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1 //=--- RegUsageInfoPropagate.cpp - Register Usage Informartion Propagation --=//
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 iterates through MachineInstrs in a given MachineFunction and at
14 /// each callsite queries RegisterUsageInfo for RegMask (calculated based on
15 /// actual register allocation) of the callee function, if the RegMask detail
16 /// is available then this pass will update the RegMask of the call instruction.
17 /// This updated RegMask will be used by the register allocator while allocating
18 /// the current MachineFunction.
19 ///
20 //===----------------------------------------------------------------------===//
21 
22 #include "llvm/CodeGen/MachineBasicBlock.h"
23 #include "llvm/CodeGen/MachineFunctionPass.h"
24 #include "llvm/CodeGen/MachineInstr.h"
25 #include "llvm/CodeGen/MachineRegisterInfo.h"
26 #include "llvm/CodeGen/Passes.h"
27 #include "llvm/CodeGen/RegisterUsageInfo.h"
28 #include "llvm/IR/Module.h"
29 #include "llvm/PassAnalysisSupport.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Target/TargetMachine.h"
33 #include <map>
34 #include <string>
35 
36 namespace llvm {
37 void initializeRegUsageInfoPropagationPassPass(PassRegistry &);
38 }
39 
40 using namespace llvm;
41 
42 #define DEBUG_TYPE "ip-regalloc"
43 
44 #define RUIP_NAME "Register Usage Information Propagation"
45 
46 namespace {
47 class RegUsageInfoPropagationPass : public MachineFunctionPass {
48 
49 public:
RegUsageInfoPropagationPass()50   RegUsageInfoPropagationPass() : MachineFunctionPass(ID) {
51     PassRegistry &Registry = *PassRegistry::getPassRegistry();
52     initializeRegUsageInfoPropagationPassPass(Registry);
53   }
54 
getPassName() const55   const char *getPassName() const override { return RUIP_NAME; }
56 
57   bool runOnMachineFunction(MachineFunction &MF) override;
58 
59   void getAnalysisUsage(AnalysisUsage &AU) const override;
60 
61   static char ID;
62 
63 private:
setRegMask(MachineInstr & MI,const uint32_t * RegMask)64   static void setRegMask(MachineInstr &MI, const uint32_t *RegMask) {
65     for (MachineOperand &MO : MI.operands()) {
66       if (MO.isRegMask())
67         MO.setRegMask(RegMask);
68     }
69   }
70 };
71 } // end of anonymous namespace
72 char RegUsageInfoPropagationPass::ID = 0;
73 
74 INITIALIZE_PASS_BEGIN(RegUsageInfoPropagationPass, "reg-usage-propagation",
75                       RUIP_NAME, false, false)
INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)76 INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)
77 INITIALIZE_PASS_END(RegUsageInfoPropagationPass, "reg-usage-propagation",
78                     RUIP_NAME, false, false)
79 
80 FunctionPass *llvm::createRegUsageInfoPropPass() {
81   return new RegUsageInfoPropagationPass();
82 }
83 
getAnalysisUsage(AnalysisUsage & AU) const84 void RegUsageInfoPropagationPass::getAnalysisUsage(AnalysisUsage &AU) const {
85   AU.addRequired<PhysicalRegisterUsageInfo>();
86   AU.setPreservesAll();
87   MachineFunctionPass::getAnalysisUsage(AU);
88 }
89 
runOnMachineFunction(MachineFunction & MF)90 bool RegUsageInfoPropagationPass::runOnMachineFunction(MachineFunction &MF) {
91   const Module *M = MF.getFunction()->getParent();
92   PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>();
93 
94   DEBUG(dbgs() << " ++++++++++++++++++++ " << getPassName()
95                << " ++++++++++++++++++++  \n");
96   DEBUG(dbgs() << "MachineFunction : " << MF.getName() << "\n");
97 
98   bool Changed = false;
99 
100   for (MachineBasicBlock &MBB : MF) {
101     for (MachineInstr &MI : MBB) {
102       if (!MI.isCall())
103         continue;
104       DEBUG(dbgs()
105             << "Call Instruction Before Register Usage Info Propagation : \n");
106       DEBUG(dbgs() << MI << "\n");
107 
108       auto UpdateRegMask = [&](const Function *F) {
109         const auto *RegMask = PRUI->getRegUsageInfo(F);
110         if (!RegMask)
111           return;
112         setRegMask(MI, &(*RegMask)[0]);
113         Changed = true;
114       };
115 
116       MachineOperand &Operand = MI.getOperand(0);
117       if (Operand.isGlobal())
118         UpdateRegMask(cast<Function>(Operand.getGlobal()));
119       else if (Operand.isSymbol())
120         UpdateRegMask(M->getFunction(Operand.getSymbolName()));
121 
122       DEBUG(dbgs()
123             << "Call Instruction After Register Usage Info Propagation : \n");
124       DEBUG(dbgs() << MI << "\n");
125     }
126   }
127 
128   DEBUG(dbgs() << " +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
129                   "++++++ \n");
130   return Changed;
131 }
132