1 //===- RegUsageInfoCollector.cpp - Register Usage Informartion Collector --===//
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 pass is required to take advantage of the interprocedural register
11 /// allocation infrastructure.
12 ///
13 /// This pass is simple MachineFunction pass which collects register usage
14 /// details by iterating through each physical registers and checking
15 /// MRI::isPhysRegUsed() then creates a RegMask based on this details.
16 /// The pass then stores this RegMask in PhysicalRegisterUsageInfo.cpp
17 ///
18 //===----------------------------------------------------------------------===//
19 
20 #include "llvm/CodeGen/MachineBasicBlock.h"
21 #include "llvm/CodeGen/MachineFunctionPass.h"
22 #include "llvm/CodeGen/MachineInstr.h"
23 #include "llvm/CodeGen/MachineOperand.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/CodeGen/Passes.h"
26 #include "llvm/CodeGen/RegisterUsageInfo.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/raw_ostream.h"
29 
30 using namespace llvm;
31 
32 #define DEBUG_TYPE "ip-regalloc"
33 
34 namespace llvm {
35 void initializeRegUsageInfoCollectorPass(PassRegistry &);
36 }
37 
38 namespace {
39 class RegUsageInfoCollector : public MachineFunctionPass {
40 public:
41   RegUsageInfoCollector() : MachineFunctionPass(ID) {
42     PassRegistry &Registry = *PassRegistry::getPassRegistry();
43     initializeRegUsageInfoCollectorPass(Registry);
44   }
45 
46   const char *getPassName() const override {
47     return "Register Usage Information Collector Pass";
48   }
49 
50   void getAnalysisUsage(AnalysisUsage &AU) const override;
51 
52   bool runOnMachineFunction(MachineFunction &MF) override;
53 
54   static char ID;
55 
56 private:
57   void markRegClobbered(const TargetRegisterInfo *TRI, uint32_t *RegMask,
58                         unsigned PReg);
59 };
60 } // end of anonymous namespace
61 
62 char RegUsageInfoCollector::ID = 0;
63 
64 INITIALIZE_PASS_BEGIN(RegUsageInfoCollector, "RegUsageInfoCollector",
65                       "Register Usage Information Collector", false, false)
66 INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)
67 INITIALIZE_PASS_END(RegUsageInfoCollector, "RegUsageInfoCollector",
68                     "Register Usage Information Collector", false, false)
69 
70 FunctionPass *llvm::createRegUsageInfoCollector() {
71   return new RegUsageInfoCollector();
72 }
73 
74 void RegUsageInfoCollector::markRegClobbered(const TargetRegisterInfo *TRI,
75                                              uint32_t *RegMask, unsigned PReg) {
76   // If PReg is clobbered then all of its alias are also clobbered.
77   for (MCRegAliasIterator AI(PReg, TRI, true); AI.isValid(); ++AI)
78     RegMask[*AI / 32] &= ~(1u << *AI % 32);
79 }
80 
81 void RegUsageInfoCollector::getAnalysisUsage(AnalysisUsage &AU) const {
82   AU.addRequired<PhysicalRegisterUsageInfo>();
83   AU.setPreservesAll();
84   MachineFunctionPass::getAnalysisUsage(AU);
85 }
86 
87 bool RegUsageInfoCollector::runOnMachineFunction(MachineFunction &MF) {
88   MachineRegisterInfo *MRI = &MF.getRegInfo();
89   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
90   const TargetMachine &TM = MF.getTarget();
91 
92   DEBUG(dbgs() << " -------------------- " << getPassName()
93                << " -------------------- \n");
94   DEBUG(dbgs() << "Function Name : " << MF.getName() << "\n");
95 
96   std::vector<uint32_t> RegMask;
97 
98   // Compute the size of the bit vector to represent all the registers.
99   // The bit vector is broken into 32-bit chunks, thus takes the ceil of
100   // the number of registers divided by 32 for the size.
101   unsigned RegMaskSize = (TRI->getNumRegs() + 31) / 32;
102   RegMask.resize(RegMaskSize, 0xFFFFFFFF);
103 
104   PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>();
105 
106   PRUI->setTargetMachine(&TM);
107 
108   DEBUG(dbgs() << "Clobbered Registers: ");
109   for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg)
110     if (!MRI->reg_nodbg_empty(PReg) && MRI->isPhysRegUsed(PReg))
111       markRegClobbered(TRI, &RegMask[0], PReg);
112 
113   const uint32_t *CallPreservedMask =
114       TRI->getCallPreservedMask(MF, MF.getFunction()->getCallingConv());
115   // Set callee saved register as preserved.
116   for (unsigned i = 0; i < RegMaskSize; ++i)
117     RegMask[i] = RegMask[i] | CallPreservedMask[i];
118 
119   for (unsigned PReg = 1, PRegE = TRI->getNumRegs(); PReg < PRegE; ++PReg)
120     if (MachineOperand::clobbersPhysReg(&(RegMask[0]), PReg))
121       DEBUG(dbgs() << TRI->getName(PReg) << " ");
122 
123   DEBUG(dbgs() << " \n----------------------------------------\n");
124 
125   PRUI->storeUpdateRegUsageInfo(MF.getFunction(), std::move(RegMask));
126 
127   return false;
128 }
129