4 files changed, 67 insertions, 31 deletions

diff --git a/include/llvm/Target/TargetInstrInfo.h b/include/llvm/Target/TargetInstrInfo.h
index ecdd682..0635c23 100644
--- a/include/llvm/Target/TargetInstrInfo.h
+++ b/include/llvm/Target/TargetInstrInfo.h
@@ -194,13 +194,11 @@ public:
   virtual MachineInstr *commuteInstruction(MachineInstr *MI,
                                            bool NewMI = false) const = 0;
 
-  /// CommuteChangesDestination - Return true if commuting the specified
-  /// instruction will also changes the destination operand. Also return the
-  /// current operand index of the would be new destination register by
-  /// reference. This can happen when the commutable instruction is also a
-  /// two-address instruction.
-  virtual bool CommuteChangesDestination(MachineInstr *MI,
-                                         unsigned &OpIdx) const = 0;
+  /// findCommutedOpIndices - If specified MI is commutable, return the two
+  /// operand indices that would swap value. Return true if the instruction
+  /// is not in a form which this routine understands.
+  virtual bool findCommutedOpIndices(MachineInstr *MI, unsigned &SrcOpIdx1,
+                                     unsigned &SrcOpIdx2) const = 0;
 
   /// AnalyzeBranch - Analyze the branching code at the end of MBB, returning
   /// true if it cannot be understood (e.g. it's a switch dispatch or isn't
@@ -495,8 +493,8 @@ protected:
 public:
   virtual MachineInstr *commuteInstruction(MachineInstr *MI,
                                            bool NewMI = false) const;
-  virtual bool CommuteChangesDestination(MachineInstr *MI,
-                                         unsigned &OpIdx) const;
+  virtual bool findCommutedOpIndices(MachineInstr *MI, unsigned &SrcOpIdx1,
+                                     unsigned &SrcOpIdx2) const;
   virtual bool PredicateInstruction(MachineInstr *MI,
                             const SmallVectorImpl<MachineOperand> &Pred) const;
   virtual void reMaterialize(MachineBasicBlock &MBB,
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 48e6d45..d1523f8 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -312,9 +312,23 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
     return false;
   MachineInstr *DefMI = li_->getInstructionFromIndex(AValNo->def);
   const TargetInstrDesc &TID = DefMI->getDesc();
-  unsigned NewDstIdx;
-  if (!TID.isCommutable() ||
-      !tii_->CommuteChangesDestination(DefMI, NewDstIdx))
+  if (!TID.isCommutable())
+    return false;
+  // If DefMI is a two-address instruction then commuting it will change the
+  // destination register.
+  int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
+  assert(DefIdx != -1);
+  unsigned UseOpIdx;
+  if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
+    return false;
+  unsigned Op1, Op2, NewDstIdx;
+  if (!tii_->findCommutedOpIndices(DefMI, Op1, Op2))
+    return false;
+  if (Op1 == UseOpIdx)
+    NewDstIdx = Op2;
+  else if (Op2 == UseOpIdx)
+    NewDstIdx = Op1;
+  else
     return false;
 
   MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
diff --git a/lib/CodeGen/TargetInstrInfoImpl.cpp b/lib/CodeGen/TargetInstrInfoImpl.cpp
index b759599..b9a6040 100644
--- a/lib/CodeGen/TargetInstrInfoImpl.cpp
+++ b/lib/CodeGen/TargetInstrInfoImpl.cpp
@@ -70,26 +70,24 @@ MachineInstr *TargetInstrInfoImpl::commuteInstruction(MachineInstr *MI,
   return MI;
 }
 
-/// CommuteChangesDestination - Return true if commuting the specified
-/// instruction will also changes the destination operand. Also return the
-/// current operand index of the would be new destination register by
-/// reference. This can happen when the commutable instruction is also a
-/// two-address instruction.
-bool TargetInstrInfoImpl::CommuteChangesDestination(MachineInstr *MI,
-                                                    unsigned &OpIdx) const{
+/// findCommutedOpIndices - If specified MI is commutable, return the two
+/// operand indices that would swap value. Return true if the instruction
+/// is not in a form which this routine understands.
+bool TargetInstrInfoImpl::findCommutedOpIndices(MachineInstr *MI,
+                                                unsigned &SrcOpIdx1,
+                                                unsigned &SrcOpIdx2) const {
   const TargetInstrDesc &TID = MI->getDesc();
-  if (!TID.getNumDefs())
+  if (!TID.isCommutable())
     return false;
-  assert(MI->getOperand(1).isReg() && MI->getOperand(2).isReg() &&
-         "This only knows how to commute register operands so far");
-  if (MI->getOperand(0).getReg() == MI->getOperand(1).getReg()) {
-    // Must be two address instruction!
-    assert(MI->getDesc().getOperandConstraint(0, TOI::TIED_TO) &&
-           "Expecting a two-address instruction!");
-    OpIdx = 2;
-    return true;
-  }
-  return false;
+  // This assumes v0 = op v1, v2 and commuting would swap v1 and v2. If this
+  // is not true, then the target must implement this.
+  SrcOpIdx1 = TID.getNumDefs();
+  SrcOpIdx2 = SrcOpIdx1 + 1;
+  if (!MI->getOperand(SrcOpIdx1).isReg() ||
+      !MI->getOperand(SrcOpIdx2).isReg())
+    // No idea.
+    return false;
+  return true;
 }
 
 
diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index be0b016..48558fe 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -1157,6 +1157,32 @@ private:
     return false;
   }
 
+  /// CommuteChangesDestination - We are looking for r0 = op r1, r2 and
+  /// where SrcReg is r1 and it is tied to r0. Return true if after
+  /// commuting this instruction it will be r0 = op r2, r1.
+  static bool CommuteChangesDestination(MachineInstr *DefMI,
+                                        const TargetInstrDesc &TID,
+                                        unsigned SrcReg,
+                                        const TargetInstrInfo *TII,
+                                        unsigned &DstIdx) {
+    if (TID.getNumDefs() != 1 && TID.getNumOperands() != 3)
+      return false;
+    if (!DefMI->getOperand(1).isReg() ||
+        DefMI->getOperand(1).getReg() != SrcReg)
+      return false;
+    unsigned DefIdx;
+    if (!DefMI->isRegTiedToDefOperand(1, &DefIdx) || DefIdx != 0)
+      return false;
+    unsigned SrcIdx1, SrcIdx2;
+    if (!TII->findCommutedOpIndices(DefMI, SrcIdx1, SrcIdx2))
+      return false;
+    if (SrcIdx1 == 1 && SrcIdx2 == 2) {
+      DstIdx = 2;
+      return true;
+    }
+    return false;
+  }
+
   /// CommuteToFoldReload -
   /// Look for
   /// r1 = load fi#1
@@ -1185,7 +1211,7 @@ private:
     unsigned NewDstIdx;
     if (DefMII != MBB.begin() &&
         TID.isCommutable() &&
-        TII->CommuteChangesDestination(DefMI, NewDstIdx)) {
+        CommuteChangesDestination(DefMI, TID, SrcReg, TII, NewDstIdx)) {
       MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
       unsigned NewReg = NewDstMO.getReg();
       if (!NewDstMO.isKill() || TRI->regsOverlap(NewReg, SrcReg))