Move RegisterPressure.h.

Make it a general utility for use by Targets.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158097 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 255 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/RegisterPressure.h b/include/llvm/CodeGen/RegisterPressure.h
new file mode 100644
index 0000000000..dd7ba86d19
--- /dev/null
+++ b/include/llvm/CodeGen/RegisterPressure.h
@@ -0,0 +1,255 @@
+//===-- RegisterPressure.h - Dynamic Register Pressure -*- C++ -*-------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the RegisterPressure class which can be used to track
+// MachineInstr level register pressure.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_REGISTERPRESSURE_H
+#define LLVM_CODEGEN_REGISTERPRESSURE_H
+
+#include "llvm/CodeGen/SlotIndexes.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/ADT/SparseSet.h"
+
+namespace llvm {
+
+class LiveIntervals;
+class RegisterClassInfo;
+class MachineInstr;
+
+/// Base class for register pressure results.
+struct RegisterPressure {
+  /// Map of max reg pressure indexed by pressure set ID, not class ID.
+  std::vector<unsigned> MaxSetPressure;
+
+  /// List of live in registers.
+  SmallVector<unsigned,8> LiveInRegs;
+  SmallVector<unsigned,8> LiveOutRegs;
+
+  /// Increase register pressure for each pressure set impacted by this register
+  /// class. Normally called by RegPressureTracker, but may be called manually
+  /// to account for live through (global liveness).
+  void increase(const TargetRegisterClass *RC, const TargetRegisterInfo *TRI);
+
+  /// Decrease register pressure for each pressure set impacted by this register
+  /// class. This is only useful to account for spilling or rematerialization.
+  void decrease(const TargetRegisterClass *RC, const TargetRegisterInfo *TRI);
+
+  void dump(const TargetRegisterInfo *TRI);
+};
+
+/// RegisterPressure computed within a region of instructions delimited by
+/// TopIdx and BottomIdx.  During pressure computation, the maximum pressure per
+/// register pressure set is increased. Once pressure within a region is fully
+/// computed, the live-in and live-out sets are recorded.
+///
+/// This is preferable to RegionPressure when LiveIntervals are available,
+/// because delimiting regions by SlotIndex is more robust and convenient than
+/// holding block iterators. The block contents can change without invalidating
+/// the pressure result.
+struct IntervalPressure : RegisterPressure {
+  /// Record the boundary of the region being tracked.
+  SlotIndex TopIdx;
+  SlotIndex BottomIdx;
+
+  void reset();
+
+  void openTop(SlotIndex NextTop);
+
+  void openBottom(SlotIndex PrevBottom);
+};
+
+/// RegisterPressure computed within a region of instructions delimited by
+/// TopPos and BottomPos. This is a less precise version of IntervalPressure for
+/// use when LiveIntervals are unavailable.
+struct RegionPressure : RegisterPressure {
+  /// Record the boundary of the region being tracked.
+  MachineBasicBlock::const_iterator TopPos;
+  MachineBasicBlock::const_iterator BottomPos;
+
+  void reset();
+
+  void openTop(MachineBasicBlock::const_iterator PrevTop);
+
+  void openBottom(MachineBasicBlock::const_iterator PrevBottom);
+};
+
+/// An element of pressure difference that identifies the pressure set and
+/// amount of increase or decrease in units of pressure.
+struct PressureElement {
+  unsigned PSetID;
+  int UnitIncrease;
+
+  PressureElement(): PSetID(~0U), UnitIncrease(0) {}
+  PressureElement(unsigned id, int inc): PSetID(id), UnitIncrease(inc) {}
+
+  bool isValid() const { return PSetID != ~0U; }
+};
+
+/// Store the effects of a change in pressure on things that MI scheduler cares
+/// about.
+///
+/// Excess records the value of the largest difference in register units beyond
+/// the target's pressure limits across the affected pressure sets, where
+/// largest is defined as the absolute value of the difference. Negative
+/// ExcessUnits indicates a reduction in pressure that had already exceeded the
+/// target's limits.
+///
+/// CriticalMax records the largest increase in the tracker's max pressure that
+/// exceeds the critical limit for some pressure set determined by the client.
+///
+/// CurrentMax records the largest increase in the tracker's max pressure that
+/// exceeds the current limit for some pressure set determined by the client.
+struct RegPressureDelta {
+  PressureElement Excess;
+  PressureElement CriticalMax;
+  PressureElement CurrentMax;
+
+  RegPressureDelta() {}
+};
+
+/// Track the current register pressure at some position in the instruction
+/// stream, and remember the high water mark within the region traversed. This
+/// does not automatically consider live-through ranges. The client may
+/// independently adjust for global liveness.
+///
+/// Each RegPressureTracker only works within a MachineBasicBlock. Pressure can
+/// be tracked across a larger region by storing a RegisterPressure result at
+/// each block boundary and explicitly adjusting pressure to account for block
+/// live-in and live-out register sets.
+///
+/// RegPressureTracker holds a reference to a RegisterPressure result that it
+/// computes incrementally. During downward tracking, P.BottomIdx or P.BottomPos
+/// is invalid until it reaches the end of the block or closeRegion() is
+/// explicitly called. Similarly, P.TopIdx is invalid during upward
+/// tracking. Changing direction has the side effect of closing region, and
+/// traversing past TopIdx or BottomIdx reopens it.
