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