Index: llvm/include/llvm/Transforms/IPO/IROutliner.h
===================================================================
--- llvm/include/llvm/Transforms/IPO/IROutliner.h
+++ llvm/include/llvm/Transforms/IPO/IROutliner.h
@@ -202,6 +202,10 @@
                                     std::vector<Function *> &FuncsToRemove,
                                     unsigned &OutlinedFunctionNum);
 
+  /// If true, enables us to outline from functions that have LinkOnceFromODR
+  /// linkages.
+  bool OutlineFromLinkODRs = false;
+
   /// The set of outlined Instructions, identified by their location in the
   /// sequential ordering of instructions in a Module.
   DenseSet<unsigned> Outlined;
Index: llvm/lib/Transforms/IPO/IROutliner.cpp
===================================================================
--- llvm/lib/Transforms/IPO/IROutliner.cpp
+++ llvm/lib/Transforms/IPO/IROutliner.cpp
@@ -29,6 +29,16 @@
 using namespace llvm;
 using namespace IRSimilarity;
 
+// Set to true if the user wants the ir outliner to run on linkonceodr linkage
+// functions. This is false by default because the linker can dedupe linkonceodr
+// functions. Since the outliner is confined to a single module (modulo LTO),
+// this is off by default. It should, however, be the default behavior in
+// LTO.
+static cl::opt<bool> EnableLinkOnceODRIROutlining(
+    "enable-linkonceodr-ir-outlining", cl::Hidden,
+    cl::desc("Enable the IR outliner on linkonceodr functions"),
+    cl::init(false));
+
 /// The OutlinableGroup holds all the overarching information for outlining
 /// a set of regions that are structurally similar to one another, such as the
 /// types of the overall function, the output blocks, the sets of stores needed
@@ -607,6 +617,10 @@
     if (IRSC.getStartBB()->hasAddressTaken())
       continue;
 
+    if (IRSC.front()->Inst->getFunction()->hasLinkOnceODRLinkage() &&
+        !OutlineFromLinkODRs)
+      continue;
+
     // Greedily prune out any regions that will overlap with already chosen
     // regions.
     if (CurrentEndIdx != 0 && StartIdx <= CurrentEndIdx)
@@ -776,7 +790,11 @@
   return OutlinedFunctionNum;
 }
 
-bool IROutliner::run(Module &M) { return doOutline(M) > 0; }
+bool IROutliner::run(Module &M) {
+  OutlineFromLinkODRs = EnableLinkOnceODRIROutlining;
+
+  return doOutline(M) > 0;
+}
 
 // Pass Manager Boilerplate
 class IROutlinerLegacyPass : public ModulePass {
Index: llvm/test/Transforms/IROutliner/outlining-odr.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/IROutliner/outlining-odr.ll
@@ -0,0 +1,70 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -verify -iroutliner < %s | FileCheck %s
+; RUN: opt -S -verify -iroutliner -enable-linkonceodr-ir-outlining < %s | FileCheck -check-prefix=ODR %s
+
+; This test looks at the constants in the regions, and if it they are the
+; same it outlines them as constants rather than elevating them to arguments.
+
+define linkonce_odr void @outline_odr1() {
+; ODR-LABEL: @outline_odr1(
+; ODR-NEXT:  entry:
+; ODR-NEXT:    [[A:%.*]] = alloca i32, align 4
+; ODR-NEXT:    [[B:%.*]] = alloca i32, align 4
+; ODR-NEXT:    [[C:%.*]] = alloca i32, align 4
+; ODR-NEXT:    call void @outlined_ir_func_0(i32* [[A]], i32* [[B]], i32* [[C]])
+; ODR-NEXT:    ret void
+; CHECK-LABEL: @outline_odr1(
+; 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 i32 2, i32* [[A]], align 4
+; CHECK-NEXT:    store i32 3, i32* [[B]], align 4
+; CHECK-NEXT:    store i32 4, i32* [[C]], align 4
+; CHECK-NEXT:    [[AL:%.*]] = load i32, i32* [[A]], align 4
+; CHECK-NEXT:    [[BL:%.*]] = load i32, i32* [[B]], align 4
+; CHECK-NEXT:    [[CL:%.*]] = load i32, i32* [[C]], align 4
+entry:
+  %a = alloca i32, align 4
+  %b = alloca i32, align 4
+  %c = alloca i32, align 4
+  store i32 2, i32* %a, align 4
+  store i32 3, i32* %b, align 4
+  store i32 4, i32* %c, align 4
+  %al = load i32, i32* %a
+  %bl = load i32, i32* %b
+  %cl = load i32, i32* %c
+  ret void
+}
+
+define void @outline_odr2() {
+; ODR-LABEL: @outline_odr2(
+; ODR-NEXT:  entry:
+; ODR-NEXT:    [[A:%.*]] = alloca i32, align 4
+; ODR-NEXT:    [[B:%.*]] = alloca i32, align 4
+; ODR-NEXT:    [[C:%.*]] = alloca i32, align 4
+; ODR-NEXT:    call void @outlined_ir_func_0(i32* [[A]], i32* [[B]], i32* [[C]])
+; ODR-NEXT:    ret void
+; CHECK-LABEL: @outline_odr2(
+; 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 i32 2, i32* [[A]], align 4
+; CHECK-NEXT:    store i32 3, i32* [[B]], align 4
+; CHECK-NEXT:    store i32 4, i32* [[C]], align 4
+; CHECK-NEXT:    [[AL:%.*]] = load i32, i32* [[A]], align 4
+; CHECK-NEXT:    [[BL:%.*]] = load i32, i32* [[B]], align 4
+; CHECK-NEXT:    [[CL:%.*]] = load i32, i32* [[C]], align 4
+entry:
+  %a = alloca i32, align 4
+  %b = alloca i32, align 4
+  %c = alloca i32, align 4
+  store i32 2, i32* %a, align 4
+  store i32 3, i32* %b, align 4
+  store i32 4, i32* %c, align 4
+  %al = load i32, i32* %a
+  %bl = load i32, i32* %b
+  %cl = load i32, i32* %c
+  ret void
+}