1 //===-- AVRRelaxMemOperations.cpp - Relax out of range loads/stores -------===//
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 // This file contains a pass which relaxes out of range memory operations into
10 // equivalent operations which handle bigger addresses.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "AVR.h"
15 #include "AVRInstrInfo.h"
16 #include "AVRTargetMachine.h"
17 #include "MCTargetDesc/AVRMCTargetDesc.h"
18 
19 #include "llvm/CodeGen/MachineFunctionPass.h"
20 #include "llvm/CodeGen/MachineInstrBuilder.h"
21 #include "llvm/CodeGen/MachineRegisterInfo.h"
22 #include "llvm/CodeGen/TargetRegisterInfo.h"
23 
24 using namespace llvm;
25 
26 #define AVR_RELAX_MEM_OPS_NAME "AVR memory operation relaxation pass"
27 
28 namespace {
29 
30 class AVRRelaxMem : public MachineFunctionPass {
31 public:
32   static char ID;
33 
34   AVRRelaxMem() : MachineFunctionPass(ID) {
35     initializeAVRRelaxMemPass(*PassRegistry::getPassRegistry());
36   }
37 
38   bool runOnMachineFunction(MachineFunction &MF) override;
39 
40   StringRef getPassName() const override { return AVR_RELAX_MEM_OPS_NAME; }
41 
42 private:
43   typedef MachineBasicBlock Block;
44   typedef Block::iterator BlockIt;
45 
46   const TargetInstrInfo *TII;
47 
48   template <unsigned OP> bool relax(Block &MBB, BlockIt MBBI);
49 
50   bool runOnBasicBlock(Block &MBB);
51   bool runOnInstruction(Block &MBB, BlockIt MBBI);
52 
53   MachineInstrBuilder buildMI(Block &MBB, BlockIt MBBI, unsigned Opcode) {
54     return BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII->get(Opcode));
55   }
56 };
57 
58 char AVRRelaxMem::ID = 0;
59 
60 bool AVRRelaxMem::runOnMachineFunction(MachineFunction &MF) {
61   bool Modified = false;
62 
63   const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
64   TII = STI.getInstrInfo();
65 
66   for (Block &MBB : MF) {
67     bool BlockModified = runOnBasicBlock(MBB);
68     Modified |= BlockModified;
69   }
70 
71   return Modified;
72 }
73 
74 bool AVRRelaxMem::runOnBasicBlock(Block &MBB) {
75   bool Modified = false;
76 
77   BlockIt MBBI = MBB.begin(), E = MBB.end();
78   while (MBBI != E) {
79     BlockIt NMBBI = std::next(MBBI);
80     Modified |= runOnInstruction(MBB, MBBI);
81     MBBI = NMBBI;
82   }
83 
84   return Modified;
85 }
86 
87 template <>
88 bool AVRRelaxMem::relax<AVR::STDWPtrQRr>(Block &MBB, BlockIt MBBI) {
89   MachineInstr &MI = *MBBI;
90 
91   MachineOperand &Ptr = MI.getOperand(0);
92   MachineOperand &Src = MI.getOperand(2);
93   int64_t Imm = MI.getOperand(1).getImm();
94 
95   // We can definitely optimise this better.
96   if (Imm > 63) {
97     // Push the previous state of the pointer register.
98     // This instruction must preserve the value.
99     buildMI(MBB, MBBI, AVR::PUSHWRr)
100       .addReg(Ptr.getReg());
101 
102     // Add the immediate to the pointer register.
103     buildMI(MBB, MBBI, AVR::SBCIWRdK)
104       .addReg(Ptr.getReg(), RegState::Define)
105       .addReg(Ptr.getReg())
106       .addImm(-Imm);
107 
108     // Store the value in the source register to the address
109     // pointed to by the pointer register.
110     buildMI(MBB, MBBI, AVR::STWPtrRr)
111       .addReg(Ptr.getReg())
112       .addReg(Src.getReg(), getKillRegState(Src.isKill()));
113 
114     // Pop the original state of the pointer register.
115     buildMI(MBB, MBBI, AVR::POPWRd)
116       .addDef(Ptr.getReg(), getKillRegState(Ptr.isKill()));
117 
118     MI.removeFromParent();
119   }
120 
121   return false;
122 }
123 
124 bool AVRRelaxMem::runOnInstruction(Block &MBB, BlockIt MBBI) {
125   MachineInstr &MI = *MBBI;
126   int Opcode = MBBI->getOpcode();
127 
128 #define RELAX(Op)                \
129   case Op:                       \
130     return relax<Op>(MBB, MI)
131 
132   switch (Opcode) {
133     RELAX(AVR::STDWPtrQRr);
134   }
135 #undef RELAX
136   return false;
137 }
138 
139 } // end of anonymous namespace
140 
141 INITIALIZE_PASS(AVRRelaxMem, "avr-relax-mem",
142                 AVR_RELAX_MEM_OPS_NAME, false, false)
143 
144 namespace llvm {
145 
146 FunctionPass *createAVRRelaxMemPass() { return new AVRRelaxMem(); }
147 
148 } // end of namespace llvm
149