[PowerPC] Put PPCVSXFMAMutate into its own source file
authorHal Finkel <hfinkel@anl.gov>
Sun, 1 Feb 2015 21:51:22 +0000 (21:51 +0000)
committerHal Finkel <hfinkel@anl.gov>
Sun, 1 Feb 2015 21:51:22 +0000 (21:51 +0000)
PPCInstrInfo.cpp has ended up containing several small MI-level passes, and
this is making the file harder to read than necessary. Split out
PPCVSXFMAMutate into its own source file. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227770 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/CMakeLists.txt
lib/Target/PowerPC/PPCInstrInfo.cpp
lib/Target/PowerPC/PPCVSXFMAMutate.cpp [new file with mode: 0644]

index 47a9474ae16134b293af50b719fed77bdf5210ef..b7f2412e8049663de2f16565a9bb6e2aae0daac7 100644 (file)
@@ -30,6 +30,7 @@ add_llvm_target(PowerPCCodeGen
   PPCTargetObjectFile.cpp
   PPCTargetTransformInfo.cpp
   PPCSelectionDAGInfo.cpp
+  PPCVSXFMAMutate.cpp
   )
 
 add_subdirectory(AsmParser)
index b844f63c86f7609d4a4a7199e1c97e803160322b..a0370a0f069362a67ae549cd97a2837ca44c96a6 100644 (file)
@@ -52,9 +52,6 @@ opt<bool> DisableCTRLoopAnal("disable-ppc-ctrloop-analysis", cl::Hidden,
 static cl::opt<bool> DisableCmpOpt("disable-ppc-cmp-opt",
 cl::desc("Disable compare instruction optimization"), cl::Hidden);
 
-static cl::opt<bool> DisableVSXFMAMutate("disable-ppc-vsx-fma-mutation",
-cl::desc("Disable VSX FMA instruction mutation"), cl::Hidden);
-
 static cl::opt<bool> VSXSelfCopyCrash("crash-on-ppc-vsx-self-copy",
 cl::desc("Causes the backend to crash instead of generating a nop VSX copy"),
 cl::Hidden);
@@ -1608,294 +1605,6 @@ unsigned PPCInstrInfo::GetInstSizeInBytes(const MachineInstr *MI) const {
   }
 }
 
-#undef DEBUG_TYPE
-#define DEBUG_TYPE "ppc-vsx-fma-mutate"
-
-namespace {
-  // PPCVSXFMAMutate pass - For copies between VSX registers and non-VSX registers
-  // (Altivec and scalar floating-point registers), we need to transform the
-  // copies into subregister copies with other restrictions.
-  struct PPCVSXFMAMutate : public MachineFunctionPass {
-    static char ID;
-    PPCVSXFMAMutate() : MachineFunctionPass(ID) {
-      initializePPCVSXFMAMutatePass(*PassRegistry::getPassRegistry());
-    }
-
-    LiveIntervals *LIS;
-    const PPCInstrInfo *TII;
-
-protected:
-    bool processBlock(MachineBasicBlock &MBB) {
-      bool Changed = false;
-
-      MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
-      const TargetRegisterInfo *TRI = &TII->getRegisterInfo();
-      for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
-           I != IE; ++I) {
-        MachineInstr *MI = I;
-
-        // The default (A-type) VSX FMA form kills the addend (it is taken from
-        // the target register, which is then updated to reflect the result of
-        // the FMA). If the instruction, however, kills one of the registers
-        // used for the product, then we can use the M-form instruction (which
-        // will take that value from the to-be-defined register).
-
-        int AltOpc = PPC::getAltVSXFMAOpcode(MI->getOpcode());
-        if (AltOpc == -1)
-          continue;
-
-        // This pass is run after register coalescing, and so we're looking for
-        // a situation like this:
-        //   ...
-        //   %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
-        //   %vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
-        //                         %RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
-        //   ...
-        //   %vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
-        //                         %RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
-        //   ...
-        // Where we can eliminate the copy by changing from the A-type to the
-        // M-type instruction. Specifically, for this example, this means:
-        //   %vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
-        //                         %RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
-        // is replaced by:
-        //   %vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
-        //                         %RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
-        // and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
-
-        SlotIndex FMAIdx = LIS->getInstructionIndex(MI);
-
-        VNInfo *AddendValNo =
-          LIS->getInterval(MI->getOperand(1).getReg()).Query(FMAIdx).valueIn();
-        MachineInstr *AddendMI = LIS->getInstructionFromIndex(AddendValNo->def);
-
-        // The addend and this instruction must be in the same block.
