1 //=--- RegUsageInfoPropagate.cpp - Register Usage Informartion Propagation --=// 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 pass is required to take advantage of the interprocedural register 10 /// allocation infrastructure. 11 /// 12 /// This pass iterates through MachineInstrs in a given MachineFunction and at 13 /// each callsite queries RegisterUsageInfo for RegMask (calculated based on 14 /// actual register allocation) of the callee function, if the RegMask detail 15 /// is available then this pass will update the RegMask of the call instruction. 16 /// This updated RegMask will be used by the register allocator while allocating 17 /// the current MachineFunction. 18 /// 19 //===----------------------------------------------------------------------===// 20 21 #include "llvm/CodeGen/MachineBasicBlock.h" 22 #include "llvm/CodeGen/MachineFunctionPass.h" 23 #include "llvm/CodeGen/MachineFrameInfo.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/Pass.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 using namespace llvm; 37 38 #define DEBUG_TYPE "ip-regalloc" 39 40 #define RUIP_NAME "Register Usage Information Propagation" 41 42 namespace { 43 44 class RegUsageInfoPropagation : public MachineFunctionPass { 45 public: 46 RegUsageInfoPropagation() : MachineFunctionPass(ID) { 47 PassRegistry &Registry = *PassRegistry::getPassRegistry(); 48 initializeRegUsageInfoPropagationPass(Registry); 49 } 50 51 StringRef getPassName() const override { return RUIP_NAME; } 52 53 bool runOnMachineFunction(MachineFunction &MF) override; 54 55 void getAnalysisUsage(AnalysisUsage &AU) const override { 56 AU.addRequired<PhysicalRegisterUsageInfo>(); 57 AU.setPreservesAll(); 58 MachineFunctionPass::getAnalysisUsage(AU); 59 } 60 61 static char ID; 62 63 private: 64 static void setRegMask(MachineInstr &MI, ArrayRef<uint32_t> RegMask) { 65 assert(RegMask.size() == 66 MachineOperand::getRegMaskSize(MI.getParent()->getParent() 67 ->getRegInfo().getTargetRegisterInfo() 68 ->getNumRegs()) 69 && "expected register mask size"); 70 for (MachineOperand &MO : MI.operands()) { 71 if (MO.isRegMask()) 72 MO.setRegMask(RegMask.data()); 73 } 74 } 75 }; 76 77 } // end of anonymous namespace 78 79 INITIALIZE_PASS_BEGIN(RegUsageInfoPropagation, "reg-usage-propagation", 80 RUIP_NAME, false, false) 81 INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo) 82 INITIALIZE_PASS_END(RegUsageInfoPropagation, "reg-usage-propagation", 83 RUIP_NAME, false, false) 84 85 char RegUsageInfoPropagation::ID = 0; 86 87 // Assumes call instructions have a single reference to a function. 88 static const Function *findCalledFunction(const Module &M, 89 const MachineInstr &MI) { 90 for (const MachineOperand &MO : MI.operands()) { 91 if (MO.isGlobal()) 92 return dyn_cast<const Function>(MO.getGlobal()); 93 94 if (MO.isSymbol()) 95 return M.getFunction(MO.getSymbolName()); 96 } 97 98 return nullptr; 99 } 100 101 bool RegUsageInfoPropagation::runOnMachineFunction(MachineFunction &MF) { 102 const Module &M = *MF.getFunction().getParent(); 103 PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>(); 104 105 LLVM_DEBUG(dbgs() << " ++++++++++++++++++++ " << getPassName() 106 << " ++++++++++++++++++++ \n"); 107 LLVM_DEBUG(dbgs() << "MachineFunction : " << MF.getName() << "\n"); 108 109 const MachineFrameInfo &MFI = MF.getFrameInfo(); 110 if (!MFI.hasCalls() && !MFI.hasTailCall()) 111 return false; 112 113 bool Changed = false; 114 115 for (MachineBasicBlock &MBB : MF) { 116 for (MachineInstr &MI : MBB) { 117 if (!MI.isCall()) 118 continue; 119 LLVM_DEBUG( 120 dbgs() 121 << "Call Instruction Before Register Usage Info Propagation : \n" 122 << MI << "\n"); 123 124 auto UpdateRegMask = [&](const Function &F) { 125 const ArrayRef<uint32_t> RegMask = PRUI->getRegUsageInfo(F); 126 if (RegMask.empty()) 127 return; 128 setRegMask(MI, RegMask); 129 Changed = true; 130 }; 131 132 if (const Function *F = findCalledFunction(M, MI)) { 133 if (F->isDefinitionExact()) { 134 UpdateRegMask(*F); 135 } else { 136 LLVM_DEBUG(dbgs() << "Function definition is not exact\n"); 137 } 138 } else { 139 LLVM_DEBUG(dbgs() << "Failed to find call target function\n"); 140 } 141 142 LLVM_DEBUG( 143 dbgs() 144 << "Call Instruction After Register Usage Info Propagation : \n" 145 << MI << '\n'); 146 } 147 } 148 149 LLVM_DEBUG( 150 dbgs() << " +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++" 151 "++++++ \n"); 152 return Changed; 153 } 154 155 FunctionPass *llvm::createRegUsageInfoPropPass() { 156 return new RegUsageInfoPropagation(); 157 } 158