+class RegPressureTracker {
+  const MachineFunction     *MF;
+  const TargetRegisterInfo  *TRI;
+  const RegisterClassInfo   *RCI;
+  const MachineRegisterInfo *MRI;
+  const LiveIntervals       *LIS;
+
+  /// We currently only allow pressure tracking within a block.
+  const MachineBasicBlock *MBB;
+
+  /// Track the max pressure within the region traversed so far.
+  RegisterPressure &P;
+
+  /// Run in two modes dependending on whether constructed with IntervalPressure
+  /// or RegisterPressure. If requireIntervals is false, LIS are ignored.
+  bool RequireIntervals;
+
+  /// Register pressure corresponds to liveness before this instruction
+  /// iterator. It may point to the end of the block rather than an instruction.
+  MachineBasicBlock::const_iterator CurrPos;
+
+  /// Pressure map indexed by pressure set ID, not class ID.
+  std::vector<unsigned> CurrSetPressure;
+
+  /// List of live registers.
+  SparseSet<unsigned> LivePhysRegs;
+  SparseSet<unsigned, VirtReg2IndexFunctor> LiveVirtRegs;
+
+public:
+  RegPressureTracker(IntervalPressure &rp) :
+    MF(0), TRI(0), RCI(0), LIS(0), MBB(0), P(rp), RequireIntervals(true) {}
+
+  RegPressureTracker(RegionPressure &rp) :
+    MF(0), TRI(0), RCI(0), LIS(0), MBB(0), P(rp), RequireIntervals(false) {}
+
+  void init(const MachineFunction *mf, const RegisterClassInfo *rci,
+            const LiveIntervals *lis, const MachineBasicBlock *mbb,
+            MachineBasicBlock::const_iterator pos);
+
+  /// Force liveness of registers. Particularly useful to initialize the
+  /// livein/out state of the tracker before the first call to advance/recede.
+  void addLiveRegs(ArrayRef<unsigned> Regs);
+
+  /// Get the MI position corresponding to this register pressure.
+  MachineBasicBlock::const_iterator getPos() const { return CurrPos; }
+
+  // Reset the MI position corresponding to the register pressure. This allows
+  // schedulers to move instructions above the RegPressureTracker's
+  // CurrPos. Since the pressure is computed before CurrPos, the iterator
+  // position changes while pressure does not.
+  void setPos(MachineBasicBlock::const_iterator Pos) { CurrPos = Pos; }
+
+  /// Recede across the previous instruction.
+  bool recede();
+
+  /// Advance across the current instruction.
+  bool advance();
+
+  /// Finalize the region boundaries and recored live ins and live outs.
+  void closeRegion();
+
+  /// Get the resulting register pressure over the traversed region.
+  /// This result is complete if either advance() or recede() has returned true,
+  /// or if closeRegion() was explicitly invoked.
+  RegisterPressure &getPressure() { return P; }
+
+  void discoverPhysLiveIn(unsigned Reg);
+  void discoverPhysLiveOut(unsigned Reg);
+
+  void discoverVirtLiveIn(unsigned Reg);
+  void discoverVirtLiveOut(unsigned Reg);
+
+  bool isTopClosed() const;
+  bool isBottomClosed() const;
+
+  void closeTop();
+  void closeBottom();
+
+  /// Consider the pressure increase caused by traversing this instruction
+  /// bottom-up. Find the pressure set with the most change beyond its pressure
+  /// limit based on the tracker's current pressure, and record the number of
+  /// excess register units of that pressure set introduced by this instruction.
+  void getMaxUpwardPressureDelta(const MachineInstr *MI,
+                                 RegPressureDelta &Delta,
+                                 ArrayRef<PressureElement> CriticalPSets,
+                                 ArrayRef<unsigned> MaxPressureLimit);
+
+  /// Consider the pressure increase caused by traversing this instruction
+  /// top-down. Find the pressure set with the most change beyond its pressure
+  /// limit based on the tracker's current pressure, and record the number of
+  /// excess register units of that pressure set introduced by this instruction.
+  void getMaxDownwardPressureDelta(const MachineInstr *MI,
+                                   RegPressureDelta &Delta,
+                                   ArrayRef<PressureElement> CriticalPSets,
+                                   ArrayRef<unsigned> MaxPressureLimit);
+
+  /// Find the pressure set with the most change beyond its pressure limit after
+  /// traversing this instruction either upward or downward depending on the
+  /// closed end of the current region.
+  void getMaxPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
+                           ArrayRef<PressureElement> CriticalPSets,
+                           ArrayRef<unsigned> MaxPressureLimit) {
+    if (isTopClosed())
+      return getMaxDownwardPressureDelta(MI, Delta, CriticalPSets,
+                                         MaxPressureLimit);
+
+    assert(isBottomClosed() && "Uninitialized pressure tracker");
+    return getMaxUpwardPressureDelta(MI, Delta, CriticalPSets,
+                                     MaxPressureLimit);
+  }
+
+protected:
+  void increasePhysRegPressure(ArrayRef<unsigned> Regs);
+  void decreasePhysRegPressure(ArrayRef<unsigned> Regs);
+
+  void increaseVirtRegPressure(ArrayRef<unsigned> Regs);
+  void decreaseVirtRegPressure(ArrayRef<unsigned> Regs);
+};
+} // end namespace llvm
+
+#endif