-
-        if (!AddendMI || AddendMI->getParent() != MI->getParent())
-          continue;
-
-        // The addend must be a full copy within the same register class.
-
-        if (!AddendMI->isFullCopy())
-          continue;
-
-        unsigned AddendSrcReg = AddendMI->getOperand(1).getReg();
-        if (TargetRegisterInfo::isVirtualRegister(AddendSrcReg)) {
-          if (MRI.getRegClass(AddendMI->getOperand(0).getReg()) !=
-              MRI.getRegClass(AddendSrcReg))
-            continue;
-        } else {
-          // If AddendSrcReg is a physical register, make sure the destination
-          // register class contains it.
-          if (!MRI.getRegClass(AddendMI->getOperand(0).getReg())
-                ->contains(AddendSrcReg))
-            continue;
-        }
-
-        // In theory, there could be other uses of the addend copy before this
-        // fma.  We could deal with this, but that would require additional
-        // logic below and I suspect it will not occur in any relevant
-        // situations.  Additionally, check whether the copy source is killed
-        // prior to the fma.  In order to replace the addend here with the
-        // source of the copy, it must still be live here.  We can't use
-        // interval testing for a physical register, so as long as we're
-        // walking the MIs we may as well test liveness here.
-        bool OtherUsers = false, KillsAddendSrc = false;
-        for (auto J = std::prev(I), JE = MachineBasicBlock::iterator(AddendMI);
-             J != JE; --J) {
-          if (J->readsVirtualRegister(AddendMI->getOperand(0).getReg())) {
-            OtherUsers = true;
-            break;
-          }
-          if (J->modifiesRegister(AddendSrcReg, TRI) ||
-              J->killsRegister(AddendSrcReg, TRI)) {
-            KillsAddendSrc = true;
-            break;
-          }
-        }
-
-        if (OtherUsers || KillsAddendSrc)
-          continue;
-
-        // Find one of the product operands that is killed by this instruction.
-
-        unsigned KilledProdOp = 0, OtherProdOp = 0;
-        if (LIS->getInterval(MI->getOperand(2).getReg())
-                     .Query(FMAIdx).isKill()) {
-          KilledProdOp = 2;
-          OtherProdOp  = 3;
-        } else if (LIS->getInterval(MI->getOperand(3).getReg())
-                     .Query(FMAIdx).isKill()) {
-          KilledProdOp = 3;
-          OtherProdOp  = 2;
-        }
-
-        // If there are no killed product operands, then this transformation is
-        // likely not profitable.
-        if (!KilledProdOp)
-          continue;
-
-        // For virtual registers, verify that the addend source register
-        // is live here (as should have been assured above).
-        assert((!TargetRegisterInfo::isVirtualRegister(AddendSrcReg) ||
-                LIS->getInterval(AddendSrcReg).liveAt(FMAIdx)) &&
-               "Addend source register is not live!");
-
-        // Transform: (O2 * O3) + O1 -> (O2 * O1) + O3.
-
-        unsigned AddReg = AddendMI->getOperand(1).getReg();
-        unsigned KilledProdReg = MI->getOperand(KilledProdOp).getReg();
-        unsigned OtherProdReg  = MI->getOperand(OtherProdOp).getReg();
-
-        unsigned AddSubReg = AddendMI->getOperand(1).getSubReg();
-        unsigned KilledProdSubReg = MI->getOperand(KilledProdOp).getSubReg();
-        unsigned OtherProdSubReg  = MI->getOperand(OtherProdOp).getSubReg();
-
-        bool AddRegKill = AddendMI->getOperand(1).isKill();
-        bool KilledProdRegKill = MI->getOperand(KilledProdOp).isKill();
-        bool OtherProdRegKill  = MI->getOperand(OtherProdOp).isKill();
-
-        bool AddRegUndef = AddendMI->getOperand(1).isUndef();
-        bool KilledProdRegUndef = MI->getOperand(KilledProdOp).isUndef();
-        bool OtherProdRegUndef  = MI->getOperand(OtherProdOp).isUndef();
-
-        unsigned OldFMAReg = MI->getOperand(0).getReg();
-
-        // The transformation doesn't work well with things like:
-        //    %vreg5 = A-form-op %vreg5, %vreg11, %vreg5;
-        // so leave such things alone.
