diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 8479aa5d4037d..eee242d566d1c 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -689,27 +689,31 @@ static AvailabilityResult CheckAvailability(ASTContext &Context,
   if (!A->getIntroduced().empty() &&
       EnclosingVersion < A->getIntroduced()) {
     IdentifierInfo *IIEnv = A->getEnvironment();
-    StringRef TargetEnv =
-        Context.getTargetInfo().getTriple().getEnvironmentName();
-    StringRef EnvName = llvm::Triple::getEnvironmentTypeName(
-        Context.getTargetInfo().getTriple().getEnvironment());
-    // Matching environment or no environment on attribute
-    if (!IIEnv || (!TargetEnv.empty() && IIEnv->getName() == TargetEnv)) {
+    auto &Triple = Context.getTargetInfo().getTriple();
+    StringRef TargetEnv = Triple.getEnvironmentName();
+    StringRef EnvName =
+        llvm::Triple::getEnvironmentTypeName(Triple.getEnvironment());
+    // Matching environment or no environment on attribute.
+    if (!IIEnv || (Triple.hasEnvironment() && IIEnv->getName() == TargetEnv)) {
       if (Message) {
         Message->clear();
         llvm::raw_string_ostream Out(*Message);
         VersionTuple VTI(A->getIntroduced());
-        Out << "introduced in " << PrettyPlatformName << " " << VTI << " "
-            << EnvName << HintMessage;
+        Out << "introduced in " << PrettyPlatformName << " " << VTI;
+        if (Triple.hasEnvironment())
+          Out << " " << EnvName;
+        Out << HintMessage;
       }
     }
-    // Non-matching environment or no environment on target
+    // Non-matching environment or no environment on target.
     else {
       if (Message) {
         Message->clear();
         llvm::raw_string_ostream Out(*Message);
-        Out << "not available on " << PrettyPlatformName << " " << EnvName
-            << HintMessage;
+        Out << "not available on " << PrettyPlatformName;
+        if (Triple.hasEnvironment())
+          Out << " " << EnvName;
+        Out << HintMessage;
       }
     }
 
diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
index 578bcea7f0389..c2547ea96c474 100644
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -134,7 +134,9 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
   // Note: ExpectedSize and ExpectedModTime will be 0 for MK_ImplicitModule
   // when using an ASTFileSignature.
   if (lookupModuleFile(FileName, ExpectedSize, ExpectedModTime, Entry)) {
-    ErrorStr = "module file out of date";
+    ErrorStr = IgnoreModTime
+                   ? "module file has a different size than expected"
+                   : "module file has a different size or mtime than expected";
     return OutOfDate;
   }
 
diff --git a/clang/test/Driver/attr-availability-erroneous-diags.c b/clang/test/Driver/attr-availability-erroneous-diags.c
new file mode 100644
index 0000000000000..5e67a461f3e19
--- /dev/null
+++ b/clang/test/Driver/attr-availability-erroneous-diags.c
@@ -0,0 +1,10 @@
+// RUN: not %clang -target x86_64-apple-darwin9 -fsyntax-only %s 2>&1 | FileCheck %s
+
+// CHECK: error:
+// CHECK-SAME: 'f0' is unavailable: introduced in macOS 11
+// CHECK-NOT: unknown 
+
+void f0(void) __attribute__((availability(macosx,strict,introduced=11)));
+
+void client(void) {
+f0(); }
diff --git a/clang/test/Driver/xros-driver.c b/clang/test/Driver/xros-driver.c
index dd2c55ed4e70c..a79b76d5fe0ba 100644
--- a/clang/test/Driver/xros-driver.c
+++ b/clang/test/Driver/xros-driver.c
@@ -30,8 +30,8 @@
 // LINK: "-platform_version" "xros" "1.0.0" "1.0.0"
 // LINK-SIM: "-platform_version" "xros-simulator" "1.0.0" "1.0.0"
 
-// OBJC-RUNTIME: "-fobjc-runtime=ios-17.0.0.0"
-// OBJC-RUNTIME2: "-fobjc-runtime=ios-18.0.0.0"
+// OBJC-RUNTIME: "-fobjc-runtime=ios-17.0.0"
+// OBJC-RUNTIME2: "-fobjc-runtime=ios-18.0.0"
 // ARC-NOT: error:
 
