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/MachineFrameInfo.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/Pass.h" 30 #include "llvm/Support/Debug.h" 31 #include "llvm/Support/raw_ostream.h" 32 33 using namespace llvm; 34 35 #define DEBUG_TYPE "ip-regalloc" 36 37 #define RUIP_NAME "Register Usage Information Propagation" 38 39 namespace { 40 41 class RegUsageInfoPropagation : public MachineFunctionPass { 42 public: 43 RegUsageInfoPropagation() : MachineFunctionPass(ID) { 44 PassRegistry &Registry = *PassRegistry::getPassRegistry(); 45 initializeRegUsageInfoPropagationPass(Registry); 46 } 47 48 StringRef getPassName() const override { return RUIP_NAME; } 49 50 bool runOnMachineFunction(MachineFunction &MF) override; 51 52 void getAnalysisUsage(AnalysisUsage &AU) const override { 53 AU.addRequired<PhysicalRegisterUsageInfo>(); 54 AU.setPreservesAll(); 55 MachineFunctionPass::getAnalysisUsage(AU); 56 } 57 58 static char ID; 59 60 private: 61 static void setRegMask(MachineInstr &MI, ArrayRef<uint32_t> RegMask) { 62 assert(RegMask.size() == 63 MachineOperand::getRegMaskSize(MI.getParent()->getParent() 64 ->getRegInfo().getTargetRegisterInfo() 65 ->getNumRegs()) 66 && "expected register mask size"); 67 for (MachineOperand &MO : MI.operands()) { 68 if (MO.isRegMask()) 69 MO.setRegMask(RegMask.data()); 70 } 71 } 72 }; 73 74 } // end of anonymous namespace 75 76 INITIALIZE_PASS_BEGIN(RegUsageInfoPropagation, "reg-usage-propagation", 77 RUIP_NAME, false, false) 78 INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo) 79 INITIALIZE_PASS_END(RegUsageInfoPropagation, "reg-usage-propagation", 80 RUIP_NAME, false, false) 81 82 char RegUsageInfoPropagation::ID = 0; 83 84 // Assumes call instructions have a single reference to a function. 85 static const Function *findCalledFunction(const Module &M, 86 const MachineInstr &MI) { 87 for (const MachineOperand &MO : MI.operands()) { 88 if (MO.isGlobal()) 89 return dyn_cast<const Function>(MO.getGlobal()); 90 91 if (MO.isSymbol()) 92 return M.getFunction(MO.getSymbolName()); 93 } 94 95 return nullptr; 96 } 97 98 bool RegUsageInfoPropagation::runOnMachineFunction(MachineFunction &MF) { 99 const Module &M = *MF.getFunction().getParent(); 100 PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>(); 101 102 LLVM_DEBUG(dbgs() << " ++++++++++++++++++++ " << getPassName() 103 << " ++++++++++++++++++++ \n"); 104 LLVM_DEBUG(dbgs() << "MachineFunction : " << MF.getName() << "\n"); 105 106 const MachineFrameInfo &MFI = MF.getFrameInfo(); 107 if (!MFI.hasCalls() && !MFI.hasTailCall()) 108 return false; 109 110 bool Changed = false; 111 112 for (MachineBasicBlock &MBB : MF) { 113 for (MachineInstr &MI : MBB) { 114 if (!MI.isCall()) 115 continue; 116 LLVM_DEBUG( 117 dbgs() 118 << "Call Instruction Before Register Usage Info Propagation : \n" 119 << MI << "\n"); 120 121 auto UpdateRegMask = [&](const Function &F) { 122 const ArrayRef<uint32_t> RegMask = PRUI->getRegUsageInfo(F); 123 if (RegMask.empty()) 124 return; 125 setRegMask(MI, RegMask); 126 Changed = true; 127 }; 128 129 if (const Function *F = findCalledFunction(M, MI)) { 130 if (F->isDefinitionExact()) { 131 UpdateRegMask(*F); 132 } else { 133 LLVM_DEBUG(dbgs() << "Function definition is not exact\n"); 134 } 135 } else { 136 LLVM_DEBUG(dbgs() << "Failed to find call target function\n"); 137 } 138 139 LLVM_DEBUG( 140 dbgs() 141 << "Call Instruction After Register Usage Info Propagation : \n" 142 << MI << '\n'); 143 } 144 } 145 146 LLVM_DEBUG( 147 dbgs() << " +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++" 148 "++++++ \n"); 149 return Changed; 150 } 151 152 FunctionPass *llvm::createRegUsageInfoPropPass() { 153 return new RegUsageInfoPropagation(); 154 } 155