llvm/lib/CodeGen/RegUsageInfoPropagate.cpp

   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 }