Reverting r352642 - Handle restore instructions in LiveDebugValues - as it's causing

assertions on some buildbots.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@352666 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineInstr.h

@@ -1399,19 +1399,6 @@ public:
   /// Return true if all the defs of this instruction are dead.
   bool allDefsAreDead() const;
 
-  /// Return a valid size if the instruction is a spill instruction.
-  Optional<unsigned> getSpillSize(const TargetInstrInfo *TII) const;
-
-  /// Return a valid size if the instruction is a folded spill instruction.
-  Optional<unsigned> getFoldedSpillSize(const TargetInstrInfo *TII) const;
-
-  /// Return a valid size if the instruction is a restore instruction.
-  Optional<unsigned> getRestoreSize(const TargetInstrInfo *TII) const;
-
-  /// Return a valid size if the instruction is a folded restore instruction.
-  Optional<unsigned>
-  getFoldedRestoreSize(const TargetInstrInfo *TII) const;
-
   /// Copy implicit register operands from specified
   /// instruction to this instruction.
   void copyImplicitOps(MachineFunction &MF, const MachineInstr &MI);

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -754,25 +754,46 @@ static bool emitComments(const MachineInstr &MI, raw_ostream &CommentOS,
   const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
 
   // Check for spills and reloads
+  int FI;
+
+  const MachineFrameInfo &MFI = MF->getFrameInfo();
   bool Commented = false;
 
+  auto getSize =
+      [&MFI](const SmallVectorImpl<const MachineMemOperand *> &Accesses) {
+        unsigned Size = 0;
+        for (auto A : Accesses)
+          if (MFI.isSpillSlotObjectIndex(
+                  cast<FixedStackPseudoSourceValue>(A->getPseudoValue())
+                      ->getFrameIndex()))
+            Size += A->getSize();
+        return Size;
+      };
+
   // We assume a single instruction only has a spill or reload, not
   // both.
-  Optional<unsigned> Size;
-  if ((Size = MI.getRestoreSize(TII))) {
-    CommentOS << *Size << "-byte Reload";
-    Commented = true;
-  } else if ((Size = MI.getFoldedRestoreSize(TII))) {
-    if (*Size) {
-      CommentOS << *Size << "-byte Folded Reload";
+  const MachineMemOperand *MMO;
+  SmallVector<const MachineMemOperand *, 2> Accesses;
+  if (TII->isLoadFromStackSlotPostFE(MI, FI)) {
+    if (MFI.isSpillSlotObjectIndex(FI)) {
+      MMO = *MI.memoperands_begin();
+      CommentOS << MMO->getSize() << "-byte Reload";
       Commented = true;
     }
-  } else if ((Size = MI.getSpillSize(TII))) {
-    CommentOS << *Size << "-byte Spill";
-    Commented = true;
-  } else if ((Size = MI.getFoldedSpillSize(TII))) {
-    if (*Size) {
-      CommentOS << *Size << "-byte Folded Spill";
+  } else if (TII->hasLoadFromStackSlot(MI, Accesses)) {
+    if (auto Size = getSize(Accesses)) {
+      CommentOS << Size << "-byte Folded Reload";
+      Commented = true;
+    }
+  } else if (TII->isStoreToStackSlotPostFE(MI, FI)) {
+    if (MFI.isSpillSlotObjectIndex(FI)) {
+      MMO = *MI.memoperands_begin();
+      CommentOS << MMO->getSize() << "-byte Spill";
+      Commented = true;
+    }
+  } else if (TII->hasStoreToStackSlot(MI, Accesses)) {
+    if (auto Size = getSize(Accesses)) {
+      CommentOS << Size << "-byte Folded Spill";
       Commented = true;
     }
   }

lib/CodeGen/LiveDebugValues.cpp

@@ -34,14 +34,13 @@
 #include "llvm/CodeGen/MachineMemOperand.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/PseudoSourceValue.h"
-#include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/CodeGen/TargetFrameLowering.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/Config/llvm-config.h"
-#include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/Function.h"
@@ -86,8 +85,6 @@ private:
   BitVector CalleeSavedRegs;
   LexicalScopes LS;
 
-  enum struct TransferKind { TransferCopy, TransferSpill, TransferRestore };
-
   /// Keeps track of lexical scopes associated with a user value's source
   /// location.
   class UserValueScopes {
@@ -127,30 +124,15 @@ private:
 
