diff --git a/llvm/include/llvm/Transforms/IPO/Attributor.h b/llvm/include/llvm/Transforms/IPO/Attributor.h
--- a/llvm/include/llvm/Transforms/IPO/Attributor.h
+++ b/llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -321,7 +321,8 @@
   /// This method will evaluate \p Pred on call sites and return
   /// true if \p Pred holds in every call sites. However, this is only possible
   /// all call sites are known, hence the function has internal linkage.
-  bool checkForAllCallSites(Function &F, std::function<bool(CallSite)> &Pred,
+  bool checkForAllCallSites(Function &F,
+                            const function_ref<bool(CallSite)> &Pred,
                             const AbstractAttribute &QueryingAA,
                             bool RequireAllCallSites);
 
diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -1043,7 +1043,7 @@
   unsigned ArgNo = getArgNo();
 
   // Callback function
-  std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
+  auto CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     auto *NonNullAA =
@@ -1245,8 +1245,16 @@
   void initialize(Attributor &A) override {
     const Function &F = getAnchorScope();
 
+    if (F.hasInternalLinkage())
+      return;
+
+    exploreFromEntry(A, F);
+  }
+
+  void exploreFromEntry(Attributor &A, const Function &F) {
     ToBeExploredPaths.insert(&(F.getEntryBlock().front()));
     AssumedLiveBlocks.insert(&(F.getEntryBlock()));
+
     for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
       if (const Instruction *NextNoReturnI =
               findNextNoReturn(A, ToBeExploredPaths[i]))
@@ -1276,7 +1284,12 @@
            "Attempted to manifest an invalid state!");
 
     ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
-    const Function &F = getAnchorScope();
+    Function &F = getAnchorScope();
+
+    if (AssumedLiveBlocks.size() == 0) {
+      F.replaceAllUsesWith(UndefValue::get(F.getType()));
+      return ChangeStatus::CHANGED;
+    }
 
     // Flag to determine if we can change an invoke to a call assuming the
     // callee is nounwind. This is not possible if the personality of the
@@ -1467,10 +1480,25 @@
 }
 
 ChangeStatus AAIsDeadImpl::updateImpl(Attributor &A) {
+  Function &F = getAnchorScope();
+  ChangeStatus Status = ChangeStatus::UNCHANGED;
+
+  if (F.hasInternalLinkage()) {
+    auto CallSiteCheck = [&](CallSite) { return false; };
+
+    // All callsites of F are dead.
+    if (A.checkForAllCallSites(F, CallSiteCheck, *this, true))
+      return ChangeStatus::UNCHANGED;
+
+    // There exists at least one live call site, so we explore the function.
+    Status = ChangeStatus::CHANGED;
+
+    exploreFromEntry(A, F);
+  }
+
   // Temporary collection to iterate over existing noreturn instructions. This
   // will alow easier modification of NoReturnCalls collection
   SmallVector<const Instruction *, 8> NoReturnChanged;
-  ChangeStatus Status = ChangeStatus::UNCHANGED;
 
   for (const Instruction *I : NoReturnCalls)
     NoReturnChanged.push_back(I);
@@ -1774,7 +1802,7 @@
   bool IsGlobal = isAssumedGlobal();
 
   // Callback function
-  std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) -> bool {
+  auto CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     // Check that DereferenceableAA is AADereferenceableCallSiteArgument.
@@ -1950,7 +1978,7 @@
   auto BeforeState = getAssumed();
 
   // Callback function
-  std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
+  auto CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     auto *AlignAA = A.getAAFor<AAAlign>(*this, *CS.getInstruction(), ArgNo);
@@ -2056,7 +2084,7 @@
 /// ----------------------------------------------------------------------------
 
 bool Attributor::checkForAllCallSites(Function &F,
-                                      std::function<bool(CallSite)> &Pred,
+                                      const function_ref<bool(CallSite)> &Pred,
                                       const AbstractAttribute &QueryingAA,
                                       bool RequireAllCallSites) {
   // We can try to determine information from
diff --git a/llvm/test/Transforms/FunctionAttrs/align.ll b/llvm/test/Transforms/FunctionAttrs/align.ll
--- a/llvm/test/Transforms/FunctionAttrs/align.ll
+++ b/llvm/test/Transforms/FunctionAttrs/align.ll
@@ -138,7 +138,8 @@
 ; TEST 7
 ; Better than IR information
 ; ATTRIBUTOR: define align 32 i32* @test7(i32* returned align 32 %p)
-define align 4 i32* @test7(i32* align 32 %p) #0 {
+define align 4 i32* @test7(i32* align 32 %p, i8* readnone %c) #0 {
+  tail call i8* @f1(i8* nonnull %c)
   ret i32* %p
 }
 
diff --git a/llvm/test/Transforms/FunctionAttrs/liveness.ll b/llvm/test/Transforms/FunctionAttrs/liveness.ll
--- a/llvm/test/Transforms/FunctionAttrs/liveness.ll
+++ b/llvm/test/Transforms/FunctionAttrs/liveness.ll
@@ -12,6 +12,28 @@
 
