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[oota-llvm.git] / lib / CodeGen / TwoAddressInstructionPass.cpp

diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index aca85b2aa17daefc081eb31fa2fdd15d4cb5067e..7ca2beef65155989c437e0336d5cafae807580ef 100644 (file)
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -43,11 +43,11 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/IR/Function.h"
 #include "llvm/MC/MCInstrItineraries.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
-#include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 using namespace llvm;
 
@@ -59,6 +59,12 @@ STATISTIC(Num3AddrSunk,        "Number of 3-address instructions sunk");
 STATISTIC(NumReSchedUps,       "Number of instructions re-scheduled up");
 STATISTIC(NumReSchedDowns,     "Number of instructions re-scheduled down");
 
+// Temporary flag to disable rescheduling.
+static cl::opt<bool>
+EnableRescheduling("twoaddr-reschedule",
+                   cl::desc("Coalesce copies by rescheduling (default=true)"),
+                   cl::init(true), cl::Hidden);
+
 namespace {
 class TwoAddressInstructionPass : public MachineFunctionPass {
   MachineFunction *MF;
@@ -120,7 +126,7 @@ class TwoAddressInstructionPass : public MachineFunctionPass {
   bool tryInstructionTransform(MachineBasicBlock::iterator &mi,
                                MachineBasicBlock::iterator &nmi,
                                unsigned SrcIdx, unsigned DstIdx,
-                               unsigned Dist);
+                               unsigned Dist, bool shouldOnlyCommute);
 
   void scanUses(unsigned DstReg);
 
@@ -427,10 +433,7 @@ static bool isKilled(MachineInstr &MI, unsigned Reg,
 /// isTwoAddrUse - Return true if the specified MI uses the specified register
 /// as a two-address use. If so, return the destination register by reference.
 static bool isTwoAddrUse(MachineInstr &MI, unsigned Reg, unsigned &DstReg) {
-  const MCInstrDesc &MCID = MI.getDesc();
-  unsigned NumOps = MI.isInlineAsm()
-    ? MI.getNumOperands() : MCID.getNumOperands();
-  for (unsigned i = 0; i != NumOps; ++i) {
+  for (unsigned i = 0, NumOps = MI.getNumOperands(); i != NumOps; ++i) {
     const MachineOperand &MO = MI.getOperand(i);
     if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg)
       continue;
@@ -581,19 +584,9 @@ commuteInstruction(MachineBasicBlock::iterator &mi,
   }
 
   DEBUG(dbgs() << "2addr: COMMUTED TO: " << *NewMI);
-  // If the instruction changed to commute it, update livevar.
-  if (NewMI != MI) {
-    if (LV)
-      // Update live variables
-      LV->replaceKillInstruction(RegC, MI, NewMI);
-    if (LIS)
-      LIS->ReplaceMachineInstrInMaps(MI, NewMI);
-
-    MBB->insert(mi, NewMI);           // Insert the new inst
-    MBB->erase(mi);                   // Nuke the old inst.
-    mi = NewMI;
-    DistanceMap.insert(std::make_pair(NewMI, Dist));
-  }
+  assert(NewMI == MI &&
+         "TargetInstrInfo::commuteInstruction() should not return a new "
+         "instruction unless it was requested.");
 
   // Update source register map.
   unsigned FromRegC = getMappedReg(RegC, SrcRegMap);
@@ -1095,11 +1088,13 @@ rescheduleKillAboveMI(MachineBasicBlock::iterator &mi,
 /// either eliminate the tied operands or improve the opportunities for
 /// coalescing away the register copy.  Returns true if no copy needs to be
 /// inserted to untie mi's operands (either because they were untied, or
-/// because mi was rescheduled, and will be visited again later).
+/// because mi was rescheduled, and will be visited again later). If the
+/// shouldOnlyCommute flag is true, only instruction commutation is attempted.
 bool TwoAddressInstructionPass::
 tryInstructionTransform(MachineBasicBlock::iterator &mi,
                         MachineBasicBlock::iterator &nmi,
-                        unsigned SrcIdx, unsigned DstIdx, unsigned Dist) {
+                        unsigned SrcIdx, unsigned DstIdx,
+                        unsigned Dist, bool shouldOnlyCommute) {
   if (OptLevel == CodeGenOpt::None)
     return false;
 
@@ -1148,9 +1143,12 @@ tryInstructionTransform(MachineBasicBlock::iterator &mi,
     return false;
   }
 
+  if (shouldOnlyCommute)
+    return false;
+
   // If there is one more use of regB later in the same MBB, consider
   // re-schedule this MI below it.
-  if (rescheduleMIBelowKill(mi, nmi, regB)) {
+  if (EnableRescheduling && rescheduleMIBelowKill(mi, nmi, regB)) {
     ++NumReSchedDowns;
     return true;
   }
@@ -1169,7 +1167,7 @@ tryInstructionTransform(MachineBasicBlock::iterator &mi,
 
   // If there is one more use of regB later in the same MBB, consider
   // re-schedule it before this MI if it's legal.
-  if (rescheduleKillAboveMI(mi, nmi, regB)) {
+  if (EnableRescheduling && rescheduleKillAboveMI(mi, nmi, regB)) {
     ++NumReSchedUps;
     return true;
   }
@@ -1223,10 +1221,12 @@ tryInstructionTransform(MachineBasicBlock::iterator &mi,
         unsigned NewDstIdx = NewMIs[1]->findRegisterDefOperandIdx(regA);
         unsigned NewSrcIdx = NewMIs[1]->findRegisterUseOperandIdx(regB);
         MachineBasicBlock::iterator NewMI = NewMIs[1];
-        bool TransformSuccess =
-          tryInstructionTransform(NewMI, mi, NewSrcIdx, NewDstIdx, Dist);
-        if (TransformSuccess ||
-            NewMIs[1]->getOperand(NewSrcIdx).isKill()) {
+        bool TransformResult =
+          tryInstructionTransform(NewMI, mi, NewSrcIdx, NewDstIdx, Dist, true);
+        (void)TransformResult;
+        assert(!TransformResult &&
+               "tryInstructionTransform() should return false.");
+        if (NewMIs[1]->getOperand(NewSrcIdx).isKill()) {
           // Success, or at least we made an improvement. Keep the unfolded
           // instructions and discard the original.
           if (LV) {
@@ -1277,8 +1277,6 @@ tryInstructionTransform(MachineBasicBlock::iterator &mi,
           }
 
           mi = NewMIs[1];
-          if (TransformSuccess)
-            return true;
         } else {
           // Transforming didn't eliminate the tie and didn't lead to an
           // improvement. Clean up the unfolded instructions and keep the
@@ -1549,7 +1547,7 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) {
           unsigned SrcReg = mi->getOperand(SrcIdx).getReg();
           unsigned DstReg = mi->getOperand(DstIdx).getReg();
           if (SrcReg != DstReg &&
-              tryInstructionTransform(mi, nmi, SrcIdx, DstIdx, Dist)) {
+              tryInstructionTransform(mi, nmi, SrcIdx, DstIdx, Dist, false)) {
             // The tied operands have been eliminated or shifted further down the
             // block to ease elimination. Continue processing with 'nmi'.
             TiedOperands.clear();