   /// A pair of debug variable and value location.
   struct VarLoc {
-    // The location at which a spilled variable resides. It consists of a
-    // register and an offset.
-    struct SpillLoc {
-      unsigned SpillBase;
-      int SpillOffset;
-      bool operator==(const SpillLoc &Other) const {
-        return SpillBase == Other.SpillBase && SpillOffset == Other.SpillOffset;
-      }
-    };
-
     const DebugVariable Var;
     const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
     mutable UserValueScopes UVS;
-    enum VarLocKind {
-      InvalidKind = 0,
-      RegisterKind,
-      SpillLocKind
-    } Kind = InvalidKind;
+    enum { InvalidKind = 0, RegisterKind } Kind = InvalidKind;
 
     /// The value location. Stored separately to avoid repeatedly
     /// extracting it from MI.
     union {
       uint64_t RegNo;
-      SpillLoc SpillLocation;
       uint64_t Hash;
     } Loc;
 
@@ -167,17 +149,6 @@ private:
       }
     }
 
-    /// The constructor for spill locations.
-    VarLoc(const MachineInstr &MI, unsigned SpillBase, int SpillOffset,
-           LexicalScopes &LS)
-        : Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
-          UVS(MI.getDebugLoc(), LS) {
-      assert(MI.isDebugValue() && "not a DBG_VALUE");
-      assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
-      Kind = SpillLocKind;
-      Loc.SpillLocation = {SpillBase, SpillOffset};
-    }
-
     /// If this variable is described by a register, return it,
     /// otherwise return 0.
     unsigned isDescribedByReg() const {
@@ -265,23 +236,15 @@ private:
 
   bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
                           unsigned &Reg);
-  /// If a given instruction is identified as a spill, return the spill location
-  /// and set \p Reg to the spilled register.
-  Optional<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI,
-                                                  MachineFunction *MF,
-                                                  unsigned &Reg);
-  /// Given a spill instruction, extract the register and offset used to
-  /// address the spill location in a target independent way.
-  VarLoc::SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI);
+  int extractSpillBaseRegAndOffset(const MachineInstr &MI, unsigned &Reg);
   void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
                                TransferMap &Transfers, VarLocMap &VarLocIDs,
-                               unsigned OldVarID, TransferKind Kind,
-                               unsigned NewReg = 0);
+                               unsigned OldVarID, unsigned NewReg = 0);
 
   void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
                           VarLocMap &VarLocIDs);
-  void transferSpillOrRestoreInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
-                                  VarLocMap &VarLocIDs, TransferMap &Transfers);
+  void transferSpillInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
+                         VarLocMap &VarLocIDs, TransferMap &Transfers);
   void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
                             VarLocMap &VarLocIDs, TransferMap &Transfers);
   void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
@@ -375,8 +338,10 @@ void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
 }
 #endif
 
-LiveDebugValues::VarLoc::SpillLoc
-LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
+/// Given a spill instruction, extract the register and offset used to
+/// address the spill location in a target independent way.
+int LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI,
+                                                  unsigned &Reg) {
   assert(MI.hasOneMemOperand() &&
          "Spill instruction does not have exactly one memory operand?");
   auto MMOI = MI.memoperands_begin();
@@ -385,9 +350,7 @@ LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
          "Inconsistent memory operand in spill instruction");
   int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
   const MachineBasicBlock *MBB = MI.getParent();
-  unsigned Reg;
-  int Offset = TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
-  return {Reg, Offset};
+  return TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
 }
 
