diff --git a/clang/include/clang/Basic/Builtins.def b/clang/include/clang/Basic/Builtins.def
--- a/clang/include/clang/Basic/Builtins.def
+++ b/clang/include/clang/Basic/Builtins.def
@@ -1571,6 +1571,7 @@
 
 // Invariants
 BUILTIN(__builtin_assume, "vb", "nE")
+BUILTIN(__builtin_assume_separate_storage, "vvCD*vCD*", "nE")
 
 // Multiprecision Arithmetic Builtins.
 BUILTIN(__builtin_addcb, "UcUcCUcCUcCUc*", "n")
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -13410,6 +13410,7 @@
   bool SemaBuiltinArithmeticFence(CallExpr *TheCall);
   bool SemaBuiltinAssume(CallExpr *TheCall);
   bool SemaBuiltinAssumeAligned(CallExpr *TheCall);
+  bool SemaBuiltinAssumeSeparateStorage(CallExpr *TheCall);
   bool SemaBuiltinLongjmp(CallExpr *TheCall);
   bool SemaBuiltinSetjmp(CallExpr *TheCall);
   ExprResult SemaBuiltinAtomicOverloaded(ExprResult TheCallResult);
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -2823,6 +2823,19 @@
     Builder.CreateCall(FnAssume, ArgValue);
     return RValue::get(nullptr);
   }
+  case Builtin::BI__builtin_assume_separate_storage: {
+    const Expr *Arg0 = E->getArg(0);
+    const Expr *Arg1 = E->getArg(1);
+
+    Value *Value0 = EmitScalarExpr(Arg0);
+    Value *Value1 = EmitScalarExpr(Arg1);
+
+    Value *Values[] = {Value0, Value1};
+    OperandBundleDefT<Value *> OBD("separate_storage", Values);
+    Builder.CreateAssumption(ConstantInt::getTrue(getLLVMContext()), {OBD});
+    return RValue::get(nullptr);
+  }
+
   case Builtin::BI__arithmetic_fence: {
     // Create the builtin call if FastMath is selected, and the target
     // supports the builtin, otherwise just return the argument.
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -2169,6 +2169,10 @@
     if (SemaBuiltinAssumeAligned(TheCall))
       return ExprError();
     break;
+  case Builtin::BI__builtin_assume_separate_storage:
+    if (SemaBuiltinAssumeSeparateStorage(TheCall))
+      return ExprError();
+    break;
   case Builtin::BI__builtin_dynamic_object_size:
   case Builtin::BI__builtin_object_size:
     if (SemaBuiltinConstantArgRange(TheCall, 1, 0, 3))
@@ -7767,6 +7771,11 @@
   return false;
 }
 
+/// Handle __builtin_assume_separate_storage. For now this is a no-op, but
+/// eventually we expect an optional multi-arg variadic version (to handle an
+/// excluded range).
+bool Sema::SemaBuiltinAssumeSeparateStorage(CallExpr *TheCall) { return false; }
+
 bool Sema::SemaBuiltinOSLogFormat(CallExpr *TheCall) {
   unsigned BuiltinID =
       cast<FunctionDecl>(TheCall->getCalleeDecl())->getBuiltinID();
diff --git a/clang/test/CodeGen/builtin-assume-separate-storage.c b/clang/test/CodeGen/builtin-assume-separate-storage.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/builtin-assume-separate-storage.c
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
+void *nonconst(void);
+
+// CHECK-LABEL: @test1
+void test1(int *a, int *b) {
+  // CHECK: store ptr %a, ptr [[A_ADDR:%.+]], align
+  // CHECK: store ptr %b, ptr [[B_ADDR:%.+]], align
+  // CHECK: [[A:%.+]] = load ptr, ptr [[A_ADDR]]
+  // CHECK: [[B:%.+]] = load ptr, ptr [[B_ADDR]]
+
+  // CHECK: call void @llvm.assume(i1 true) [ "separate_storage"(ptr [[A]], ptr [[B]]) ]
+  __builtin_assume_separate_storage(a, b);
+}
+
+// Separate storage assumptions evaluate their arguments unconditionally, like
+// assume_aligned but *unlike* assume. Check that we actually do so.
+// CHECK-LABEL: @test2
+void test2(int *a, int *b) {
+  // CHECK: call ptr @nonconst()
+  // CHECK: call void @llvm.assume
+  __builtin_assume_separate_storage(a, nonconst());
+}
diff --git a/clang/test/Sema/builtin-assume-separate-storage.c b/clang/test/Sema/builtin-assume-separate-storage.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Sema/builtin-assume-separate-storage.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -fsyntax-only -verify %s
+
+void *nonconst(void);
+
+void test1(int *a, int *b) {
+  __builtin_assume_separate_storage(a, b);
+  // Separate storage assumptions evaluate their arguments unconditionally, like
+  // assume_aligned but *unlike* assume. Check that we don't warn on it.
+  __builtin_assume_separate_storage(a, nonconst());
+  __builtin_assume_separate_storage(nonconst(), a);
+  __builtin_assume_separate_storage(a, 3); // expected-error {{incompatible integer to pointer conversion}}
+  __builtin_assume_separate_storage(3, a); // expected-error {{incompatible integer to pointer conversion}}
+}