X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FMachineCSE.cpp;h=d228286d9db89b188d7f61a75ccd72335bd81166;hb=1039e106d095979b3707bb27cfa765cd2c0f3b54;hp=896461fd194b52936db2b67755f419337cf91cfe;hpb=5fa2d458af8522a0fc3c6c93227d8cb3c0dc2862;p=oota-llvm.git

diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 896461fd194..d228286d9db 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -15,17 +15,17 @@
 
 #define DEBUG_TYPE "machine-cse"
 #include "llvm/CodeGen/Passes.h"
-#include "llvm/CodeGen/MachineDominators.h"
-#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/ScopedHashTable.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/RecyclingAllocator.h"
+#include "llvm/Target/TargetInstrInfo.h"
 using namespace llvm;
 
 STATISTIC(NumCoalesces, "Number of copies coalesced");
@@ -63,8 +63,6 @@ namespace {
     virtual void releaseMemory() {
       ScopeMap.clear();
       Exps.clear();
-      AllocatableRegs.clear();
-      ReservedRegs.clear();
     }
 
   private:
@@ -78,8 +76,6 @@ namespace {
     ScopedHTType VNT;
     SmallVector<MachineInstr*, 64> Exps;
     unsigned CurrVN;
-    BitVector AllocatableRegs;
-    BitVector ReservedRegs;
 
     bool PerformTrivialCoalescing(MachineInstr *MI, MachineBasicBlock *MBB);
     bool isPhysDefTriviallyDead(unsigned Reg,
@@ -88,10 +84,11 @@ namespace {
     bool hasLivePhysRegDefUses(const MachineInstr *MI,
                                const MachineBasicBlock *MBB,
                                SmallSet<unsigned,8> &PhysRefs,
-                               SmallVector<unsigned,2> &PhysDefs) const;
+                               SmallVectorImpl<unsigned> &PhysDefs,
+                               bool &PhysUseDef) const;
     bool PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
                           SmallSet<unsigned,8> &PhysRefs,
-                          SmallVector<unsigned,2> &PhysDefs,
+                          SmallVectorImpl<unsigned> &PhysDefs,
                           bool &NonLocal) const;
     bool isCSECandidate(MachineInstr *MI);
     bool isProfitableToCSE(unsigned CSReg, unsigned Reg,
@@ -129,8 +126,6 @@ bool MachineCSE::PerformTrivialCoalescing(MachineInstr *MI,
       // deleted.
       continue;
     MachineInstr *DefMI = MRI->getVRegDef(Reg);
-    if (DefMI->getParent() != MBB)
-      continue;
     if (!DefMI->isCopy())
       continue;
     unsigned SrcReg = DefMI->getOperand(1).getReg();
@@ -198,37 +193,58 @@ MachineCSE::isPhysDefTriviallyDead(unsigned Reg,
 bool MachineCSE::hasLivePhysRegDefUses(const MachineInstr *MI,
                                        const MachineBasicBlock *MBB,
                                        SmallSet<unsigned,8> &PhysRefs,
-                                       SmallVector<unsigned,2> &PhysDefs) const{
-  MachineBasicBlock::const_iterator I = MI; I = llvm::next(I);
+                                       SmallVectorImpl<unsigned> &PhysDefs,
+                                       bool &PhysUseDef) const{
+  // First, add all uses to PhysRefs.
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     const MachineOperand &MO = MI->getOperand(i);
-    if (!MO.isReg())
+    if (!MO.isReg() || MO.isDef())
       continue;
     unsigned Reg = MO.getReg();
     if (!Reg)
       continue;
     if (TargetRegisterInfo::isVirtualRegister(Reg))
       continue;
-    // If the def is dead, it's ok. But the def may not marked "dead". That's
-    // common since this pass is run before livevariables. We can scan
-    // forward a few instructions and check if it is obviously dead.
-    if (MO.isDef() &&
-        (MO.isDead() || isPhysDefTriviallyDead(Reg, I, MBB->end())))
-      continue;
     // Reading constant physregs is ok.
     if (!MRI->isConstantPhysReg(Reg, *MBB->getParent()))
       for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
         PhysRefs.insert(*AI);
-    if (MO.isDef())
+  }
+
+  // Next, collect all defs into PhysDefs.  If any is already in PhysRefs
+  // (which currently contains only uses), set the PhysUseDef flag.
+  PhysUseDef = false;
+  MachineBasicBlock::const_iterator I = MI; I = llvm::next(I);
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    if (!MO.isReg() || !MO.isDef())
+      continue;
+    unsigned Reg = MO.getReg();
+    if (!Reg)
+      continue;
+    if (TargetRegisterInfo::isVirtualRegister(Reg))
+      continue;
+    // Check against PhysRefs even if the def is "dead".
+    if (PhysRefs.count(Reg))
+      PhysUseDef = true;
+    // If the def is dead, it's ok. But the def may not marked "dead". That's
+    // common since this pass is run before livevariables. We can scan
+    // forward a few instructions and check if it is obviously dead.
+    if (!MO.isDead() && !isPhysDefTriviallyDead(Reg, I, MBB->end()))
       PhysDefs.push_back(Reg);
   }
 
