1 //===-- StatepointLowering.h - SDAGBuilder's statepoint code -*- C++ -*---===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file includes support code use by SelectionDAGBuilder when lowering a
11 // statepoint sequence in SelectionDAG IR.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_LIB_CODEGEN_SELECTIONDAG_STATEPOINTLOWERING_H
16 #define LLVM_LIB_CODEGEN_SELECTIONDAG_STATEPOINTLOWERING_H
17 
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/CodeGen/SelectionDAG.h"
20 #include "llvm/CodeGen/SelectionDAGNodes.h"
21 #include <vector>
22 
23 namespace llvm {
24 class SelectionDAGBuilder;
25 
26 /// This class tracks both per-statepoint and per-selectiondag information.
27 /// For each statepoint it tracks locations of it's gc valuess (incoming and
28 /// relocated) and list of gcreloc calls scheduled for visiting (this is
29 /// used for a debug mode consistency check only).  The spill slot tracking
30 /// works in concert with information in FunctionLoweringInfo.
31 class StatepointLoweringState {
32 public:
StatepointLoweringState()33   StatepointLoweringState() : NextSlotToAllocate(0) {}
34 
35   /// Reset all state tracking for a newly encountered safepoint.  Also
36   /// performs some consistency checking.
37   void startNewStatepoint(SelectionDAGBuilder &Builder);
38 
39   /// Clear the memory usage of this object.  This is called from
40   /// SelectionDAGBuilder::clear.  We require this is never called in the
41   /// midst of processing a statepoint sequence.
42   void clear();
43 
44   /// Returns the spill location of a value incoming to the current
45   /// statepoint.  Will return SDValue() if this value hasn't been
46   /// spilled.  Otherwise, the value has already been spilled and no
47   /// further action is required by the caller.
getLocation(SDValue val)48   SDValue getLocation(SDValue val) {
49     if (!Locations.count(val))
50       return SDValue();
51     return Locations[val];
52   }
setLocation(SDValue val,SDValue Location)53   void setLocation(SDValue val, SDValue Location) {
54     assert(!Locations.count(val) &&
55            "Trying to allocate already allocated location");
56     Locations[val] = Location;
57   }
58 
59   /// Record the fact that we expect to encounter a given gc_relocate
60   /// before the next statepoint.  If we don't see it, we'll report
61   /// an assertion.
scheduleRelocCall(const CallInst & RelocCall)62   void scheduleRelocCall(const CallInst &RelocCall) {
63     PendingGCRelocateCalls.push_back(&RelocCall);
64   }
65   /// Remove this gc_relocate from the list we're expecting to see
66   /// before the next statepoint.  If we weren't expecting to see
67   /// it, we'll report an assertion.
relocCallVisited(const CallInst & RelocCall)68   void relocCallVisited(const CallInst &RelocCall) {
69     SmallVectorImpl<const CallInst *>::iterator itr =
70         std::find(PendingGCRelocateCalls.begin(), PendingGCRelocateCalls.end(),
71                   &RelocCall);
72     assert(itr != PendingGCRelocateCalls.end() &&
73            "Visited unexpected gcrelocate call");
74     PendingGCRelocateCalls.erase(itr);
75   }
76 
77   // TODO: Should add consistency tracking to ensure we encounter
78   // expected gc_result calls too.
79 
80   /// Get a stack slot we can use to store an value of type ValueType.  This
81   /// will hopefully be a recylced slot from another statepoint.
82   SDValue allocateStackSlot(EVT ValueType, SelectionDAGBuilder &Builder);
83 
reserveStackSlot(int Offset)84   void reserveStackSlot(int Offset) {
85     assert(Offset >= 0 && Offset < (int)AllocatedStackSlots.size() &&
86            "out of bounds");
87     assert(!AllocatedStackSlots[Offset] && "already reserved!");
88     assert(NextSlotToAllocate <= (unsigned)Offset && "consistency!");
89     AllocatedStackSlots[Offset] = true;
90   }
isStackSlotAllocated(int Offset)91   bool isStackSlotAllocated(int Offset) {
92     assert(Offset >= 0 && Offset < (int)AllocatedStackSlots.size() &&
93            "out of bounds");
94     return AllocatedStackSlots[Offset];
95   }
96 
97 private:
98   /// Maps pre-relocation value (gc pointer directly incoming into statepoint)
99   /// into it's location (currently only stack slots)
100   DenseMap<SDValue, SDValue> Locations;
101 
102   /// A boolean indicator for each slot listed in the FunctionInfo as to
103   /// whether it has been used in the current statepoint.  Since we try to
104   /// preserve stack slots across safepoints, there can be gaps in which
105   /// slots have been allocated.
106   SmallVector<bool, 50> AllocatedStackSlots;
107 
108   /// Points just beyond the last slot known to have been allocated
109   unsigned NextSlotToAllocate;
110 
111   /// Keep track of pending gcrelocate calls for consistency check
112   SmallVector<const CallInst *, 10> PendingGCRelocateCalls;
113 };
114 } // end namespace llvm
115 
116 #endif // LLVM_LIB_CODEGEN_SELECTIONDAG_STATEPOINTLOWERING_H
117