1 //===-- llvm/CodeGen/SelectionDAGAddressAnalysis.cpp ------- DAG Address
2 //Analysis ---*- C++ -*-===//
3 //
4 //                     The LLVM Compiler Infrastructure
5 //
6 // This file is distributed under the University of Illinois Open Source
7 // License. See LICENSE.TXT for details.
8 //
9 //===----------------------------------------------------------------------===//
10 //
11 
12 #include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
13 #include "llvm/CodeGen/ISDOpcodes.h"
14 #include "llvm/CodeGen/MachineFrameInfo.h"
15 #include "llvm/CodeGen/SelectionDAG.h"
16 #include "llvm/CodeGen/SelectionDAGNodes.h"
17 #include "llvm/Target/TargetLowering.h"
18 
19 namespace llvm {
20 
21 bool BaseIndexOffset::equalBaseIndex(BaseIndexOffset &Other,
22                                      const SelectionDAG &DAG, int64_t &Off) {
23   // Initial Offset difference.
24   Off = Other.Offset - Offset;
25 
26   if ((Other.Index == Index) && (Other.IsIndexSignExt == IsIndexSignExt)) {
27     // Trivial match.
28     if (Other.Base == Base)
29       return true;
30 
31     // Match GlobalAddresses
32     if (auto *A = dyn_cast<GlobalAddressSDNode>(Base))
33       if (auto *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
34         if (A->getGlobal() == B->getGlobal()) {
35           Off += B->getOffset() - A->getOffset();
36           return true;
37         }
38 
39     const MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
40 
41     // Match non-equal FrameIndexes - If both frame indices are fixed
42     // we know their relative offsets and can compare them. Otherwise
43     // we must be conservative.
44     if (auto *A = dyn_cast<FrameIndexSDNode>(Base))
45       if (auto *B = dyn_cast<FrameIndexSDNode>(Other.Base))
46         if (MFI.isFixedObjectIndex(A->getIndex()) &&
47             MFI.isFixedObjectIndex(B->getIndex())) {
48           Off += MFI.getObjectOffset(B->getIndex()) -
49                  MFI.getObjectOffset(A->getIndex());
50           return true;
51         }
52   }
53   return false;
54 }
55 
56 /// Parses tree in Ptr for base, index, offset addresses.
57 BaseIndexOffset BaseIndexOffset::match(SDValue Ptr, const SelectionDAG &DAG) {
58   // (((B + I*M) + c)) + c ...
59   SDValue Base = DAG.getTargetLoweringInfo().unwrapAddress(Ptr);
60   SDValue Index = SDValue();
61   int64_t Offset = 0;
62   bool IsIndexSignExt = false;
63 
64   // Consume constant adds & ors with appropriate masking.
65   while (Base->getOpcode() == ISD::ADD || Base->getOpcode() == ISD::OR) {
66     if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1))) {
67       // Only consider ORs which act as adds.
68       if (Base->getOpcode() == ISD::OR &&
69           !DAG.MaskedValueIsZero(Base->getOperand(0), C->getAPIntValue()))
70         break;
71       Offset += C->getSExtValue();
72       Base = Base->getOperand(0);
73       continue;
74     }
75     break;
76   }
77 
78   if (Base->getOpcode() == ISD::ADD) {
79     // TODO: The following code appears to be needless as it just
80     //       bails on some Ptrs early, reducing the cases where we
81     //       find equivalence. We should be able to remove this.
82     // Inside a loop the current BASE pointer is calculated using an ADD and a
83     // MUL instruction. In this case Base is the actual BASE pointer.
84     // (i64 add (i64 %array_ptr)
85     //          (i64 mul (i64 %induction_var)
86     //                   (i64 %element_size)))
87     if (Base->getOperand(1)->getOpcode() == ISD::MUL)
88       return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
89 
90     // Look at Base + Index + Offset cases.
91     Index = Base->getOperand(1);
92     SDValue PotentialBase = Base->getOperand(0);
93 
94     // Skip signextends.
95     if (Index->getOpcode() == ISD::SIGN_EXTEND) {
96       Index = Index->getOperand(0);
97       IsIndexSignExt = true;
98     }
99 
100     // Check if Index Offset pattern
101     if (Index->getOpcode() != ISD::ADD ||
102         !isa<ConstantSDNode>(Index->getOperand(1)))
103       return BaseIndexOffset(PotentialBase, Index, Offset, IsIndexSignExt);
104 
105     Offset += cast<ConstantSDNode>(Index->getOperand(1))->getSExtValue();
106     Index = Index->getOperand(0);
107     if (Index->getOpcode() == ISD::SIGN_EXTEND) {
108       Index = Index->getOperand(0);
109       IsIndexSignExt = true;
110     } else
111       IsIndexSignExt = false;
112     Base = PotentialBase;
113   }
114   return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
115 }
116 } // end namespace llvm
117