diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/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; }
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
--- a/clang/lib/AST/ASTContext.cpp
+++ b/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:
diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/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;
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
@@ -40,6 +40,7 @@
     TLSSupported = true;
     IntWidth = IntAlign = 32;
     LongWidth = LongLongWidth = LongAlign = LongLongAlign = 64;
+    Int128Align = 64;
     PointerWidth = PointerAlign = 64;
     LongDoubleWidth = 128;
     LongDoubleAlign = 64;
diff --git a/clang/test/CodeGen/SystemZ/align-systemz.c b/clang/test/CodeGen/SystemZ/align-systemz.c
--- a/clang/test/CodeGen/SystemZ/align-systemz.c
+++ b/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
-
diff --git a/clang/test/CodeGen/SystemZ/systemz-abi.c b/clang/test/CodeGen/SystemZ/systemz-abi.c
--- a/clang/test/CodeGen/SystemZ/systemz-abi.c
+++ b/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 %{{.*}})
diff --git a/clang/test/CodeGen/SystemZ/zos-alignment.c b/clang/test/CodeGen/SystemZ/zos-alignment.c
--- a/clang/test/CodeGen/SystemZ/zos-alignment.c
+++ b/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;
diff --git a/llvm/test/CodeGen/SystemZ/unaligned-02.ll b/llvm/test/CodeGen/SystemZ/unaligned-02.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/unaligned-02.ll
@@ -0,0 +1,13 @@
+; Check that an unaligned i128 access get the correct alignment added.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -stop-after=pre-isel-intrinsic-lowering \
+; RUN:   | FileCheck %s
+
+define void @f1(ptr %ptr) {
+; CHECK:       define void @f1(ptr %ptr) {
+; CHECK-NEXT:    store i128 0, ptr %ptr, align 8
+; CHECK-NEXT:    ret void
+; CHECK-NEXT:  }
+  store i128 0, ptr %ptr
+  ret void
+}