CodeGen: Add/Factor out LiveRegUnits class; NFCI

This is a set of register units intended to track register liveness, it
is similar in spirit to LivePhysRegs.
You can also think of this as the liveness tracking parts of the
RegisterScavenger factored out into an own class.

This was proposed in http://llvm.org/PR27609

Differential Revision: http://reviews.llvm.org/D21916

llvm-svn: 292542

include/llvm/CodeGen/LiveRegUnits.h

@@ -0,0 +1,116 @@
+//===- llvm/CodeGen/LiveRegUnits.h - Register Unit Set ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// A set of register units. It is intended for register liveness tracking.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_LIVEREGUNITS_H
+#define LLVM_CODEGEN_LIVEREGUNITS_H
+
+#include "llvm/ADT/BitVector.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+
+namespace llvm {
+
+class MachineInstr;
+class MachineBasicBlock;
+
+/// A set of register units used to track register liveness.
+class LiveRegUnits {
+  const TargetRegisterInfo *TRI;
+  BitVector Units;
+
+public:
+  /// Constructs a new empty LiveRegUnits set.
+  LiveRegUnits() : TRI(nullptr) {}
+
+  /// Constructs and initialize an empty LiveRegUnits set.
+  LiveRegUnits(const TargetRegisterInfo &TRI) {
+    init(TRI);
+  }
+
+  /// Initialize and clear the set.
+  void init(const TargetRegisterInfo &TRI) {
+    this->TRI = &TRI;
+    Units.reset();
+    Units.resize(TRI.getNumRegUnits());
+  }
+
+  /// Clears the set.
+  void clear() { Units.reset(); }
+
+  /// Returns true if the set is empty.
+  bool empty() const { return Units.empty(); }
+
+  /// Adds register units covered by physical register \p Reg.
+  void addReg(unsigned Reg) {
+    for (MCRegUnitIterator Unit(Reg, TRI); Unit.isValid(); ++Unit)
+      Units.set(*Unit);
+  }
+
+  /// \brief Adds register units covered by physical register \p Reg that are
+  /// part of the lanemask \p Mask.
+  void addRegMasked(unsigned Reg, LaneBitmask Mask) {
+    for (MCRegUnitMaskIterator Unit(Reg, TRI); Unit.isValid(); ++Unit) {
+      LaneBitmask UnitMask = (*Unit).second;
+      if (UnitMask.none() || (UnitMask & Mask).any())
+        Units.set((*Unit).first);
+    }
+  }
+
+  /// Removes all register units covered by physical register \p Reg.
+  void removeReg(unsigned Reg) {
+    for (MCRegUnitIterator Unit(Reg, TRI); Unit.isValid(); ++Unit)
+      Units.reset(*Unit);
+  }
+
+  /// Removes register units not preserved by the regmask \p RegMask.
+  /// The regmask has the same format as the one in the RegMask machine operand.
+  void removeRegsNotPreserved(const uint32_t *RegMask);
+
+  /// Returns true if no part of physical register \p Reg is live.
+  bool available(unsigned Reg) const {
+    for (MCRegUnitIterator Unit(Reg, TRI); Unit.isValid(); ++Unit) {
+      if (Units.test(*Unit))
+        return false;
+    }
+    return true;
+  }
+
+  /// Updates liveness when stepping backwards over the instruction \p MI.
+  void stepBackward(const MachineInstr &MI);
+
+  /// Adds registers living out of block \p MBB.
+  /// Live out registers are the union of the live-in registers of the successor
+  /// blocks and pristine registers. Live out registers of the end block are the
+  /// callee saved registers.
+  void addLiveOuts(const MachineBasicBlock &MBB);
+
+  /// Adds registers living into block \p MBB.
+  void addLiveIns(const MachineBasicBlock &MBB);
+
+  /// Adds all register units marked in the bitvector \p RegUnits.
+  void addUnits(const BitVector &RegUnits) {
+    Units |= RegUnits;
+  }
+  /// Removes all register units marked in the bitvector \p RegUnits.
+  void removeUnits(const BitVector &RegUnits) {
+    Units.reset(RegUnits);
+  }
+  /// Return the internal bitvector representation of the set.
+  const BitVector &getBitVector() const {
+    return Units;
+  }
+};
+
+} // namespace llvm
+
+#endif

include/llvm/CodeGen/RegisterScavenging.h

@@ -19,6 +19,7 @@
 #define LLVM_CODEGEN_REGISTERSCAVENGING_H
 
 #include "llvm/ADT/BitVector.h"
+#include "llvm/CodeGen/LiveRegUnits.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 
@@ -58,10 +59,7 @@ class RegScavenger {
   /// A vector of information on scavenged registers.
   SmallVector<ScavengedInfo, 2> Scavenged;
 
-  /// The current state of each reg unit immediately before MBBI.
-  /// One bit per register unit. If bit is not set it means any
-  /// register containing that register unit is currently being used.
-  BitVector RegUnitsAvailable;
+  LiveRegUnits LiveUnits;
 