 /// End all previous ranges related to @MI and start a new range from @MI
@@ -423,28 +386,11 @@ void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
 /// otherwise it is variable's location on the stack.
 void LiveDebugValues::insertTransferDebugPair(
     MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
-    VarLocMap &VarLocIDs, unsigned OldVarID, TransferKind Kind,
-    unsigned NewReg) {
+    VarLocMap &VarLocIDs, unsigned OldVarID, unsigned NewReg) {
   const MachineInstr *DMI = &VarLocIDs[OldVarID].MI;
   MachineFunction *MF = MI.getParent()->getParent();
   MachineInstr *NewDMI;
-
-  auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers,
-                        &VarLocIDs](VarLoc &VL, MachineInstr *NewDMI) {
-    unsigned LocId = VarLocIDs.insert(VL);
-    OpenRanges.insert(LocId, VL.Var);
-    // The newly created DBG_VALUE instruction NewDMI must be inserted after
-    // MI. Keep track of the pairing.
-    TransferDebugPair MIP = {&MI, NewDMI};
-    Transfers.push_back(MIP);
-  };
-
-  // End all previous ranges of Var.
-  OpenRanges.erase(VarLocIDs[OldVarID].Var);
-  switch (Kind) {
-  case TransferKind::TransferCopy: {
-    assert(NewReg &&
-           "No register supplied when handling a copy of a debug value");
+  if (NewReg) {
     // Create a DBG_VALUE instruction to describe the Var in its new
     // register location.
     NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(),
@@ -452,43 +398,33 @@ void LiveDebugValues::insertTransferDebugPair(
                      DMI->getDebugVariable(), DMI->getDebugExpression());
     if (DMI->isIndirectDebugValue())
       NewDMI->getOperand(1).setImm(DMI->getOperand(1).getImm());
-    VarLoc VL(*NewDMI, LS);
-    ProcessVarLoc(VL, NewDMI);
     LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: ";
                NewDMI->print(dbgs(), false, false, false, TII));
-    return;
-  }
-  case TransferKind::TransferSpill: {
+  } else {
     // Create a DBG_VALUE instruction to describe the Var in its spilled
     // location.
-    VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
-    auto *SpillExpr =
-        DIExpression::prepend(DMI->getDebugExpression(), DIExpression::NoDeref,
-                              SpillLocation.SpillOffset);
-    NewDMI =
-        BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), true,
-                SpillLocation.SpillBase, DMI->getDebugVariable(), SpillExpr);
-    VarLoc VL(*NewDMI, SpillLocation.SpillBase, SpillLocation.SpillOffset, LS);
-    ProcessVarLoc(VL, NewDMI);
+    unsigned SpillBase;
+    int SpillOffset = extractSpillBaseRegAndOffset(MI, SpillBase);
+    auto *SpillExpr = DIExpression::prepend(DMI->getDebugExpression(),
+                                            DIExpression::NoDeref, SpillOffset);
+    NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), true, SpillBase,
+                     DMI->getDebugVariable(), SpillExpr);
     LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
                NewDMI->print(dbgs(), false, false, false, TII));
-    return;
-  }
-  case TransferKind::TransferRestore: {
-    assert(NewReg &&
-           "No register supplied when handling a restore of a debug value");
-    MachineFunction *MF = MI.getMF();
-    DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent());
-    NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), false, NewReg,
-                     DMI->getDebugVariable(), DIB.createExpression());
-    VarLoc VL(*NewDMI, LS);
-    ProcessVarLoc(VL, NewDMI);
-    LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: ";
-               NewDMI->print(dbgs(), false, false, false, TII));
-    return;
-  }
   }
-  llvm_unreachable("Invalid transfer kind");
+
+  // The newly created DBG_VALUE instruction NewDMI must be inserted after
+  // MI. Keep track of the pairing.
+  TransferDebugPair MIP = {&MI, NewDMI};
+  Transfers.push_back(MIP);
+
+  // End all previous ranges of Var.
+  OpenRanges.erase(VarLocIDs[OldVarID].Var);
+
+  // Add the VarLoc to OpenRanges.
+  VarLoc VL(*NewDMI, LS);
+  unsigned LocID = VarLocIDs.insert(VL);
+  OpenRanges.insert(LocID, VL.Var);
 }
 
 /// A definition of a register may mark the end of a range.
@@ -534,15 +470,24 @@ void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
 /// other spills). We do not handle this yet (more than one memory operand).
 bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
                                          MachineFunction *MF, unsigned &Reg) {
+  const MachineFrameInfo &FrameInfo = MF->getFrameInfo();
+  int FI;
   SmallVector<const MachineMemOperand*, 1> Accesses;
 
   // TODO: Handle multiple stores folded into one.
   if (!MI.hasOneMemOperand())
     return false;
 
-  if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII))
-    return false; // This is not a spill instruction, since no valid size was
-                  // returned from either function.
+  // To identify a spill instruction, use the same criteria as in AsmPrinter.
+  if (!((TII->isStoreToStackSlotPostFE(MI, FI) &&
+         FrameInfo.isSpillSlotObjectIndex(FI)) ||
+        (TII->hasStoreToStackSlot(MI, Accesses) &&
+         llvm::any_of(Accesses, [&FrameInfo](const MachineMemOperand *MMO) {
+           return FrameInfo.isSpillSlotObjectIndex(
+               cast<FixedStackPseudoSourceValue>(MMO->getPseudoValue())
+                   ->getFrameIndex());
+         }))))
+    return false;
 
   auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
     if (!MO.isReg() || !MO.isUse()) {
@@ -579,64 +524,29 @@ bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
   return false;
 }
 
