1 //==- llvm/CodeGen/SelectionDAGAddressAnalysis.cpp - DAG Address Analysis --==//
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 #include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
11 #include "llvm/CodeGen/ISDOpcodes.h"
12 #include "llvm/CodeGen/MachineFrameInfo.h"
13 #include "llvm/CodeGen/MachineFunction.h"
14 #include "llvm/CodeGen/SelectionDAG.h"
15 #include "llvm/CodeGen/SelectionDAGNodes.h"
16 #include "llvm/CodeGen/TargetLowering.h"
17 #include "llvm/Support/Casting.h"
18 #include <cstdint>
19
20 using namespace llvm;
21
equalBaseIndex(BaseIndexOffset & Other,const SelectionDAG & DAG,int64_t & Off)22 bool BaseIndexOffset::equalBaseIndex(BaseIndexOffset &Other,
23 const SelectionDAG &DAG, int64_t &Off) {
24 // Conservatively fail if we a match failed..
25 if (!Base.getNode() || !Other.Base.getNode())
26 return false;
27 // Initial Offset difference.
28 Off = Other.Offset - Offset;
29
30 if ((Other.Index == Index) && (Other.IsIndexSignExt == IsIndexSignExt)) {
31 // Trivial match.
32 if (Other.Base == Base)
33 return true;
34
35 // Match GlobalAddresses
36 if (auto *A = dyn_cast<GlobalAddressSDNode>(Base))
37 if (auto *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
38 if (A->getGlobal() == B->getGlobal()) {
39 Off += B->getOffset() - A->getOffset();
40 return true;
41 }
42
43 // Match Constants
44 if (auto *A = dyn_cast<ConstantPoolSDNode>(Base))
45 if (auto *B = dyn_cast<ConstantPoolSDNode>(Other.Base)) {
46 bool IsMatch =
47 A->isMachineConstantPoolEntry() == B->isMachineConstantPoolEntry();
48 if (IsMatch) {
49 if (A->isMachineConstantPoolEntry())
50 IsMatch = A->getMachineCPVal() == B->getMachineCPVal();
51 else
52 IsMatch = A->getConstVal() == B->getConstVal();
53 }
54 if (IsMatch) {
55 Off += B->getOffset() - A->getOffset();
56 return true;
57 }
58 }
59
60 const MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
61
62 // Match non-equal FrameIndexes - If both frame indices are fixed
63 // we know their relative offsets and can compare them. Otherwise
64 // we must be conservative.
65 if (auto *A = dyn_cast<FrameIndexSDNode>(Base))
66 if (auto *B = dyn_cast<FrameIndexSDNode>(Other.Base))
67 if (MFI.isFixedObjectIndex(A->getIndex()) &&
68 MFI.isFixedObjectIndex(B->getIndex())) {
69 Off += MFI.getObjectOffset(B->getIndex()) -
70 MFI.getObjectOffset(A->getIndex());
71 return true;
72 }
73 }
74 return false;
75 }
76
77 /// Parses tree in Ptr for base, index, offset addresses.
match(LSBaseSDNode * N,const SelectionDAG & DAG)78 BaseIndexOffset BaseIndexOffset::match(LSBaseSDNode *N,
79 const SelectionDAG &DAG) {
80 SDValue Ptr = N->getBasePtr();
81
82 // (((B + I*M) + c)) + c ...
83 SDValue Base = DAG.getTargetLoweringInfo().unwrapAddress(Ptr);
84 SDValue Index = SDValue();
85 int64_t Offset = 0;
86 bool IsIndexSignExt = false;
87
88 // pre-inc/pre-dec ops are components of EA.
89 if (N->getAddressingMode() == ISD::PRE_INC) {
90 if (auto *C = dyn_cast<ConstantSDNode>(N->getOffset()))
91 Offset += C->getSExtValue();
92 else // If unknown, give up now.
93 return BaseIndexOffset(SDValue(), SDValue(), 0, false);
94 } else if (N->getAddressingMode() == ISD::PRE_DEC) {
95 if (auto *C = dyn_cast<ConstantSDNode>(N->getOffset()))
96 Offset -= C->getSExtValue();
97 else // If unknown, give up now.
98 return BaseIndexOffset(SDValue(), SDValue(), 0, false);
99 }
100
101 // Consume constant adds & ors with appropriate masking.
102 while (true) {
103 switch (Base->getOpcode()) {
104 case ISD::OR:
105 // Only consider ORs which act as adds.
106 if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1)))
107 if (DAG.MaskedValueIsZero(Base->getOperand(0), C->getAPIntValue())) {
108 Offset += C->getSExtValue();
109 Base = Base->getOperand(0);
110 continue;
111 }
112 break;
113 case ISD::ADD:
114 if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1))) {
115 Offset += C->getSExtValue();
116 Base = Base->getOperand(0);
117 continue;
118 }
119 break;
120 case ISD::LOAD:
121 case ISD::STORE: {
122 auto *LSBase = cast<LSBaseSDNode>(Base.getNode());
123 unsigned int IndexResNo = (Base->getOpcode() == ISD::LOAD) ? 1 : 0;
124 if (LSBase->isIndexed() && Base.getResNo() == IndexResNo)
125 if (auto *C = dyn_cast<ConstantSDNode>(LSBase->getOffset())) {
126 auto Off = C->getSExtValue();
127 if (LSBase->getAddressingMode() == ISD::PRE_DEC ||
128 LSBase->getAddressingMode() == ISD::POST_DEC)
129 Offset -= Off;
130 else
131 Offset += Off;
132 Base = LSBase->getBasePtr();
133 continue;
134 }
135 break;
136 }
137 }
138 // If we get here break out of the loop.
139 break;
140 }
141
142 if (Base->getOpcode() == ISD::ADD) {
143 // TODO: The following code appears to be needless as it just
144 // bails on some Ptrs early, reducing the cases where we
145 // find equivalence. We should be able to remove this.
146 // Inside a loop the current BASE pointer is calculated using an ADD and a
147 // MUL instruction. In this case Base is the actual BASE pointer.
148 // (i64 add (i64 %array_ptr)
149 // (i64 mul (i64 %induction_var)
150 // (i64 %element_size)))
151 if (Base->getOperand(1)->getOpcode() == ISD::MUL)
152 return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
153
154 // Look at Base + Index + Offset cases.
155 Index = Base->getOperand(1);
156 SDValue PotentialBase = Base->getOperand(0);
157
158 // Skip signextends.
159 if (Index->getOpcode() == ISD::SIGN_EXTEND) {
160 Index = Index->getOperand(0);
161 IsIndexSignExt = true;
162 }
163
164 // Check if Index Offset pattern
165 if (Index->getOpcode() != ISD::ADD ||
166 !isa<ConstantSDNode>(Index->getOperand(1)))
167 return BaseIndexOffset(PotentialBase, Index, Offset, IsIndexSignExt);
168
169 Offset += cast<ConstantSDNode>(Index->getOperand(1))->getSExtValue();
170 Index = Index->getOperand(0);
171 if (Index->getOpcode() == ISD::SIGN_EXTEND) {
172 Index = Index->getOperand(0);
173 IsIndexSignExt = true;
174 } else
175 IsIndexSignExt = false;
176 Base = PotentialBase;
177 }
178 return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
179 }
180