llvm/lib/CodeGen/LiveStacks.cpp

   1 //===-- LiveStacks.cpp - Live Stack Slot Analysis -------------------------===//
   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 file implements the live stack slot analysis pass. It is analogous to
  10 // live interval analysis except it's analyzing liveness of stack slots rather
  11 // than registers.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/CodeGen/LiveStacks.h"
  16 #include "llvm/CodeGen/TargetRegisterInfo.h"
  17 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  18 #include "llvm/InitializePasses.h"
  19 using namespace llvm;
  20
  21 #define DEBUG_TYPE "livestacks"
  22
  23 char LiveStacks::ID = 0;
  24 INITIALIZE_PASS_BEGIN(LiveStacks, DEBUG_TYPE,
  25                 "Live Stack Slot Analysis", false, false)
  26 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
  27 INITIALIZE_PASS_END(LiveStacks, DEBUG_TYPE,
  28                 "Live Stack Slot Analysis", false, false)
  29
  30 char &llvm::LiveStacksID = LiveStacks::ID;
  31
  32 void LiveStacks::getAnalysisUsage(AnalysisUsage &AU) const {
  33   AU.setPreservesAll();
  34   AU.addPreserved<SlotIndexes>();
  35   AU.addRequiredTransitive<SlotIndexes>();
  36   MachineFunctionPass::getAnalysisUsage(AU);
  37 }
  38
  39 void LiveStacks::releaseMemory() {
  40   // Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
  41   VNInfoAllocator.Reset();
  42   S2IMap.clear();
  43   S2RCMap.clear();
  44 }
  45
  46 bool LiveStacks::runOnMachineFunction(MachineFunction &MF) {
  47   TRI = MF.getSubtarget().getRegisterInfo();
  48   // FIXME: No analysis is being done right now. We are relying on the
  49   // register allocators to provide the information.
  50   return false;
  51 }
  52
  53 LiveInterval &
  54 LiveStacks::getOrCreateInterval(int Slot, const TargetRegisterClass *RC) {
  55   assert(Slot >= 0 && "Spill slot indice must be >= 0");
  56   SS2IntervalMap::iterator I = S2IMap.find(Slot);
  57   if (I == S2IMap.end()) {
  58     I = S2IMap
  59             .emplace(
  60                 std::piecewise_construct, std::forward_as_tuple(Slot),
  61                 std::forward_as_tuple(Register::index2StackSlot(Slot), 0.0F))
  62             .first;
  63     S2RCMap.insert(std::make_pair(Slot, RC));
  64   } else {
  65     // Use the largest common subclass register class.
  66     const TargetRegisterClass *OldRC = S2RCMap[Slot];
  67     S2RCMap[Slot] = TRI->getCommonSubClass(OldRC, RC);
  68   }
  69   return I->second;
  70 }
  71
  72 /// print - Implement the dump method.
  73 void LiveStacks::print(raw_ostream &OS, const Module*) const {
  74
  75   OS << "********** INTERVALS **********\n";
  76   for (const_iterator I = begin(), E = end(); I != E; ++I) {
  77     I->second.print(OS);
  78     int Slot = I->first;
  79     const TargetRegisterClass *RC = getIntervalRegClass(Slot);
  80     if (RC)
  81       OS << " [" << TRI->getRegClassName(RC) << "]\n";
  82     else
  83       OS << " [Unknown]\n";
  84   }
  85 }