[llvm] r200947 - [CodeGenPrepare] Move away sign extensions that get in the way of addressing

Quentin Colombet qcolombet at apple.com
Thu Feb 6 13:44:57 PST 2014


Author: qcolombet
Date: Thu Feb  6 15:44:56 2014
New Revision: 200947

URL: http://llvm.org/viewvc/llvm-project?rev=200947&view=rev
Log:
[CodeGenPrepare] Move away sign extensions that get in the way of addressing
mode.

Basically the idea is to transform code like this:
%idx = add nsw i32 %a, 1
%sextidx = sext i32 %idx to i64
%gep = gep i8* %myArray, i64 %sextidx
load i8* %gep

Into:
%sexta = sext i32 %a to i64
%idx = add nsw i64 %sexta, 1
%gep = gep i8* %myArray, i64 %idx
load i8* %gep

That way the computation can be folded into the addressing mode.

This transformation is done as part of the addressing mode matcher.
If the matching fails (not profitable, addressing mode not legal, etc.), the
matcher will revert the related promotions.

<rdar://problem/15519855>

Added:
    llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=200947&r1=200946&r2=200947&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Thu Feb  6 15:44:56 2014
@@ -70,6 +70,9 @@ static cl::opt<bool> DisableSelectToBran
   cl::desc("Disable select to branch conversion."));
 
 namespace {
+typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
+typedef DenseMap<Instruction *, Type *> InstrToOrigTy;
+
   class CodeGenPrepare : public FunctionPass {
     /// TLI - Keep a pointer of a TargetLowering to consult for determining
     /// transformation profitability.
@@ -88,6 +91,12 @@ namespace {
     /// multiple load/stores of the same address.
     ValueMap<Value*, Value*> SunkAddrs;
 
+    /// Keeps track of all truncates inserted for the current function.
+    SetOfInstrs InsertedTruncsSet;
+    /// Keeps track of the type of the related instruction before their
+    /// promotion for the current function.
+    InstrToOrigTy PromotedInsts;
+
     /// ModifiedDT - If CFG is modified in anyway, dominator tree may need to
     /// be updated.
     bool ModifiedDT;
@@ -149,6 +158,9 @@ FunctionPass *llvm::createCodeGenPrepare
 
 bool CodeGenPrepare::runOnFunction(Function &F) {
   bool EverMadeChange = false;
+  // Clear per function information.
+  InsertedTruncsSet.clear();
+  PromotedInsts.clear();
 
   ModifiedDT = false;
   if (TM) TLI = TM->getTargetLowering();
@@ -882,6 +894,415 @@ void ExtAddrMode::dump() const {
 }
 #endif
 
