diff --git a/clang/include/clang/Basic/BuiltinsPPC.def b/clang/include/clang/Basic/BuiltinsPPC.def
--- a/clang/include/clang/Basic/BuiltinsPPC.def
+++ b/clang/include/clang/Basic/BuiltinsPPC.def
@@ -45,6 +45,8 @@
 BUILTIN(__builtin_ppc_dcbtst, "vv*", "")
 BUILTIN(__builtin_ppc_dcbz, "vv*", "")
 BUILTIN(__builtin_ppc_icbt, "vv*", "")
+BUILTIN(__builtin_ppc_compare_and_swap, "iiD*i*i", "")
+BUILTIN(__builtin_ppc_compare_and_swaplp, "iLiD*Li*Li", "")
 
 BUILTIN(__builtin_ppc_get_timebase, "ULLi", "n")
 
diff --git a/clang/lib/Basic/Targets/PPC.cpp b/clang/lib/Basic/Targets/PPC.cpp
--- a/clang/lib/Basic/Targets/PPC.cpp
+++ b/clang/lib/Basic/Targets/PPC.cpp
@@ -97,6 +97,9 @@
   Builder.defineMacro("__dcbtst", "__builtin_ppc_dcbtst");
   Builder.defineMacro("__dcbz", "__builtin_ppc_dcbz");
   Builder.defineMacro("__icbt", "__builtin_ppc_icbt");
+  Builder.defineMacro("__compare_and_swap", "__builtin_ppc_compare_and_swap");
+  Builder.defineMacro("__compare_and_swaplp",
+                      "__builtin_ppc_compare_and_swaplp");
 }
 
 /// PPCTargetInfo::getTargetDefines - Return a set of the PowerPC-specific
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -15427,6 +15427,18 @@
     Value *Call = Builder.CreateCall(F, CallOps);
     return Builder.CreateAlignedStore(Call, Ops[0], MaybeAlign(64));
   }
+
+  case PPC::BI__builtin_ppc_compare_and_swap:
+  case PPC::BI__builtin_ppc_compare_and_swaplp:
+    Address Addr = EmitPointerWithAlignment(E->getArg(0));
+    Address OldValAddr = EmitPointerWithAlignment(E->getArg(1));
+    Value *OldVal = Builder.CreateLoad(OldValAddr);
+    QualType AtomicTy = E->getArg(0)->getType()->getPointeeType();
+    LValue LV = MakeAddrLValue(Addr, AtomicTy);
+    auto Pair = EmitAtomicCompareExchange(
+        LV, RValue::get(OldVal), RValue::get(Ops[2]), E->getExprLoc(),
+        llvm::AtomicOrdering::Monotonic, llvm::AtomicOrdering::Monotonic, true);
+    return Pair.second;
   }
 }
 
diff --git a/clang/test/CodeGen/builtins-ppc-xlcompat-cas-error.c b/clang/test/CodeGen/builtins-ppc-xlcompat-cas-error.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/builtins-ppc-xlcompat-cas-error.c
@@ -0,0 +1,19 @@
+// REQUIRES: powerpc-registered-target
+// RUN: %clang_cc1 -triple powerpc64-unknown-aix -target-cpu pwr8 \
+// RUN:   -verify %s
+
+void test_builtin_ppc_compare_and_swap() {
+  volatile int a = 0;
+  long b = 0, c = 0;
+
+  __compare_and_swap(&a, &b, c); // expected-warning {{incompatible pointer types passing 'long *' to parameter of type 'int *'}}
+
+}
+
+void test_builtin_ppc_compare_and_swaplp() {
+  volatile long a = 0;
+  int b = 0, c = 0;
+
+  __compare_and_swaplp(&a, &b, c);// expected-warning {{incompatible pointer types passing 'int *' to parameter of type 'long *'}}
+
+}
diff --git a/clang/test/CodeGen/builtins-ppc-xlcompat-cas.c b/clang/test/CodeGen/builtins-ppc-xlcompat-cas.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/builtins-ppc-xlcompat-cas.c
@@ -0,0 +1,52 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// REQUIRES: powerpc-registered-target
+// RUN: %clang_cc1 -triple powerpc64-unknown-unknown \
+// RUN:    -emit-llvm %s -o -  -target-cpu pwr8 | FileCheck %s
+// RUN: %clang_cc1 -triple powerpc64le-unknown-unknown \
+// RUN:   -emit-llvm %s -o -  -target-cpu pwr8 | FileCheck %s
+
+// CHECK-LABEL: @test_builtin_ppc_compare_and_swap(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[B:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[C:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store volatile i32 0, i32* [[A]], align 4
+// CHECK-NEXT:    store i32 0, i32* [[B]], align 4
+// CHECK-NEXT:    store i32 0, i32* [[C]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* [[C]], align 4
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* [[B]], align 4
+// CHECK-NEXT:    [[TMP2:%.*]] = cmpxchg weak volatile i32* [[A]], i32 [[TMP1]], i32 [[TMP0]] monotonic monotonic, align 4
+// CHECK-NEXT:    [[TMP3:%.*]] = extractvalue { i32, i1 } [[TMP2]], 0
+// CHECK-NEXT:    [[TMP4:%.*]] = extractvalue { i32, i1 } [[TMP2]], 1
+// CHECK-NEXT:    ret void
+//
+void test_builtin_ppc_compare_and_swap() {
+  volatile int a = 0;
+  int b = 0, c = 0;
+
+  __compare_and_swap(&a, &b, c);
+
+}
+
+// CHECK-LABEL: @test_builtin_ppc_compare_and_swaplp(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[B:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[C:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    store volatile i64 0, i64* [[A]], align 8
+// CHECK-NEXT:    store i64 0, i64* [[B]], align 8
+// CHECK-NEXT:    store i64 0, i64* [[C]], align 8
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, i64* [[C]], align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = load i64, i64* [[B]], align 8
+// CHECK-NEXT:    [[TMP2:%.*]] = cmpxchg weak volatile i64* [[A]], i64 [[TMP1]], i64 [[TMP0]] monotonic monotonic, align 8
+// CHECK-NEXT:    [[TMP3:%.*]] = extractvalue { i64, i1 } [[TMP2]], 0
+// CHECK-NEXT:    [[TMP4:%.*]] = extractvalue { i64, i1 } [[TMP2]], 1
+// CHECK-NEXT:    ret void
+//
+void test_builtin_ppc_compare_and_swaplp() {
+  volatile long a = 0;
+  long b = 0, c = 0;
+
+  __compare_and_swaplp(&a, &b, c);
+
+}