1 //===- LiveIntervalCalc.h - Calculate live intervals -----------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // The LiveIntervalCalc class is an extension of LiveRangeCalc targeted to the
10 // computation and modification of the LiveInterval variants of LiveRanges.
11 // LiveIntervals are meant to track liveness of registers and stack slots and
12 // LiveIntervalCalc adds to LiveRangeCalc all the machinery requied to
13 // construct the liveness of virtual registers tracked by a LiveInterval.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #ifndef LLVM_LIB_CODEGEN_LIVEINTERVALCALC_H
18 #define LLVM_LIB_CODEGEN_LIVEINTERVALCALC_H
19 
20 #include "llvm/CodeGen/LiveRangeCalc.h"
21 
22 namespace llvm {
23 
24 template <class NodeT> class DomTreeNodeBase;
25 
26 using MachineDomTreeNode = DomTreeNodeBase<MachineBasicBlock>;
27 
28 class LiveIntervalCalc : public LiveRangeCalc {
29   /// Extend the live range of @p LR to reach all uses of Reg.
30   ///
31   /// If @p LR is a main range, or if @p LI is null, then all uses must be
32   /// jointly dominated by the definitions from @p LR. If @p LR is a subrange
33   /// of the live interval @p LI, corresponding to lane mask @p LaneMask,
34   /// all uses must be jointly dominated by the definitions from @p LR
35   /// together with definitions of other lanes where @p LR becomes undefined
36   /// (via <def,read-undef> operands).
37   /// If @p LR is a main range, the @p LaneMask should be set to ~0, i.e.
38   /// LaneBitmask::getAll().
39   void extendToUses(LiveRange &LR, Register Reg, LaneBitmask LaneMask,
40                     LiveInterval *LI = nullptr);
41 
42 public:
43   LiveIntervalCalc() = default;
44 
45   /// createDeadDefs - Create a dead def in LI for every def operand of Reg.
46   /// Each instruction defining Reg gets a new VNInfo with a corresponding
47   /// minimal live range.
48   void createDeadDefs(LiveRange &LR, Register Reg);
49 
50   /// Extend the live range of @p LR to reach all uses of Reg.
51   ///
52   /// All uses must be jointly dominated by existing liveness.  PHI-defs are
53   /// inserted as needed to preserve SSA form.
54   void extendToUses(LiveRange &LR, MCRegister PhysReg) {
55     extendToUses(LR, PhysReg, LaneBitmask::getAll());
56   }
57 
58   /// Calculates liveness for the register specified in live interval @p LI.
59   /// Creates subregister live ranges as needed if subreg liveness tracking is
60   /// enabled.
61   void calculate(LiveInterval &LI, bool TrackSubRegs);
62 
63   /// For live interval \p LI with correct SubRanges construct matching
64   /// information for the main live range. Expects the main live range to not
65   /// have any segments or value numbers.
66   void constructMainRangeFromSubranges(LiveInterval &LI);
67 };
68 
69 } // end namespace llvm
70 
71 #endif // LLVM_LIB_CODEGEN_LIVEINTERVALCALC_H
72