X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FLiveRangeEdit.cpp;h=7793e96c354096d770d458f166fa370818aadbeb;hb=46abfcf4187432da728cbe452c32143da077e07f;hp=8bdad5a4ff3546faf075962ca1f1e7040b42dce5;hpb=20942dcd8634ad75091fe89669868cfebf74e869;p=oota-llvm.git

diff --git a/lib/CodeGen/LiveRangeEdit.cpp b/lib/CodeGen/LiveRangeEdit.cpp
index 8bdad5a4ff3..7793e96c354 100644
--- a/lib/CodeGen/LiveRangeEdit.cpp
+++ b/lib/CodeGen/LiveRangeEdit.cpp
@@ -12,16 +12,16 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "regalloc"
-#include "VirtRegMap.h"
+#include "llvm/CodeGen/LiveRangeEdit.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/CalcSpillWeights.h"
 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
-#include "llvm/CodeGen/LiveRangeEdit.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/CodeGen/VirtRegMap.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrInfo.h"
 
 using namespace llvm;
 
@@ -77,21 +77,32 @@ bool LiveRangeEdit::anyRematerializable(AliasAnalysis *aa) {
 /// OrigIdx are also available with the same value at UseIdx.
 bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
                                        SlotIndex OrigIdx,
-                                       SlotIndex UseIdx) {
+                                       SlotIndex UseIdx) const {
   OrigIdx = OrigIdx.getRegSlot(true);
   UseIdx = UseIdx.getRegSlot(true);
   for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
     const MachineOperand &MO = OrigMI->getOperand(i);
-    if (!MO.isReg() || !MO.getReg() || MO.isDef())
-      continue;
-    // Reserved registers are OK.
-    if (MO.isUndef() || !LIS.hasInterval(MO.getReg()))
+    if (!MO.isReg() || !MO.getReg() || !MO.readsReg())
       continue;
 
+    // We can't remat physreg uses, unless it is a constant.
+    if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
+      if (MRI.isConstantPhysReg(MO.getReg(), *OrigMI->getParent()->getParent()))
+        continue;
+      return false;
+    }
+
     LiveInterval &li = LIS.getInterval(MO.getReg());
     const VNInfo *OVNI = li.getVNInfoAt(OrigIdx);
     if (!OVNI)
       continue;
+
+    // Don't allow rematerialization immediately after the original def.
+    // It would be incorrect if OrigMI redefines the register.
+    // See PR14098.
+    if (SlotIndex::isSameInstr(OrigIdx, UseIdx))
+      return false;
+
     if (OVNI != li.getVNInfoAt(UseIdx))
       return false;
   }
@@ -173,6 +184,19 @@ bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
   if (!DefMI || !UseMI)
     return false;
 
+  // Since we're moving the DefMI load, make sure we're not extending any live
+  // ranges.
+  if (!allUsesAvailableAt(DefMI,
+                          LIS.getInstructionIndex(DefMI),
+                          LIS.getInstructionIndex(UseMI)))
+    return false;
+
+  // We also need to make sure it is safe to move the load.
+  // Assume there are stores between DefMI and UseMI.
+  bool SawStore = true;
+  if (!DefMI->isSafeToMove(&TII, 0, SawStore))
+    return false;
+
   DEBUG(dbgs() << "Try to fold single def: " << *DefMI
                << "       into single use: " << *UseMI);
 
@@ -220,14 +244,22 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
 
       DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
 
+      // Collect virtual registers to be erased after MI is gone.
+      SmallVector<unsigned, 8> RegsToErase;
+      bool ReadsPhysRegs = false;
+
       // Check for live intervals that may shrink
       for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
              MOE = MI->operands_end(); MOI != MOE; ++MOI) {
         if (!MOI->isReg())
           continue;
         unsigned Reg = MOI->getReg();
-        if (!TargetRegisterInfo::isVirtualRegister(Reg))
+        if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
+          // Check if MI reads any unreserved physregs.
+          if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
+            ReadsPhysRegs = true;
           continue;
+        }
         LiveInterval &LI = LIS.getInterval(Reg);
 
         // Shrink read registers, unless it is likely to be expensive and
@@ -245,19 +277,46 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
             if (TheDelegate)
               TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
             LI.removeValNo(VNI);
-            if (LI.empty()) {
-              ToShrink.remove(&LI);
-              eraseVirtReg(Reg);
-            }
+            if (LI.empty())
+              RegsToErase.push_back(Reg);
           }
         }
       }
 
-      if (TheDelegate)
-        TheDelegate->LRE_WillEraseInstruction(MI);
-      LIS.RemoveMachineInstrFromMaps(MI);
-      MI->eraseFromParent();
-      ++NumDCEDeleted;
+      // Currently, we don't support DCE of physreg live ranges. If MI reads
+      // any unreserved physregs, don't erase the instruction, but turn it into
+      // a KILL instead. This way, the physreg live ranges don't end up
+      // dangling.
+      // FIXME: It would be better to have something like shrinkToUses() for
+      // physregs. That could potentially enable more DCE and it would free up
+      // the physreg. It would not happen often, though.
+      if (ReadsPhysRegs) {
+        MI->setDesc(TII.get(TargetOpcode::KILL));
+        // Remove all operands that aren't physregs.
+        for (unsigned i = MI->getNumOperands(); i; --i) {
+          const MachineOperand &MO = MI->getOperand(i-1);
+          if (MO.isReg() && TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
+            continue;
+          MI->RemoveOperand(i-1);
+        }
+        DEBUG(dbgs() << "Converted physregs to:\t" << *MI);
+      } else {
+        if (TheDelegate)
+          TheDelegate->LRE_WillEraseInstruction(MI);
+        LIS.RemoveMachineInstrFromMaps(MI);
+        MI->eraseFromParent();
+        ++NumDCEDeleted;
+      }
+
+      // Erase any virtregs that are now empty and unused. There may be <undef>
+      // uses around. Keep the empty live range in that case.
+      for (unsigned i = 0, e = RegsToErase.size(); i != e; ++i) {
+        unsigned Reg = RegsToErase[i];
+        if (LIS.hasInterval(Reg) && MRI.reg_nodbg_empty(Reg)) {
+          ToShrink.remove(&LIS.getInterval(Reg));
+          eraseVirtReg(Reg);
+        }
+      }
     }
 
     if (ToShrink.empty())
@@ -308,6 +367,10 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
         TheDelegate->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
     }
     ConEQ.Distribute(&Dups[0], MRI);
+    DEBUG({
+      for (unsigned i = 0; i != NumComp; ++i)
+        dbgs() << '\t' << *Dups[i] << '\n';
+    });
   }
 }