Revert "Use a simpler data structure to calculate the least recently used register...

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

diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index 2518ce152090833b2922e94863748b5fb6f50b5d..179984f2a998a15949ba3f39f2418360f1365de6 100644 (file)
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -64,7 +64,7 @@ void RegScavenger::initRegState() {
     return;
 
   // Live-in registers are in use.
-  for (MachineBasicBlock::const_livein_iterator I = MBB->livein_begin(),
+  for (MachineBasicBlock::livein_iterator I = MBB->livein_begin(),
          E = MBB->livein_end(); I != E; ++I)
     setUsed(*I);
 
@@ -100,11 +100,8 @@ void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) {
         CalleeSavedRegs.set(CSRegs[i]);
   }
 
-  // RS used within emit{Pro,Epi}logue()
-  if (mbb != MBB) {
-    MBB = mbb;
-    initRegState();
-  }
+  MBB = mbb;
+  initRegState();
 
   Tracking = false;
 }
@@ -128,7 +125,7 @@ void RegScavenger::forward() {
     Tracking = true;
   } else {
     assert(MBBI != MBB->end() && "Already at the end of the basic block!");
-    MBBI = next(MBBI);
+    MBBI = llvm::next(MBBI);
   }
 
   MachineInstr *MI = MBBI;
@@ -139,6 +136,9 @@ void RegScavenger::forward() {
     ScavengeRestore = NULL;
   }
 
+  if (MI->isDebugValue())
+    return;
+
   // Find out which registers are early clobbered, killed, defined, and marked
   // def-dead in this instruction.
   BitVector EarlyClobberRegs(NumPhysRegs);
@@ -177,7 +177,24 @@ void RegScavenger::forward() {
     if (!Reg || isReserved(Reg))
       continue;
     if (MO.isUse()) {
-      assert(isUsed(Reg) && "Using an undefined register!");
+      if (!isUsed(Reg)) {
+        // Check if it's partial live: e.g.
+        // D0 = insert_subreg D0<undef>, S0
+        // ... D0
+        // The problem is the insert_subreg could be eliminated. The use of
+        // D0 is using a partially undef value. This is not *incorrect* since
+        // S1 is can be freely clobbered.
+        // Ideally we would like a way to model this, but leaving the
+        // insert_subreg around causes both correctness and performance issues.
+        bool SubUsed = false;
+        for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
+             unsigned SubReg = *SubRegs; ++SubRegs)
+          if (isUsed(SubReg)) {
+            SubUsed = true;
+            break;
+          }
+        assert(SubUsed && "Using an undefined register!");
+      }
       assert((!EarlyClobberRegs.test(Reg) || MI->isRegTiedToDefOperand(i)) &&
              "Using an early clobbered register!");
     } else {
@@ -227,7 +244,7 @@ unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RC) const {
 ///
 /// No more than InstrLimit instructions are inspected.
 ///
-unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI,
+unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator StartMI,
                                        BitVector &Candidates,
                                        unsigned InstrLimit,
                                        MachineBasicBlock::iterator &UseMI) {
@@ -235,19 +252,37 @@ unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI,
   assert(Survivor > 0 && "No candidates for scavenging");
 
   MachineBasicBlock::iterator ME = MBB->getFirstTerminator();
-  assert(MI != ME && "MI already at terminator");
+  assert(StartMI != ME && "MI already at terminator");
+  MachineBasicBlock::iterator RestorePointMI = StartMI;
+  MachineBasicBlock::iterator MI = StartMI;
 
+  bool inVirtLiveRange = false;
   for (++MI; InstrLimit > 0 && MI != ME; ++MI, --InstrLimit) {
+    bool isVirtKillInsn = false;
+    bool isVirtDefInsn = false;
     // Remove any candidates touched by instruction.
     for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
       const MachineOperand &MO = MI->getOperand(i);
-      if (!MO.isReg() || MO.isUndef() || !MO.getReg() ||
-          TargetRegisterInfo::isVirtualRegister(MO.getReg()))
+      if (!MO.isReg() || MO.isUndef() || !MO.getReg())
         continue;
+      if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
+        if (MO.isDef())
+          isVirtDefInsn = true;
+        else if (MO.isKill())
+          isVirtKillInsn = true;
+        continue;
+      }
       Candidates.reset(MO.getReg());
       for (const unsigned *R = TRI->getAliasSet(MO.getReg()); *R; R++)
         Candidates.reset(*R);
     }
+    // If we're not in a virtual reg's live range, this is a valid
+    // restore point.
+    if (!inVirtLiveRange) RestorePointMI = MI;
+
+    // Update whether we're in the live range of a virtual register
+    if (isVirtKillInsn) inVirtLiveRange = false;
+    if (isVirtDefInsn) inVirtLiveRange = true;
 
     // Was our survivor untouched by this instruction?
     if (Candidates.test(Survivor))
@@ -259,9 +294,13 @@ unsigned RegScavenger::findSurvivorReg(MachineBasicBlock::iterator MI,
 
     Survivor = Candidates.find_first();
   }
+  // If we ran off the end, that's where we want to restore.
+  if (MI == ME) RestorePointMI = ME;
+  assert (RestorePointMI != StartMI &&
+          "No available scavenger restore location!");
 
   // We ran out of candidates, so stop the search.
-  UseMI = MI;
+  UseMI = RestorePointMI;
   return Survivor;
 }