-Optional<LiveDebugValues::VarLoc::SpillLoc>
-LiveDebugValues::isRestoreInstruction(const MachineInstr &MI,
-                                      MachineFunction *MF, unsigned &Reg) {
-  if (!MI.hasOneMemOperand())
-    return None;
-
-  // FIXME: Handle folded restore instructions with more than one memory
-  // operand.
-  if (MI.getRestoreSize(TII)) {
-    Reg = MI.getOperand(0).getReg();
-    return extractSpillBaseRegAndOffset(MI);
-  }
-  return None;
-}
-
 /// A spilled register may indicate that we have to end the current range of
 /// a variable and create a new one for the spill location.
-/// A restored register may indicate the reverse situation.
 /// We don't want to insert any instructions in process(), so we just create
 /// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
 /// It will be inserted into the BB when we're done iterating over the
 /// instructions.
-void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI,
-                                                 OpenRangesSet &OpenRanges,
-                                                 VarLocMap &VarLocIDs,
-                                                 TransferMap &Transfers) {
-  MachineFunction *MF = MI.getMF();
-  TransferKind TKind;
+void LiveDebugValues::transferSpillInst(MachineInstr &MI,
+                                        OpenRangesSet &OpenRanges,
+                                        VarLocMap &VarLocIDs,
+                                        TransferMap &Transfers) {
   unsigned Reg;
-  Optional<VarLoc::SpillLoc> Loc;
+  MachineFunction *MF = MI.getMF();
+  if (!isSpillInstruction(MI, MF, Reg))
+    return;
 
-  if (isSpillInstruction(MI, MF, Reg)) {
-    TKind = TransferKind::TransferSpill;
-    LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump(););
-    LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
-                      << "\n");
-  } else {
-    if (!(Loc = isRestoreInstruction(MI, MF, Reg)))
-      return;
-    TKind = TransferKind::TransferRestore;
-    LLVM_DEBUG(dbgs() << "Recognized as restore: "; MI.dump(););
-    LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
-                      << "\n");
-  }
-  // Check if the register or spill location is the location of a debug value.
+  // Check if the register is the location of a debug value.
   for (unsigned ID : OpenRanges.getVarLocs()) {
-    if (TKind == TransferKind::TransferSpill &&
-        VarLocIDs[ID].isDescribedByReg() == Reg) {
+    if (VarLocIDs[ID].isDescribedByReg() == Reg) {
       LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
                         << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
-    } else if (TKind == TransferKind::TransferRestore &&
-               VarLocIDs[ID].Loc.SpillLocation == *Loc) {
-      LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
-                        << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
-    } else
-      continue;
-    insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, TKind,
-                            Reg);
+      insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID);
+      return;
+    }
   }
 }
 
@@ -674,7 +584,7 @@ void LiveDebugValues::transferRegisterCopy(MachineInstr &MI,
   for (unsigned ID : OpenRanges.getVarLocs()) {
     if (VarLocIDs[ID].isDescribedByReg() == SrcReg) {
       insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID,
-                              TransferKind::TransferCopy, DestReg);
+                              DestReg);
       return;
     }
   }
@@ -714,7 +624,7 @@ bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
   transferRegisterDef(MI, OpenRanges, VarLocIDs);
   if (transferChanges) {
     transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
-    transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers);
+    transferSpillInst(MI, OpenRanges, VarLocIDs, Transfers);
   }
   Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
   return Changed;

