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/SelectionDAG.h"
15 #include "llvm/CodeGen/SelectionDAGNodes.h"
16 
17 namespace llvm {
18 
19 bool BaseIndexOffset::equalBaseIndex(BaseIndexOffset &Other,
20                                      const SelectionDAG &DAG, int64_t &Off) {
21   // Obvious equivalent
22   Off = Other.Offset - Offset;
23   if (Other.Base == Base && Other.Index == Index &&
24       Other.IsIndexSignExt == IsIndexSignExt)
25     return true;
26 
27   // Match GlobalAddresses
28   if (Index == Other.Index)
29     if (GlobalAddressSDNode *A = dyn_cast<GlobalAddressSDNode>(Base))
30       if (GlobalAddressSDNode *B = dyn_cast<GlobalAddressSDNode>(Other.Base))
31         if (A->getGlobal() == B->getGlobal()) {
32           Off += B->getOffset() - A->getOffset();
33           return true;
34         }
35 
36   // TODO: we should be able to add FrameIndex analysis improvements here.
37 
38   return false;
39 }
40 
41 /// Parses tree in Ptr for base, index, offset addresses.
42 BaseIndexOffset BaseIndexOffset::match(SDValue Ptr) {
43   // (((B + I*M) + c)) + c ...
44   SDValue Base = Ptr;
45   SDValue Index = SDValue();
46   int64_t Offset = 0;
47   bool IsIndexSignExt = false;
48 
49   // Consume constant adds
50   while (Base->getOpcode() == ISD::ADD &&
51          isa<ConstantSDNode>(Base->getOperand(1))) {
52     int64_t POffset = cast<ConstantSDNode>(Base->getOperand(1))->getSExtValue();
53     Offset += POffset;
54     Base = Base->getOperand(0);
55   }
56 
57   if (Base->getOpcode() == ISD::ADD) {
58     // TODO: The following code appears to be needless as it just
59     //       bails on some Ptrs early, reducing the cases where we
60     //       find equivalence. We should be able to remove this.
61     // Inside a loop the current BASE pointer is calculated using an ADD and a
62     // MUL instruction. In this case Base is the actual BASE pointer.
63     // (i64 add (i64 %array_ptr)
64     //          (i64 mul (i64 %induction_var)
65     //                   (i64 %element_size)))
66     if (Base->getOperand(1)->getOpcode() == ISD::MUL)
67       return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
68 
69     // Look at Base + Index + Offset cases.
70     Index = Base->getOperand(1);
71     SDValue PotentialBase = Base->getOperand(0);
72 
73     // Skip signextends.
74     if (Index->getOpcode() == ISD::SIGN_EXTEND) {
75       Index = Index->getOperand(0);
76       IsIndexSignExt = true;
77     }
78 
79     // Check if Index Offset pattern
80     if (Index->getOpcode() != ISD::ADD ||
81         !isa<ConstantSDNode>(Index->getOperand(1)))
82       return BaseIndexOffset(PotentialBase, Index, Offset, IsIndexSignExt);
83 
84     Offset += cast<ConstantSDNode>(Index->getOperand(1))->getSExtValue();
85     Index = Index->getOperand(0);
86     if (Index->getOpcode() == ISD::SIGN_EXTEND) {
87       Index = Index->getOperand(0);
88       IsIndexSignExt = true;
89     } else
90       IsIndexSignExt = false;
91     Base = PotentialBase;
92   }
93   return BaseIndexOffset(Base, Index, Offset, IsIndexSignExt);
94 }
95 } // end namespace llvm
96