 // SSP_ON: "-stack-protector" "1"
diff --git a/clang/test/Modules/explicit-build.cpp b/clang/test/Modules/explicit-build.cpp
index d8834ec304f64..97e50f3769eed 100644
--- a/clang/test/Modules/explicit-build.cpp
+++ b/clang/test/Modules/explicit-build.cpp
@@ -199,6 +199,6 @@
 // RUN:            -fmodule-file=%t/c.pcm \
 // RUN:            %s -DHAVE_A -DHAVE_B -DHAVE_C 2>&1 | FileCheck --check-prefix=CHECK-MISMATCHED-B %s
 //
-// CHECK-MISMATCHED-B:      fatal error: module file '{{.*}}b.pcm' is out of date and needs to be rebuilt: module file out of date
+// CHECK-MISMATCHED-B:      fatal error: module file '{{.*}}b.pcm' is out of date and needs to be rebuilt: module file has a different size than expected
 // CHECK-MISMATCHED-B-NEXT: note: imported by module 'c'
 // CHECK-MISMATCHED-B-NOT:  note:
diff --git a/llvm/include/llvm/Support/VersionTuple.h b/llvm/include/llvm/Support/VersionTuple.h
index ff43e00b73aed..f236d8f778aa8 100644
--- a/llvm/include/llvm/Support/VersionTuple.h
+++ b/llvm/include/llvm/Support/VersionTuple.h
@@ -103,9 +103,7 @@ class VersionTuple {
 
   /// Return a version tuple that contains a different major version but
   /// everything else is the same.
-  VersionTuple withMajorReplaced(unsigned NewMajor) const {
-    return VersionTuple(NewMajor, Minor, Subminor, Build);
-  }
+  VersionTuple withMajorReplaced(unsigned NewMajor) const;
 
   /// Return a version tuple that contains only components that are non-zero.
   VersionTuple normalize() const {
diff --git a/llvm/lib/Support/VersionTuple.cpp b/llvm/lib/Support/VersionTuple.cpp
index a4224f23b2f94..c6e20f1bd3ef4 100644
--- a/llvm/lib/Support/VersionTuple.cpp
+++ b/llvm/lib/Support/VersionTuple.cpp
@@ -108,3 +108,13 @@ bool VersionTuple::tryParse(StringRef input) {
   *this = VersionTuple(major, minor, micro, build);
   return false;
 }
+
+VersionTuple VersionTuple::withMajorReplaced(unsigned NewMajor) const {
+  if (HasBuild)
+    return VersionTuple(NewMajor, Minor, Subminor, Build);
+  if (HasSubminor)
+    return VersionTuple(NewMajor, Minor, Subminor);
+  if (HasMinor)
+    return VersionTuple(NewMajor, Minor);
+  return VersionTuple(NewMajor);
+}
diff --git a/llvm/unittests/Support/VersionTupleTest.cpp b/llvm/unittests/Support/VersionTupleTest.cpp
index af6c0a7febad5..d498d670fb710 100644
--- a/llvm/unittests/Support/VersionTupleTest.cpp
+++ b/llvm/unittests/Support/VersionTupleTest.cpp
@@ -47,3 +47,33 @@ TEST(VersionTuple, tryParse) {
   EXPECT_TRUE(VT.tryParse("1 "));
   EXPECT_TRUE(VT.tryParse("."));
 }
+
+TEST(VersionTuple, withMajorReplaced) {
+  VersionTuple VT(2);
+  VersionTuple ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_FALSE(ReplacedVersion.getMinor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7), ReplacedVersion);
+
+  VT = VersionTuple(100, 1);
+  ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_TRUE(ReplacedVersion.getMinor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7, 1), ReplacedVersion);
+
+  VT = VersionTuple(101, 11, 12);
+  ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_TRUE(ReplacedVersion.getMinor().has_value());
+  EXPECT_TRUE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7, 11, 12), ReplacedVersion);
+
+  VT = VersionTuple(101, 11, 12, 2);
+  ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_TRUE(ReplacedVersion.getMinor().has_value());
+  EXPECT_TRUE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_TRUE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7, 11, 12, 2), ReplacedVersion);
+}