Revert r294356, "DebugInfo: Track spilled variables in LiveDebugValues"

It caused undefined behavior in VarLoc. As far as I investigated,

  - VarLoc::VarLoc() treats negative offset value as InvalidKind.
    Consider the case that (int64_t)MI.getOperand(1).getImm() is negative and whether it satisfies ((uint64_t)Offset < (1ULL << 32)).

  - Comparison operators in VarLoc behave undefined since VarLoc::Loc.Hash is uninitialized in case of InvalidKind.

I guess Offset (in VarLoc) could be made aware of signed, but I am not sure.
So I have reverted it for now.

llvm-svn: 294447

1 files changed, 7 insertions, 137 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index 2759b56f8c0..131167630d6 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -24,16 +24,13 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/UniqueVector.h"
 #include "llvm/CodeGen/LexicalScopes.h"
-#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineMemOperand.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetRegisterInfo.h"
@@ -64,7 +61,6 @@ class LiveDebugValues : public MachineFunctionPass {
 private:
   const TargetRegisterInfo *TRI;
   const TargetInstrInfo *TII;
-  const TargetFrameLowering *TFI;
   LexicalScopes LS;
 
   /// Keeps track of lexical scopes associated with a user value's source
@@ -173,11 +169,6 @@ private:
   typedef UniqueVector<VarLoc> VarLocMap;
   typedef SparseBitVector<> VarLocSet;
   typedef SmallDenseMap<const MachineBasicBlock *, VarLocSet> VarLocInMBB;
-  struct SpillDebugPair {
-    MachineInstr *SpillInst;
-    MachineInstr *DebugInst;
-  };
-  typedef SmallVector<SpillDebugPair, 4> SpillMap;
 
   /// This holds the working set of currently open ranges. For fast
   /// access, this is done both as a set of VarLocIDs, and a map of
@@ -227,21 +218,14 @@ private:
     }
   };
 
-  bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
-                          unsigned &Reg);
-  int extractSpillBaseRegAndOffset(const MachineInstr &MI, unsigned &Reg);
-
   void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
                           VarLocMap &VarLocIDs);
-  void transferSpillInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
-                         VarLocMap &VarLocIDs, SpillMap &Spills);
   void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
                            const VarLocMap &VarLocIDs);
   bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
                               VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
   bool transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
-                VarLocInMBB &OutLocs, VarLocMap &VarLocIDs, SpillMap &Spills,
-                bool transferSpills);
+                VarLocInMBB &OutLocs, VarLocMap &VarLocIDs);
 
   bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
             const VarLocMap &VarLocIDs,
@@ -321,21 +305,6 @@ void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
 }
 #endif
 
-/// 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();
-  const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
-  assert(PVal->kind() == PseudoSourceValue::FixedStack &&
-         "Inconsistent memory operand in spill instruction");
-  int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
-  const MachineBasicBlock *MBB = MI.getParent();
-  return TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
-}
-
 /// End all previous ranges related to @MI and start a new range from @MI
 /// if it is a DBG_VALUE instr.
 void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
@@ -393,85 +362,6 @@ void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
   OpenRanges.erase(KillSet, VarLocIDs);
 }
 
