Fix for PR1306.

- A register def / use now implicitly affects sub-register liveness but does
not affect liveness information of super-registers.
- Def of a larger register (if followed by a use later) is treated as
read/mod/write of a smaller register.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36434 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 200 insertions, 50 deletions

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 29d053910a..a42471d631 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -255,7 +255,7 @@ namespace llvm {
     /// handleLiveInRegister - Create interval for a livein register.
     void handleLiveInRegister(MachineBasicBlock* mbb,
                               unsigned MIIdx,
-                              LiveInterval &interval);
+                              LiveInterval &interval, bool isAlias = false);
 
     /// Return true if the two specified registers belong to different
     /// register classes.  The registers may be either phys or virt regs.
diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index d87d64bb82..da267c5ddd 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/include/llvm/CodeGen/LiveVariables.h
@@ -124,8 +124,25 @@ private:   // Intermediate data structures
 
   const MRegisterInfo *RegInfo;
 
-  MachineInstr **PhysRegInfo;
-  bool          *PhysRegUsed;
+  // PhysRegInfo - Keep track of which instruction was the last def/use of a
+  // physical register. This is a purely local property, because all physical
+  // register references as presumed dead across basic blocks.
+  std::vector<MachineInstr*> PhysRegInfo;
+
+  // PhysRegUsed - Keep track whether the physical register has been used after
+  // its last definition. This is local property.
+  BitVector                  PhysRegUsed;
+
+  // PhysRegPartDef - Keep track of a list of instructions which "partially"
+  // defined the physical register (e.g. on X86 AX partially defines EAX).
+  // These are turned into use/mod/write if there is a use of the register
+  // later in the same block. This is local property.
+  std::vector<std::vector<MachineInstr*> > PhysRegPartDef;
+
+  // PhysRegPartUse - Keep track of which instruction was the last partial use
+  // of a physical register (e.g. on X86 a def of EAX followed by a use of AX).
+  // This is a purely local property.
+  std::vector<MachineInstr*> PhysRegPartUse;
 
   typedef std::map<const MachineBasicBlock*,
                    std::vector<unsigned> > PHIVarInfoMap;
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 6521d97805..e936158f3e 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -675,8 +675,12 @@ void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
 exit:
   assert(start < end && "did not find end of interval?");
 
-  LiveRange LR(start, end, interval.getNextValue(SrcReg != 0 ? start : ~0U,
-                                                 SrcReg));
+  // Already exists? Extend old live interval.
+  LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start);
+  unsigned Id = (OldLR != interval.end())
+    ? OldLR->ValId
+    : interval.getNextValue(SrcReg != 0 ? start : ~0U, SrcReg);
+  LiveRange LR(start, end, Id);
   interval.addRange(LR);
   DOUT << " +" << LR << '\n';
 }
@@ -692,14 +696,17 @@ void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
     if (!tii_->isMoveInstr(*MI, SrcReg, DstReg))
       SrcReg = 0;
     handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg), SrcReg);
-    for (const unsigned* AS = mri_->getAliasSet(reg); *AS; ++AS)
-      handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(*AS), 0);
+    // Def of a register also defines its sub-registers.
+    for (const unsigned* AS = mri_->getSubRegisters(reg); *AS; ++AS)
+      // Avoid processing some defs more than once.
+      if (!MI->findRegisterDefOperand(*AS))
+        handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(*AS), 0);
   }
 }
 
 void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
                                          unsigned MIIdx,
-                                         LiveInterval &interval) {
+                                         LiveInterval &interval, bool isAlias) {
   DOUT << "\t\tlivein register: "; DEBUG(printRegName(interval.reg));
 
   // Look for kills, if it reaches a def before it's killed, then it shouldn't
@@ -728,6 +735,12 @@ void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
   }
 
 exit:
+  // Alias of a live-in register might not be used at all.
+  if (isAlias && end == 0) {
+    DOUT << " dead";
+    end = getDefIndex(start) + 1;
+  }
+
   assert(start < end && "did not find end of interval?");
 
   LiveRange LR(start, end, interval.getNextValue(~0U, 0));
@@ -757,8 +770,10 @@ void LiveIntervals::computeIntervals() {
       for (MachineBasicBlock::const_livein_iterator LI = MBB->livein_begin(),
              LE = MBB->livein_end(); LI != LE; ++LI) {
         handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI));
-        for (const unsigned* AS = mri_->getAliasSet(*LI); *AS; ++AS)
-          handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS));
+        // Multiple live-ins can alias the same register.
+        for (const unsigned* AS = mri_->getSubRegisters(*LI); *AS; ++AS)
+          if (!hasInterval(*AS))
+            handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS), true);
       }
     }
     