lib/CodeGen/MachineInstr.cpp

@@ -25,7 +25,6 @@
 #include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/CodeGen/GlobalISel/RegisterBank.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
-#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineInstrBundle.h"
@@ -50,9 +49,9 @@
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ModuleSlotTracker.h"
-#include "llvm/IR/Operator.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Value.h"
+#include "llvm/IR/Operator.h"
 #include "llvm/MC/MCInstrDesc.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSymbol.h"
@@ -2101,54 +2100,3 @@ void MachineInstr::changeDebugValuesDefReg(unsigned Reg) {
   for (auto *DBI : DbgValues)
     DBI->getOperand(0).setReg(Reg);
 }
-
-using MMOList = SmallVector<const MachineMemOperand *, 2>;
-
-static unsigned getSpillSlotSize(MMOList &Accesses,
-                                 const MachineFrameInfo &MFI) {
-  unsigned Size = 0;
-  for (auto A : Accesses)
-    if (MFI.isSpillSlotObjectIndex(
-            cast<FixedStackPseudoSourceValue>(A->getPseudoValue())
-                ->getFrameIndex()))
-      Size += A->getSize();
-  return Size;
-}
-
-Optional<unsigned>
-MachineInstr::getSpillSize(const TargetInstrInfo *TII) const {
-  int FI;
-  if (TII->isStoreToStackSlotPostFE(*this, FI)) {
-    const MachineFrameInfo &MFI = getMF()->getFrameInfo();
-    if (MFI.isSpillSlotObjectIndex(FI))
-      return (*memoperands_begin())->getSize();
-  }
-  return None;
-}
-
-Optional<unsigned>
-MachineInstr::getFoldedSpillSize(const TargetInstrInfo *TII) const {
-  MMOList Accesses;
-  if (TII->hasStoreToStackSlot(*this, Accesses))
-    return getSpillSlotSize(Accesses, getMF()->getFrameInfo());
-  return None;
-}
-
-Optional<unsigned>
-MachineInstr::getRestoreSize(const TargetInstrInfo *TII) const {
-  int FI;
-  if (TII->isLoadFromStackSlotPostFE(*this, FI)) {
-    const MachineFrameInfo &MFI = getMF()->getFrameInfo();
-    if (MFI.isSpillSlotObjectIndex(FI))
-      return (*memoperands_begin())->getSize();
-  }
-  return None;
-}
-
-Optional<unsigned>
-MachineInstr::getFoldedRestoreSize(const TargetInstrInfo *TII) const {
-  MMOList Accesses;
-  if (TII->hasLoadFromStackSlot(*this, Accesses))
-    return getSpillSlotSize(Accesses, getMF()->getFrameInfo());
-  return None;
-}

