llvm/lib/CodeGen/LiveDebugValues/LiveDebugValues.cpp

   1 //===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
   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 #include "LiveDebugValues.h"
  10
  11 #include "llvm/CodeGen/MachineBasicBlock.h"
  12 #include "llvm/CodeGen/MachineFrameInfo.h"
  13 #include "llvm/CodeGen/MachineFunctionPass.h"
  14 #include "llvm/CodeGen/Passes.h"
  15 #include "llvm/InitializePasses.h"
  16 #include "llvm/Pass.h"
  17 #include "llvm/Support/CommandLine.h"
  18 #include "llvm/Target/TargetMachine.h"
  19
  20 /// \file LiveDebugValues.cpp
  21 ///
  22 /// The LiveDebugValues pass extends the range of variable locations
  23 /// (specified by DBG_VALUE instructions) from single blocks to successors
  24 /// and any other code locations where the variable location is valid.
  25 /// There are currently two implementations: the "VarLoc" implementation
  26 /// explicitly tracks the location of a variable, while the "InstrRef"
  27 /// implementation tracks the values defined by instructions through locations.
  28 ///
  29 /// This file implements neither; it merely registers the pass, allows the
  30 /// user to pick which implementation will be used to propagate variable
  31 /// locations.
  32
  33 #define DEBUG_TYPE "livedebugvalues"
  34
  35 using namespace llvm;
  36
  37 static cl::opt<bool>
  38     ForceInstrRefLDV("force-instr-ref-livedebugvalues", cl::Hidden,
  39                      cl::desc("Use instruction-ref based LiveDebugValues with "
  40                               "normal DBG_VALUE inputs"),
  41                      cl::init(false));
  42
  43 static cl::opt<cl::boolOrDefault> ValueTrackingVariableLocations(
  44     "experimental-debug-variable-locations",
  45     cl::desc("Use experimental new value-tracking variable locations"));
  46
  47 // Options to prevent pathological compile-time behavior. If InputBBLimit and
  48 // InputDbgValueLimit are both exceeded, range extension is disabled.
  49 static cl::opt<unsigned> InputBBLimit(
  50     "livedebugvalues-input-bb-limit",
  51     cl::desc("Maximum input basic blocks before DBG_VALUE limit applies"),
  52     cl::init(10000), cl::Hidden);
  53 static cl::opt<unsigned> InputDbgValueLimit(
  54     "livedebugvalues-input-dbg-value-limit",
  55     cl::desc(
  56         "Maximum input DBG_VALUE insts supported by debug range extension"),
  57     cl::init(50000), cl::Hidden);
  58
  59 namespace {
  60 /// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or
  61 /// InstrRefBasedLDV to perform location propagation, via the LDVImpl
  62 /// base class.
  63 class LiveDebugValues : public MachineFunctionPass {
  64 public:
  65   static char ID;
  66
  67   LiveDebugValues();
  68   ~LiveDebugValues() {}
  69
  70   /// Calculate the liveness information for the given machine function.
  71   bool runOnMachineFunction(MachineFunction &MF) override;
  72
  73   MachineFunctionProperties getRequiredProperties() const override {
  74     return MachineFunctionProperties().set(
  75         MachineFunctionProperties::Property::NoVRegs);
  76   }
  77
  78   void getAnalysisUsage(AnalysisUsage &AU) const override {
  79     AU.setPreservesCFG();
  80     MachineFunctionPass::getAnalysisUsage(AU);
  81   }
  82
  83 private:
  84   std::unique_ptr<LDVImpl> InstrRefImpl;
  85   std::unique_ptr<LDVImpl> VarLocImpl;
  86   TargetPassConfig *TPC;
  87   MachineDominatorTree MDT;
  88 };
  89 } // namespace
  90
  91 char LiveDebugValues::ID = 0;
  92
  93 char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
  94
  95 INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis", false,
  96                 false)
  97
  98 /// Default construct and initialize the pass.
  99 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
 100   initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
 101   InstrRefImpl =
 102       std::unique_ptr<LDVImpl>(llvm::makeInstrRefBasedLiveDebugValues());
 103   VarLocImpl = std::unique_ptr<LDVImpl>(llvm::makeVarLocBasedLiveDebugValues());
 104 }
 105
 106 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
 107   bool InstrRefBased = MF.useDebugInstrRef();
 108   // Allow the user to force selection of InstrRef LDV.
 109   InstrRefBased |= ForceInstrRefLDV;
 110
 111   TPC = getAnalysisIfAvailable<TargetPassConfig>();
 112   LDVImpl *TheImpl = &*VarLocImpl;
 113
 114   MachineDominatorTree *DomTree = nullptr;
 115   if (InstrRefBased) {
 116     DomTree = &MDT;
 117     MDT.calculate(MF);
 118     TheImpl = &*InstrRefImpl;
 119   }
 120
 121   return TheImpl->ExtendRanges(MF, DomTree, TPC, InputBBLimit,
 122                                InputDbgValueLimit);
 123 }
 124
 125 bool llvm::debuginfoShouldUseDebugInstrRef(const Triple &T) {
 126   // Enable by default on x86_64, disable if explicitly turned off on cmdline.
 127   if (T.getArch() == llvm::Triple::x86_64 &&
 128       ValueTrackingVariableLocations != cl::boolOrDefault::BOU_FALSE)
 129     return true;
 130
 131   // Otherwise: enable if explicitly requestedo n command line.
 132   return ValueTrackingVariableLocations == cl::boolOrDefault::BOU_TRUE;
 133 }