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      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/MachineFrameInfo.h"
     18 #include "llvm/CodeGen/MachineFunction.h"
     19 #include "llvm/CodeGen/MachineFunctionAnalysis.h"
     20 #include "llvm/CodeGen/Passes.h"
     21 #include "llvm/CodeGen/StackMapLivenessAnalysis.h"
     22 #include "llvm/Support/CommandLine.h"
     23 #include "llvm/Support/Debug.h"
     24 
     25 
     26 using namespace llvm;
     27 
     28 #define DEBUG_TYPE "stackmaps"
     29 
     30 namespace llvm {
     31 cl::opt<bool> EnablePatchPointLiveness("enable-patchpoint-liveness",
     32   cl::Hidden, cl::init(true),
     33   cl::desc("Enable PatchPoint Liveness Analysis Pass"));
     34 }
     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 char StackMapLiveness::ID = 0;
     43 char &llvm::StackMapLivenessID = StackMapLiveness::ID;
     44 INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
     45                 "StackMap Liveness Analysis", false, false)
     46 
     47 /// Default construct and initialize the pass.
     48 StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
     49   initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
     50 }
     51 
     52 /// Tell the pass manager which passes we depend on and what information we
     53 /// preserve.
     54 void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
     55   // We preserve all information.
     56   AU.setPreservesAll();
     57   AU.setPreservesCFG();
     58   // Default dependencie for all MachineFunction passes.
     59   AU.addRequired<MachineFunctionAnalysis>();
     60 }
     61 
     62 /// Calculate the liveness information for the given machine function.
     63 bool StackMapLiveness::runOnMachineFunction(MachineFunction &_MF) {
     64   if (!EnablePatchPointLiveness)
     65     return false;
     66 
     67   DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: "
     68                << _MF.getName() << " **********\n");
     69   MF = &_MF;
     70   TRI = MF->getTarget().getRegisterInfo();
     71   ++NumStackMapFuncVisited;
     72 
     73   // Skip this function if there are no patchpoints to process.
     74   if (!MF->getFrameInfo()->hasPatchPoint()) {
     75     ++NumStackMapFuncSkipped;
     76     return false;
     77   }
     78   return calculateLiveness();
     79 }
     80 
     81 /// Performs the actual liveness calculation for the function.
     82 bool StackMapLiveness::calculateLiveness() {
     83   bool HasChanged = false;
     84   // For all basic blocks in the function.
     85   for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
     86        MBBI != MBBE; ++MBBI) {
     87     DEBUG(dbgs() << "****** BB " << MBBI->getName() << " ******\n");
     88     LiveRegs.init(TRI);
     89     LiveRegs.addLiveOuts(MBBI);
     90     bool HasStackMap = false;
     91     // Reverse iterate over all instructions and add the current live register
     92     // set to an instruction if we encounter a patchpoint instruction.
     93     for (MachineBasicBlock::reverse_iterator I = MBBI->rbegin(),
     94          E = MBBI->rend(); I != E; ++I) {
     95       if (I->getOpcode() == TargetOpcode::PATCHPOINT) {
     96         addLiveOutSetToMI(*I);
     97         HasChanged = true;
     98         HasStackMap = true;
     99         ++NumStackMaps;
    100       }
    101       DEBUG(dbgs() << "   " << LiveRegs << "   " << *I);
    102       LiveRegs.stepBackward(*I);
    103     }
    104     ++NumBBsVisited;
    105     if (!HasStackMap)
    106       ++NumBBsHaveNoStackmap;
    107   }
    108   return HasChanged;
    109 }
    110 
    111 /// Add the current register live set to the instruction.
    112 void StackMapLiveness::addLiveOutSetToMI(MachineInstr &MI) {
    113   uint32_t *Mask = createRegisterMask();
    114   MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
    115   MI.addOperand(*MF, MO);
    116 }
    117 
    118 /// Create a register mask and initialize it with the registers from the
    119 /// register live set.
    120 uint32_t *StackMapLiveness::createRegisterMask() const {
    121   // The mask is owned and cleaned up by the Machine Function.
    122   uint32_t *Mask = MF->allocateRegisterMask(TRI->getNumRegs());
    123   for (LivePhysRegs::const_iterator RI = LiveRegs.begin(), RE = LiveRegs.end();
    124        RI != RE; ++RI)
    125     Mask[*RI / 32] |= 1U << (*RI % 32);
    126   return Mask;
    127 }
    128