Index: clang/include/clang/Basic/TargetInfo.h
===================================================================
--- clang/include/clang/Basic/TargetInfo.h
+++ clang/include/clang/Basic/TargetInfo.h
@@ -78,6 +78,7 @@
   unsigned char LargeArrayMinWidth, LargeArrayAlign;
   unsigned char LongWidth, LongAlign;
   unsigned char LongLongWidth, LongLongAlign;
+  unsigned char Int128Align;
 
   // Fixed point bit widths
   unsigned char ShortAccumWidth, ShortAccumAlign;
@@ -470,6 +471,9 @@
   unsigned getLongLongWidth() const { return LongLongWidth; }
   unsigned getLongLongAlign() const { return LongLongAlign; }
 
+  /// getInt128Align() - Returns the alignment of Int128.
+  unsigned getInt128Align() const { return Int128Align; }
+
   /// getShortAccumWidth/Align - Return the size of 'signed short _Accum' and
   /// 'unsigned short _Accum' for this target, in bits.
   unsigned getShortAccumWidth() const { return ShortAccumWidth; }
Index: clang/lib/AST/ASTContext.cpp
===================================================================
--- clang/lib/AST/ASTContext.cpp
+++ clang/lib/AST/ASTContext.cpp
@@ -2082,7 +2082,7 @@
     case BuiltinType::Int128:
     case BuiltinType::UInt128:
       Width = 128;
-      Align = 128; // int128_t is 128-bit aligned on all targets.
+      Align = Target->getInt128Align();
       break;
     case BuiltinType::ShortAccum:
     case BuiltinType::UShortAccum:
Index: clang/lib/Basic/TargetInfo.cpp
===================================================================
--- clang/lib/Basic/TargetInfo.cpp
+++ clang/lib/Basic/TargetInfo.cpp
@@ -45,6 +45,7 @@
   IntWidth = IntAlign = 32;
   LongWidth = LongAlign = 32;
   LongLongWidth = LongLongAlign = 64;
+  Int128Align = 128;
 
   // Fixed point default bit widths
   ShortAccumWidth = ShortAccumAlign = 16;
Index: clang/lib/Basic/Targets/SystemZ.h
===================================================================
--- clang/lib/Basic/Targets/SystemZ.h
+++ clang/lib/Basic/Targets/SystemZ.h
@@ -40,6 +40,7 @@
     TLSSupported = true;
     IntWidth = IntAlign = 32;
     LongWidth = LongLongWidth = LongAlign = LongLongAlign = 64;
+    Int128Align = 64;
     PointerWidth = PointerAlign = 64;
     LongDoubleWidth = 128;
     LongDoubleAlign = 64;
@@ -54,9 +55,9 @@
       // - 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");
+          "E-m:l-i1:8:16-i8:8:16-i64:64-i128:64-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");
+      resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-i128:64-f128:64-a:8:16-n32:64");
     MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
     HasStrictFP = true;
   }
@@ -173,7 +174,7 @@
     // If we use the vector ABI, vector types are 64-bit aligned.
     if (HasVector && !getTriple().isOSzOS()) {
       MaxVectorAlign = 64;
-      resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64"
+      resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-i128:64-f128:64"
                       "-v128:64-a:8:16-n32:64");
     }
     return true;
Index: clang/test/CodeGen/SystemZ/align-systemz.c
===================================================================
--- clang/test/CodeGen/SystemZ/align-systemz.c
+++ clang/test/CodeGen/SystemZ/align-systemz.c
@@ -26,6 +26,14 @@
 }
 
 
+// The SystemZ ABI aligns __int128_t to only eight bytes.
+
+struct S_int128 {  __int128_t B; } Obj_I128;
+__int128_t GlobI128;
+// CHECK: @Obj_I128 = global %struct.S_int128 zeroinitializer, align 8
+// CHECK: @GlobI128 = global i128 0, align 8
+
+
 // Alignment should be respected for coerced argument loads
 
 struct arg { long y __attribute__((packed, aligned(4))); };
@@ -40,4 +48,3 @@
 
 // CHECK-LABEL: @test
 // CHECK: load i64, i64* getelementptr inbounds (%struct.arg, %struct.arg* @x, i32 0, i32 0), align 4
-
Index: clang/test/CodeGen/SystemZ/systemz-abi.c
===================================================================
--- clang/test/CodeGen/SystemZ/systemz-abi.c
+++ clang/test/CodeGen/SystemZ/systemz-abi.c
@@ -43,7 +43,7 @@
 // CHECK-LABEL: define{{.*}} i64 @pass_longlong(i64 %{{.*}})
 
 __int128 pass_int128(__int128 arg) { return arg; }
-// CHECK-LABEL: define{{.*}} void @pass_int128(i128* noalias sret(i128) align 16 %{{.*}}, i128* %0)
+// CHECK-LABEL: define{{.*}} void @pass_int128(i128* noalias sret(i128) align 8 %{{.*}}, i128* %0)
 
 float pass_float(float arg) { return arg; }
 // CHECK-LABEL: define{{.*}} float @pass_float(float %{{.*}})
Index: clang/test/CodeGen/SystemZ/zos-alignment.c
===================================================================
--- clang/test/CodeGen/SystemZ/zos-alignment.c
+++ clang/test/CodeGen/SystemZ/zos-alignment.c
@@ -160,6 +160,13 @@
 // CHECK-NEXT:         8 |   char b
 // CHECK-NEXT:           | [sizeof=16, align=8]
 
+struct s12 {
+  __int128_t a;
+} S12;
+// CHECK:              0 | struct s12
+// CHECK-NEXT:         0 |   __int128_t a
+// CHECK-NEXT:           | [sizeof=16, align=8]
+
 union u0 {
   unsigned short d1 __attribute__((packed));
   int d2 : 10;
Index: clang/test/CodeGen/target-data.c
===================================================================
--- clang/test/CodeGen/target-data.c
+++ clang/test/CodeGen/target-data.c
@@ -223,11 +223,11 @@
 // RUN: FileCheck %s -check-prefix=SYSTEMZ
 // RUN: %clang_cc1 -triple s390x-unknown -target-cpu z13 -target-feature +soft-float -o - -emit-llvm %s | \
 // RUN: FileCheck %s -check-prefix=SYSTEMZ
-// SYSTEMZ: target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64"
+// SYSTEMZ: target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-i128:64-f128:64-a:8:16-n32:64"
 
 // RUN: %clang_cc1 -triple s390x-unknown -target-cpu z13 -o - -emit-llvm %s | \
 // 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"
+// SYSTEMZ-VECTOR: target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-i128:64-f128:64-v128:64-a:8:16-n32:64"
 
 // RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z10 -o - -emit-llvm %s | \
 // RUN: FileCheck %s -check-prefix=ZOS
@@ -235,7 +235,7 @@
 // RUN: FileCheck %s -check-prefix=ZOS
 // RUN: %clang_cc1 -triple s390x-none-zos -target-cpu z13 -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"
+// ZOS: target datalayout = "E-m:l-i1:8:16-i8:8:16-i64:64-i128:64-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
Index: llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
===================================================================
--- llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
+++ llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
@@ -89,6 +89,9 @@
   // 64-bit integers are naturally aligned.
   Ret += "-i64:64";
 
+  // 128-bit integers are aligned only to 64 bits.
+  Ret += "-i128:64";
+
   // 128-bit floats are aligned only to 64 bits.
   Ret += "-f128:64";