-        if (OldFMAReg == KilledProdReg)
-          continue;
-
-        assert(OldFMAReg == AddendMI->getOperand(0).getReg() &&
-               "Addend copy not tied to old FMA output!");
-
-        DEBUG(dbgs() << "VSX FMA Mutation:\n    " << *MI;);
-
-        MI->getOperand(0).setReg(KilledProdReg);
-        MI->getOperand(1).setReg(KilledProdReg);
-        MI->getOperand(3).setReg(AddReg);
-        MI->getOperand(2).setReg(OtherProdReg);
-
-        MI->getOperand(0).setSubReg(KilledProdSubReg);
-        MI->getOperand(1).setSubReg(KilledProdSubReg);
-        MI->getOperand(3).setSubReg(AddSubReg);
-        MI->getOperand(2).setSubReg(OtherProdSubReg);
-
-        MI->getOperand(1).setIsKill(KilledProdRegKill);
-        MI->getOperand(3).setIsKill(AddRegKill);
-        MI->getOperand(2).setIsKill(OtherProdRegKill);
-
-        MI->getOperand(1).setIsUndef(KilledProdRegUndef);
-        MI->getOperand(3).setIsUndef(AddRegUndef);
-        MI->getOperand(2).setIsUndef(OtherProdRegUndef);
-
-        MI->setDesc(TII->get(AltOpc));
-
-        DEBUG(dbgs() << " -> " << *MI);
-
-        // The killed product operand was killed here, so we can reuse it now
-        // for the result of the fma.
-
-        LiveInterval &FMAInt = LIS->getInterval(OldFMAReg);
-        VNInfo *FMAValNo = FMAInt.getVNInfoAt(FMAIdx.getRegSlot());
-        for (auto UI = MRI.reg_nodbg_begin(OldFMAReg), UE = MRI.reg_nodbg_end();
-             UI != UE;) {
-          MachineOperand &UseMO = *UI;
-          MachineInstr *UseMI = UseMO.getParent();
-          ++UI;
-
-          // Don't replace the result register of the copy we're about to erase.
-          if (UseMI == AddendMI)
-            continue;
-
-          UseMO.setReg(KilledProdReg);
-          UseMO.setSubReg(KilledProdSubReg);
-        }
-
-        // Extend the live intervals of the killed product operand to hold the
-        // fma result.
-
-        LiveInterval &NewFMAInt = LIS->getInterval(KilledProdReg);
-        for (LiveInterval::iterator AI = FMAInt.begin(), AE = FMAInt.end();
-             AI != AE; ++AI) {
-          // Don't add the segment that corresponds to the original copy.
-          if (AI->valno == AddendValNo)
-            continue;
-
-          VNInfo *NewFMAValNo =
-            NewFMAInt.getNextValue(AI->start,
-                                   LIS->getVNInfoAllocator());
-
-          NewFMAInt.addSegment(LiveInterval::Segment(AI->start, AI->end,
-                                                     NewFMAValNo));
-        }
-        DEBUG(dbgs() << "  extended: " << NewFMAInt << '\n');
-
-        FMAInt.removeValNo(FMAValNo);
-        DEBUG(dbgs() << "  trimmed:  " << FMAInt << '\n');
-
-        // Remove the (now unused) copy.
-
-        DEBUG(dbgs() << "  removing: " << *AddendMI << '\n');
-        LIS->RemoveMachineInstrFromMaps(AddendMI);
-        AddendMI->eraseFromParent();
-
-        Changed = true;
-      }
-
-      return Changed;
-    }
-
-public:
-    bool runOnMachineFunction(MachineFunction &MF) override {
-      // If we don't have VSX then go ahead and return without doing
-      // anything.
