAllocaArgs = SROAArgValues.size();
 
@@ -2911,8 +2939,7 @@ InlineResult CallAnalyzer::analyze() {
     if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
       if (BI->isConditional()) {
         Value *Cond = BI->getCondition();
-        if (ConstantInt *SimpleCond =
-                dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) {
+        if (ConstantInt *SimpleCond = getSimplifiedValue<ConstantInt>(Cond)) {
           BasicBlock *NextBB = BI->getSuccessor(SimpleCond->isZero() ? 1 : 0);
           BBWorklist.insert(NextBB);
           KnownSuccessors[BB] = NextBB;
@@ -2922,8 +2949,7 @@ InlineResult CallAnalyzer::analyze() {
       }
     } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
       Value *Cond = SI->getCondition();
-      if (ConstantInt *SimpleCond =
-              dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) {
+      if (ConstantInt *SimpleCond = getSimplifiedValue<ConstantInt>(Cond)) {
         BasicBlock *NextBB = SI->findCaseValue(SimpleCond)->getCaseSuccessor();
         BBWorklist.insert(NextBB);
         KnownSuccessors[BB] = NextBB;