+/// \brief This class provides transaction based operation on the IR.
+/// Every change made through this class is recorded in the internal state and
+/// can be undone (rollback) until commit is called.
+class TypePromotionTransaction {
+
+  /// \brief This represents the common interface of the individual transaction.
+  /// Each class implements the logic for doing one specific modification on
+  /// the IR via the TypePromotionTransaction.
+  class TypePromotionAction {
+  protected:
+    /// The Instruction modified.
+    Instruction *Inst;
+
+  public:
+    /// \brief Constructor of the action.
+    /// The constructor performs the related action on the IR.
+    TypePromotionAction(Instruction *Inst) : Inst(Inst) {}
+
+    virtual ~TypePromotionAction() {}
+
+    /// \brief Undo the modification done by this action.
+    /// When this method is called, the IR must be in the same state as it was
+    /// before this action was applied.
+    /// \pre Undoing the action works if and only if the IR is in the exact same
+    /// state as it was directly after this action was applied.
+    virtual void undo() = 0;
+
+    /// \brief Advocate every change made by this action.
+    /// When the results on the IR of the action are to be kept, it is important
+    /// to call this function, otherwise hidden information may be kept forever.
+    virtual void commit() {
+      // Nothing to be done, this action is not doing anything.
+    }
+  };
+
+  /// \brief Utility to remember the position of an instruction.
+  class InsertionHandler {
+    /// Position of an instruction.
+    /// Either an instruction:
+    /// - Is the first in a basic block: BB is used.
+    /// - Has a previous instructon: PrevInst is used.
+    union {
+      Instruction *PrevInst;
+      BasicBlock *BB;
+    } Point;
+    /// Remember whether or not the instruction had a previous instruction.
+    bool HasPrevInstruction;
+
+  public:
+    /// \brief Record the position of \p Inst.
+    InsertionHandler(Instruction *Inst) {
+      BasicBlock::iterator It = Inst;
+      HasPrevInstruction = (It != (Inst->getParent()->begin()));
+      if (HasPrevInstruction)
+        Point.PrevInst = --It;
+      else
+        Point.BB = Inst->getParent();
+    }
+
+    /// \brief Insert \p Inst at the recorded position.
+    void insert(Instruction *Inst) {
+      if (HasPrevInstruction) {
+        if (Inst->getParent())
+          Inst->removeFromParent();
+        Inst->insertAfter(Point.PrevInst);
+      } else {
+        Instruction *Position = Point.BB->getFirstInsertionPt();
+        if (Inst->getParent())
+          Inst->moveBefore(Position);
+        else
+          Inst->insertBefore(Position);
+      }
+    }
+  };
+
+  /// \brief Move an instruction before another.
+  class InstructionMoveBefore : public TypePromotionAction {
+    /// Original position of the instruction.
+    InsertionHandler Position;
+
+  public:
+    /// \brief Move \p Inst before \p Before.
+    InstructionMoveBefore(Instruction *Inst, Instruction *Before)
+        : TypePromotionAction(Inst), Position(Inst) {
+      DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before << "\n");
+      Inst->moveBefore(Before);
+    }
+
+    /// \brief Move the instruction back to its original position.
+    void undo() {
+      DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n");
+      Position.insert(Inst);
+    }
+  };
+
+  /// \brief Set the operand of an instruction with a new value.
+  class OperandSetter : public TypePromotionAction {
+    /// Original operand of the instruction.
+    Value *Origin;
+    /// Index of the modified instruction.
+    unsigned Idx;
+
+  public:
+    /// \brief Set \p Idx operand of \p Inst with \p NewVal.
+    OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal)
+        : TypePromotionAction(Inst), Idx(Idx) {
+      DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n"
+                   << "for:" << *Inst << "\n"
+                   << "with:" << *NewVal << "\n");
+      Origin = Inst->getOperand(Idx);
+      Inst->setOperand(Idx, NewVal);
+    }
+
+    /// \brief Restore the original value of the instruction.
+    void undo() {
+      DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n"
+                   << "for: " << *Inst << "\n"
+                   << "with: " << *Origin << "\n");
+      Inst->setOperand(Idx, Origin);
+    }
+  };
+
+  /// \brief Hide the operands of an instruction.
+  /// Do as if this instruction was not using any of its operands.
+  class OperandsHider : public TypePromotionAction {
+    /// The list of original operands.
+    SmallVector<Value *, 4> OriginalValues;
+
+  public:
+    /// \brief Remove \p Inst from the uses of the operands of \p Inst.
+    OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) {
+      DEBUG(dbgs() << "Do: OperandsHider: " << *Inst << "\n");
+      unsigned NumOpnds = Inst->getNumOperands();
+      OriginalValues.reserve(NumOpnds);
