Index: llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
===================================================================
--- llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -537,6 +537,7 @@
     case Intrinsic::is_constant:
     case Intrinsic::lifetime_start:
     case Intrinsic::lifetime_end:
+    case Intrinsic::noalias_decl:
     case Intrinsic::objectsize:
     case Intrinsic::ptr_annotation:
     case Intrinsic::var_annotation:
Index: llvm/lib/Analysis/AliasSetTracker.cpp
===================================================================
--- llvm/lib/Analysis/AliasSetTracker.cpp
+++ llvm/lib/Analysis/AliasSetTracker.cpp
@@ -438,6 +438,7 @@
       break;
       // FIXME: Add lifetime/invariant intrinsics (See: PR30807).
     case Intrinsic::assume:
+    case Intrinsic::noalias_decl:
     case Intrinsic::sideeffect:
     case Intrinsic::pseudoprobe:
       return;
Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -952,6 +952,10 @@
   if (isIntrinsicCall(Call, Intrinsic::assume))
     return ModRefInfo::NoModRef;
 
+  // The same is true for the llvm.noalias.decl intrinsic.
+  if (isIntrinsicCall(Call, Intrinsic::noalias_decl))
+    return ModRefInfo::NoModRef;
+
   // Like assumes, guard intrinsics are also marked as arbitrarily writing so
   // that proper control dependencies are maintained but they never mods any
   // particular memory location.
@@ -1005,6 +1009,11 @@
       isIntrinsicCall(Call2, Intrinsic::assume))
     return ModRefInfo::NoModRef;
 
+  // The same is true for the llvm.noalias.decl intrinsic.
+  if (isIntrinsicCall(Call1, Intrinsic::noalias_decl) ||
+      isIntrinsicCall(Call2, Intrinsic::noalias_decl))
+    return ModRefInfo::NoModRef;
+
   // Like assumes, guard intrinsics are also marked as arbitrarily writing so
   // that proper control dependencies are maintained but they never mod any
   // particular memory location.
Index: llvm/lib/Analysis/MemorySSA.cpp
===================================================================
--- llvm/lib/Analysis/MemorySSA.cpp
+++ llvm/lib/Analysis/MemorySSA.cpp
@@ -285,6 +285,7 @@
     case Intrinsic::invariant_start:
     case Intrinsic::invariant_end:
     case Intrinsic::assume:
+    case Intrinsic::noalias_decl:
       return {false, NoAlias};
     case Intrinsic::dbg_addr:
     case Intrinsic::dbg_declare:
@@ -1767,9 +1768,15 @@
   // dependencies here.
   // FIXME: Replace this special casing with a more accurate modelling of
   // assume's control dependency.
-  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
-    if (II->getIntrinsicID() == Intrinsic::assume)
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+    switch (II->getIntrinsicID()) {
+    default:
+      break;
+    case Intrinsic::assume:
+    case Intrinsic::noalias_decl:
       return nullptr;
+    }
+  }
 
   // Using a nonstandard AA pipelines might leave us with unexpected modref
   // results for I, so add a check to not model instructions that may not read
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -536,6 +536,7 @@
       case Intrinsic::invariant_end:
       case Intrinsic::lifetime_start:
       case Intrinsic::lifetime_end:
+      case Intrinsic::noalias_decl:
       case Intrinsic::objectsize:
       case Intrinsic::ptr_annotation:
       case Intrinsic::var_annotation:
Index: llvm/lib/Analysis/VectorUtils.cpp
===================================================================
--- llvm/lib/Analysis/VectorUtils.cpp
+++ llvm/lib/Analysis/VectorUtils.cpp
@@ -125,7 +125,8 @@
 
