Extract method for detecting constant unallocatable physregs.

It is safe to move uses of such registers.

llvm-svn: 148259

llvm/include/llvm/CodeGen/MachineRegisterInfo.h

@@ -64,6 +64,9 @@ class MachineRegisterInfo {
   /// started.
   BitVector ReservedRegs;
 
+  /// AllocatableRegs - From TRI->getAllocatableSet.
+  mutable BitVector AllocatableRegs;
+
   /// LiveIns/LiveOuts - Keep track of the physical registers that are
   /// livein/liveout of the function.  Live in values are typically arguments in
   /// registers, live out values are typically return values in registers.
@@ -215,7 +218,12 @@ public:
 #ifndef NDEBUG
   void dumpUses(unsigned RegNo) const;
 #endif
-  
+
+  /// isConstantPhysReg - Returns true if PhysReg is unallocatable and constant
+  /// throughout the function.  It is safe to move instructions that read such
+  /// a physreg.
+  bool isConstantPhysReg(unsigned PhysReg, const MachineFunction &MF) const;
+
   //===--------------------------------------------------------------------===//
   // Virtual Register Info
   //===--------------------------------------------------------------------===//

llvm/lib/CodeGen/MachineLICM.cpp

@@ -81,8 +81,6 @@ namespace {
     MachineLoop *CurLoop;          // The current loop we are working on.
     MachineBasicBlock *CurPreheader; // The preheader for CurLoop.
 
-    BitVector AllocatableSet;
-
     // Track 'estimated' register pressure.
     SmallSet<unsigned, 32> RegSeen;
     SmallVector<unsigned, 8> RegPressure;
@@ -331,7 +329,6 @@ bool MachineLICM::runOnMachineFunction(MachineFunction &MF) {
   MFI = MF.getFrameInfo();
   MRI = &MF.getRegInfo();
   InstrItins = TM->getInstrItineraryData();
-  AllocatableSet = TRI->getAllocatableSet(MF);
 
   if (PreRegAlloc) {
     // Estimate register pressure during pre-regalloc pass.
@@ -905,18 +902,8 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) {
         // If the physreg has no defs anywhere, it's just an ambient register
         // and we can freely move its uses. Alternatively, if it's allocatable,
         // it could get allocated to something with a def during allocation.
-        if (!MRI->def_empty(Reg))
+        if (!MRI->isConstantPhysReg(Reg, *I.getParent()->getParent()))
           return false;
-        if (AllocatableSet.test(Reg))
-          return false;
-        // Check for a def among the register's aliases too.
-        for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
-          unsigned AliasReg = *Alias;
-          if (!MRI->def_empty(AliasReg))
-            return false;
-          if (AllocatableSet.test(AliasReg))
-            return false;
-        }
         // Otherwise it's safe to move.
         continue;
       } else if (!MO.isDead()) {

llvm/lib/CodeGen/MachineRegisterInfo.cpp

@@ -263,3 +263,21 @@ void MachineRegisterInfo::dumpUses(unsigned Reg) const {
 void MachineRegisterInfo::freezeReservedRegs(const MachineFunction &MF) {
   ReservedRegs = TRI->getReservedRegs(MF);
 }
+
+bool MachineRegisterInfo::isConstantPhysReg(unsigned PhysReg,
+                                            const MachineFunction &MF) const {
+  assert(TargetRegisterInfo::isPhysicalRegister(PhysReg));
+
+  // Check if any overlapping register is modified.
+  for (const unsigned *R = TRI->getOverlaps(PhysReg); *R; ++R)
+    if (!def_empty(*R))
+      return false;
+
+  // Check if any overlapping register is allocatable so it may be used later.
+  if (AllocatableRegs.empty())
+    AllocatableRegs = TRI->getAllocatableSet(MF);
+  for (const unsigned *R = TRI->getOverlaps(PhysReg); *R; ++R)
+    if (AllocatableRegs.test(*R))
+      return false;
+  return true;
+}

llvm/lib/CodeGen/MachineSink.cpp

@@ -485,21 +485,8 @@ MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI,
         // If the physreg has no defs anywhere, it's just an ambient register
         // and we can freely move its uses. Alternatively, if it's allocatable,
         // it could get allocated to something with a def during allocation.
-        if (!MRI->def_empty(Reg))
+        if (!MRI->isConstantPhysReg(Reg, *MBB->getParent()))
           return NULL;
-
-        if (AllocatableSet.test(Reg))
-          return NULL;
-
-        // Check for a def among the register's aliases too.
-        for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
-          unsigned AliasReg = *Alias;
-          if (!MRI->def_empty(AliasReg))
-            return NULL;
-
-          if (AllocatableSet.test(AliasReg))
-            return NULL;
-        }
       } else if (!MO.isDead()) {
         // A def that isn't dead. We can't move it.
         return NULL;

llvm/lib/CodeGen/TargetInstrInfoImpl.cpp

@@ -380,7 +380,6 @@ isReallyTriviallyReMaterializableGeneric(const MachineInstr *MI,
   const MachineRegisterInfo &MRI = MF.getRegInfo();
   const TargetMachine &TM = MF.getTarget();
   const TargetInstrInfo &TII = *TM.getInstrInfo();
-  const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
 
   // Remat clients assume operand 0 is the defined register.
   if (!MI->getNumOperands() || !MI->getOperand(0).isReg())
@@ -432,19 +431,8 @@ isReallyTriviallyReMaterializableGeneric(const MachineInstr *MI,
         // If the physreg has no defs anywhere, it's just an ambient register
         // and we can freely move its uses. Alternatively, if it's allocatable,
         // it could get allocated to something with a def during allocation.
-        if (!MRI.def_empty(Reg))
+        if (!MRI.isConstantPhysReg(Reg, MF))
           return false;
-        BitVector AllocatableRegs = TRI.getAllocatableSet(MF, 0);
-        if (AllocatableRegs.test(Reg))
-          return false;
-        // Check for a def among the register's aliases too.
-        for (const unsigned *Alias = TRI.getAliasSet(Reg); *Alias; ++Alias) {
-          unsigned AliasReg = *Alias;
-          if (!MRI.def_empty(AliasReg))
-            return false;
-          if (AllocatableRegs.test(AliasReg))
-            return false;
-        }
       } else {
         // A physreg def. We can't remat it.
         return false;