+      for (unsigned It = 0; It < NumOpnds; ++It) {
+        // Save the current operand.
+        Value *Val = Inst->getOperand(It);
+        OriginalValues.push_back(Val);
+        // Set a dummy one.
+        // We could use OperandSetter here, but that would implied an overhead
+        // that we are not willing to pay.
+        Inst->setOperand(It, UndefValue::get(Val->getType()));
+      }
+    }
+
+    /// \brief Restore the original list of uses.
+    void undo() {
+      DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n");
+      for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It)
+        Inst->setOperand(It, OriginalValues[It]);
+    }
+  };
+
+  /// \brief Build a truncate instruction.
+  class TruncBuilder : public TypePromotionAction {
+  public:
+    /// \brief Build a truncate instruction of \p Opnd producing a \p Ty
+    /// result.
+    /// trunc Opnd to Ty.
+    TruncBuilder(Instruction *Opnd, Type *Ty) : TypePromotionAction(Opnd) {
+      IRBuilder<> Builder(Opnd);
+      Inst = cast<Instruction>(Builder.CreateTrunc(Opnd, Ty, "promoted"));
+      DEBUG(dbgs() << "Do: TruncBuilder: " << *Inst << "\n");
+    }
+
+    /// \brief Get the built instruction.
+    Instruction *getBuiltInstruction() { return Inst; }
+
+    /// \brief Remove the built instruction.
+    void undo() {
+      DEBUG(dbgs() << "Undo: TruncBuilder: " << *Inst << "\n");
+      Inst->eraseFromParent();
+    }
+  };
+
+  /// \brief Build a sign extension instruction.
+  class SExtBuilder : public TypePromotionAction {
+  public:
+    /// \brief Build a sign extension instruction of \p Opnd producing a \p Ty
+    /// result.
+    /// sext Opnd to Ty.
+    SExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
+        : TypePromotionAction(Inst) {
+      IRBuilder<> Builder(InsertPt);
+      Inst = cast<Instruction>(Builder.CreateSExt(Opnd, Ty, "promoted"));
+      DEBUG(dbgs() << "Do: SExtBuilder: " << *Inst << "\n");
+    }
+
+    /// \brief Get the built instruction.
+    Instruction *getBuiltInstruction() { return Inst; }
+
+    /// \brief Remove the built instruction.
+    void undo() {
+      DEBUG(dbgs() << "Undo: SExtBuilder: " << *Inst << "\n");
+      Inst->eraseFromParent();
+    }
+  };
+
+  /// \brief Mutate an instruction to another type.
+  class TypeMutator : public TypePromotionAction {
+    /// Record the original type.
+    Type *OrigTy;
+
+  public:
+    /// \brief Mutate the type of \p Inst into \p NewTy.
+    TypeMutator(Instruction *Inst, Type *NewTy)
+        : TypePromotionAction(Inst), OrigTy(Inst->getType()) {
+      DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy
+                   << "\n");
+      Inst->mutateType(NewTy);
+    }
+
+    /// \brief Mutate the instruction back to its original type.
+    void undo() {
+      DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy
+                   << "\n");
+      Inst->mutateType(OrigTy);
+    }
+  };
+
+  /// \brief Replace the uses of an instruction by another instruction.
+  class UsesReplacer : public TypePromotionAction {
+    /// Helper structure to keep track of the replaced uses.
+    struct InstructionAndIdx {
+      /// The instruction using the instruction.
+      Instruction *Inst;
+      /// The index where this instruction is used for Inst.
+      unsigned Idx;
+      InstructionAndIdx(Instruction *Inst, unsigned Idx)
+          : Inst(Inst), Idx(Idx) {}
+    };
+
+    /// Keep track of the original uses (pair Instruction, Index).
+    SmallVector<InstructionAndIdx, 4> OriginalUses;
+    typedef SmallVectorImpl<InstructionAndIdx>::iterator use_iterator;
+
+  public:
+    /// \brief Replace all the use of \p Inst by \p New.
+    UsesReplacer(Instruction *Inst, Value *New) : TypePromotionAction(Inst) {
+      DEBUG(dbgs() << "Do: UsersReplacer: " << *Inst << " with " << *New
+                   << "\n");
+      // Record the original uses.
+      for (Value::use_iterator UseIt = Inst->use_begin(),
+                               EndIt = Inst->use_end();
+           UseIt != EndIt; ++UseIt) {
+        Instruction *Use = cast<Instruction>(*UseIt);
+        OriginalUses.push_back(InstructionAndIdx(Use, UseIt.getOperandNo()));
+      }
+      // Now, we can replace the uses.
+      Inst->replaceAllUsesWith(New);
+    }
+
+    /// \brief Reassign the original uses of Inst to Inst.
+    void undo() {
+      DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n");
+      for (use_iterator UseIt = OriginalUses.begin(),
+                        EndIt = OriginalUses.end();
+           UseIt != EndIt; ++UseIt) {
+        UseIt->Inst->setOperand(UseIt->Idx, Inst);
+      }
+    }
+  };
+
+  /// \brief Remove an instruction from the IR.
+  class InstructionRemover : public TypePromotionAction {
+    /// Original position of the instruction.
+    InsertionHandler Inserter;
+    /// Helper structure to hide all the link to the instruction. In other
+    /// words, this helps to do as if the instruction was removed.