   // These BitVectors are only used internally to forward(). They are members
   // to avoid frequent reallocations.
@@ -171,11 +169,11 @@ private:
 
   /// setUsed / setUnused - Mark the state of one or a number of register units.
   ///
-  void setUsed(BitVector &RegUnits) {
-    RegUnitsAvailable.reset(RegUnits);
+  void setUsed(const BitVector &RegUnits) {
+    LiveUnits.addUnits(RegUnits);
   }
-  void setUnused(BitVector &RegUnits) {
-    RegUnitsAvailable |= RegUnits;
+  void setUnused(const BitVector &RegUnits) {
+    LiveUnits.removeUnits(RegUnits);
   }
 
   /// Processes the current instruction and fill the KillRegUnits and

lib/CodeGen/CMakeLists.txt

@@ -46,6 +46,7 @@ add_llvm_library(LLVMCodeGen
   LiveRangeCalc.cpp
   LiveRangeEdit.cpp
   LiveRegMatrix.cpp
+  LiveRegUnits.cpp
   LiveStackAnalysis.cpp
   LiveVariables.cpp
   LLVMTargetMachine.cpp

lib/CodeGen/LiveRegUnits.cpp

@@ -0,0 +1,97 @@
+//===--- LiveRegUnits.cpp - Register Unit Set -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This file imlements the LiveRegUnits set.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/LiveRegUnits.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBundle.h"
+using namespace llvm;
+
+void LiveRegUnits::removeRegsNotPreserved(const uint32_t *RegMask) {
+  for (unsigned U = 0, E = TRI->getNumRegUnits(); U != E; ++U) {
+    for (MCRegUnitRootIterator RootReg(U, TRI); RootReg.isValid(); ++RootReg) {
+      if (MachineOperand::clobbersPhysReg(RegMask, *RootReg))
+        Units.reset(U);
+    }
+  }
+}
+
+void LiveRegUnits::stepBackward(const MachineInstr &MI) {
+  // Remove defined registers and regmask kills from the set.
+  for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
+    if (O->isReg()) {
+      if (!O->isDef())
+        continue;
+      unsigned Reg = O->getReg();
+      if (!TargetRegisterInfo::isPhysicalRegister(Reg))
+        continue;
+      removeReg(Reg);
+    } else if (O->isRegMask())
+      removeRegsNotPreserved(O->getRegMask());
+  }
+
+  // Add uses to the set.
+  for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
+    if (!O->isReg() || !O->readsReg())
+      continue;
+    unsigned Reg = O->getReg();
+    if (!TargetRegisterInfo::isPhysicalRegister(Reg))
+      continue;
+    addReg(Reg);
+  }
+}
+
+/// Add live-in registers of basic block \p MBB to \p LiveUnits.
+static void addLiveIns(LiveRegUnits &LiveUnits, const MachineBasicBlock &MBB) {
+  for (const auto &LI : MBB.liveins())
+    LiveUnits.addRegMasked(LI.PhysReg, LI.LaneMask);
+}
+
+static void addLiveOuts(LiveRegUnits &LiveUnits, const MachineBasicBlock &MBB) {
+  // To get the live-outs we simply merge the live-ins of all successors.
+  for (const MachineBasicBlock *Succ : MBB.successors())
+    addLiveIns(LiveUnits, *Succ);
+}
+
+/// Add pristine registers to the given \p LiveUnits. This function removes
+/// actually saved callee save registers when \p InPrologueEpilogue is false.
+static void removeSavedRegs(LiveRegUnits &LiveUnits, const MachineFunction &MF,
+                            const MachineFrameInfo &MFI,
+                            const TargetRegisterInfo &TRI) {
+  for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
+    LiveUnits.removeReg(Info.getReg());
+}
+
+void LiveRegUnits::addLiveOuts(const MachineBasicBlock &MBB) {
+  const MachineFunction &MF = *MBB.getParent();
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  if (MFI.isCalleeSavedInfoValid()) {
+    for (const MCPhysReg *I = TRI->getCalleeSavedRegs(&MF); *I; ++I)
+      addReg(*I);
+    if (!MBB.isReturnBlock())
+      removeSavedRegs(*this, MF, MFI, *TRI);
+  }
+  ::addLiveOuts(*this, MBB);
+}
+
+void LiveRegUnits::addLiveIns(const MachineBasicBlock &MBB) {
+  const MachineFunction &MF = *MBB.getParent();
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  if (MFI.isCalleeSavedInfoValid()) {
+    for (const MCPhysReg *I = TRI->getCalleeSavedRegs(&MF); *I; ++I)
+      addReg(*I);
+    if (&MBB != &MF.front())
+      removeSavedRegs(*this, MF, MFI, *TRI);
+  }
+  ::addLiveIns(*this, MBB);
+}

lib/CodeGen/RegisterScavenging.cpp

@@ -32,11 +32,7 @@ using namespace llvm;
 #define DEBUG_TYPE "reg-scavenging"
 