-      const PPCSubtarget &STI = MF.getSubtarget<PPCSubtarget>();
-      if (!STI.hasVSX())
-        return false;
-
-      LIS = &getAnalysis<LiveIntervals>();
-
-      TII = STI.getInstrInfo();
-
-      bool Changed = false;
-
-      if (DisableVSXFMAMutate)
-        return Changed;
-
-      for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
-        MachineBasicBlock &B = *I++;
-        if (processBlock(B))
-          Changed = true;
-      }
-
-      return Changed;
-    }
-
-    void getAnalysisUsage(AnalysisUsage &AU) const override {
-      AU.addRequired<LiveIntervals>();
-      AU.addPreserved<LiveIntervals>();
-      AU.addRequired<SlotIndexes>();
-      AU.addPreserved<SlotIndexes>();
-      MachineFunctionPass::getAnalysisUsage(AU);
-    }
-  };
-}
-
-INITIALIZE_PASS_BEGIN(PPCVSXFMAMutate, DEBUG_TYPE,
-                      "PowerPC VSX FMA Mutation", false, false)
-INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
-INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
-INITIALIZE_PASS_END(PPCVSXFMAMutate, DEBUG_TYPE,
-                    "PowerPC VSX FMA Mutation", false, false)
-
-char &llvm::PPCVSXFMAMutateID = PPCVSXFMAMutate::ID;
-
-char PPCVSXFMAMutate::ID = 0;
-FunctionPass*
-llvm::createPPCVSXFMAMutatePass() { return new PPCVSXFMAMutate(); }
-
 #undef DEBUG_TYPE
 #define DEBUG_TYPE "ppc-vsx-copy"
 
diff --git a/lib/Target/PowerPC/PPCVSXFMAMutate.cpp b/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
new file mode 100644 (file)
index 0000000..e047d95
--- /dev/null
@@ -0,0 +1,336 @@
+//===--------------- PPCVSXFMAMutate.cpp - VSX FMA Mutation ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass mutates the form of VSX FMA instructions to avoid unnecessary
+// copies.
+//
+//===----------------------------------------------------------------------===//
+
+#include "PPCInstrInfo.h"
+#include "MCTargetDesc/PPCPredicates.h"
+#include "PPC.h"
+#include "PPCInstrBuilder.h"
+#include "PPCMachineFunctionInfo.h"
+#include "PPCTargetMachine.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineMemOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/PseudoSourceValue.h"
+#include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/CodeGen/SlotIndexes.h"
+#include "llvm/CodeGen/StackMaps.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+static cl::opt<bool> DisableVSXFMAMutate("disable-ppc-vsx-fma-mutation",
+cl::desc("Disable VSX FMA instruction mutation"), cl::Hidden);
+
+#define DEBUG_TYPE "ppc-vsx-fma-mutate"
+
+namespace llvm { namespace PPC {
+  int getAltVSXFMAOpcode(uint16_t Opcode);
+} }
+
+namespace {
+  // PPCVSXFMAMutate pass - For copies between VSX registers and non-VSX registers
+  // (Altivec and scalar floating-point registers), we need to transform the
+  // copies into subregister copies with other restrictions.
+  struct PPCVSXFMAMutate : public MachineFunctionPass {
+    static char ID;
+    PPCVSXFMAMutate() : MachineFunctionPass(ID) {
+      initializePPCVSXFMAMutatePass(*PassRegistry::getPassRegistry());
+    }
+
+    LiveIntervals *LIS;
+    const PPCInstrInfo *TII;
+
+protected:
+    bool processBlock(MachineBasicBlock &MBB) {
+      bool Changed = false;
+
+      MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+      const TargetRegisterInfo *TRI = &TII->getRegisterInfo();
+      for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
+           I != IE; ++I) {
+        MachineInstr *MI = I;
+
+        // The default (A-type) VSX FMA form kills the addend (it is taken from
+        // the target register, which is then updated to reflect the result of
+        // the FMA). If the instruction, however, kills one of the registers
+        // used for the product, then we can use the M-form instruction (which
+        // will take that value from the to-be-defined register).
+
+        int AltOpc = PPC::getAltVSXFMAOpcode(MI->getOpcode());
+        if (AltOpc == -1)
+          continue;
+
+        // This pass is run after register coalescing, and so we're looking for
+        // a situation like this:
+        //   ...
+        //   %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
+        //   %vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
+        //                         %RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
+        //   ...
+        //   %vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
+        //                         %RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
+        //   ...
+        // Where we can eliminate the copy by changing from the A-type to the
+        // M-type instruction. Specifically, for this example, this means:
+        //   %vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
+        //                         %RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
+        // is replaced by:
+        //   %vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
+        //                         %RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
+        // and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
+
+        SlotIndex FMAIdx = LIS->getInstructionIndex(MI);
+
+        VNInfo *AddendValNo =
+          LIS->getInterval(MI->getOperand(1).getReg()).Query(FMAIdx).valueIn();
+        MachineInstr *AddendMI = LIS->getInstructionFromIndex(AddendValNo->def);
+
+        // The addend and this instruction must be in the same block.
+
+        if (!AddendMI || AddendMI->getParent() != MI->getParent())
+          continue;
+
+        // The addend must be a full copy within the same register class.
