diff --git a/lib/Target/R600/SIInstrInfo.cpp b/lib/Target/R600/SIInstrInfo.cpp
index eb8d38cd184..691e108442b 100644
--- a/lib/Target/R600/SIInstrInfo.cpp
+++ b/lib/Target/R600/SIInstrInfo.cpp
@@ -779,6 +779,12 @@ bool SIInstrInfo::findCommutedOpIndices(MachineInstr *MI,
   if (!MI->getOperand(Src1Idx).isReg())
     return false;
 
+  // If any source modifiers are set, the generic instruction commuting won't
+  // understand how to copy the source modifiers.
+  if (hasModifiersSet(*MI, AMDGPU::OpName::src0_modifiers) ||
+      hasModifiersSet(*MI, AMDGPU::OpName::src1_modifiers))
+    return false;
+
   SrcOpIdx1 = Src0Idx;
   SrcOpIdx2 = Src1Idx;
   return true;
@@ -982,6 +988,12 @@ bool SIInstrInfo::hasModifiers(unsigned Opcode) const {
                                     AMDGPU::OpName::src0_modifiers) != -1;
 }
 
+bool SIInstrInfo::hasModifiersSet(const MachineInstr &MI,
+                                  unsigned OpName) const {
+  const MachineOperand *Mods = getNamedOperand(MI, OpName);
+  return Mods && Mods->getImm();
+}
+
 bool SIInstrInfo::usesConstantBus(const MachineRegisterInfo &MRI,
                                   const MachineOperand &MO) const {
   // Literal constants use the constant bus.
@@ -2300,7 +2312,7 @@ void SIInstrInfo::reserveIndirectRegisters(BitVector &Reserved,
 }
 
 MachineOperand *SIInstrInfo::getNamedOperand(MachineInstr &MI,
-                                                   unsigned OperandName) const {
+                                             unsigned OperandName) const {
   int Idx = AMDGPU::getNamedOperandIdx(MI.getOpcode(), OperandName);
   if (Idx == -1)
     return nullptr;
diff --git a/lib/Target/R600/SIInstrInfo.h b/lib/Target/R600/SIInstrInfo.h
index f2edd8cc2c1..5c5d8476235 100644
--- a/lib/Target/R600/SIInstrInfo.h
+++ b/lib/Target/R600/SIInstrInfo.h
@@ -151,6 +151,10 @@ public:
   /// \brief Return true if this instruction has any modifiers.
   ///  e.g. src[012]_mod, omod, clamp.
   bool hasModifiers(unsigned Opcode) const;
+
+  bool hasModifiersSet(const MachineInstr &MI,
+                       unsigned OpName) const;
+
   bool verifyInstruction(const MachineInstr *MI,
                          StringRef &ErrInfo) const override;
 
@@ -231,6 +235,11 @@ public:
   /// \brief Returns the operand named \p Op.  If \p MI does not have an
   /// operand named \c Op, this function returns nullptr.
   MachineOperand *getNamedOperand(MachineInstr &MI, unsigned OperandName) const;
+
+  const MachineOperand *getNamedOperand(const MachineInstr &MI,
+                                        unsigned OpName) const {
+    return getNamedOperand(const_cast<MachineInstr &>(MI), OpName);
+  }
 };
 
 namespace AMDGPU {