Convert register liveness tracking to work on a sub-register level instead of just register units.

Reviewed by Andy

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197315 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LivePhysRegs.h

@@ -0,0 +1,146 @@
+//===- llvm/CodeGen/LivePhysRegs.h - Live Physical Register Set -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the LivePhysRegs utility for tracking liveness of
+// physical registers. This can be used for ad-hoc liveness tracking after
+// register allocation. You can start with the live-ins/live-outs at the
+// beginning/end of a block and update the information while walking the
+// instructions inside the block. This implementation tracks the liveness on a
+// sub-register granularity.
+//
+// We assume that the high bits of a physical super-register are not preserved
+// unless the instruction has an implicit-use operand reading the super-
+// register.
+//
+// X86 Example:
+// %YMM0<def> = ...
+// %XMM0<def> = ... (Kills %XMM0, all %XMM0s sub-registers, and %YMM0)
+//
+// %YMM0<def> = ...
+// %XMM0<def> = ..., %YMM0<imp-use> (%YMM0 and all its sub-registers are alive)
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_LIVE_PHYS_REGS_H
+#define LLVM_CODEGEN_LIVE_PHYS_REGS_H
+
+#include "llvm/ADT/SparseSet.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include <cassert>
+
+namespace llvm {
+
+class MachineInstr;
+
+/// \brief A set of live physical registers with functions to track liveness
+/// when walking backward/forward through a basic block.
+class LivePhysRegs {
+  const TargetRegisterInfo *TRI;
+  SparseSet<unsigned> LiveRegs;
+
+  LivePhysRegs(const LivePhysRegs&) LLVM_DELETED_FUNCTION;
+  LivePhysRegs &operator=(const LivePhysRegs&) LLVM_DELETED_FUNCTION;
+public:
+  /// \brief Constructs a new empty LivePhysRegs set.
+  LivePhysRegs() : TRI(0), LiveRegs() {}
+
+  /// \brief Constructs and initialize an empty LivePhysRegs set.
+  LivePhysRegs(const TargetRegisterInfo *TRI) : TRI(TRI) {
+    assert(TRI && "Invalid TargetRegisterInfo pointer.");
+    LiveRegs.setUniverse(TRI->getNumRegs());
+  }
+
+  /// \brief Clear and initialize the LivePhysRegs set.
+  void init(const TargetRegisterInfo *_TRI) {
+    assert(_TRI && "Invalid TargetRegisterInfo pointer.");
+    TRI = _TRI;
+    LiveRegs.clear();
+    LiveRegs.setUniverse(TRI->getNumRegs());
+  }
+
+  /// \brief Clears the LivePhysRegs set.
+  void clear() { LiveRegs.clear(); }
+
+  /// \brief Returns true if the set is empty.
+  bool empty() const { return LiveRegs.empty(); }
+
+  /// \brief Adds a physical register and all its sub-registers to the set.
+  void addReg(unsigned Reg) {
+    assert(TRI && "LivePhysRegs is not initialized.");
+    assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
+    for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+         SubRegs.isValid(); ++SubRegs)
+      LiveRegs.insert(*SubRegs);
+  }
+
+  /// \brief Removes a physical register, all its sub-registers, and all its
+  /// super-registers from the set.
+  void removeReg(unsigned Reg) {
+    assert(TRI && "LivePhysRegs is not initialized.");
+    assert(Reg <= TRI->getNumRegs() && "Expected a physical register.");
+    for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+         SubRegs.isValid(); ++SubRegs)
+      LiveRegs.erase(*SubRegs);
+    for (MCSuperRegIterator SuperRegs(Reg, TRI, /*IncludeSelf=*/false);
+         SuperRegs.isValid(); ++SuperRegs)
+      LiveRegs.erase(*SuperRegs);
+  }
+
+  /// \brief Removes physical registers clobbered by the regmask operand @p MO.
+  void removeRegsInMask(const MachineOperand &MO);
+
+  /// \brief Returns true if register @p Reg is contained in the set. This also
+  /// works if only the super register of @p Reg has been defined, because we
+  /// always add also all sub-registers to the set.
+  bool contains(unsigned Reg) const { return LiveRegs.count(Reg); }
+
+  /// \brief Simulates liveness when stepping backwards over an
+  /// instruction(bundle): Remove Defs, add uses. This is the recommended way of
+  /// calculating liveness.
+  void stepBackward(const MachineInstr &MI);
+
+  /// \brief Simulates liveness when stepping forward over an
+  /// instruction(bundle): Remove killed-uses, add defs. This is the not
+  /// recommended way, because it depends on accurate kill flags. If possible
+  /// use stepBackwards() instead of this function.
+  void stepForward(const MachineInstr &MI);
+
+  /// \brief Adds all live-in registers of basic block @p MBB.
+  void addLiveIns(const MachineBasicBlock *MBB) {
+    for (MachineBasicBlock::livein_iterator LI = MBB->livein_begin(),
+         LE = MBB->livein_end(); LI != LE; ++LI)
+      addReg(*LI);
+  }
+
+  /// \brief Adds all live-out registers of basic block @p MBB.
+  void addLiveOuts(const MachineBasicBlock *MBB) {
+    for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
+         SE = MBB->succ_end(); SI != SE; ++SI)
+      addLiveIns(*SI);
+  }
+
+  typedef SparseSet<unsigned>::const_iterator const_iterator;
+  const_iterator begin() const { return LiveRegs.begin(); }
+  const_iterator end() const { return LiveRegs.end(); }
+
+  /// \brief Prints the currently live registers to @p OS.
+  void print(raw_ostream &OS) const;
+
+  /// \brief Dumps the currently live registers to the debug output.
+  void dump() const;
+};
+
+inline raw_ostream &operator<<(raw_ostream &OS, const LivePhysRegs& LR) {
+  LR.print(OS);
+  return OS;
+}
+
+} // namespace llvm
+
+#endif // LLVM_CODEGEN_LIVE_PHYS_REGS_H