- Add TargetInstrInfo::isIdentical(). It's similar to MachineInstr::isIdentical

except it doesn't care if the definitions' virtual registers differ. This is
  used by machine LICM and other MI passes to perform CSE.
- Teach Thumb2InstrInfo::isIdentical() to check two t2LDRpci_pic are identical.
  Since pc relative constantpool entries are always different, this requires it
  it check if the values can actually the same.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86328 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineLICM.cpp

@@ -22,6 +22,7 @@
 
 #define DEBUG_TYPE "machine-licm"
 #include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineMemOperand.h"
@@ -43,6 +44,7 @@ STATISTIC(NumCSEed,   "Number of hoisted machine instructions CSEed");
 
 namespace {
   class MachineLICM : public MachineFunctionPass {
+    MachineConstantPool *MCP;
     const TargetMachine   *TM;
     const TargetInstrInfo *TII;
     const TargetRegisterInfo *TRI;
@@ -111,6 +113,11 @@ namespace {
     /// be hoistable.
     MachineInstr *ExtractHoistableLoad(MachineInstr *MI);
 
+    /// LookForDuplicate - Find an instruction amount PrevMIs that is a
+    /// duplicate of MI. Return this instruction if it's found.
+    const MachineInstr *LookForDuplicate(const MachineInstr *MI,
+                                     std::vector<const MachineInstr*> &PrevMIs);
+
     /// EliminateCSE - Given a LICM'ed instruction, look for an instruction on
     /// the preheader that compute the same value. If it's found, do a RAU on
     /// with the definition of the existing instruction rather than hoisting
@@ -153,6 +160,7 @@ bool MachineLICM::runOnMachineFunction(MachineFunction &MF) {
   DEBUG(errs() << "******** Machine LICM ********\n");
 
   Changed = FirstInLoop = false;
+  MCP = MF.getConstantPool();
   TM = &MF.getTarget();
   TII = TM->getInstrInfo();
   TRI = TM->getRegisterInfo();
@@ -432,32 +440,12 @@ void MachineLICM::InitCSEMap(MachineBasicBlock *BB) {
   }
 }
 
-static const MachineInstr *LookForDuplicate(const MachineInstr *MI,
-                                      std::vector<const MachineInstr*> &PrevMIs,
-                                      MachineRegisterInfo *RegInfo) {
-  unsigned NumOps = MI->getNumOperands();
+const MachineInstr*
+MachineLICM::LookForDuplicate(const MachineInstr *MI,
+                              std::vector<const MachineInstr*> &PrevMIs) {
   for (unsigned i = 0, e = PrevMIs.size(); i != e; ++i) {
     const MachineInstr *PrevMI = PrevMIs[i];
-    unsigned NumOps2 = PrevMI->getNumOperands();
-    if (NumOps != NumOps2)
-      continue;
-    bool IsSame = true;
-    for (unsigned j = 0; j != NumOps; ++j) {
-      const MachineOperand &MO = MI->getOperand(j);
-      if (MO.isReg() && MO.isDef()) {
-        if (RegInfo->getRegClass(MO.getReg()) !=
-            RegInfo->getRegClass(PrevMI->getOperand(j).getReg())) {
-          IsSame = false;
-          break;
-        }
-        continue;
-      }
-      if (!MO.isIdenticalTo(PrevMI->getOperand(j))) {
-        IsSame = false;
-        break;
-      }
-    }
-    if (IsSame)
+    if (TII->isIdentical(MI, PrevMI, RegInfo))
       return PrevMI;
   }
   return 0;
@@ -465,18 +453,19 @@ static const MachineInstr *LookForDuplicate(const MachineInstr *MI,
 
