lib/CodeGen/StackMapLivenessAnalysis.cpp

   1 //===-- StackMapLivenessAnalysis.cpp - StackMap live Out Analysis ----------===//
   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 file implements the StackMap Liveness analysis pass. The pass calculates
  11 // the liveness for each basic block in a function and attaches the register
  12 // live-out information to a stackmap or patchpoint intrinsic if present.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/ADT/Statistic.h"
  17 #include "llvm/CodeGen/LivePhysRegs.h"
  18 #include "llvm/CodeGen/MachineFrameInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineFunctionAnalysis.h"
  21 #include "llvm/CodeGen/MachineFunctionPass.h"
  22 #include "llvm/CodeGen/Passes.h"
  23 #include "llvm/Support/CommandLine.h"
  24 #include "llvm/Support/Debug.h"
  25 #include "llvm/Support/raw_ostream.h"
  26 #include "llvm/Target/TargetSubtargetInfo.h"
  27
  28 using namespace llvm;
  29
  30 #define DEBUG_TYPE "stackmaps"
  31
  32 static cl::opt<bool> EnablePatchPointLiveness(
  33     "enable-patchpoint-liveness", cl::Hidden, cl::init(true),
  34     cl::desc("Enable PatchPoint Liveness Analysis Pass"));
  35
  36 STATISTIC(NumStackMapFuncVisited, "Number of functions visited");
  37 STATISTIC(NumStackMapFuncSkipped, "Number of functions skipped");
  38 STATISTIC(NumBBsVisited,          "Number of basic blocks visited");
  39 STATISTIC(NumBBsHaveNoStackmap,   "Number of basic blocks with no stackmap");
  40 STATISTIC(NumStackMaps,           "Number of StackMaps visited");
  41
  42 namespace {
  43 /// \brief This pass calculates the liveness information for each basic block in
  44 /// a function and attaches the register live-out information to a patchpoint
  45 /// intrinsic if present.
  46 ///
  47 /// This pass can be disabled via the -enable-patchpoint-liveness=false flag.
  48 /// The pass skips functions that don't have any patchpoint intrinsics. The
  49 /// information provided by this pass is optional and not required by the
  50 /// aformentioned intrinsic to function.
  51 class StackMapLiveness : public MachineFunctionPass {
  52   const TargetRegisterInfo *TRI;
  53   LivePhysRegs LiveRegs;
  54
  55 public:
  56   static char ID;
  57
  58   /// \brief Default construct and initialize the pass.
  59   StackMapLiveness();
  60
  61   /// \brief Tell the pass manager which passes we depend on and what
  62   /// information we preserve.
  63   void getAnalysisUsage(AnalysisUsage &AU) const override;
  64
  65   /// \brief Calculate the liveness information for the given machine function.
  66   bool runOnMachineFunction(MachineFunction &MF) override;
  67
  68 private:
  69   /// \brief Performs the actual liveness calculation for the function.
  70   bool calculateLiveness(MachineFunction &MF);
  71
  72   /// \brief Add the current register live set to the instruction.
  73   void addLiveOutSetToMI(MachineFunction &MF, MachineInstr &MI);
  74
  75   /// \brief Create a register mask and initialize it with the registers from
  76   /// the register live set.
  77   uint32_t *createRegisterMask(MachineFunction &MF) const;
  78 };
  79 } // namespace
  80
  81 char StackMapLiveness::ID = 0;
  82 char &llvm::StackMapLivenessID = StackMapLiveness::ID;
  83 INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
  84                 "StackMap Liveness Analysis", false, false)
  85
  86 /// Default construct and initialize the pass.
  87 StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
  88   initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
  89 }
  90
  91 /// Tell the pass manager which passes we depend on and what information we
  92 /// preserve.
  93 void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
  94   // We preserve all information.
  95   AU.setPreservesAll();
  96   AU.setPreservesCFG();
  97   MachineFunctionPass::getAnalysisUsage(AU);
  98 }
  99
 100 /// Calculate the liveness information for the given machine function.
 101 bool StackMapLiveness::runOnMachineFunction(MachineFunction &MF) {
 102   if (!EnablePatchPointLiveness)
 103     return false;
 104
 105   DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: " << MF.getName()
 106                << " **********\n");
 107   TRI = MF.getSubtarget().getRegisterInfo();
 108   ++NumStackMapFuncVisited;
 109
 110   // Skip this function if there are no patchpoints to process.
 111   if (!MF.getFrameInfo()->hasPatchPoint()) {
 112     ++NumStackMapFuncSkipped;
 113     return false;
 114   }
 115   return calculateLiveness(MF);
 116 }
 117
 118 /// Performs the actual liveness calculation for the function.
 119 bool StackMapLiveness::calculateLiveness(MachineFunction &MF) {
 120   bool HasChanged = false;
 121   // For all basic blocks in the function.
 122   for (auto &MBB : MF) {
 123     DEBUG(dbgs() << "****** BB " << MBB.getName() << " ******\n");
 124     LiveRegs.init(TRI);
 125     LiveRegs.addLiveOuts(&MBB);
 126     bool HasStackMap = false;
 127     // Reverse iterate over all instructions and add the current live register
 128     // set to an instruction if we encounter a patchpoint instruction.
 129     for (auto I = MBB.rbegin(), E = MBB.rend(); I != E; ++I) {
 130       if (I->getOpcode() == TargetOpcode::PATCHPOINT) {
 131         addLiveOutSetToMI(MF, *I);
 132         HasChanged = true;
 133         HasStackMap = true;
 134         ++NumStackMaps;
 135       }
 136       DEBUG(dbgs() << "   " << LiveRegs << "   " << *I);
 137       LiveRegs.stepBackward(*I);
 138     }
 139     ++NumBBsVisited;
 140     if (!HasStackMap)
 141       ++NumBBsHaveNoStackmap;
 142   }
 143   return HasChanged;
 144 }
 145
 146 /// Add the current register live set to the instruction.
 147 void StackMapLiveness::addLiveOutSetToMI(MachineFunction &MF,
 148                                          MachineInstr &MI) {
 149   uint32_t *Mask = createRegisterMask(MF);
 150   MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
 151   MI.addOperand(MF, MO);
 152 }
 153
 154 /// Create a register mask and initialize it with the registers from the
 155 /// register live set.
 156 uint32_t *StackMapLiveness::createRegisterMask(MachineFunction &MF) const {
 157   // The mask is owned and cleaned up by the Machine Function.
 158   uint32_t *Mask = MF.allocateRegisterMask(TRI->getNumRegs());
 159   for (auto Reg : LiveRegs)
 160     Mask[Reg / 32] |= 1U << (Reg % 32);
 161
 162   // Give the target a chance to adjust the mask.
 163   TRI->adjustStackMapLiveOutMask(Mask);
 164
 165   return Mask;
 166 }