+    OperandsHider Hider;
+    /// Keep track of the uses replaced, if any.
+    UsesReplacer *Replacer;
+
+  public:
+    /// \brief Remove all reference of \p Inst and optinally replace all its
+    /// uses with New.
+    /// \pre If !Inst->use_empty(), then New != NULL
+    InstructionRemover(Instruction *Inst, Value *New = NULL)
+        : TypePromotionAction(Inst), Inserter(Inst), Hider(Inst),
+          Replacer(NULL) {
+      if (New)
+        Replacer = new UsesReplacer(Inst, New);
+      DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n");
+      Inst->removeFromParent();
+    }
+
+    ~InstructionRemover() { delete Replacer; }
+
+    /// \brief Really remove the instruction.
+    void commit() { delete Inst; }
+
+    /// \brief Resurrect the instruction and reassign it to the proper uses if
+    /// new value was provided when build this action.
+    void undo() {
+      DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n");
+      Inserter.insert(Inst);
+      if (Replacer)
+        Replacer->undo();
+      Hider.undo();
+    }
+  };
+
+public:
+  /// Restoration point.
+  /// The restoration point is a pointer to an action instead of an iterator
+  /// because the iterator may be invalidated but not the pointer.
+  typedef const TypePromotionAction *ConstRestorationPt;
+  /// Advocate every changes made in that transaction.
+  void commit();
+  /// Undo all the changes made after the given point.
+  void rollback(ConstRestorationPt Point);
+  /// Get the current restoration point.
+  ConstRestorationPt getRestorationPoint() const;
+
+  /// \name API for IR modification with state keeping to support rollback.
+  /// @{
+  /// Same as Instruction::setOperand.
+  void setOperand(Instruction *Inst, unsigned Idx, Value *NewVal);
+  /// Same as Instruction::eraseFromParent.
+  void eraseInstruction(Instruction *Inst, Value *NewVal = NULL);
+  /// Same as Value::replaceAllUsesWith.
+  void replaceAllUsesWith(Instruction *Inst, Value *New);
+  /// Same as Value::mutateType.
+  void mutateType(Instruction *Inst, Type *NewTy);
+  /// Same as IRBuilder::createTrunc.
+  Instruction *createTrunc(Instruction *Opnd, Type *Ty);
+  /// Same as IRBuilder::createSExt.
+  Instruction *createSExt(Instruction *Inst, Value *Opnd, Type *Ty);
+  /// Same as Instruction::moveBefore.
+  void moveBefore(Instruction *Inst, Instruction *Before);
+  /// @}
+
+  ~TypePromotionTransaction();
+
+private:
+  /// The ordered list of actions made so far.
+  SmallVector<TypePromotionAction *, 16> Actions;
+  typedef SmallVectorImpl<TypePromotionAction *>::iterator CommitPt;
+};
+
+void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx,
+                                          Value *NewVal) {
+  Actions.push_back(
+      new TypePromotionTransaction::OperandSetter(Inst, Idx, NewVal));
+}
+
+void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
+                                                Value *NewVal) {
+  Actions.push_back(
+      new TypePromotionTransaction::InstructionRemover(Inst, NewVal));
+}
+
+void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
+                                                  Value *New) {
+  Actions.push_back(new TypePromotionTransaction::UsesReplacer(Inst, New));
+}
+
+void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
+  Actions.push_back(new TypePromotionTransaction::TypeMutator(Inst, NewTy));
+}
+
+Instruction *TypePromotionTransaction::createTrunc(Instruction *Opnd,
+                                                   Type *Ty) {
+  TruncBuilder *TB = new TruncBuilder(Opnd, Ty);
+  Actions.push_back(TB);
+  return TB->getBuiltInstruction();
+}
+
+Instruction *TypePromotionTransaction::createSExt(Instruction *Inst,
+                                                  Value *Opnd, Type *Ty) {
+  SExtBuilder *SB = new SExtBuilder(Inst, Opnd, Ty);
+  Actions.push_back(SB);
+  return SB->getBuiltInstruction();
+}
+
+void TypePromotionTransaction::moveBefore(Instruction *Inst,
+                                          Instruction *Before) {
+  Actions.push_back(
+      new TypePromotionTransaction::InstructionMoveBefore(Inst, Before));
+}
+
+TypePromotionTransaction::ConstRestorationPt
+TypePromotionTransaction::getRestorationPoint() const {
+  return Actions.rbegin() != Actions.rend() ? *Actions.rbegin() : NULL;
+}
+
+void TypePromotionTransaction::commit() {
+  for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt;
+       ++It) {
+    (*It)->commit();
+    delete *It;
+  }
+  Actions.clear();
+}
+
+void TypePromotionTransaction::rollback(
+    TypePromotionTransaction::ConstRestorationPt Point) {
+  while (!Actions.empty() && Point != (*Actions.rbegin())) {
+    TypePromotionAction *Curr = Actions.pop_back_val();
+    Curr->undo();
+    delete Curr;
+  }
+}
+
+TypePromotionTransaction::~TypePromotionTransaction() {
+  for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt; ++It)
+    delete *It;
+  Actions.clear();
+}
 