test/DebugInfo/MIR/X86/live-debug-values-restore.mir

@@ -1,189 +0,0 @@
-# RUN: llc -run-pass livedebugvalues -march=x86-64 -o - %s | FileCheck %s
-
-# Generated from the following source with:
-# clang -g -mllvm -stop-before=livedebugvalues -S -O2 test.c -o test.mir
-
-# #define FORCE_SPILL() \
-#   __asm volatile("" : : : \
-#                    "rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "r8", \
-#                    "r9", "r10", "r11", "r12", "r13", "r14", "r15")
-# int f(int *p) {
-#   if (p) {
-#     FORCE_SPILL();
-#   }
-#   return *(p + 1);
-# }
-
-# Ascertain that the spill has been recognized and manifested in a DBG_VALUE.
-# CHECK: MOV64mr $rsp,{{.*-8.*}}killed{{.*}}$rdi :: (store 8 into %stack.0)
-# CHECK-NEXT: DBG_VALUE $rsp,{{.*}}![[MDIX:[0-9]+]],{{.*}}!DIExpression(DW_OP_constu, 8, DW_OP_minus)
-
-# Check for the restore.
-# CHECK: $rdi = MOV64rm $rsp,{{.*-8.*}}:: (load 8 from %stack.0)
-# CHECK-NEXT: DBG_VALUE $rdi,{{.*}}![[MDIX]], !DIExpression()
-
---- |
-  define dso_local i32 @f(i32* readonly %p) local_unnamed_addr !dbg !7 {
-  entry:
-    call void @llvm.dbg.value(metadata i32* %p, metadata !13, metadata !DIExpression()), !dbg !14
-    %tobool = icmp eq i32* %p, null, !dbg !15
-    br i1 %tobool, label %if.end, label %if.then, !dbg !17
-  
-  if.then:                                          ; preds = %entry
-    tail call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"(), !dbg !18, !srcloc !20
-    br label %if.end, !dbg !21
-  
-  if.end:                                           ; preds = %entry, %if.then
-    %add.ptr = getelementptr inbounds i32, i32* %p, i64 1, !dbg !22
-    %0 = load i32, i32* %add.ptr, align 4, !dbg !23, !tbaa !24
-    ret i32 %0, !dbg !28
-  }
-  
-  declare void @llvm.dbg.value(metadata, metadata, metadata)
-  
-  !llvm.dbg.cu = !{!0}
-  !llvm.module.flags = !{!3, !4, !5}
-  !llvm.ident = !{!6}
-  
-  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 9.0.0 (https://git.llvm.org/git/clang.git/ 57a6ce7ac318de98e3e777e09cb9ed8282b5cc03) (https://git.llvm.org/git/llvm.git/ ff54a19e4912d7f15cb02798a7f2048441bff751)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
-  !1 = !DIFile(filename: "test2.c", directory: "/home/test")
-  !2 = !{}
-  !3 = !{i32 2, !"Dwarf Version", i32 4}
-  !4 = !{i32 2, !"Debug Info Version", i32 3}
-  !5 = !{i32 1, !"wchar_size", i32 4}
-  !6 = !{!"clang version 9.0.0 (https://git.llvm.org/git/clang.git/ 57a6ce7ac318de98e3e777e09cb9ed8282b5cc03) (https://git.llvm.org/git/llvm.git/ ff54a19e4912d7f15cb02798a7f2048441bff751)"}
-  !7 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 5, type: !8, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
-  !8 = !DISubroutineType(types: !9)
-  !9 = !{!10, !11}
-  !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
-  !11 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
-  !12 = !{!13}
-  !13 = !DILocalVariable(name: "p", arg: 1, scope: !7, file: !1, line: 5, type: !11)
-  !14 = !DILocation(line: 5, column: 12, scope: !7)
-  !15 = !DILocation(line: 6, column: 7, scope: !16)
-  !16 = distinct !DILexicalBlock(scope: !7, file: !1, line: 6, column: 7)
-  !17 = !DILocation(line: 6, column: 7, scope: !7)
-  !18 = !DILocation(line: 7, column: 5, scope: !19)
-  !19 = distinct !DILexicalBlock(scope: !16, file: !1, line: 6, column: 10)
-  !20 = !{i32 -2147471544}
-  !21 = !DILocation(line: 8, column: 3, scope: !19)
-  !22 = !DILocation(line: 9, column: 14, scope: !7)
-  !23 = !DILocation(line: 9, column: 10, scope: !7)
-  !24 = !{!25, !25, i64 0}
-  !25 = !{!"int", !26, i64 0}
-  !26 = !{!"omnipotent char", !27, i64 0}
-  !27 = !{!"Simple C/C++ TBAA"}
-  !28 = !DILocation(line: 9, column: 3, scope: !7)
-
-...
----
-name:            f
-alignment:       4
-exposesReturnsTwice: false
-legalized:       false
-regBankSelected: false
-selected:        false
-failedISel:      false
-tracksRegLiveness: true
-hasWinCFI:       false
-registers:       []
-liveins:         
-  - { reg: '$rdi', virtual-reg: '' }
-frameInfo:       
-  isFrameAddressTaken: false
-  isReturnAddressTaken: false
-  hasStackMap:     false
-  hasPatchPoint:   false
-  stackSize:       48
-  offsetAdjustment: -48
-  maxAlignment:    8
-  adjustsStack:    false
-  hasCalls:        false
-  stackProtector:  ''
-  maxCallFrameSize: 0
-  cvBytesOfCalleeSavedRegisters: 48
-  hasOpaqueSPAdjustment: false
-  hasVAStart:      false
-  hasMustTailInVarArgFunc: false
-  localFrameSize:  0
-  savePoint:       ''
-  restorePoint:    ''
-fixedStack:      
-  - { id: 0, type: spill-slot, offset: -56, size: 8, alignment: 8, stack-id: 0, 