 void RegScavenger::setRegUsed(unsigned Reg, LaneBitmask LaneMask) {
-  for (MCRegUnitMaskIterator RUI(Reg, TRI); RUI.isValid(); ++RUI) {
-    LaneBitmask UnitMask = (*RUI).second;
-    if (UnitMask.none() || (LaneMask & UnitMask).any())
-      RegUnitsAvailable.reset((*RUI).first);
-  }
+  LiveUnits.addRegMasked(Reg, LaneMask);
 }
 
 void RegScavenger::init(MachineBasicBlock &MBB) {
@@ -44,6 +40,7 @@ void RegScavenger::init(MachineBasicBlock &MBB) {
   TII = MF.getSubtarget().getInstrInfo();
   TRI = MF.getSubtarget().getRegisterInfo();
   MRI = &MF.getRegInfo();
+  LiveUnits.init(*TRI);
 
   assert((NumRegUnits == 0 || NumRegUnits == TRI->getNumRegUnits()) &&
          "Target changed?");
@@ -51,7 +48,6 @@ void RegScavenger::init(MachineBasicBlock &MBB) {
   // Self-initialize.
   if (!this->MBB) {
     NumRegUnits = TRI->getNumRegUnits();
-    RegUnitsAvailable.resize(NumRegUnits);
     KillRegUnits.resize(NumRegUnits);
     DefRegUnits.resize(NumRegUnits);
     TmpRegUnits.resize(NumRegUnits);
@@ -64,32 +60,17 @@ void RegScavenger::init(MachineBasicBlock &MBB) {
     I->Restore = nullptr;
   }
 
-  // All register units start out unused.
-  RegUnitsAvailable.set();
-
-  // Pristine CSRs are not available.
-  BitVector PR = MF.getFrameInfo().getPristineRegs(MF);
-  for (int I = PR.find_first(); I>0; I = PR.find_next(I))
-    setRegUsed(I);
-
   Tracking = false;
 }
 
-void RegScavenger::setLiveInsUsed(const MachineBasicBlock &MBB) {
-  for (const auto &LI : MBB.liveins())
-    setRegUsed(LI.PhysReg, LI.LaneMask);
-}
-
 void RegScavenger::enterBasicBlock(MachineBasicBlock &MBB) {
   init(MBB);
-  setLiveInsUsed(MBB);
+  LiveUnits.addLiveIns(MBB);
 }
 
 void RegScavenger::enterBasicBlockEnd(MachineBasicBlock &MBB) {
   init(MBB);
-  // Merge live-ins of successors to get live-outs.
-  for (const MachineBasicBlock *Succ : MBB.successors())
-    setLiveInsUsed(*Succ);
+  LiveUnits.addLiveOuts(MBB);
 
   // Move internal iterator at the last instruction of the block.
   if (MBB.begin() != MBB.end()) {
@@ -263,36 +244,7 @@ void RegScavenger::backward() {
   assert(Tracking && "Must be tracking to determine kills and defs");
 
   const MachineInstr &MI = *MBBI;
-  // Defined or clobbered registers are available now.
-  for (const MachineOperand &MO : MI.operands()) {
-    if (MO.isRegMask()) {
-      for (unsigned RU = 0, RUEnd = TRI->getNumRegUnits(); RU != RUEnd;
-           ++RU) {
-        for (MCRegUnitRootIterator RURI(RU, TRI); RURI.isValid(); ++RURI) {
-          if (MO.clobbersPhysReg(*RURI)) {
-            RegUnitsAvailable.set(RU);
-            break;
-          }
-        }
-      }
-    } else if (MO.isReg() && MO.isDef()) {
-      unsigned Reg = MO.getReg();
-      if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg) ||
-          isReserved(Reg))
-        continue;
-      addRegUnits(RegUnitsAvailable, Reg);
-    }
-  }
-  // Mark read registers as unavailable.
-  for (const MachineOperand &MO : MI.uses()) {
-    if (MO.isReg() && MO.readsReg()) {
-      unsigned Reg = MO.getReg();
-      if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg) ||
-          isReserved(Reg))
-        continue;
-      removeRegUnits(RegUnitsAvailable, Reg);
-    }
-  }
+  LiveUnits.stepBackward(MI);
 
   if (MBBI == MBB->begin()) {
     MBBI = MachineBasicBlock::iterator(nullptr);
@@ -302,12 +254,9 @@ void RegScavenger::backward() {
 }
 
 bool RegScavenger::isRegUsed(unsigned Reg, bool includeReserved) const {
-  if (includeReserved && isReserved(Reg))
-    return true;
-  for (MCRegUnitIterator RUI(Reg, TRI); RUI.isValid(); ++RUI)
-    if (!RegUnitsAvailable.test(*RUI))
-      return true;
-  return false;
+  if (isReserved(Reg))
+    return includeReserved;
+  return !LiveUnits.available(Reg);
 }
 
 unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RC) const {