Index: include/llvm/CodeGen/GlobalISel/InstructionSelector.h
===================================================================
--- include/llvm/CodeGen/GlobalISel/InstructionSelector.h
+++ include/llvm/CodeGen/GlobalISel/InstructionSelector.h
@@ -361,20 +361,6 @@
                                      const TargetRegisterInfo &TRI,
                                      const RegisterBankInfo &RBI) const;
 
-  /// Mutate the newly-selected instruction \p I to constrain its (possibly
-  /// generic) virtual register operands to the instruction's register class.
-  /// This could involve inserting COPYs before (for uses) or after (for defs).
-  /// This requires the number of operands to match the instruction description.
-  /// \returns whether operand regclass constraining succeeded.
-  ///
-  // FIXME: Not all instructions have the same number of operands. We should
-  // probably expose a constrain helper per operand and let the target selector
-  // constrain individual registers, like fast-isel.
-  bool constrainSelectedInstRegOperands(MachineInstr &I,
-                                        const TargetInstrInfo &TII,
-                                        const TargetRegisterInfo &TRI,
-                                        const RegisterBankInfo &RBI) const;
-
   bool isOperandImmEqual(const MachineOperand &MO, int64_t Value,
                          const MachineRegisterInfo &MRI) const;
 
Index: include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
===================================================================
--- include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
+++ include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
@@ -19,6 +19,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
 #include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"
+#include "llvm/CodeGen/GlobalISel/Utils.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
Index: include/llvm/CodeGen/GlobalISel/Utils.h
===================================================================
--- include/llvm/CodeGen/GlobalISel/Utils.h
+++ include/llvm/CodeGen/GlobalISel/Utils.h
@@ -59,6 +59,19 @@
                                   MachineInstr &InsertPt, const MCInstrDesc &II,
                                   unsigned Reg, unsigned OpIdx);
 
+/// Mutate the newly-selected instruction \p I to constrain its (possibly
+/// generic) virtual register operands to the instruction's register class.
+/// This could involve inserting COPYs before (for uses) or after (for defs).
+/// This requires the number of operands to match the instruction description.
+/// \returns whether operand regclass constraining succeeded.
+///
+// FIXME: Not all instructions have the same number of operands. We should
+// probably expose a constrain helper per operand and let the target selector
+// constrain individual registers, like fast-isel.
+bool constrainSelectedInstRegOperands(MachineInstr &I,
+                                      const TargetInstrInfo &TII,
+                                      const TargetRegisterInfo &TRI,
+                                      const RegisterBankInfo &RBI);
 /// Check whether an instruction \p MI is dead: it only defines dead virtual
 /// registers, and doesn't have other side effects.
 bool isTriviallyDead(const MachineInstr &MI, const MachineRegisterInfo &MRI);
Index: include/llvm/CodeGen/MachineInstrBuilder.h
===================================================================
--- include/llvm/CodeGen/MachineInstrBuilder.h
+++ include/llvm/CodeGen/MachineInstrBuilder.h
@@ -20,6 +20,7 @@
 #define LLVM_CODEGEN_MACHINEINSTRBUILDER_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/CodeGen/GlobalISel/Utils.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstr.h"
@@ -283,6 +284,12 @@
     MI->copyImplicitOps(*MF, OtherMI);
     return *this;
   }
+
+  bool constrainAllUses(const TargetInstrInfo &TII,
+                        const TargetRegisterInfo &TRI,
+                        const RegisterBankInfo &RBI) const {
+    return constrainSelectedInstRegOperands(*MI, TII, TRI, RBI);
+  }
 };
 
 /// Builder interface. Specify how to create the initial instruction itself.
Index: lib/CodeGen/GlobalISel/InstructionSelector.cpp
===================================================================
--- lib/CodeGen/GlobalISel/InstructionSelector.cpp
+++ lib/CodeGen/GlobalISel/InstructionSelector.cpp
@@ -46,50 +46,6 @@
       constrainRegToClass(MRI, TII, RBI, I, I.getOperand(OpIdx).getReg(), RC);
 }
 