 /// \brief A helper class for matching addressing modes.
 ///
@@ -899,6 +1320,13 @@ class AddressingModeMatcher {
   /// part of the return value of this addressing mode matching stuff.
   ExtAddrMode &AddrMode;
 
+  /// The truncate instruction inserted by other CodeGenPrepare optimizations.
+  const SetOfInstrs &InsertedTruncs;
+  /// A map from the instructions to their type before promotion.
+  InstrToOrigTy &PromotedInsts;
+  /// The ongoing transaction where every action should be registered.
+  TypePromotionTransaction &TPT;
+
   /// IgnoreProfitability - This is set to true when we should not do
   /// profitability checks.  When true, IsProfitableToFoldIntoAddressingMode
   /// always returns true.
@@ -906,8 +1334,12 @@ class AddressingModeMatcher {
 
   AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI,
                         const TargetLowering &T, Type *AT,
-                        Instruction *MI, ExtAddrMode &AM)
-    : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM) {
+                        Instruction *MI, ExtAddrMode &AM,
+                        const SetOfInstrs &InsertedTruncs,
+                        InstrToOrigTy &PromotedInsts,
+                        TypePromotionTransaction &TPT)
+      : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM),
+        InsertedTruncs(InsertedTruncs), PromotedInsts(PromotedInsts), TPT(TPT) {
     IgnoreProfitability = false;
   }
 public:
@@ -915,22 +1347,31 @@ public:
   /// Match - Find the maximal addressing mode that a load/store of V can fold,
   /// give an access type of AccessTy.  This returns a list of involved
   /// instructions in AddrModeInsts.
+  /// \p InsertedTruncs The truncate instruction inserted by other
+  /// CodeGenPrepare
+  /// optimizations.
+  /// \p PromotedInsts maps the instructions to their type before promotion.
+  /// \p The ongoing transaction where every action should be registered.
   static ExtAddrMode Match(Value *V, Type *AccessTy,
                            Instruction *MemoryInst,
                            SmallVectorImpl<Instruction*> &AddrModeInsts,
-                           const TargetLowering &TLI) {
+                           const TargetLowering &TLI,
+                           const SetOfInstrs &InsertedTruncs,
+                           InstrToOrigTy &PromotedInsts,
+                           TypePromotionTransaction &TPT) {
     ExtAddrMode Result;
 
-    bool Success =
-      AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
-                            MemoryInst, Result).MatchAddr(V, 0);
+    bool Success = AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
+                                         MemoryInst, Result, InsertedTruncs,
+                                         PromotedInsts, TPT).MatchAddr(V, 0);
     (void)Success; assert(Success && "Couldn't select *anything*?");
     return Result;
   }
 private:
   bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
   bool MatchAddr(Value *V, unsigned Depth);
-  bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth);
+  bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth,
+                          bool *MovedAway = NULL);
   bool IsProfitableToFoldIntoAddressingMode(Instruction *I,
                                             ExtAddrMode &AMBefore,
                                             ExtAddrMode &AMAfter);
@@ -1022,14 +1463,292 @@ static bool MightBeFoldableInst(Instruct
   }
 }
 