-      callee-saved-register: '$rbx', callee-saved-restored: true, debug-info-variable: '', 
-      debug-info-expression: '', debug-info-location: '' }
-  - { id: 1, type: spill-slot, offset: -48, size: 8, alignment: 16, stack-id: 0, 
-      callee-saved-register: '$r12', callee-saved-restored: true, debug-info-variable: '', 
-      debug-info-expression: '', debug-info-location: '' }
-  - { id: 2, type: spill-slot, offset: -40, size: 8, alignment: 8, stack-id: 0, 
-      callee-saved-register: '$r13', callee-saved-restored: true, debug-info-variable: '', 
-      debug-info-expression: '', debug-info-location: '' }
-  - { id: 3, type: spill-slot, offset: -32, size: 8, alignment: 16, stack-id: 0, 
-      callee-saved-register: '$r14', callee-saved-restored: true, debug-info-variable: '', 
-      debug-info-expression: '', debug-info-location: '' }
-  - { id: 4, type: spill-slot, offset: -24, size: 8, alignment: 8, stack-id: 0, 
-      callee-saved-register: '$r15', callee-saved-restored: true, debug-info-variable: '', 
-      debug-info-expression: '', debug-info-location: '' }
-  - { id: 5, type: spill-slot, offset: -16, size: 8, alignment: 16, stack-id: 0, 
-      callee-saved-register: '$rbp', callee-saved-restored: true, debug-info-variable: '', 
-      debug-info-expression: '', debug-info-location: '' }
-stack:           
-  - { id: 0, name: '', type: spill-slot, offset: -64, size: 8, alignment: 8, 
-      stack-id: 0, callee-saved-register: '', callee-saved-restored: true, 
-      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
-constants:       []
-body:             |
-  bb.0.entry:
-    successors: %bb.2(0x30000000), %bb.1(0x50000000)
-    liveins: $rdi, $rbx, $r12, $r13, $r14, $r15, $rbp
-  
-    DBG_VALUE $rdi, $noreg, !13, !DIExpression(), debug-location !14
-    DBG_VALUE $rdi, $noreg, !13, !DIExpression(), debug-location !14
-    TEST64rr renamable $rdi, renamable $rdi, implicit-def $eflags, debug-location !15
-    JE_1 %bb.2, implicit $eflags, debug-location !17
-  
-  bb.1.if.then:
-    successors: %bb.2(0x80000000)
-    liveins: $rdi, $rbp, $r15, $r14, $r13, $r12, $rbx
-  
-    frame-setup PUSH64r killed $rbp, implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 16
-    frame-setup PUSH64r killed $r15, implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 24
-    frame-setup PUSH64r killed $r14, implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 32
-    frame-setup PUSH64r killed $r13, implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 40
-    frame-setup PUSH64r killed $r12, implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 48
-    frame-setup PUSH64r killed $rbx, implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 56
-    CFI_INSTRUCTION offset $rbx, -56
-    CFI_INSTRUCTION offset $r12, -48
-    CFI_INSTRUCTION offset $r13, -40
-    CFI_INSTRUCTION offset $r14, -32
-    CFI_INSTRUCTION offset $r15, -24
-    CFI_INSTRUCTION offset $rbp, -16
-    MOV64mr $rsp, 1, $noreg, -8, $noreg, killed renamable $rdi :: (store 8 into %stack.0)
-    INLINEASM &"", 1, 12, implicit-def dead early-clobber $rax, 12, implicit-def dead early-clobber $rbx, 12, implicit-def dead early-clobber $rcx, 12, implicit-def dead early-clobber $rdx, 12, implicit-def dead early-clobber $rsi, 12, implicit-def dead early-clobber $rdi, 12, implicit-def dead early-clobber $rbp, 12, implicit-def dead early-clobber $r8, 12, implicit-def dead early-clobber $r9, 12, implicit-def dead early-clobber $r10, 12, implicit-def dead early-clobber $r11, 12, implicit-def dead early-clobber $r12, 12, implicit-def dead early-clobber $r13, 12, implicit-def dead early-clobber $r14, 12, implicit-def dead early-clobber $r15, 12, implicit-def dead early-clobber $eflags, !20, debug-location !18
-    renamable $rdi = MOV64rm $rsp, 1, $noreg, -8, $noreg :: (load 8 from %stack.0)
-    $rbx = frame-destroy POP64r implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 48
-    $r12 = frame-destroy POP64r implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 40
-    $r13 = frame-destroy POP64r implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 32
-    $r14 = frame-destroy POP64r implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 24
-    $r15 = frame-destroy POP64r implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 16
-    $rbp = frame-destroy POP64r implicit-def $rsp, implicit $rsp
-    CFI_INSTRUCTION def_cfa_offset 8
-  
-  bb.2.if.end:
-    liveins: $rdi, $rbx, $r12, $r13, $r14, $r15, $rbp
-  
-    renamable $eax = MOV32rm killed renamable $rdi, 1, $noreg, 4, $noreg, debug-location !23 :: (load 4 from %ir.add.ptr, !tbaa !24)
-    RETQ $eax, debug-location !28
-
-...