 bool MachineLICM::EliminateCSE(MachineInstr *MI,
           DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator &CI) {
-  if (CI != CSEMap.end()) {
-    if (const MachineInstr *Dup = LookForDuplicate(MI, CI->second, RegInfo)) {
-      DEBUG(errs() << "CSEing " << *MI << " with " << *Dup);
-      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
-        const MachineOperand &MO = MI->getOperand(i);
-        if (MO.isReg() && MO.isDef())
-          RegInfo->replaceRegWith(MO.getReg(), Dup->getOperand(i).getReg());
-      }
-      MI->eraseFromParent();
-      ++NumCSEed;
-      return true;
+  if (CI == CSEMap.end())
+    return false;
+
+  if (const MachineInstr *Dup = LookForDuplicate(MI, CI->second)) {
+    DEBUG(errs() << "CSEing " << *MI << " with " << *Dup);
+    for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+      const MachineOperand &MO = MI->getOperand(i);
+      if (MO.isReg() && MO.isDef())
+        RegInfo->replaceRegWith(MO.getReg(), Dup->getOperand(i).getReg());
     }
+    MI->eraseFromParent();
+    ++NumCSEed;
+    return true;
   }
   return false;
 }

lib/CodeGen/TargetInstrInfoImpl.cpp

@@ -143,6 +143,37 @@ void TargetInstrInfoImpl::reMaterialize(MachineBasicBlock &MBB,
   MBB.insert(I, MI);
 }
 
+bool
+TargetInstrInfoImpl::isIdentical(const MachineInstr *MI,
+                                 const MachineInstr *Other,
+                                 const MachineRegisterInfo *MRI) const {
+  if (MI->getOpcode() != Other->getOpcode() ||
+      MI->getNumOperands() != Other->getNumOperands())
+    return false;
+
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    const MachineOperand &OMO = Other->getOperand(i);
+    if (MO.isReg() && MO.isDef()) {
+      assert(OMO.isReg() && OMO.isDef());
+      unsigned Reg = MO.getReg();
+      if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
+        if (Reg != OMO.getReg())
+          return false;
+      } else if (MRI->getRegClass(MO.getReg()) !=
+                 MRI->getRegClass(OMO.getReg()))
+        return false;
+
+      continue;
+    }
+
+    if (!MO.isIdenticalTo(OMO))
+      return false;
+  }
+
+  return true;
+}
+
 unsigned
 TargetInstrInfoImpl::GetFunctionSizeInBytes(const MachineFunction &MF) const {
   unsigned FnSize = 0;

lib/Target/ARM/ARMConstantPoolValue.cpp

@@ -62,9 +62,10 @@ int ARMConstantPoolValue::getExistingMachineCPValue(MachineConstantPool *CP,
       ARMConstantPoolValue *CPV =
         (ARMConstantPoolValue *)Constants[i].Val.MachineCPVal;
       if (CPV->CVal == CVal &&
-          CPV->S == S &&
           CPV->LabelId == LabelId &&
-          CPV->PCAdjust == PCAdjust)
+          CPV->PCAdjust == PCAdjust &&
+          (CPV->S == S || strcmp(CPV->S, S) == 0) &&
+          (CPV->Modifier == Modifier || strcmp(CPV->Modifier, Modifier) == 0))
         return i;
     }
   }
@@ -84,6 +85,23 @@ ARMConstantPoolValue::AddSelectionDAGCSEId(FoldingSetNodeID &ID) {
   ID.AddInteger(PCAdjust);
 }
 
+bool
+ARMConstantPoolValue::hasSameValue(ARMConstantPoolValue *ACPV) {
+  if (ACPV->Kind == Kind &&
+      ACPV->CVal == CVal &&
+      ACPV->PCAdjust == PCAdjust &&
+      (ACPV->S == S || strcmp(ACPV->S, S) == 0) &&
+      (ACPV->Modifier == Modifier || strcmp(ACPV->Modifier, Modifier) == 0)) {
+    if (ACPV->LabelId == LabelId)
+      return true;
+    // Two PC relative constpool entries containing the same GV address or
+    // external symbols. FIXME: What about blockaddress?
+    if (Kind == ARMCP::CPValue || Kind == ARMCP::CPExtSymbol)
+      return true;
+  }
+  return false;
+}
+
 void ARMConstantPoolValue::dump() const {
   errs() << "  " << *this;
 }

lib/Target/ARM/ARMConstantPoolValue.h

@@ -81,6 +81,10 @@ public:
 
   virtual void AddSelectionDAGCSEId(FoldingSetNodeID &ID);
 
