New files

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5262 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 390 insertions, 0 deletions

diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
new file mode 100644
index 0000000000..d845f0646f
--- /dev/null
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -0,0 +1,257 @@
+//===-- LiveVariables.cpp - Live Variable Analysis for Machine Code -------===//
+// 
+// This file implements the LiveVariable analysis pass.
+//   
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Target/MachineInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CFG.h"
+#include "Support/DepthFirstIterator.h"
+
+static RegisterAnalysis<LiveVariables> X("livevars", "Live Variable Analysis");
+
+void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo,
+					    const BasicBlock *BB) {
+  const std::pair<MachineBasicBlock*,unsigned> &Info = BBMap.find(BB)->second;
+  MachineBasicBlock *MBB = Info.first;
+  unsigned BBNum = Info.second;
+
+  // Check to see if this basic block is one of the killing blocks.  If so,
+  // remove it...
+  for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i)
+    if (VRInfo.Kills[i].first == MBB) {
+      VRInfo.Kills.erase(VRInfo.Kills.begin()+i);  // Erase entry
+      break;
+    }
+
+  if (MBB == VRInfo.DefBlock) return;  // Terminate recursion
+
+  if (VRInfo.AliveBlocks.size() <= BBNum)
+    VRInfo.AliveBlocks.resize(BBNum+1);  // Make space...
+
+  if (VRInfo.AliveBlocks[BBNum])
+    return;  // We already know the block is live
+
+  // Mark the variable known alive in this bb
+  VRInfo.AliveBlocks[BBNum] = true;
+
+  for (pred_const_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
+    MarkVirtRegAliveInBlock(VRInfo, *PI);
+}
+
+void LiveVariables::HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
+				     MachineInstr *MI) {
+  // Check to see if this basic block is already a kill block...
+  if (!VRInfo.Kills.empty() && VRInfo.Kills.back().first == MBB) {
+    // Yes, this register is killed in this basic block already.  Increase the
+    // live range by updating the kill instruction.
+    VRInfo.Kills.back().second = MI;
+    return;
+  }
+
+#ifndef NDEBUG
+  for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i)
+    assert(VRInfo.Kills[i].first != MBB && "entry should be at end!");
+#endif
+
+  assert(MBB != VRInfo.DefBlock && "Should have kill for defblock!");
+
+  // Add a new kill entry for this basic block.
+  VRInfo.Kills.push_back(std::make_pair(MBB, MI));
+
+  // Update all dominating blocks to mark them known live.
+  const BasicBlock *BB = MBB->getBasicBlock();
+  for (pred_const_iterator PI = pred_begin(BB), E = pred_end(BB);
+       PI != E; ++PI)
+    MarkVirtRegAliveInBlock(VRInfo, *PI);
+}
+
+void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
+  if (PhysRegInfo[Reg]) {
+    PhysRegInfo[Reg] = MI;
+    PhysRegUsed[Reg] = true;
+  } else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg)) {
+    for (; unsigned NReg = AliasSet[0]; ++AliasSet)
+      if (MachineInstr *LastUse = PhysRegInfo[NReg]) {
+	PhysRegInfo[NReg] = MI;
+	PhysRegUsed[NReg] = true;
+      }
+  }
+}
+
+void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
+  // Does this kill a previous version of this register?
+  if (MachineInstr *LastUse = PhysRegInfo[Reg]) {
+    if (PhysRegUsed[Reg])
+      RegistersKilled.insert(std::make_pair(LastUse, Reg));
+    else
+      RegistersDead.insert(std::make_pair(LastUse, Reg));
+  } else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg)) {
+    for (; unsigned NReg = AliasSet[0]; ++AliasSet)
+      if (MachineInstr *LastUse = PhysRegInfo[NReg]) {
+	if (PhysRegUsed[NReg])
+	  RegistersKilled.insert(std::make_pair(LastUse, NReg));
+	else
+	  RegistersDead.insert(std::make_pair(LastUse, NReg));
+	PhysRegInfo[NReg] = 0;  // Kill the aliased register
+      }
+  }
+  PhysRegInfo[Reg] = MI;
+  PhysRegUsed[Reg] = false;
+}
+
+bool LiveVariables::runOnMachineFunction(MachineFunction &MF) {
+  // Build BBMap... 