-/// Decide if @MI is a spill instruction and return true if it is. We use 2
-/// criteria to make this decision:
-/// - Is this instruction a store to a spill slot?
-/// - Is there a register operand that is both used and killed?
-bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
-                                         MachineFunction *MF, unsigned &Reg) {
-  const MachineFrameInfo &FrameInfo = MF->getFrameInfo();
-  int FI;
-  const MachineMemOperand *MMO;
-
-  // To identify a spill instruction, use the same criteria as in AsmPrinter.
-  if (!((TII->isStoreToStackSlotPostFE(MI, FI) ||
-         TII->hasStoreToStackSlot(MI, MMO, FI)) &&
-        FrameInfo.isSpillSlotObjectIndex(FI)))
-    return false;
-
-  // In a spill instruction generated by the InlineSpiller the spilled register
-  // has its kill flag set. Return false if we don't find such a register.
-  Reg = 0;
-  for (const MachineOperand &MO : MI.operands()) {
-    if (MO.isReg() && MO.isUse() && MO.isKill()) {
-      Reg = MO.getReg();
-      break;
-    }
-  }
-  return Reg != 0;
-}
-
-/// 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.
-/// We don't want to insert any instructions in transfer(), so we just create
-/// the DBG_VALUE witout inserting it and keep track of it in @Spills.
-/// It will be inserted into the BB when we're done iterating over the
-/// instructions.
-void LiveDebugValues::transferSpillInst(MachineInstr &MI,
-                                        OpenRangesSet &OpenRanges,
-                                        VarLocMap &VarLocIDs,
-                                        SpillMap &Spills) {
-  unsigned Reg;
-  MachineFunction *MF = MI.getParent()->getParent();
-  if (!isSpillInstruction(MI, MF, Reg))
-    return;
-
-  // Check if the register is the location of a debug value.
-  for (unsigned ID : OpenRanges.getVarLocs()) {
-    if (VarLocIDs[ID].isDescribedByReg() == Reg) {
-      DEBUG(dbgs() << "Spilling Register " << PrintReg(Reg, TRI) << '('
-                   << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
-
-      // Create a DBG_VALUE instruction to describe the Var in its spilled
-      // location, but don't insert it yet to avoid invalidating the
-      // iterator in our caller.
-      unsigned SpillBase;
-      int SpillOffset = extractSpillBaseRegAndOffset(MI, SpillBase);
-      const MachineInstr *DMI = &VarLocIDs[ID].MI;
-      MachineInstr *SpDMI =
-          BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), true, SpillBase, 0,
-                  DMI->getDebugVariable(), DMI->getDebugExpression());
-      SpDMI->getOperand(1).setImm(SpillOffset);
-      DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
-            SpDMI->print(dbgs(), false, TII));
-
-      // The newly created DBG_VALUE instruction SpDMI must be inserted after
-      // MI. Keep track of the pairing.
-      SpillDebugPair MIP = {&MI, SpDMI};
-      Spills.push_back(MIP);
-
-      // End all previous ranges of Var.
-      OpenRanges.erase(VarLocIDs[ID].Var);
-
-      // Add the VarLoc to OpenRanges.
-      VarLoc VL(*SpDMI, LS);
-      unsigned SpillLocID = VarLocIDs.insert(VL);
-      OpenRanges.insert(SpillLocID, VL.Var);
-      return;
-    }
-  }
-}
-
 /// Terminate all open ranges at the end of the current basic block.
 bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
                                              OpenRangesSet &OpenRanges,
@@ -497,13 +387,10 @@ bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
 
 /// This routine creates OpenRanges and OutLocs.
 bool LiveDebugValues::transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
-                               VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
-                               SpillMap &Spills, bool transferSpills) {
+                               VarLocInMBB &OutLocs, VarLocMap &VarLocIDs) {
   bool Changed = false;
   transferDebugValue(MI, OpenRanges, VarLocIDs);
   transferRegisterDef(MI, OpenRanges, VarLocIDs);
-  if (transferSpills)
-    transferSpillInst(MI, OpenRanges, VarLocIDs, Spills);
   Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
   return Changed;
 }
@@ -592,11 +479,10 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
   bool OLChanged = false;
   bool MBBJoined = false;
 
-  VarLocMap VarLocIDs;      // Map VarLoc<>unique ID for use in bitvectors.
+  VarLocMap VarLocIDs;   // Map VarLoc<>unique ID for use in bitvectors.
   OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
-  VarLocInMBB OutLocs;      // Ranges that exist beyond bb.
-  VarLocInMBB InLocs;       // Ranges that are incoming after joining.
-  SpillMap Spills;          // DBG_VALUEs associated with spills.
+  VarLocInMBB OutLocs;   // Ranges that exist beyond bb.
+  VarLocInMBB InLocs;    // Ranges that are incoming after joining.
 
   DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
   DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
@@ -608,14 +494,9 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
       Pending;
 
   // Initialize every mbb with OutLocs.
-  // We are not looking at any spill instructions during the initial pass
-  // over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
-  // instructions for spills of registers that are known to be user variables
-  // within the BB in which the spill occurs.
   for (auto &MBB : MF)
     for (auto &MI : MBB)
-      transfer(MI, OpenRanges, OutLocs, VarLocIDs, Spills,
-               /*transferSpills=*/false);
+      transfer(MI, OpenRanges, OutLocs, VarLocIDs);
 
   DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after initialization",
                          dbgs()));
@@ -647,18 +528,8 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
       if (MBBJoined) {
         MBBJoined = false;
         Changed = true;
-        // Now that we have started to extend ranges across BBs we need to
-        // examine spill instructions to see whether they spill registers that
-        // correspond to user variables.
         for (auto &MI : *MBB)
-          OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs, Spills,
-                                /*transferSpills=*/true);
-
-        // Add any DBG_VALUE instructions necessitated by spills.
-        for (auto &SP : Spills)
-          MBB->insertAfter(MachineBasicBlock::iterator(*SP.SpillInst),
-                           SP.DebugInst);
-        Spills.clear();
+          OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs);
 
         DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
                                "OutLocs after propagating", dbgs()));
@@ -692,7 +563,6 @@ bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
 
   TRI = MF.getSubtarget().getRegisterInfo();
   TII = MF.getSubtarget().getInstrInfo();
-  TFI = MF.getSubtarget().getFrameLowering();
   LS.initialize(MF);
 
   bool Changed = ExtendRanges(MF);