+
+        if (!AddendMI->isFullCopy())
+          continue;
+
+        unsigned AddendSrcReg = AddendMI->getOperand(1).getReg();
+        if (TargetRegisterInfo::isVirtualRegister(AddendSrcReg)) {
+          if (MRI.getRegClass(AddendMI->getOperand(0).getReg()) !=
+              MRI.getRegClass(AddendSrcReg))
+            continue;
+        } else {
+          // If AddendSrcReg is a physical register, make sure the destination
+          // register class contains it.
+          if (!MRI.getRegClass(AddendMI->getOperand(0).getReg())
+                ->contains(AddendSrcReg))
+            continue;
+        }
+
+        // In theory, there could be other uses of the addend copy before this
+        // fma.  We could deal with this, but that would require additional
+        // logic below and I suspect it will not occur in any relevant
+        // situations.  Additionally, check whether the copy source is killed
+        // prior to the fma.  In order to replace the addend here with the
+        // source of the copy, it must still be live here.  We can't use
+        // interval testing for a physical register, so as long as we're
+        // walking the MIs we may as well test liveness here.
+        bool OtherUsers = false, KillsAddendSrc = false;
+        for (auto J = std::prev(I), JE = MachineBasicBlock::iterator(AddendMI);
+             J != JE; --J) {
+          if (J->readsVirtualRegister(AddendMI->getOperand(0).getReg())) {
+            OtherUsers = true;
+            break;
+          }
+          if (J->modifiesRegister(AddendSrcReg, TRI) ||
+              J->killsRegister(AddendSrcReg, TRI)) {
+            KillsAddendSrc = true;
+            break;
+          }
+        }
+
+        if (OtherUsers || KillsAddendSrc)
+          continue;
+
+        // Find one of the product operands that is killed by this instruction.
+
+        unsigned KilledProdOp = 0, OtherProdOp = 0;
+        if (LIS->getInterval(MI->getOperand(2).getReg())
+                     .Query(FMAIdx).isKill()) {
+          KilledProdOp = 2;
+          OtherProdOp  = 3;
+        } else if (LIS->getInterval(MI->getOperand(3).getReg())
+                     .Query(FMAIdx).isKill()) {
+          KilledProdOp = 3;
+          OtherProdOp  = 2;
+        }
+
+        // If there are no killed product operands, then this transformation is
+        // likely not profitable.
+        if (!KilledProdOp)
+          continue;
+
+        // For virtual registers, verify that the addend source register
+        // is live here (as should have been assured above).
+        assert((!TargetRegisterInfo::isVirtualRegister(AddendSrcReg) ||
+                LIS->getInterval(AddendSrcReg).liveAt(FMAIdx)) &&
+               "Addend source register is not live!");
+
+        // Transform: (O2 * O3) + O1 -> (O2 * O1) + O3.
+
+        unsigned AddReg = AddendMI->getOperand(1).getReg();
+        unsigned KilledProdReg = MI->getOperand(KilledProdOp).getReg();
+        unsigned OtherProdReg  = MI->getOperand(OtherProdOp).getReg();
+
+        unsigned AddSubReg = AddendMI->getOperand(1).getSubReg();
+        unsigned KilledProdSubReg = MI->getOperand(KilledProdOp).getSubReg();
+        unsigned OtherProdSubReg  = MI->getOperand(OtherProdOp).getSubReg();
+
+        bool AddRegKill = AddendMI->getOperand(1).isKill();
+        bool KilledProdRegKill = MI->getOperand(KilledProdOp).isKill();
+        bool OtherProdRegKill  = MI->getOperand(OtherProdOp).isKill();
+
+        bool AddRegUndef = AddendMI->getOperand(1).isUndef();
+        bool KilledProdRegUndef = MI->getOperand(KilledProdOp).isUndef();
+        bool OtherProdRegUndef  = MI->getOperand(OtherProdOp).isUndef();
+
+        unsigned OldFMAReg = MI->getOperand(0).getReg();
+
+        // The transformation doesn't work well with things like:
+        //    %vreg5 = A-form-op %vreg5, %vreg11, %vreg5;
+        // so leave such things alone.