+/// \brief Hepler class to perform type promotion.
+class TypePromotionHelper {
+  /// \brief Utility function to check whether or not a sign extension of
+  /// \p Inst with \p ConsideredSExtType can be moved through \p Inst by either
+  /// using the operands of \p Inst or promoting \p Inst.
+  /// In other words, check if:
+  /// sext (Ty Inst opnd1 opnd2 ... opndN) to ConsideredSExtType.
+  /// #1 Promotion applies:
+  /// ConsideredSExtType Inst (sext opnd1 to ConsideredSExtType, ...).
+  /// #2 Operand reuses:
+  /// sext opnd1 to ConsideredSExtType.
+  /// \p PromotedInsts maps the instructions to their type before promotion.
+  static bool canGetThrough(const Instruction *Inst, Type *ConsideredSExtType,
+                            const InstrToOrigTy &PromotedInsts);
+
+  /// \brief Utility function to determine if \p OpIdx should be promoted when
+  /// promoting \p Inst.
+  static bool shouldSExtOperand(const Instruction *Inst, int OpIdx) {
+    if (isa<SelectInst>(Inst) && OpIdx == 0)
+      return false;
+    return true;
+  }
+
+  /// \brief Utility function to promote the operand of \p SExt when this
+  /// operand is a promotable trunc or sext.
+  /// \p PromotedInsts maps the instructions to their type before promotion.
+  /// \p CreatedInsts[out] contains how many non-free instructions have been
+  /// created to promote the operand of SExt.
+  /// Should never be called directly.
+  /// \return The promoted value which is used instead of SExt.
+  static Value *promoteOperandForTruncAndSExt(Instruction *SExt,
+                                              TypePromotionTransaction &TPT,
+                                              InstrToOrigTy &PromotedInsts,
+                                              unsigned &CreatedInsts);
+
+  /// \brief Utility function to promote the operand of \p SExt when this
+  /// operand is promotable and is not a supported trunc or sext.
+  /// \p PromotedInsts maps the instructions to their type before promotion.
+  /// \p CreatedInsts[out] contains how many non-free instructions have been
+  /// created to promote the operand of SExt.
+  /// Should never be called directly.
+  /// \return The promoted value which is used instead of SExt.
+  static Value *promoteOperandForOther(Instruction *SExt,
+                                       TypePromotionTransaction &TPT,
+                                       InstrToOrigTy &PromotedInsts,
+                                       unsigned &CreatedInsts);
+
+public:
+  /// Type for the utility function that promotes the operand of SExt.
+  typedef Value *(*Action)(Instruction *SExt, TypePromotionTransaction &TPT,
+                           InstrToOrigTy &PromotedInsts,
+                           unsigned &CreatedInsts);
+  /// \brief Given a sign extend instruction \p SExt, return the approriate
+  /// action to promote the operand of \p SExt instead of using SExt.
+  /// \return NULL if no promotable action is possible with the current
+  /// sign extension.
+  /// \p InsertedTruncs keeps track of all the truncate instructions inserted by
+  /// the others CodeGenPrepare optimizations. This information is important
+  /// because we do not want to promote these instructions as CodeGenPrepare
+  /// will reinsert them later. Thus creating an infinite loop: create/remove.
+  /// \p PromotedInsts maps the instructions to their type before promotion.
+  static Action getAction(Instruction *SExt, const SetOfInstrs &InsertedTruncs,
+                          const TargetLowering &TLI,
+                          const InstrToOrigTy &PromotedInsts);
+};
+
+bool TypePromotionHelper::canGetThrough(const Instruction *Inst,
+                                        Type *ConsideredSExtType,
+                                        const InstrToOrigTy &PromotedInsts) {
+  // We can always get through sext.
+  if (isa<SExtInst>(Inst))
+    return true;
+
+  // We can get through binary operator, if it is legal. In other words, the
+  // binary operator must have a nuw or nsw flag.
+  const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst);
+  if (BinOp && isa<OverflowingBinaryOperator>(BinOp) &&
+      (BinOp->hasNoUnsignedWrap() || BinOp->hasNoSignedWrap()))
+    return true;
+