 declare i32 @bar() nosync readnone
 
+; This internal function has no live call sites, so all its BBs are considered dead,
+; and nothing should be deduced for it.
+
+; CHECK: Function Attrs: nofree noreturn nosync nounwind
+; CHECK-NEXT: define internal i32 @dead_internal_func(i32 %0)
+define internal i32 @dead_internal_func(i32 %0) {
+  %2 = icmp slt i32 %0, 1
+  br i1 %2, label %3, label %5
+
+; <label>:3:                                      ; preds = %5, %1
+  %4 = phi i32 [ 1, %1 ], [ %8, %5 ]
+  ret i32 %4
+
+; <label>:5:                                      ; preds = %1, %5
+  %6 = phi i32 [ %9, %5 ], [ 1, %1 ]
+  %7 = phi i32 [ %8, %5 ], [ 1, %1 ]
+  %8 = mul nsw i32 %6, %7
+  %9 = add nuw nsw i32 %6, 1
+  %10 = icmp eq i32 %6, %0
+  br i1 %10, label %3, label %5
+}
+
 ; CHECK: Function Attrs: nofree norecurse nounwind uwtable willreturn
 define i32 @volatile_load(i32*) norecurse nounwind uwtable {
   %2 = load volatile i32, i32* %0, align 4
@@ -24,6 +46,7 @@
   %2 = load i32, i32* %0, align 4
   ret i32 %2
 }
+
 ; TEST 1: Only first block is live.
 
 ; CHECK: Function Attrs: nofree noreturn nosync nounwind
@@ -35,6 +58,8 @@
   call void @no_return_call()
   ; CHECK: call void @no_return_call()
   ; CHECK-NEXT: unreachable
+  call i32 @dead_internal_func(i32 10)
+  ; CHECK call i32 undef(i32 10)
   %cmp = icmp eq i32 %a, 0
   br i1 %cmp, label %cond.true, label %cond.false
 
@@ -96,6 +121,8 @@
   call void @no_return_call()
   ; CHECK: call void @no_return_call()
   ; CHECK-NEXT: unreachable
+  call i32 @dead_internal_func(i32 10)
+  ; CHECK call i32 undef(i32 10)
   %call = call i32 @foo()
   br label %cond.end
 
@@ -104,6 +131,8 @@
   ; CHECK: call void @no_return_call()
   ; CHECK-NEXT: unreachable
   %call1 = call i32 @bar()
+  call i32 @dead_internal_func(i32 10)
+  ; CHECK call i32 undef(i32 10)
   br label %cond.end
 
 cond.end:                                         ; preds = %cond.false, %cond.true
@@ -311,3 +340,73 @@
   %8 = phi i32 [ %1, %cond.elseif ], [ 0, %cond.else ], [ 0, %cond.if ]
   ret i32 %8
 }
+
+; SCC test
+;
+; char a1 __attribute__((aligned(8)));
+; char a2 __attribute__((aligned(16)));
+;
+; char* f1(char* a ){
+;     return a?a:f2(&a1);
+; }
+; char* f2(char* a){
+;     return a?f1(a):f3(&a2);
+; }
+;
+; char* f3(char* a){
+;     return a?&a1: f1(&a2);
+; }
+
+@a1 = common global i8 0, align 8
+@a2 = common global i8 0, align 16
+
+define internal i8* @f1(i8* readnone %0) local_unnamed_addr #0 {
+; ATTRIBUTOR: define internal i8* @f1(i8* readnone %0)
+  %2 = icmp eq i8* %0, null
+  br i1 %2, label %3, label %5
+
+; <label>:3:                                      ; preds = %1
+; ATTRIBUTOR: %4 = tail call i8* undef(i8* nonnull align 8 @a1)
+  %4 = tail call i8* @f2(i8* nonnull @a1)
+  br label %5
+
+; <label>:5:                                      ; preds = %1, %3
+  %6 = phi i8* [ %4, %3 ], [ %0, %1 ]
+  ret i8* %6
+}
+
+define internal i8* @f2(i8* readnone %0) local_unnamed_addr #0 {
+; ATTRIBUTOR: define internal i8* @f2(i8* readnone %0)
+  %2 = icmp eq i8* %0, null
+  br i1 %2, label %5, label %3
+
+; <label>:3:                                      ; preds = %1
+
+; ATTRIBUTOR: %4 = tail call i8* undef(i8* nonnull align 8 %0)
+  %4 = tail call i8* @f1(i8* nonnull %0)
+  br label %7
+
+; <label>:5:                                      ; preds = %1
+; ATTRIBUTOR: %6 = tail call i8* undef(i8* nonnull align 16 @a2)
+  %6 = tail call i8* @f3(i8* nonnull @a2)
+  br label %7
+
+; <label>:7:                                      ; preds = %5, %3
+  %8 = phi i8* [ %4, %3 ], [ %6, %5 ]
+  ret i8* %8
+}
+
+define internal i8* @f3(i8* readnone %0) local_unnamed_addr #0 {
+; ATTRIBUTOR: define internal i8* @f3(i8* readnone %0)
+  %2 = icmp eq i8* %0, null
+  br i1 %2, label %3, label %5
+
+; <label>:3:                                      ; preds = %1
+; ATTRIBUTOR: %4 = tail call i8* undef(i8* nonnull align 16 @a2)
+  %4 = tail call i8* @f1(i8* nonnull @a2)
+  br label %5
+
+; <label>:5:                                      ; preds = %1, %3
+  %6 = phi i8* [ %4, %3 ], [ @a1, %1 ]
+  ret i8* %6
+}