Index: llvm/trunk/include/llvm/CodeGen/MIRYamlMapping.h
===================================================================
--- llvm/trunk/include/llvm/CodeGen/MIRYamlMapping.h
+++ llvm/trunk/include/llvm/CodeGen/MIRYamlMapping.h
@@ -310,9 +310,11 @@
   UnsignedValue ID;
   StringValue Value;
   unsigned Alignment = 0;
+  bool IsTargetSpecific = false;
   bool operator==(const MachineConstantPoolValue &Other) const {
     return ID == Other.ID && Value == Other.Value &&
-           Alignment == Other.Alignment;
+           Alignment == Other.Alignment &&
+           IsTargetSpecific == Other.IsTargetSpecific;
   }
 };
 
@@ -321,6 +323,7 @@
     YamlIO.mapRequired("id", Constant.ID);
     YamlIO.mapOptional("value", Constant.Value, StringValue());
     YamlIO.mapOptional("alignment", Constant.Alignment, (unsigned)0);
+    YamlIO.mapOptional("isTargetSpecific", Constant.IsTargetSpecific, false);
   }
 };
 
Index: llvm/trunk/lib/CodeGen/MIRParser/MIRParser.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRParser/MIRParser.cpp
+++ llvm/trunk/lib/CodeGen/MIRParser/MIRParser.cpp
@@ -719,6 +719,10 @@
   const auto &M = *MF.getFunction()->getParent();
   SMDiagnostic Error;
   for (const auto &YamlConstant : YamlMF.Constants) {
+    if (YamlConstant.IsTargetSpecific)
+      // FIXME: Support target-specific constant pools
+      return error(YamlConstant.Value.SourceRange.Start,
+                   "Can't parse target-specific constant pool entries yet");
     const Constant *Value = dyn_cast_or_null<Constant>(
         parseConstantValue(YamlConstant.Value.Value, Error, M));
     if (!Value)
Index: llvm/trunk/lib/CodeGen/MIRPrinter.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRPrinter.cpp
+++ llvm/trunk/lib/CodeGen/MIRPrinter.cpp
@@ -458,17 +458,20 @@
                          const MachineConstantPool &ConstantPool) {
   unsigned ID = 0;
   for (const MachineConstantPoolEntry &Constant : ConstantPool.getConstants()) {
-    // TODO: Serialize target specific constant pool entries.
-    if (Constant.isMachineConstantPoolEntry())
-      llvm_unreachable("Can't print target specific constant pool entries yet");
-
-    yaml::MachineConstantPoolValue YamlConstant;
     std::string Str;
     raw_string_ostream StrOS(Str);
-    Constant.Val.ConstVal->printAsOperand(StrOS);
+    if (Constant.isMachineConstantPoolEntry()) {
+      Constant.Val.MachineCPVal->print(StrOS);
+    } else {
+      Constant.Val.ConstVal->printAsOperand(StrOS);
+    }
+
+    yaml::MachineConstantPoolValue YamlConstant;
     YamlConstant.ID = ID++;
     YamlConstant.Value = StrOS.str();
     YamlConstant.Alignment = Constant.getAlignment();
+    YamlConstant.IsTargetSpecific = Constant.isMachineConstantPoolEntry();
+
     MF.Constants.push_back(YamlConstant);
   }
 }
Index: llvm/trunk/test/CodeGen/MIR/ARM/target-constant-pools-error.mir
===================================================================
--- llvm/trunk/test/CodeGen/MIR/ARM/target-constant-pools-error.mir
+++ llvm/trunk/test/CodeGen/MIR/ARM/target-constant-pools-error.mir
@@ -0,0 +1,27 @@
+# RUN: not llc -mtriple arm-unknown -run-pass none -o /dev/null %s 2>&1 | FileCheck %s
+--- |
+  target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+  @g = private global i32 4
+  define void @target_constant_pool() { ret void }
+...
+---
+name:            target_constant_pool
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gpr, preferred-register: '' }
+  - { id: 1, class: gpr, preferred-register: '' }
+constants:
+  - id:              0
+  # CHECK: [[@LINE+1]]:22: Can't parse target-specific constant pool entries yet
+    value:           'g-(LPC0+8)'
+    alignment:       4
+    isTargetSpecific: true
+body:             |
+  bb.0.entry:
+    %0 = LDRi12 %const.0, 0, 14, _ :: (load 4 from constant-pool)
+    %1 = PICLDR killed %0, 0, 14, _ :: (dereferenceable load 4 from @g)
+    %r0 = COPY %1
+    BX_RET 14, _, implicit %r0
+
+...
Index: llvm/trunk/test/CodeGen/MIR/X86/constant-pool.mir
===================================================================
--- llvm/trunk/test/CodeGen/MIR/X86/constant-pool.mir
+++ llvm/trunk/test/CodeGen/MIR/X86/constant-pool.mir
@@ -46,9 +46,11 @@
 # CHECK-NEXT: - id: 0
 # CHECK-NEXT:   value: 'double 3.250000e+00'
 # CHECK-NEXT:   alignment: 8
+# CHECK-NEXT:   isTargetSpecific: false
 # CHECK-NEXT: - id: 1
 # CHECK-NEXT:   value: 'float 6.250000e+00'
 # CHECK-NEXT:   alignment: 4
+# CHECK-NEXT:   isTargetSpecific: false
 name:            test
 constants:
   - id:          0
@@ -74,9 +76,11 @@
 # CHECK-NEXT: - id: 0
 # CHECK-NEXT:   value: 'double 3.250000e+00'
 # CHECK-NEXT:   alignment: 8
+# CHECK-NEXT:   isTargetSpecific: false
 # CHECK-NEXT: - id: 1
 # CHECK-NEXT:   value: 'float 6.250000e+00'
 # CHECK-NEXT:   alignment: 4
+# CHECK-NEXT:   isTargetSpecific: false
 name:            test2
 constants:
   - id:          0
@@ -98,9 +102,11 @@
 # CHECK-NEXT: - id: 0
 # CHECK-NEXT:   value: 'double 3.250000e+00'
 # CHECK-NEXT:   alignment: 128
+# CHECK-NEXT:   isTargetSpecific: false
 # CHECK-NEXT: - id: 1
 # CHECK-NEXT:   value: 'float 6.250000e+00'
 # CHECK-NEXT:   alignment: 1
+# CHECK-NEXT:   isTargetSpecific: false
 name:            test3
 constants:
   - id:          0