+  // Check if we can do the following simplification.
+  // sext(trunc(sext)) --> sext
+  if (!isa<TruncInst>(Inst))
+    return false;
+
+  Value *OpndVal = Inst->getOperand(0);
+  // Check if we can use this operand in the sext.
+  // If the type is larger than the result type of the sign extension,
+  // we cannot.
+  if (OpndVal->getType()->getIntegerBitWidth() >
+      ConsideredSExtType->getIntegerBitWidth())
+    return false;
+
+  // If the operand of the truncate is not an instruction, we will not have
+  // any information on the dropped bits.
+  // (Actually we could for constant but it is not worth the extra logic).
+  Instruction *Opnd = dyn_cast<Instruction>(OpndVal);
+  if (!Opnd)
+    return false;
+
+  // Check if the source of the type is narrow enough.
+  // I.e., check that trunc just drops sign extended bits.
+  // #1 get the type of the operand.
+  const Type *OpndType;
+  InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd);
+  if (It != PromotedInsts.end())
+    OpndType = It->second;
+  else if (isa<SExtInst>(Opnd))
+    OpndType = cast<Instruction>(Opnd)->getOperand(0)->getType();
+  else
+    return false;
+
+  // #2 check that the truncate just drop sign extended bits.
+  if (Inst->getType()->getIntegerBitWidth() >= OpndType->getIntegerBitWidth())
+    return true;
+
+  return false;
+}
+
+TypePromotionHelper::Action TypePromotionHelper::getAction(
+    Instruction *SExt, const SetOfInstrs &InsertedTruncs,
+    const TargetLowering &TLI, const InstrToOrigTy &PromotedInsts) {
+  Instruction *SExtOpnd = dyn_cast<Instruction>(SExt->getOperand(0));
+  Type *SExtTy = SExt->getType();
+  // If the operand of the sign extension is not an instruction, we cannot
+  // get through.
+  // If it, check we can get through.
+  if (!SExtOpnd || !canGetThrough(SExtOpnd, SExtTy, PromotedInsts))
+    return NULL;
+
+  // Do not promote if the operand has been added by codegenprepare.
+  // Otherwise, it means we are undoing an optimization that is likely to be
+  // redone, thus causing potential infinite loop.
+  if (isa<TruncInst>(SExtOpnd) && InsertedTruncs.count(SExtOpnd))
+    return NULL;
+
+  // SExt or Trunc instructions.
+  // Return the related handler.
+  if (isa<SExtInst>(SExtOpnd) || isa<TruncInst>(SExtOpnd))
+    return promoteOperandForTruncAndSExt;
+
+  // Regular instruction.
+  // Abort early if we will have to insert non-free instructions.
+  if (!SExtOpnd->hasOneUse() &&
+      !TLI.isTruncateFree(SExtTy, SExtOpnd->getType()))
+    return NULL;
+  return promoteOperandForOther;
+}
+
+Value *TypePromotionHelper::promoteOperandForTruncAndSExt(
+    llvm::Instruction *SExt, TypePromotionTransaction &TPT,
+    InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts) {
+  // By construction, the operand of SExt is an instruction. Otherwise we cannot
+  // get through it and this method should not be called.
+  Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
+  // Replace sext(trunc(opnd)) or sext(sext(opnd))
+  // => sext(opnd).
+  TPT.setOperand(SExt, 0, SExtOpnd->getOperand(0));
+  CreatedInsts = 0;
+
+  // Remove dead code.
+  if (SExtOpnd->use_empty())
+    TPT.eraseInstruction(SExtOpnd);
+
+  // Check if the sext is still needed.
+  if (SExt->getType() != SExt->getOperand(0)->getType())
+    return SExt;
+
+  // At this point we have: sext ty opnd to ty.
+  // Reassign the uses of SExt to the opnd and remove SExt.
+  Value *NextVal = SExt->getOperand(0);
+  TPT.eraseInstruction(SExt, NextVal);
+  return NextVal;
+}
+
+Value *
+TypePromotionHelper::promoteOperandForOther(Instruction *SExt,
+                                            TypePromotionTransaction &TPT,
+                                            InstrToOrigTy &PromotedInsts,
+                                            unsigned &CreatedInsts) {
+  // By construction, the operand of SExt is an instruction. Otherwise we cannot
+  // get through it and this method should not be called.
+  Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
+  CreatedInsts = 0;
+  if (!SExtOpnd->hasOneUse()) {
+    // SExtOpnd will be promoted.
+    // All its uses, but SExt, will need to use a truncated value of the
+    // promoted version.
+    // Create the truncate now.
+    Instruction *Trunc = TPT.createTrunc(SExt, SExtOpnd->getType());