-bool InstructionSelector::constrainSelectedInstRegOperands(
-    MachineInstr &I, const TargetInstrInfo &TII, const TargetRegisterInfo &TRI,
-    const RegisterBankInfo &RBI) const {
-  MachineBasicBlock &MBB = *I.getParent();
-  MachineFunction &MF = *MBB.getParent();
-  MachineRegisterInfo &MRI = MF.getRegInfo();
-
-  for (unsigned OpI = 0, OpE = I.getNumExplicitOperands(); OpI != OpE; ++OpI) {
-    MachineOperand &MO = I.getOperand(OpI);
-
-    // There's nothing to be done on non-register operands.
-    if (!MO.isReg())
-      continue;
-
-    DEBUG(dbgs() << "Converting operand: " << MO << '\n');
-    assert(MO.isReg() && "Unsupported non-reg operand");
-
-    unsigned Reg = MO.getReg();
-    // Physical registers don't need to be constrained.
-    if (TRI.isPhysicalRegister(Reg))
-      continue;
-
-    // Register operands with a value of 0 (e.g. predicate operands) don't need
-    // to be constrained.
-    if (Reg == 0)
-      continue;
-
-    // If the operand is a vreg, we should constrain its regclass, and only
-    // insert COPYs if that's impossible.
-    // constrainOperandRegClass does that for us.
-    MO.setReg(constrainOperandRegClass(MF, TRI, MRI, TII, RBI, I, I.getDesc(),
-                                       Reg, OpI));
-
-    // Tie uses to defs as indicated in MCInstrDesc if this hasn't already been
-    // done.
-    if (MO.isUse()) {
-      int DefIdx = I.getDesc().getOperandConstraint(OpI, MCOI::TIED_TO);
-      if (DefIdx != -1 && !I.isRegTiedToUseOperand(DefIdx))
-        I.tieOperands(DefIdx, OpI);
-    }
-  }
-  return true;
-}
-
 bool InstructionSelector::isOperandImmEqual(
     const MachineOperand &MO, int64_t Value,
     const MachineRegisterInfo &MRI) const {
Index: lib/CodeGen/GlobalISel/Utils.cpp
===================================================================
--- lib/CodeGen/GlobalISel/Utils.cpp
+++ lib/CodeGen/GlobalISel/Utils.cpp
@@ -56,6 +56,51 @@
   return constrainRegToClass(MRI, TII, RBI, InsertPt, Reg, *RegClass);
 }
 
+bool llvm::constrainSelectedInstRegOperands(MachineInstr &I,
+                                            const TargetInstrInfo &TII,
+                                            const TargetRegisterInfo &TRI,
+                                            const RegisterBankInfo &RBI) {
+  MachineBasicBlock &MBB = *I.getParent();
+  MachineFunction &MF = *MBB.getParent();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+
+  for (unsigned OpI = 0, OpE = I.getNumExplicitOperands(); OpI != OpE; ++OpI) {
+    MachineOperand &MO = I.getOperand(OpI);
+
+    // There's nothing to be done on non-register operands.
+    if (!MO.isReg())
+      continue;
+
+    DEBUG(dbgs() << "Converting operand: " << MO << '\n');
+    assert(MO.isReg() && "Unsupported non-reg operand");
+
+    unsigned Reg = MO.getReg();
+    // Physical registers don't need to be constrained.
+    if (TRI.isPhysicalRegister(Reg))
+      continue;
+
+    // Register operands with a value of 0 (e.g. predicate operands) don't need
+    // to be constrained.
+    if (Reg == 0)
+      continue;
+
+    // If the operand is a vreg, we should constrain its regclass, and only
+    // insert COPYs if that's impossible.
+    // constrainOperandRegClass does that for us.
+    MO.setReg(constrainOperandRegClass(MF, TRI, MRI, TII, RBI, I, I.getDesc(),
+                                       Reg, OpI));
+
+    // Tie uses to defs as indicated in MCInstrDesc if this hasn't already been
+    // done.
+    if (MO.isUse()) {
+      int DefIdx = I.getDesc().getOperandConstraint(OpI, MCOI::TIED_TO);
+      if (DefIdx != -1 && !I.isRegTiedToUseOperand(DefIdx))
+        I.tieOperands(DefIdx, OpI);
+    }
+  }
+  return true;
+}
+
 bool llvm::isTriviallyDead(const MachineInstr &MI,
                            const MachineRegisterInfo &MRI) {
   // If we can move an instruction, we can remove it.  Otherwise, it has
Index: lib/Target/AArch64/AArch64InstructionSelector.cpp
===================================================================
--- lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -570,11 +570,11 @@
   else
     return false;
 
-  auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(CBOpc))
-                 .addUse(LHS)
-                 .addMBB(DestMBB);
+  BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(CBOpc))
+      .addUse(LHS)
+      .addMBB(DestMBB)
+      .constrainAllUses(TII, TRI, RBI);
 
-  constrainSelectedInstRegOperands(*MIB.getInstr(), TII, TRI, RBI);
   I.eraseFromParent();
   return true;
 }
Index: lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
+++ lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
@@ -17,6 +17,7 @@
 #include "AMDGPURegisterBankInfo.h"
 #include "AMDGPURegisterInfo.h"
 #include "AMDGPUSubtarget.h"
+#include "llvm/CodeGen/GlobalISel/Utils.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstr.h"