@@ -856,7 +871,8 @@ bool LiveIntervals::AdjustCopiesBackFrom(LiveInterval &IntA, LiveInterval &IntB,
   // If the IntB live range is assigned to a physical register, and if that
   // physreg has aliases, 
   if (MRegisterInfo::isPhysicalRegister(IntB.reg)) {
-    for (const unsigned *AS = mri_->getAliasSet(IntB.reg); *AS; ++AS) {
+    // Update the liveintervals of sub-registers.
+    for (const unsigned *AS = mri_->getSubRegisters(IntB.reg); *AS; ++AS) {
       LiveInterval &AliasLI = getInterval(*AS);
       AliasLI.addRange(LiveRange(FillerStart, FillerEnd,
                                  AliasLI.getNextValue(~0U, 0)));
@@ -1055,8 +1071,9 @@ bool LiveIntervals::JoinCopy(MachineInstr *CopyMI,
   // we have to update any aliased register's live ranges to indicate that they
   // have clobbered values for this range.
   if (MRegisterInfo::isPhysicalRegister(repDstReg)) {
-    for (const unsigned *AS = mri_->getAliasSet(repDstReg); *AS; ++AS)
-      getInterval(*AS).MergeInClobberRanges(SrcInt);
+    // Update the liveintervals of sub-registers.
+    for (const unsigned *AS = mri_->getSubRegisters(repDstReg); *AS; ++AS)
+        getInterval(*AS).MergeInClobberRanges(SrcInt);
   } else {
     // Merge use info if the destination is a virtual register.
     LiveVariables::VarInfo& dVI = lv_->getVarInfo(repDstReg);
@@ -1279,6 +1296,27 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
   SmallVector<int, 16> LHSValNoAssignments;
   SmallVector<int, 16> RHSValNoAssignments;
   SmallVector<std::pair<unsigned,unsigned>, 16> ValueNumberInfo;
+
+  // If a live interval is a physical register, conservatively check if any
+  // of its sub-registers is overlapping the live interval of the virtual
+  // register. If so, do not coalesce.
+  if (MRegisterInfo::isPhysicalRegister(LHS.reg) &&
+      *mri_->getSubRegisters(LHS.reg)) {
+    for (const unsigned* SR = mri_->getSubRegisters(LHS.reg); *SR; ++SR)
+      if (hasInterval(*SR) && RHS.overlaps(getInterval(*SR))) {
+        DOUT << "Interfere with sub-register ";
+        DEBUG(getInterval(*SR).print(DOUT, mri_));
+        return false;
+      }
+  } else if (MRegisterInfo::isPhysicalRegister(RHS.reg) &&
+             *mri_->getSubRegisters(RHS.reg)) {
+    for (const unsigned* SR = mri_->getSubRegisters(RHS.reg); *SR; ++SR)
+      if (hasInterval(*SR) && LHS.overlaps(getInterval(*SR))) {
+        DOUT << "Interfere with sub-register ";
+        DEBUG(getInterval(*SR).print(DOUT, mri_));
+        return false;
+      }
+  }
                           
   // Compute ultimate value numbers for the LHS and RHS values.
   if (RHS.containsOneValue()) {
diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index 0e0fecedf5..310b53a757 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -77,7 +77,10 @@ bool LiveVariables::KillsRegister(MachineInstr *MI, unsigned Reg) const {
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
     if (MO.isReg() && MO.isKill()) {
-      if (RegInfo->regsOverlap(Reg, MO.getReg()))
+      if ((MO.getReg() == Reg) ||
+          (MRegisterInfo::isPhysicalRegister(MO.getReg()) &&
+           MRegisterInfo::isPhysicalRegister(Reg) &&
+           RegInfo->isSubRegister(MO.getReg(), Reg)))
         return true;
     }
   }
@@ -87,9 +90,13 @@ bool LiveVariables::KillsRegister(MachineInstr *MI, unsigned Reg) const {
 bool LiveVariables::RegisterDefIsDead(MachineInstr *MI, unsigned Reg) const {
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
-    if (MO.isReg() && MO.isDead())
-      if (RegInfo->regsOverlap(Reg, MO.getReg()))
+    if (MO.isReg() && MO.isDead()) {
+      if ((MO.getReg() == Reg) ||
+          (MRegisterInfo::isPhysicalRegister(MO.getReg()) &&
+           MRegisterInfo::isPhysicalRegister(Reg) &&
+           RegInfo->isSubRegister(MO.getReg(), Reg)))
         return true;
+    }
   }
   return false;
 }
@@ -97,10 +104,8 @@ bool LiveVariables::RegisterDefIsDead(MachineInstr *MI, unsigned Reg) const {
 bool LiveVariables::ModifiesRegister(MachineInstr *MI, unsigned Reg) const {
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
-    if (MO.isReg() && MO.isDef()) {
-      if (RegInfo->regsOverlap(Reg, MO.getReg()))
-        return true;
-    }
+    if (MO.isReg() && MO.isDef() && MO.getReg() == Reg)
+      return true;
   }
   return false;
 }
@@ -166,57 +171,145 @@ void LiveVariables::HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
 }
 