+  /// hasSameValue - Return true if this ARM constpool value
+  /// can share the same constantpool entry as another ARM constpool value.
+  bool hasSameValue(ARMConstantPoolValue *ACPV);
+
   void print(raw_ostream *O) const { if (O) print(*O); }
   void print(raw_ostream &O) const;
   void dump() const;

lib/Target/ARM/Thumb2InstrInfo.cpp

@@ -175,6 +175,32 @@ void Thumb2InstrInfo::reMaterialize(MachineBasicBlock &MBB,
   NewMI->getOperand(0).setSubReg(SubIdx);
 }
 
+bool Thumb2InstrInfo::isIdentical(const MachineInstr *MI0,
+                                  const MachineInstr *MI1,
+                                  const MachineRegisterInfo *MRI) const {
+  unsigned Opcode = MI0->getOpcode();
+  if (Opcode == ARM::t2LDRpci_pic) {
+    const MachineOperand &MO0 = MI0->getOperand(1);
+    const MachineOperand &MO1 = MI1->getOperand(1);
+    if (MO0.getOffset() != MO1.getOffset())
+      return false;
+
+    const MachineFunction *MF = MI0->getParent()->getParent();
+    const MachineConstantPool *MCP = MF->getConstantPool();
+    int CPI0 = MO0.getIndex();
+    int CPI1 = MO1.getIndex();
+    const MachineConstantPoolEntry &MCPE0 = MCP->getConstants()[CPI0];
+    const MachineConstantPoolEntry &MCPE1 = MCP->getConstants()[CPI1];
+    ARMConstantPoolValue *ACPV0 =
+      static_cast<ARMConstantPoolValue*>(MCPE0.Val.MachineCPVal);
+    ARMConstantPoolValue *ACPV1 =
+      static_cast<ARMConstantPoolValue*>(MCPE1.Val.MachineCPVal);
+    return ACPV0->hasSameValue(ACPV1);
+  }
+
+  return TargetInstrInfoImpl::isIdentical(MI0, MI1, MRI);
+}
+
 void llvm::emitT2RegPlusImmediate(MachineBasicBlock &MBB,
                                MachineBasicBlock::iterator &MBBI, DebugLoc dl,
                                unsigned DestReg, unsigned BaseReg, int NumBytes,

lib/Target/ARM/Thumb2InstrInfo.h

@@ -54,6 +54,10 @@ public:
                      unsigned DestReg, unsigned SubIdx,
                      const MachineInstr *Orig) const;
 
+  bool isIdentical(const MachineInstr *MI,
+                   const MachineInstr *Other,
+                   const MachineRegisterInfo *MRI) const;
+
   /// getRegisterInfo - TargetInstrInfo is a superset of MRegister info.  As
   /// such, whenever a client has an instance of instruction info, it should
   /// always be able to get register info as well (through this method).

test/CodeGen/Thumb2/machine-licm.ll

@@ -15,11 +15,13 @@ entry:
 
 bb.nph:                                           ; preds = %entry
 ; CHECK: BB#1
-; CHECK: ldr{{.*}} r{{[0-9]+}}, LCPI1_0
-; CHECK: ldr{{.*}} r{{[0-9]+}}, LCPI1_1
-; CHECK: add r{{[0-9]+}}, pc
-; CHECK: add r{{[0-9]+}}, pc
+; CHECK: ldr.n r2, LCPI1_0
+; CHECK: add r2, pc
+; CHECK: ldr r{{[0-9]+}}, [r2]
 ; CHECK: LBB1_2
+; CHECK: LCPI1_0:
+; CHECK-NOT: LCPI1_1:
+; CHECK: .section
   %.pre = load i32* @GV, align 4                  ; <i32> [#uses=1]
   br label %bb