   if (isTriviallyVectorizable(ID) || ID == Intrinsic::lifetime_start ||
       ID == Intrinsic::lifetime_end || ID == Intrinsic::assume ||
-      ID == Intrinsic::sideeffect || ID == Intrinsic::pseudoprobe)
+      ID == Intrinsic::noalias_decl || ID == Intrinsic::sideeffect ||
+      ID == Intrinsic::pseudoprobe)
     return ID;
   return Intrinsic::not_intrinsic;
 }
Index: llvm/lib/CodeGen/Analysis.cpp
===================================================================
--- llvm/lib/CodeGen/Analysis.cpp
+++ llvm/lib/CodeGen/Analysis.cpp
@@ -540,11 +540,12 @@
     // Pseudo probe intrinsics do not block tail call optimization either.
     if (isa<PseudoProbeInst>(BBI))
       continue;
-    // A lifetime end or assume intrinsic should not stop tail call
-    // optimization.
+    // A lifetime end, assume or noalias.decl intrinsic should not stop tail
+    // call optimization.
     if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
       if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
-          II->getIntrinsicID() == Intrinsic::assume)
+          II->getIntrinsicID() == Intrinsic::assume ||
+          II->getIntrinsicID() == Intrinsic::noalias_decl)
         continue;
     if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
         !isSafeToSpeculativelyExecute(&*BBI))
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1748,6 +1748,8 @@
     }
     break;
   }
+  case Intrinsic::noalias_decl:
+    break;
   default: {
     // Handle target specific intrinsics
     Optional<Instruction *> V = targetInstCombineIntrinsic(*II);
Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2551,6 +2551,7 @@
           case Intrinsic::lifetime_start:
           case Intrinsic::lifetime_end:
           case Intrinsic::objectsize:
+          case Intrinsic::noalias_decl:
             Users.emplace_back(I);
             continue;
           }
Index: llvm/lib/Transforms/Scalar/EarlyCSE.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -1226,6 +1226,13 @@
       continue;
     }
 
+    // Likewise, noalias intrinsics don't actually write.
+    if (match(&Inst, m_Intrinsic<Intrinsic::noalias_decl>())) {
+      LLVM_DEBUG(dbgs() << "EarlyCSE skipping noalias intrinsic: " << Inst
+                        << '\n');
+      continue;
+    }
+
     // Skip sideeffect intrinsics, for the same reason as assume intrinsics.
     if (match(&Inst, m_Intrinsic<Intrinsic::sideeffect>())) {
       LLVM_DEBUG(dbgs() << "EarlyCSE skipping sideeffect: " << Inst << '\n');
Index: llvm/test/Transforms/Coroutines/coro-retcon-resume-values.ll
===================================================================
--- llvm/test/Transforms/Coroutines/coro-retcon-resume-values.ll
+++ llvm/test/Transforms/Coroutines/coro-retcon-resume-values.ll
@@ -76,15 +76,9 @@
 
 ;  FIXME: After introduction of llvm.noalias.decl, this is not fully optimzed
 ;  with the new pass manager.
-; NPM-NEXT:    store i32 1, i32* [[SLOT]], align 4
 ; NPM-NEXT:    call i8* @llvm.noalias.decl.p0i8.p0p0i8.i64
-; NPM-NEXT:    [[RELOAD0:%.+]] = load i32, i32* [[SLOT]], align 4
-; NPM-NEXT:    [[SUM0:%.+]] = add i32 [[RELOAD0]], 2
-; NPM-NEXT:    store i32 [[SUM0]], i32* [[SLOT]], align 4
 ; NPM-NEXT:    call i8* @llvm.noalias.decl.p0i8.p0p0i8.i64
-; NPM-NEXT:    [[RELOAD1:%.+]] = load i32, i32* [[SLOT]], align 4
-; NPM-NEXT:    [[SUM2:%.+]] = add i32 [[RELOAD1]], 4
-; NPM-NEXT:    store i32 [[SUM2]], i32* [[SLOT]], align 4
+; NPM-NEXT:    store i32 7, i32* [[SLOT]], align 4
 ; NPM-NEXT:    call i8* @llvm.noalias.decl.p0i8.p0p0i8.i64
 ; NPM-NEXT:    [[RELOAD2:%.+]] = load i32, i32* [[SLOT]], align 4
 ; NPM-NEXT:    call void @print(i32 [[RELOAD2]])