diff --git a/clang/lib/Basic/Targets/SystemZ.h b/clang/lib/Basic/Targets/SystemZ.h
--- a/clang/lib/Basic/Targets/SystemZ.h
+++ b/clang/lib/Basic/Targets/SystemZ.h
@@ -46,7 +46,17 @@
     LongDoubleFormat = &llvm::APFloat::IEEEquad();
     DefaultAlignForAttributeAligned = 64;
     MinGlobalAlign = 16;
-    resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64");
+    if (Triple.isOSzOS()) {
+      // All vector types are default aligned on an 8-byte boundary, even if the
+      // vector facility is not available. That is different from Linux.
+      MaxVectorAlign = 64;
+      // Compared to Linux/ELF, the data layout differs only in some details:
+      // - name mangling is GOFF
+      // - 128 bit vector types are 64 bit aligned
+      resetDataLayout(
+          "E-m:l-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64");
+    } else
+      resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64");
     MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
     HasStrictFP = true;
   }
@@ -129,7 +139,7 @@
     HasVector &= !SoftFloat;
 
     // If we use the vector ABI, vector types are 64-bit aligned.
-    if (HasVector) {
+    if (HasVector && !getTriple().isOSzOS()) {
       MaxVectorAlign = 64;
       resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64"
                       "-v128:64-a:8:16-n32:64");
diff --git a/clang/test/CodeGen/target-data.c b/clang/test/CodeGen/target-data.c
--- a/clang/test/CodeGen/target-data.c
+++ b/clang/test/CodeGen/target-data.c
@@ -253,6 +253,40 @@
 // RUN: FileCheck %s -check-prefix=SYSTEMZ-VECTOR
 // SYSTEMZ-VECTOR: target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
 
+// RUN: %clang_cc1 -triple s390x-none-zos -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z10 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch8 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z196 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch9 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu zEC12 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch10 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z13 -target-feature +soft-float -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// ZOS: target datalayout = "E-m:l-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z13 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS-VECTOR
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch11 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS-VECTOR
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z14 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS-VECTOR
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch12 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS-VECTOR
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z15 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS-VECTOR
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch13 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS-VECTOR
+// RUN: %clang_cc1 -triple s390x-none-zos -target-cpu arch14 -o - -emit-llvm %s | \
+// RUN: FileCheck %s -check-prefix=ZOS
+// ZOS-VECTOR: target datalayout = "E-m:l-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+
 // RUN: %clang_cc1 -triple msp430-unknown -o - -emit-llvm %s | \
 // RUN: FileCheck %s -check-prefix=MSP430
 // MSP430: target datalayout = "e-m:e-p:16:16-i32:16-i64:16-f32:16-f64:16-a:8-n8:16-S16"
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -2593,6 +2593,7 @@
     options are
 
     * ``e``: ELF mangling: Private symbols get a ``.L`` prefix.
+    * ``l``: GOFF mangling: Private symbols get a ``.L`` prefix.
     * ``m``: Mips mangling: Private symbols get a ``$`` prefix.
     * ``o``: Mach-O mangling: Private symbols get ``L`` prefix. Other
       symbols get a ``_`` prefix.
diff --git a/llvm/include/llvm/IR/DataLayout.h b/llvm/include/llvm/IR/DataLayout.h
--- a/llvm/include/llvm/IR/DataLayout.h
+++ b/llvm/include/llvm/IR/DataLayout.h
@@ -135,6 +135,7 @@
     MM_MachO,
     MM_WinCOFF,
     MM_WinCOFFX86,
+    MM_GOFF,
     MM_Mips,
     MM_XCOFF
   };
@@ -316,6 +317,7 @@
     switch (ManglingMode) {
     case MM_None:
     case MM_ELF:
+    case MM_GOFF:
     case MM_Mips:
     case MM_WinCOFF:
     case MM_XCOFF:
@@ -332,6 +334,7 @@
     case MM_None:
       return "";
     case MM_ELF:
+    case MM_GOFF:
     case MM_WinCOFF:
       return ".L";
     case MM_Mips:
diff --git a/llvm/lib/IR/DataLayout.cpp b/llvm/lib/IR/DataLayout.cpp
--- a/llvm/lib/IR/DataLayout.cpp
+++ b/llvm/lib/IR/DataLayout.cpp
@@ -151,6 +151,8 @@
 //===----------------------------------------------------------------------===//
 
 const char *DataLayout::getManglingComponent(const Triple &T) {
+  if (T.isOSBinFormatGOFF())
+    return "-m:l";
   if (T.isOSBinFormatMachO())
     return "-m:o";
   if (T.isOSWindows() && T.isOSBinFormatCOFF())
@@ -500,6 +502,9 @@
       case 'e':
         ManglingMode = MM_ELF;
         break;
+      case 'l':
+        ManglingMode = MM_GOFF;
+        break;
       case 'o':
         ManglingMode = MM_MachO;
         break;
diff --git a/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp b/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
--- a/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
@@ -84,8 +84,9 @@
   // 128-bit floats are aligned only to 64 bits.
   Ret += "-f128:64";
 
-  // When using the vector ABI, 128-bit vectors are also aligned to 64 bits.
-  if (VectorABI)
+  // When using the vector ABI on Linux, 128-bit vectors are also aligned to 64
+  // bits. On z/OS, vector types are always aligned to 64 bits.
+  if (VectorABI || TT.isOSzOS())
     Ret += "-v128:64";
 
   // We prefer 16 bits of aligned for all globals; see above.
diff --git a/llvm/unittests/IR/ManglerTest.cpp b/llvm/unittests/IR/ManglerTest.cpp
--- a/llvm/unittests/IR/ManglerTest.cpp
+++ b/llvm/unittests/IR/ManglerTest.cpp
@@ -156,4 +156,22 @@
             "L..foo");
 }
 
+TEST(ManglerTest, GOFF) {
+  LLVMContext Ctx;
+  DataLayout DL("m:l"); // GOFF
+  Module Mod("test", Ctx);
+  Mod.setDataLayout(DL);
+  Mangler Mang;
+
+  EXPECT_EQ(mangleStr("foo", Mang, DL), "foo");
+  EXPECT_EQ(mangleStr("\01foo", Mang, DL), "foo");
+  EXPECT_EQ(mangleStr("?foo", Mang, DL), "?foo");
+  EXPECT_EQ(mangleFunc("foo", llvm::GlobalValue::ExternalLinkage,
+                       llvm::CallingConv::C, Mod, Mang),
+            "foo");
+  EXPECT_EQ(mangleFunc("foo", llvm::GlobalValue::PrivateLinkage,
+                       llvm::CallingConv::C, Mod, Mang),
+            ".Lfoo");
+}
+
 } // end anonymous namespace