diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -368,6 +368,10 @@
 LANGOPT(RegisterStaticDestructors, 1, 1, "Register C++ static destructors")
 
 LANGOPT(MatrixTypes, 1, 0, "Enable or disable the builtin matrix type")
+LANGOPT(PassByValueNoAlias, 1, 0, "Allows assuming no references to passed by "
+                                  "value escape before transferring execution "
+                                  "to the called function. Note that this does "
+                                  "not hold for C++")
 
 COMPATIBLE_VALUE_LANGOPT(MaxTokens, 32, 0, "Max number of tokens per TU or 0")
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4284,6 +4284,10 @@
 def fcompatibility_qualified_id_block_param_type_checking : Flag<["-"], "fcompatibility-qualified-id-block-type-checking">,
   HelpText<"Allow using blocks with parameters of more specific type than "
            "the type system guarantees when a parameter is qualified id">;
+def fpass_by_value_noalias: Flag<["-"], "fpass-by-value-noalias">,
+  HelpText<"Allows assuming no references to passed by value escape before "
+           "transferring execution to the called function. Note that this "
+           "does not hold for C++">;
 
 // FIXME: Remove these entirely once functionality/tests have been excised.
 def fobjc_gc_only : Flag<["-"], "fobjc-gc-only">, Group<f_Group>,
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2184,6 +2184,11 @@
       if (AI.getIndirectByVal())
         Attrs.addByValAttr(getTypes().ConvertTypeForMem(ParamType));
 
+      if (getLangOpts().PassByValueNoAlias)
+        // When calling the function, the pointer passed in will be the only
+        // reference to the underlying object. Mark it accordingly.
+        Attrs.addAttribute(llvm::Attribute::NoAlias);
+
       CharUnits Align = AI.getIndirectAlign();
 
       // In a byval argument, it is important that the required
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3419,6 +3419,7 @@
   Opts.PCHInstantiateTemplates = Args.hasArg(OPT_fpch_instantiate_templates);
 
   Opts.MatrixTypes = Args.hasArg(OPT_fenable_matrix);
+  Opts.PassByValueNoAlias = Args.hasArg(OPT_fpass_by_value_noalias);
 
   Opts.MaxTokens = getLastArgIntValue(Args, OPT_fmax_tokens_EQ, 0, Diags);
 
diff --git a/clang/test/CodeGen/pass-by-value-noalias.c b/clang/test/CodeGen/pass-by-value-noalias.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/pass-by-value-noalias.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fpass-by-value-noalias -triple arm64-apple-iphoneos -emit-llvm -disable-llvm-optzns %s -o - 2>&1 | FileCheck --check-prefix=WITH_NOALIAS %s
+// RUN: %clang_cc1 -triple arm64-apple-iphoneos -emit-llvm -disable-llvm-optzns %s -o - 2>&1 | FileCheck --check-prefix=NO_NOALIAS %s
+
+struct Foo {
+  int a;
+  int b;
+  int c;
+  int d;
+  int e;
+  int f;
+};
+
+// WITH_NOALIAS: define void @take(%struct.Foo* noalias %arg)
+// NO_NOALIAS: define void @take(%struct.Foo* %arg)
+void take(struct Foo arg) {}