+  unsigned BBNum = 0;
+  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
+    BBMap[I->getBasicBlock()] = std::make_pair(I, BBNum++);
+
+  // 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.
+  //
+  MachineInstr *PhysRegInfoA[MRegisterInfo::FirstVirtualRegister];
+  bool          PhysRegUsedA[MRegisterInfo::FirstVirtualRegister];
+  std::fill(PhysRegInfoA, PhysRegInfoA+MRegisterInfo::FirstVirtualRegister,
+	    (MachineInstr*)0);
+  PhysRegInfo = PhysRegInfoA;
+  PhysRegUsed = PhysRegUsedA;
+
+  const TargetInstrInfo &TII = MF.getTarget().getInstrInfo();
+  RegInfo = MF.getTarget().getRegisterInfo();
+
+  /// Get some space for a respectable number of registers...
+  VirtRegInfo.resize(64);
+  
+  // Calculate live variable information in depth first order on the CFG of the
+  // function.  This guarantees that we will see the definition of a virtual
+  // register before its uses due to dominance properties of SSA (except for PHI
+  // nodes, which are treated as a special case).
+  //
+  const BasicBlock *Entry = MF.getFunction()->begin();
+  for (df_iterator<const BasicBlock*> DFI = df_begin(Entry), E = df_end(Entry);
+       DFI != E; ++DFI) {
+    const BasicBlock *BB = *DFI;
+    std::pair<MachineBasicBlock*, unsigned> &BBRec = BBMap.find(BB)->second;
+    MachineBasicBlock *MBB = BBRec.first;
+    unsigned BBNum = BBRec.second;
+
+    // Loop over all of the instructions, processing them.
+    for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
+	 I != E; ++I) {
+      MachineInstr *MI = *I;
+      const TargetInstrDescriptor &MID = TII.get(MI->getOpcode());
+
+      // Process all of the operands of the instruction...
+      unsigned NumOperandsToProcess = MI->getNumOperands();
+
+      // Unless it is a PHI node.  In this case, ONLY process the DEF, not any
+      // of the uses.  They will be handled in other basic blocks.
+      if (MI->getOpcode() == TargetInstrInfo::PHI)      
+	NumOperandsToProcess = 1;
+
+      // Loop over implicit uses, using them.
+      if (const unsigned *ImplicitUses = MID.ImplicitUses)
+	for (unsigned i = 0; ImplicitUses[i]; ++i)
+	  HandlePhysRegUse(ImplicitUses[i], MI);
+
+      // Process all explicit uses...
+      for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
+	MachineOperand &MO = MI->getOperand(i);
+	if (MO.opIsUse() || MO.opIsDefAndUse()) {
+	  if (MO.isVirtualRegister() && !MO.getVRegValueOrNull()) {
+	    unsigned RegIdx = MO.getReg()-MRegisterInfo::FirstVirtualRegister;
+	    HandleVirtRegUse(getVarInfo(RegIdx), MBB, MI);
+	  } else if (MO.isPhysicalRegister() && MO.getReg() != 0
+		   /// FIXME: This is a gross hack, due to us not being able to
+		   /// say that some registers are defined on entry to the
+		   /// function.  5 = ESP
+&& MO.getReg() != 5
+) {
+	    HandlePhysRegUse(MO.getReg(), MI);
+	  }
+	}
+      }
+
+      // Loop over implicit defs, defining them.
+      if (const unsigned *ImplicitDefs = MID.ImplicitDefs)
+	for (unsigned i = 0; ImplicitDefs[i]; ++i)
+	  HandlePhysRegDef(ImplicitDefs[i], MI);
+
+      // Process all explicit defs...
