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/MachineFrameInfo.h"
25 #include "llvm/CodeGen/MachineInstr.h"
26 #include "llvm/CodeGen/MachineRegisterInfo.h"
27 #include "llvm/CodeGen/Passes.h"
28 #include "llvm/CodeGen/RegisterUsageInfo.h"
29 #include "llvm/IR/Module.h"
30 #include "llvm/PassAnalysisSupport.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include "llvm/Target/TargetMachine.h"
34 #include <map>
35 #include <string>
36 
37 namespace llvm {
38 void initializeRegUsageInfoPropagationPassPass(PassRegistry &);
39 }
40 
41 using namespace llvm;
42 
43 #define DEBUG_TYPE "ip-regalloc"
44 
45 #define RUIP_NAME "Register Usage Information Propagation"
46 
47 namespace {
48 class RegUsageInfoPropagationPass : public MachineFunctionPass {
49 
50 public:
51   RegUsageInfoPropagationPass() : MachineFunctionPass(ID) {
52     PassRegistry &Registry = *PassRegistry::getPassRegistry();
53     initializeRegUsageInfoPropagationPassPass(Registry);
54   }
55 
56   StringRef getPassName() const override { return RUIP_NAME; }
57 
58   bool runOnMachineFunction(MachineFunction &MF) override;
59 
60   void getAnalysisUsage(AnalysisUsage &AU) const override;
61 
62   static char ID;
63 
64 private:
65   static void setRegMask(MachineInstr &MI, const uint32_t *RegMask) {
66     for (MachineOperand &MO : MI.operands()) {
67       if (MO.isRegMask())
68         MO.setRegMask(RegMask);
69     }
70   }
71 };
72 } // end of anonymous namespace
73 char RegUsageInfoPropagationPass::ID = 0;
74 
75 INITIALIZE_PASS_BEGIN(RegUsageInfoPropagationPass, "reg-usage-propagation",
76                       RUIP_NAME, false, false)
77 INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)
78 INITIALIZE_PASS_END(RegUsageInfoPropagationPass, "reg-usage-propagation",
79                     RUIP_NAME, false, false)
80 
81 FunctionPass *llvm::createRegUsageInfoPropPass() {
82   return new RegUsageInfoPropagationPass();
83 }
84 
85 void RegUsageInfoPropagationPass::getAnalysisUsage(AnalysisUsage &AU) const {
86   AU.addRequired<PhysicalRegisterUsageInfo>();
87   AU.setPreservesAll();
88   MachineFunctionPass::getAnalysisUsage(AU);
89 }
90 
91 bool RegUsageInfoPropagationPass::runOnMachineFunction(MachineFunction &MF) {
92   const Module *M = MF.getFunction()->getParent();
93   PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>();
94 
95   DEBUG(dbgs() << " ++++++++++++++++++++ " << getPassName()
96                << " ++++++++++++++++++++  \n");
97   DEBUG(dbgs() << "MachineFunction : " << MF.getName() << "\n");
98 
99   const MachineFrameInfo &MFI = MF.getFrameInfo();
100   if (!MFI.hasCalls() && !MFI.hasTailCall())
101     return false;
102 
103   bool Changed = false;
104 
105   for (MachineBasicBlock &MBB : MF) {
106     for (MachineInstr &MI : MBB) {
107       if (!MI.isCall())
108         continue;
109       DEBUG(dbgs()
110             << "Call Instruction Before Register Usage Info Propagation : \n");
111       DEBUG(dbgs() << MI << "\n");
112 
113       auto UpdateRegMask = [&](const Function *F) {
114         const auto *RegMask = PRUI->getRegUsageInfo(F);
115         if (!RegMask)
116           return;
117         setRegMask(MI, &(*RegMask)[0]);
118         Changed = true;
119       };
120 
121       MachineOperand &Operand = MI.getOperand(0);
122       if (Operand.isGlobal())
123         UpdateRegMask(cast<Function>(Operand.getGlobal()));
124       else if (Operand.isSymbol())
125         UpdateRegMask(M->getFunction(Operand.getSymbolName()));
126 
127       DEBUG(dbgs()
128             << "Call Instruction After Register Usage Info Propagation : \n");
129       DEBUG(dbgs() << MI << "\n");
130     }
131   }
132 
133   DEBUG(dbgs() << " +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
134                   "++++++ \n");
135   return Changed;
136 }
137