Index: llvm/lib/Transforms/IPO/IROutliner.cpp
===================================================================
--- llvm/lib/Transforms/IPO/IROutliner.cpp
+++ llvm/lib/Transforms/IPO/IROutliner.cpp
@@ -58,6 +58,10 @@
   /// index in ArgumentTypes is an output argument.
   unsigned NumAggregateInputs = 0;
 
+  /// The argument that needs to be marked with the swifterr attribute.  If not
+  /// needed, there is no value.
+  Optional<unsigned> SwiftErrorArgument;
+
   /// For the \ref Regions, we look at every Value.  If it is a constant,
   /// we check whether it is the same in Region.
   ///
@@ -277,6 +281,11 @@
       Group.OutlinedFunctionType, GlobalValue::InternalLinkage,
       "outlined_ir_func_" + std::to_string(FunctionNameSuffix), M);
 
+  // Transfer the swifterr attribute to the correct function parameter.
+  if (Group.SwiftErrorArgument.hasValue())
+    Group.OutlinedFunction->addParamAttr(Group.SwiftErrorArgument.getValue(),
+                                         Attribute::SwiftError);
+
   Group.OutlinedFunction->addFnAttr(Attribute::OptimizeForSize);
   Group.OutlinedFunction->addFnAttr(Attribute::MinSize);
 
@@ -421,15 +430,24 @@
     assert(InputOpt.hasValue() && "Global value number not found?");
     Value *Input = InputOpt.getValue();
 
-    if (!Group.InputTypesSet)
-      Group.ArgumentTypes.push_back(Input->getType());
-
     // It is not a constant, check if it is a sunken alloca.  If it is not,
     // create the mapping from extracted to overall.  If it is, create the
     // mapping of the index to the value.
     unsigned Found = ArgInputs.count(Input);
     assert(Found && "Input cannot be found!");
 
+    if (!Group.InputTypesSet) {
+      Group.ArgumentTypes.push_back(Input->getType());
+      // If the input value has a swifterr attribute, make sure to mark the
+      // argument in the overall function.
+      if (Input->isSwiftError()) {
+        assert(
+            !Group.SwiftErrorArgument.hasValue() &&
+            "Argument already marked with swifterr for this OutlinableGroup!");
+        Group.SwiftErrorArgument = TypeIndex;
+      }
+    }
+
     Region.ExtractedArgToAgg.insert(std::make_pair(OriginalIndex, TypeIndex));
     Region.AggArgToExtracted.insert(std::make_pair(TypeIndex, OriginalIndex));
     OriginalIndex++;
@@ -489,7 +507,15 @@
 
   LLVM_DEBUG(dbgs() << "Replace call to " << *Call << " with call to "
                     << *AggFunc << " with same number of arguments\n");
+
   Call->setCalledFunction(AggFunc);
+
+  // Make sure that the argument in the new function has the SwiftError
+  // argument.
+  if (Group.SwiftErrorArgument.hasValue())
+    Call->addParamAttr(Group.SwiftErrorArgument.getValue(),
+                       Attribute::SwiftError);
+
   return Call;
 }
 
Index: llvm/test/Transforms/IROutliner/outlining-swift-error.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/IROutliner/outlining-swift-error.ll
@@ -0,0 +1,48 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -verify -iroutliner < %s | FileCheck %s
+
+%swift.error = type opaque
+
+define void @outlining_swifterror1(%swift.error** swifterror %err) {
+; CHECK-LABEL: @outlining_swifterror1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[X:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[TMP0:%.*]] = mul i64 5, 5
+; CHECK-NEXT:    call void @outlined_ir_func_0(i64 [[TMP0]], i64* [[X]], %swift.error** swifterror [[ERR:%.*]])
+; CHECK-NEXT:    ret void
+;
+entry:
+  %x = alloca i64
+  %0 = mul i64 5, 5
+  %1 = add i64 %0, %0
+  store i64 %1, i64* %x
+  %casted = bitcast i64* %x to %swift.error*
+  store %swift.error* %casted, %swift.error** %err
+  ret void
+}
+
+define void @outlining_swifterror2(%swift.error** swifterror %err) {
+; CHECK-LABEL: @outlining_swifterror2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[X:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[TMP0:%.*]] = mul i64 3, 3
+; CHECK-NEXT:    call void @outlined_ir_func_0(i64 [[TMP0]], i64* [[X]], %swift.error** swifterror [[ERR:%.*]])
+; CHECK-NEXT:    ret void
+;
+entry:
+  %x = alloca i64
+  %0 = mul i64 3, 3
+  %1 = add i64 %0, %0
+  store i64 %1, i64* %x
+  %casted = bitcast i64* %x to %swift.error*
+  store %swift.error* %casted, %swift.error** %err
+  ret void
+}
+
+; CHECK: define internal void @outlined_ir_func_0(i64 [[ARG0:%.*]], i64* [[ARG1:%.*]], %swift.error** swifterror [[ARG2:%.*]])
+; CHECK: entry_to_outline:
+; CHECK-NEXT:  [[TMP0:%.*]] = add i64 [[ARG0]], [[ARG0]]
+; CHECK-NEXT:  store i64 [[TMP0]], i64* [[ARG1]], align 4
+; CHECK-NEXT:  %casted = bitcast i64* [[ARG1]] to %swift.error*
+; CHECK-NEXT:  store %swift.error* %casted, %swift.error** [[ARG2]], align 8
+; CHECK-NEXT:  br label %entry_after_outline.exitStub