+      for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
+	MachineOperand &MO = MI->getOperand(i);
+	if (MO.opIsDef() || MO.opIsDefAndUse()) {
+	  if (MO.isVirtualRegister()) {
+	    unsigned RegIdx = MO.getReg()-MRegisterInfo::FirstVirtualRegister;
+	    VarInfo &VRInfo = getVarInfo(RegIdx);
+
+	    assert(VRInfo.DefBlock == 0 && "Variable multiply defined!");
+	    VRInfo.DefBlock = MBB;                           // Created here...
+	    VRInfo.DefInst = MI;
+	    VRInfo.Kills.push_back(std::make_pair(MBB, MI)); // Defaults to dead
+	  } else if (MO.isPhysicalRegister() && MO.getReg() != 0
+		   /// FIXME: This is a gross hack, due to us not being able to
+		   /// say that some registers are defined on entry to the
+		   /// function.  5 = ESP
+&& MO.getReg() != 5
+) {
+	    HandlePhysRegDef(MO.getReg(), MI);
+	  }
+	}
+      }
+    }
+
+    // Handle any virtual assignments from PHI nodes which might be at the
+    // bottom of this basic block.  We check all of our successor blocks to see
+    // if they have PHI nodes, and if so, we simulate an assignment at the end
+    // of the current block.
+    for (succ_const_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I){
+      MachineBasicBlock *Succ = BBMap.find(*I)->second.first;
+      
+      // PHI nodes are guaranteed to be at the top of the block...
+      for (MachineBasicBlock::iterator I = Succ->begin(), E = Succ->end();
+	   I != E && (*I)->getOpcode() == TargetInstrInfo::PHI; ++I) {
+	for (unsigned i = 1; ; i += 2)
+	  if ((*I)->getOperand(i+1).getMachineBasicBlock() == MBB) {
+	    MachineOperand &MO = (*I)->getOperand(i);
+	    if (!MO.getVRegValueOrNull()) {
+	      unsigned RegIdx = MO.getReg()-MRegisterInfo::FirstVirtualRegister;
+	      VarInfo &VRInfo = getVarInfo(RegIdx);
+
+	      // Only mark it alive only in the block we are representing...
+	      MarkVirtRegAliveInBlock(VRInfo, BB);
+	      break;   // Found the PHI entry for this block...
+	    }
+	  }
+      }
+    }
+    
+    // Loop over PhysRegInfo, killing any registers that are available at the
+    // end of the basic block.  This also resets the PhysRegInfo map.
+    for (unsigned i = 0, e = MRegisterInfo::FirstVirtualRegister; i != e; ++i)
+      if (PhysRegInfo[i])
+	HandlePhysRegDef(i, 0);
+  }
+
+  BBMap.clear();
+
+  // Convert the information we have gathered into VirtRegInfo and transform it
+  // into a form usable by RegistersKilled.
+  //
+  for (unsigned i = 0, e = VirtRegInfo.size(); i != e; ++i)
+    for (unsigned j = 0, e = VirtRegInfo[i].Kills.size(); j != e; ++j) {
+      if (VirtRegInfo[i].Kills[j].second == VirtRegInfo[i].DefInst)
+	RegistersDead.insert(std::make_pair(VirtRegInfo[i].Kills[j].second,
+		    i + MRegisterInfo::FirstVirtualRegister));
+
+      else
+	RegistersKilled.insert(std::make_pair(VirtRegInfo[i].Kills[j].second,
+		    i + MRegisterInfo::FirstVirtualRegister));
+    }
+  
+  return false;
+}
diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
new file mode 100644
index 0000000000..ca243b8aae
--- /dev/null
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -0,0 +1,133 @@
+//===-- PhiElimination.cpp - Eliminate PHI nodes by inserting copies ------===//
+//
+// This pass eliminates machine instruction PHI nodes by inserting copy
+// instructions.  This destroys SSA information, but is the desired input for
+// some register allocators.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/SSARegMap.h"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/Target/MachineInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+
+namespace {
+  struct PNE : public MachineFunctionPass {
+    bool runOnMachineFunction(MachineFunction &Fn) {
+      bool Changed = false;
+
+      // Eliminate PHI instructions by inserting copies into predecessor blocks.
