Index: lib/Analysis/ConstantFolding.cpp
===================================================================
--- lib/Analysis/ConstantFolding.cpp
+++ lib/Analysis/ConstantFolding.cpp
@@ -1379,6 +1379,7 @@
   case Intrinsic::fma:
   case Intrinsic::fmuladd:
   case Intrinsic::copysign:
+  case Intrinsic::invariant_group_barrier:
   case Intrinsic::round:
   case Intrinsic::masked_load:
   case Intrinsic::sadd_with_overflow:
@@ -1769,7 +1770,14 @@
 
     if (isa<UndefValue>(Operands[0])) {
       if (IntrinsicID == Intrinsic::bswap ||
-          IntrinsicID == Intrinsic::bitreverse)
+          IntrinsicID == Intrinsic::bitreverse ||
+          IntrinsicID == Intrinsic::invariant_group_barrier)
+        return Operands[0];
+      return nullptr;
+    }
+
+    if (isa<ConstantPointerNull>(Operands[0])) {
+      if (IntrinsicID == Intrinsic::invariant_group_barrier)
         return Operands[0];
       return nullptr;
     }
Index: test/Transforms/InstCombine/invariant.group.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/invariant.group.ll
@@ -0,0 +1,17 @@
+; RUN: opt  -instcombine -S < %s | FileCheck %s
+
+; CHECK-LABEL: define i8* @siplifyNullBarrier()
+define i8* @siplifyNullBarrier() {
+; CHECK-NEXT: ret i8* null
+  %b2 = call i8* @llvm.invariant.group.barrier(i8* null)
+  ret i8* %b2
+}
+
+; CHECK-LABEL: define i8* @siplifyUndefBarrier()
+define i8* @siplifyUndefBarrier() {
+; CHECK-NEXT: ret i8* undef
+  %b2 = call i8* @llvm.invariant.group.barrier(i8* undef)
+  ret i8* %b2
+}
+
+declare i8* @llvm.invariant.group.barrier(i8*)