+  // Finally, add all defs to PhysRefs as well.
+  for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i)
+    for (MCRegAliasIterator AI(PhysDefs[i], TRI, true); AI.isValid(); ++AI)
+      PhysRefs.insert(*AI);
+
   return !PhysRefs.empty();
 }
 
 bool MachineCSE::PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
                                   SmallSet<unsigned,8> &PhysRefs,
-                                  SmallVector<unsigned,2> &PhysDefs,
+                                  SmallVectorImpl<unsigned> &PhysDefs,
                                   bool &NonLocal) const {
   // For now conservatively returns false if the common subexpression is
   // not in the same basic block as the given instruction. The only exception
@@ -242,7 +258,7 @@ bool MachineCSE::PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
       return false;
 
     for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i) {
-      if (AllocatableRegs.test(PhysDefs[i]) || ReservedRegs.test(PhysDefs[i]))
+      if (MRI->isAllocatable(PhysDefs[i]) || MRI->isReserved(PhysDefs[i]))
         // Avoid extending live range of physical registers if they are
         //allocatable or reserved.
         return false;
@@ -411,8 +427,8 @@ void MachineCSE::ExitScope(MachineBasicBlock *MBB) {
   DEBUG(dbgs() << "Exiting: " << MBB->getName() << '\n');
   DenseMap<MachineBasicBlock*, ScopeType*>::iterator SI = ScopeMap.find(MBB);
   assert(SI != ScopeMap.end());
-  ScopeMap.erase(SI);
   delete SI->second;
+  ScopeMap.erase(SI);
 }
 
 bool MachineCSE::ProcessBlock(MachineBasicBlock *MBB) {
@@ -463,16 +479,22 @@ bool MachineCSE::ProcessBlock(MachineBasicBlock *MBB) {
     bool CrossMBBPhysDef = false;
     SmallSet<unsigned, 8> PhysRefs;
     SmallVector<unsigned, 2> PhysDefs;
-    if (FoundCSE && hasLivePhysRegDefUses(MI, MBB, PhysRefs, PhysDefs)) {
+    bool PhysUseDef = false;
+    if (FoundCSE && hasLivePhysRegDefUses(MI, MBB, PhysRefs,
+                                          PhysDefs, PhysUseDef)) {
       FoundCSE = false;
 
       // ... Unless the CS is local or is in the sole predecessor block
       // and it also defines the physical register which is not clobbered
       // in between and the physical register uses were not clobbered.
-      unsigned CSVN = VNT.lookup(MI);
-      MachineInstr *CSMI = Exps[CSVN];
-      if (PhysRegDefsReach(CSMI, MI, PhysRefs, PhysDefs, CrossMBBPhysDef))
-        FoundCSE = true;
+      // This can never be the case if the instruction both uses and
+      // defines the same physical register, which was detected above.
+      if (!PhysUseDef) {
+        unsigned CSVN = VNT.lookup(MI);
+        MachineInstr *CSMI = Exps[CSVN];
+        if (PhysRegDefsReach(CSMI, MI, PhysRefs, PhysDefs, CrossMBBPhysDef))
+          FoundCSE = true;
+      }
     }
 
     if (!FoundCSE) {
@@ -635,7 +657,5 @@ bool MachineCSE::runOnMachineFunction(MachineFunction &MF) {
   MRI = &MF.getRegInfo();
   AA = &getAnalysis<AliasAnalysis>();
   DT = &getAnalysis<MachineDominatorTree>();
-  AllocatableRegs = TRI->getAllocatableSet(MF);
-  ReservedRegs = TRI->getReservedRegs(MF);
   return PerformCSE(DT->getRootNode());
 }