 void LiveVariables::addRegisterKilled(unsigned IncomingReg, MachineInstr *MI) {
+  bool Found = false;
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
-    if (MO.isReg() && MO.isUse() && MO.getReg() == IncomingReg) {
-      MO.setIsKill();
-      break;
+    if (MO.isReg() && MO.isUse()) {
+      unsigned Reg = MO.getReg();
+      if (!Reg)
+        continue;
+      if (Reg == IncomingReg) {
+        MO.setIsKill();
+        Found = true;
+        break;
+      } else if (MRegisterInfo::isPhysicalRegister(Reg) &&
+                 MRegisterInfo::isPhysicalRegister(IncomingReg) &&
+                 RegInfo->isSuperRegister(IncomingReg, Reg) &&
+                 MO.isKill())
+        // A super-register kill already exists.
+        return;
     }
   }
+
+  // If not found, this means an alias of one of the operand is killed. Add a
+  // new implicit operand.
+  if (!Found)
+    MI->addRegOperand(IncomingReg, false/*IsDef*/,true/*IsImp*/,true/*IsKill*/);
 }
 
 void LiveVariables::addRegisterDead(unsigned IncomingReg, MachineInstr *MI) {
+  bool Found = false;
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
-    if (MO.isReg() && MO.isDef() && MO.getReg() == IncomingReg) {
-      MO.setIsDead();
-      break;
+    if (MO.isReg() && MO.isDef()) {
+      unsigned Reg = MO.getReg();
+      if (!Reg)
+        continue;
+      if (Reg == IncomingReg) {
+        MO.setIsDead();
+        Found = true;
+        break;
+      } else if (MRegisterInfo::isPhysicalRegister(Reg) &&
+                 MRegisterInfo::isPhysicalRegister(IncomingReg) &&
+                 RegInfo->isSuperRegister(IncomingReg, Reg) &&
+                 MO.isDead())
+        // There exists a super-register that's marked dead.
+        return;
     }
   }
+
+  // If not found, this means an alias of one of the operand is dead. Add a
+  // new implicit operand.
+  if (!Found)
+    MI->addRegOperand(IncomingReg, true/*IsDef*/,true/*IsImp*/,false/*IsKill*/,
+                      true/*IsDead*/);
 }
 
 void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
+  // There is a now a proper use, forget about the last partial use.
+  PhysRegPartUse[Reg] = NULL;
+
+  // Turn previous partial def's into read/mod/write.
+  for (unsigned i = 0, e = PhysRegPartDef[Reg].size(); i != e; ++i) {
+    MachineInstr *Def = PhysRegPartDef[Reg][i];
+    // First one is just a def. This means the use is reading some undef bits.
+    if (i != 0)
+      Def->addRegOperand(Reg, false/*IsDef*/,true/*IsImp*/,true/*IsKill*/);
+    Def->addRegOperand(Reg, true/*IsDef*/,true/*IsImp*/);
+  }
+  PhysRegPartDef[Reg].clear();
+
+  // There was an earlier def of a super-register. Add implicit def to that MI.
+  // A: EAX = ...
+  // B:     = AX
+  // Add implicit def to A.
+  if (PhysRegInfo[Reg] && !PhysRegUsed[Reg]) {
+    MachineInstr *Def = PhysRegInfo[Reg];
+    if (!Def->findRegisterDefOperand(Reg))
+      Def->addRegOperand(Reg, true/*IsDef*/,true/*IsImp*/);
+  }
+
   PhysRegInfo[Reg] = MI;
   PhysRegUsed[Reg] = true;
 
