1 files changed, 175 insertions, 0 deletions
diff --git a/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp b/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
new file mode 100644
index 0000000000..61032548ea
--- /dev/null
+++ b/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
@@ -0,0 +1,175 @@
+//===-- llvm/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DbgValueHistoryCalculator.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include <algorithm>
+#include <map>
+
+#define DEBUG_TYPE "dwarfdebug"
+
+namespace llvm {
+
+// \brief If @MI is a DBG_VALUE with debug value described by a
+// defined register, returns the number of this register.
+// In the other case, returns 0.
+static unsigned isDescribedByReg(const MachineInstr &MI) {
+  assert(MI.isDebugValue());
+  assert(MI.getNumOperands() == 3);
+  // If location of variable is described using a register (directly or
+  // indirecltly), this register is always a first operand.
+  return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
+}
+
+void DbgValueHistoryMap::startInstrRange(const MDNode *Var,
+                                         const MachineInstr &MI) {
+  // Instruction range should start with a DBG_VALUE instruction for the
+  // variable.
+  assert(MI.isDebugValue() && MI.getDebugVariable() == Var);
+  auto &Ranges = VarInstrRanges[Var];
+  if (!Ranges.empty() && Ranges.back().second == nullptr &&
+      Ranges.back().first->isIdenticalTo(&MI)) {
+    DEBUG(dbgs() << "Coalescing identical DBG_VALUE entries:\n"
+                 << "\t" << Ranges.back().first << "\t" << MI << "\n");
+    return;
+  }
+  Ranges.push_back(std::make_pair(&MI, nullptr));
+}
+
+void DbgValueHistoryMap::endInstrRange(const MDNode *Var,
+                                       const MachineInstr &MI) {
+  auto &Ranges = VarInstrRanges[Var];
+  // Verify that the current instruction range is not yet closed.
+  assert(!Ranges.empty() && Ranges.back().second == nullptr);
+  // For now, instruction ranges are not allowed to cross basic block
+  // boundaries.
+  assert(Ranges.back().first->getParent() == MI.getParent());
+  Ranges.back().second = &MI;
+}
+
+unsigned DbgValueHistoryMap::getRegisterForVar(const MDNode *Var) const {
+  const auto &I = VarInstrRanges.find(Var);
+  if (I == VarInstrRanges.end())
+    return 0;
+  const auto &Ranges = I->second;
+  if (Ranges.empty() || Ranges.back().second != nullptr)
+    return 0;
+  return isDescribedByReg(*Ranges.back().first);
+}
+
+namespace {
+// Maps physreg numbers to the variables they describe.
+typedef std::map<unsigned, SmallVector<const MDNode *, 1>> RegDescribedVarsMap;
+}
+
+// \brief Claim that @Var is not described by @RegNo anymore.
+static void dropRegDescribedVar(RegDescribedVarsMap &RegVars,
+                                unsigned RegNo, const MDNode *Var) {
+  const auto &I = RegVars.find(RegNo);
+  assert(RegNo != 0U && I != RegVars.end());
+  auto &VarSet = I->second;
+  const auto &VarPos = std::find(VarSet.begin(), VarSet.end(), Var);
+  assert(VarPos != VarSet.end());
+  VarSet.erase(VarPos);
+  // Don't keep empty sets in a map to keep it as small as possible.
+  if (VarSet.empty())
+    RegVars.erase(I);
+}
+
+// \brief Claim that @Var is now described by @RegNo.
+static void addRegDescribedVar(RegDescribedVarsMap &RegVars,
+                               unsigned RegNo, const MDNode *Var) {
+  assert(RegNo != 0U);
+  auto &VarSet = RegVars[RegNo];
+  assert(std::find(VarSet.begin(), VarSet.end(), Var) == VarSet.end());
+  VarSet.push_back(Var);
+}
+
+// \brief Terminate the location range for variables described by register
+// @RegNo by inserting @ClobberingInstr to their history.
+static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo,
+                                DbgValueHistoryMap &HistMap,
+                                const MachineInstr &ClobberingInstr) {
+  const auto &I = RegVars.find(RegNo);
+  if (I == RegVars.end())
+    return;
+  // Iterate over all variables described by this register and add this
+  // instruction to their history, clobbering it.
+  for (const auto &Var : I->second)
+    HistMap.endInstrRange(Var, ClobberingInstr);
+  RegVars.erase(I);
+}
+
+// \brief Terminate location ranges for all variables, described by registers
+// clobbered by @MI.
+static void clobberRegisterUses(RegDescribedVarsMap &RegVars,
+                                const MachineInstr &MI,
+                                const TargetRegisterInfo *TRI,
+                                DbgValueHistoryMap &HistMap) {
+  for (const MachineOperand &MO : MI.operands()) {
+    if (!MO.isReg() || !MO.isDef() || !MO.getReg())
+      continue;
+    for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
+         ++AI) {
+      unsigned RegNo = *AI;
+      clobberRegisterUses(RegVars, RegNo, HistMap, MI);
+    }
+  }
+}
+
+// \brief Terminate the location range for all register-described variables
+// by inserting @ClobberingInstr to their history.
+static void clobberAllRegistersUses(RegDescribedVarsMap &RegVars,
+                                    DbgValueHistoryMap &HistMap,
+                                    const MachineInstr &ClobberingInstr) {
+  for (const auto &I : RegVars)
+    for (const auto &Var : I.second)
+      HistMap.endInstrRange(Var, ClobberingInstr);
+  RegVars.clear();
+}
+
+void calculateDbgValueHistory(const MachineFunction *MF,
+                              const TargetRegisterInfo *TRI,
+                              DbgValueHistoryMap &Result) {
+  RegDescribedVarsMap RegVars;
+
+  for (const auto &MBB : *MF) {
+    for (const auto &MI : MBB) {
+      if (!MI.isDebugValue()) {
+        // Not a DBG_VALUE instruction. It may clobber registers which describe
+        // some variables.
+        clobberRegisterUses(RegVars, MI, TRI, Result);
+        continue;
+      }
+
+      assert(MI.getNumOperands() > 1 && "Invalid DBG_VALUE instruction!");
+      const MDNode *Var = MI.getDebugVariable();
+
+      if (unsigned PrevReg = Result.getRegisterForVar(Var))
+        dropRegDescribedVar(RegVars, PrevReg, Var);
+
+      Result.startInstrRange(Var, MI);
+
+      if (unsigned NewReg = isDescribedByReg(MI))
+        addRegDescribedVar(RegVars, NewReg, Var);
+    }
+
+    // Make sure locations for register-described variables are valid only
+    // until the end of the basic block (unless it's the last basic block, in
+    // which case let their liveness run off to the end of the function).
+    if (!MBB.empty() &&  &MBB != &MF->back())
+      clobberAllRegistersUses(RegVars, Result, MBB.back());
+  }
+}
+
+}