+      //
+      for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
+	Changed |= EliminatePHINodes(Fn, *I);
+
+      //std::cerr << "AFTER PHI NODE ELIM:\n";
+      //Fn.dump();
+      return Changed;
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addPreserved<LiveVariables>();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+
+  private:
+    /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
+    /// in predecessor basic blocks.
+    ///
+    bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
+  };
+
+  RegisterPass<PNE> X("phi-node-elimination",
+		      "Eliminate PHI nodes for register allocation");
+}
+
+const PassInfo *PHIEliminationID = X.getPassInfo();
+
+/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in
+/// predecessor basic blocks.
+///
+bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
+  if (MBB.front()->getOpcode() != TargetInstrInfo::PHI)
+    return false;   // Quick exit for normal case...
+
+  LiveVariables *LV = getAnalysisToUpdate<LiveVariables>();
+  const TargetInstrInfo &MII = MF.getTarget().getInstrInfo();
+  const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
+
+  while (MBB.front()->getOpcode() == TargetInstrInfo::PHI) {
+    MachineInstr *MI = MBB.front();
+    // Unlink the PHI node from the basic block... but don't delete the PHI yet
+    MBB.erase(MBB.begin());
+
+    assert(MI->getOperand(0).isVirtualRegister() &&
+           "PHI node doesn't write virt reg?");
+
+    unsigned DestReg = MI->getOperand(0).getAllocatedRegNum();
+    
+    // Create a new register for the incoming PHI arguments
+    const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg);
+    unsigned IncomingReg = MF.getSSARegMap()->createVirtualRegister(RC);
+
+    // Insert a register to register copy in the top of the current block (by
+    // after any remaining phi nodes) which copies the new incoming register
+    // into the phi node destination.
+    //
+    MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
+    while ((*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI) ++AfterPHIsIt;
+    RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
+
+    // Add information to LiveVariables to know that the incoming value is dead
+    if (LV) LV->addVirtualRegisterKill(IncomingReg, *(AfterPHIsIt-1));
+
+    // Now loop over all of the incoming arguments turning them into copies into
+    // the IncomingReg register in the corresponding predecessor basic block.
+    //
+    for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) {
+      MachineOperand &opVal = MI->getOperand(i-1);
+      
+      // Get the MachineBasicBlock equivalent of the BasicBlock that is the
+      // source path the phi
+      MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock();
+
+      // Check to make sure we haven't already emitted the copy for this block.
+      // This can happen because PHI nodes may have multiple entries for the
+      // same basic block.  It doesn't matter which entry we use though, because
+      // all incoming values are guaranteed to be the same for a particular bb.
+      //
+      // Note that this is N^2 in the number of phi node entries, but since the
+      // # of entries is tiny, this is not a problem.
+      //
+      bool HaveNotEmitted = true;
+      for (int op = MI->getNumOperands() - 1; op != i; op -= 2)
+        if (&opBlock == MI->getOperand(op).getMachineBasicBlock()) {
+          HaveNotEmitted = false;
+          break;
+        }
+
+      if (HaveNotEmitted) {
+        MachineBasicBlock::iterator I = opBlock.end()-1;
+        
+        // must backtrack over ALL the branches in the previous block
+        while (MII.isTerminatorInstr((*I)->getOpcode()) && I != opBlock.begin())
+          --I;
+        
+        // move back to the first branch instruction so new instructions
+        // are inserted right in front of it and not in front of a non-branch
+        if (!MII.isTerminatorInstr((*I)->getOpcode()))
+          ++I;
+
+	assert(opVal.isVirtualRegister() &&
+	       "Machine PHI Operands must all be virtual registers!");
+	RegInfo->copyRegToReg(opBlock, I, IncomingReg, opVal.getReg(), RC);
+      }
+    }
+    
+    // really delete the PHI instruction now!
+    delete MI;
+  }
+
+  return true;
+}