-  for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
-       unsigned Alias = *AliasSet; ++AliasSet) {
-    PhysRegInfo[Alias] = MI;
-    PhysRegUsed[Alias] = true;
+  for (const unsigned *SubRegs = RegInfo->getSubRegisters(Reg);
+       unsigned SubReg = *SubRegs; ++SubRegs) {
+    PhysRegInfo[SubReg] = MI;
+    PhysRegUsed[SubReg] = true;
   }
+
+  // Remember the partial uses.
+  for (const unsigned *SuperRegs = RegInfo->getSuperRegisters(Reg);
+       unsigned SuperReg = *SuperRegs; ++SuperRegs)
+    PhysRegPartUse[SuperReg] = MI;
 }
 
 void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
   // Does this kill a previous version of this register?
-  if (MachineInstr *LastUse = PhysRegInfo[Reg]) {
+  if (MachineInstr *LastRef = PhysRegInfo[Reg]) {
     if (PhysRegUsed[Reg])
-      addRegisterKilled(Reg, LastUse);
+      addRegisterKilled(Reg, LastRef);
+    else if (PhysRegPartUse[Reg])
+      // Add implicit use / kill to last use of a sub-register.
+      addRegisterKilled(Reg, PhysRegPartUse[Reg]);
     else
-      addRegisterDead(Reg, LastUse);
+      addRegisterDead(Reg, LastRef);
   }
   PhysRegInfo[Reg] = MI;
   PhysRegUsed[Reg] = false;
-
-  for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
-       unsigned Alias = *AliasSet; ++AliasSet) {
-    if (MachineInstr *LastUse = PhysRegInfo[Alias]) {
-      if (PhysRegUsed[Alias])
-        addRegisterKilled(Alias, LastUse);
+  PhysRegPartUse[Reg] = NULL;
+
+  for (const unsigned *SubRegs = RegInfo->getSubRegisters(Reg);
+       unsigned SubReg = *SubRegs; ++SubRegs) {
+    if (MachineInstr *LastRef = PhysRegInfo[SubReg]) {
+      if (PhysRegUsed[SubReg])
+        addRegisterKilled(SubReg, LastRef);
+      else if (PhysRegPartUse[SubReg])
+        // Add implicit use / kill to last use of a sub-register.
+        addRegisterKilled(SubReg, PhysRegPartUse[SubReg]);
       else
-        addRegisterDead(Alias, LastUse);
+        addRegisterDead(SubReg, LastRef);
     }
-    PhysRegInfo[Alias] = MI;
-    PhysRegUsed[Alias] = false;
+    PhysRegInfo[SubReg] = MI;
+    PhysRegUsed[SubReg] = false;
+  }
+
+  if (MI)
+    for (const unsigned *SuperRegs = RegInfo->getSuperRegisters(Reg);
+         unsigned SuperReg = *SuperRegs; ++SuperRegs) {
+      if (PhysRegInfo[SuperReg]) {
+        // The larger register is previously defined. Now a smaller part is
+        // being re-defined. Treat it as read/mod/write.
+        // EAX =
+        // AX  =        EAX<imp-use,kill>, EAX<imp-def>
+        MI->addRegOperand(SuperReg, false/*IsDef*/,true/*IsImp*/,true/*IsKill*/);
+        MI->addRegOperand(SuperReg, true/*IsDef*/,true/*IsImp*/);
+        PhysRegInfo[SuperReg] = MI;
+        PhysRegUsed[SuperReg] = false;
+      } else {
+        // Remember this partial def.
+        PhysRegPartDef[SuperReg].push_back(MI);
+      }
   }
 }
 
@@ -228,14 +321,10 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
 
   ReservedRegisters = RegInfo->getReservedRegs(mf);
 
-  // PhysRegInfo - Keep track of which instruction was the last use of a
-  // physical register.  This is a purely local property, because all physical
-  // register references as presumed dead across basic blocks.
-  //
-  PhysRegInfo = (MachineInstr**)alloca(sizeof(MachineInstr*) *
-                                       RegInfo->getNumRegs());
-  PhysRegUsed = (bool*)alloca(sizeof(bool)*RegInfo->getNumRegs());
-  std::fill(PhysRegInfo, PhysRegInfo+RegInfo->getNumRegs(), (MachineInstr*)0);
+  PhysRegInfo.resize(RegInfo->getNumRegs(), (MachineInstr*)NULL);
+  PhysRegUsed.resize(RegInfo->getNumRegs());
+  PhysRegPartDef.resize(RegInfo->getNumRegs());
+  PhysRegPartUse.resize(RegInfo->getNumRegs(), (MachineInstr*)NULL);
 
   /// Get some space for a respectable number of registers...
   VirtRegInfo.resize(64);
@@ -342,6 +431,12 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
     for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
       if (PhysRegInfo[i])
         HandlePhysRegDef(i, 0);
+
+    // Clear some states between BB's. These are purely local information.
+    for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i) {
+      PhysRegPartDef[i].clear();
+      PhysRegPartUse[i] = NULL;
+    }
   }
 
   // Convert and transfer the dead / killed information we have gathered into