+        if (OldFMAReg == KilledProdReg)
+          continue;
+
+        assert(OldFMAReg == AddendMI->getOperand(0).getReg() &&
+               "Addend copy not tied to old FMA output!");
+
+        DEBUG(dbgs() << "VSX FMA Mutation:\n    " << *MI;);
+
+        MI->getOperand(0).setReg(KilledProdReg);
+        MI->getOperand(1).setReg(KilledProdReg);
+        MI->getOperand(3).setReg(AddReg);
+        MI->getOperand(2).setReg(OtherProdReg);
+
+        MI->getOperand(0).setSubReg(KilledProdSubReg);
+        MI->getOperand(1).setSubReg(KilledProdSubReg);
+        MI->getOperand(3).setSubReg(AddSubReg);
+        MI->getOperand(2).setSubReg(OtherProdSubReg);
+
+        MI->getOperand(1).setIsKill(KilledProdRegKill);
+        MI->getOperand(3).setIsKill(AddRegKill);
+        MI->getOperand(2).setIsKill(OtherProdRegKill);
+
+        MI->getOperand(1).setIsUndef(KilledProdRegUndef);
+        MI->getOperand(3).setIsUndef(AddRegUndef);
+        MI->getOperand(2).setIsUndef(OtherProdRegUndef);
+
+        MI->setDesc(TII->get(AltOpc));
+
+        DEBUG(dbgs() << " -> " << *MI);
+
+        // The killed product operand was killed here, so we can reuse it now
+        // for the result of the fma.
+
+        LiveInterval &FMAInt = LIS->getInterval(OldFMAReg);
+        VNInfo *FMAValNo = FMAInt.getVNInfoAt(FMAIdx.getRegSlot());
+        for (auto UI = MRI.reg_nodbg_begin(OldFMAReg), UE = MRI.reg_nodbg_end();
+             UI != UE;) {
+          MachineOperand &UseMO = *UI;
+          MachineInstr *UseMI = UseMO.getParent();
+          ++UI;
+
+          // Don't replace the result register of the copy we're about to erase.
+          if (UseMI == AddendMI)
+            continue;
+
+          UseMO.setReg(KilledProdReg);
+          UseMO.setSubReg(KilledProdSubReg);
+        }
+
+        // Extend the live intervals of the killed product operand to hold the
+        // fma result.
+
+        LiveInterval &NewFMAInt = LIS->getInterval(KilledProdReg);
+        for (LiveInterval::iterator AI = FMAInt.begin(), AE = FMAInt.end();
+             AI != AE; ++AI) {
+          // Don't add the segment that corresponds to the original copy.
+          if (AI->valno == AddendValNo)
+            continue;
+
+          VNInfo *NewFMAValNo =
+            NewFMAInt.getNextValue(AI->start,
+                                   LIS->getVNInfoAllocator());
+
+          NewFMAInt.addSegment(LiveInterval::Segment(AI->start, AI->end,
+                                                     NewFMAValNo));
+        }
+        DEBUG(dbgs() << "  extended: " << NewFMAInt << '\n');
+
+        FMAInt.removeValNo(FMAValNo);
+        DEBUG(dbgs() << "  trimmed:  " << FMAInt << '\n');
+
+        // Remove the (now unused) copy.
+
+        DEBUG(dbgs() << "  removing: " << *AddendMI << '\n');
+        LIS->RemoveMachineInstrFromMaps(AddendMI);
+        AddendMI->eraseFromParent();
+
+        Changed = true;
+      }
+
+      return Changed;
+    }
+
+public:
+    bool runOnMachineFunction(MachineFunction &MF) override {
+      // If we don't have VSX then go ahead and return without doing
+      // anything.
+      const PPCSubtarget &STI = MF.getSubtarget<PPCSubtarget>();
+      if (!STI.hasVSX())
+        return false;
+
+      LIS = &getAnalysis<LiveIntervals>();
+
+      TII = STI.getInstrInfo();
+
+      bool Changed = false;
+
+      if (DisableVSXFMAMutate)
+        return Changed;
+
+      for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
+        MachineBasicBlock &B = *I++;
+        if (processBlock(B))
+          Changed = true;
+      }
+
+      return Changed;
+    }
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addRequired<LiveIntervals>();
+      AU.addPreserved<LiveIntervals>();
+      AU.addRequired<SlotIndexes>();
+      AU.addPreserved<SlotIndexes>();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  };
+}
+
+INITIALIZE_PASS_BEGIN(PPCVSXFMAMutate, DEBUG_TYPE,
+                      "PowerPC VSX FMA Mutation", false, false)
+INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
+INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
+INITIALIZE_PASS_END(PPCVSXFMAMutate, DEBUG_TYPE,
+                    "PowerPC VSX FMA Mutation", false, false)
+
+char &llvm::PPCVSXFMAMutateID = PPCVSXFMAMutate::ID;
+
+char PPCVSXFMAMutate::ID = 0;
+FunctionPass*
+llvm::createPPCVSXFMAMutatePass() { return new PPCVSXFMAMutate(); }
+
+