+    Trunc->removeFromParent();
+    // Insert it just after the definition.
+    Trunc->insertAfter(SExtOpnd);
+
+    TPT.replaceAllUsesWith(SExtOpnd, Trunc);
+    // Restore the operand of SExt (which has been replace by the previous call
+    // to replaceAllUsesWith) to avoid creating a cycle trunc <-> sext.
+    TPT.setOperand(SExt, 0, SExtOpnd);
+  }
+
+  // Get through the Instruction:
+  // 1. Update its type.
+  // 2. Replace the uses of SExt by Inst.
+  // 3. Sign extend each operand that needs to be sign extended.
+
+  // Remember the original type of the instruction before promotion.
+  // This is useful to know that the high bits are sign extended bits.
+  PromotedInsts.insert(
+      std::pair<Instruction *, Type *>(SExtOpnd, SExtOpnd->getType()));
+  // Step #1.
+  TPT.mutateType(SExtOpnd, SExt->getType());
+  // Step #2.
+  TPT.replaceAllUsesWith(SExt, SExtOpnd);
+  // Step #3.
+  Instruction *SExtForOpnd = SExt;
+
+  DEBUG(dbgs() << "Propagate SExt to operands\n");
+  for (int OpIdx = 0, EndOpIdx = SExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
+       ++OpIdx) {
+    DEBUG(dbgs() << "Operand:\n" << *(SExtOpnd->getOperand(OpIdx)) << '\n');
+    if (SExtOpnd->getOperand(OpIdx)->getType() == SExt->getType() ||
+        !shouldSExtOperand(SExtOpnd, OpIdx)) {
+      DEBUG(dbgs() << "No need to propagate\n");
+      continue;
+    }
+    // Check if we can statically sign extend the operand.
+    Value *Opnd = SExtOpnd->getOperand(OpIdx);
+    if (const ConstantInt *Cst = dyn_cast<ConstantInt>(Opnd)) {
+      DEBUG(dbgs() << "Statically sign extend\n");
+      TPT.setOperand(
+          SExtOpnd, OpIdx,
+          ConstantInt::getSigned(SExt->getType(), Cst->getSExtValue()));
+      continue;
+    }
+    // UndefValue are typed, so we have to statically sign extend them.
+    if (isa<UndefValue>(Opnd)) {
+      DEBUG(dbgs() << "Statically sign extend\n");
+      TPT.setOperand(SExtOpnd, OpIdx, UndefValue::get(SExt->getType()));
+      continue;
+    }
+
+    // Otherwise we have to explicity sign extend the operand.
+    // Check if SExt was reused to sign extend an operand.
+    if (!SExtForOpnd) {
+      // If yes, create a new one.
+      DEBUG(dbgs() << "More operands to sext\n");
+      SExtForOpnd = TPT.createSExt(SExt, Opnd, SExt->getType());
+      ++CreatedInsts;
+    }
+
+    TPT.setOperand(SExtForOpnd, 0, Opnd);
+
+    // Move the sign extension before the insertion point.
+    TPT.moveBefore(SExtForOpnd, SExtOpnd);
+    TPT.setOperand(SExtOpnd, OpIdx, SExtForOpnd);
+    // If more sext are required, new instructions will have to be created.
+    SExtForOpnd = NULL;
+  }
+  if (SExtForOpnd == SExt) {
+    DEBUG(dbgs() << "Sign extension is useless now\n");
+    TPT.eraseInstruction(SExt);
+  }
+  return SExtOpnd;
+}
+
 /// MatchOperationAddr - Given an instruction or constant expr, see if we can
 /// fold the operation into the addressing mode.  If so, update the addressing
 /// mode and return true, otherwise return false without modifying AddrMode.
+/// If \p MovedAway is not NULL, it contains the information of whether or
+/// not AddrInst has to be folded into the addressing mode on success.
+/// If \p MovedAway == true, \p AddrInst will not be part of the addressing
+/// because it has been moved away.
+/// Thus AddrInst must not be added in the matched instructions.
+/// This state can happen when AddrInst is a sext, since it may be moved away.
+/// Therefore, AddrInst may not be valid when MovedAway is true and it must
+/// not be referenced anymore.
 bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
-                                               unsigned Depth) {
+                                               unsigned Depth,
+                                               bool *MovedAway) {
   // Avoid exponential behavior on extremely deep expression trees.
   if (Depth >= 5) return false;
 
+  // By default, all matched instructions stay in place.
+  if (MovedAway)
+    *MovedAway = false;
+
   switch (Opcode) {
   case Instruction::PtrToInt:
     // PtrToInt is always a noop, as we know that the int type is pointer sized.
@@ -1055,6 +1774,13 @@ bool AddressingModeMatcher::MatchOperati
     // Check to see if we can merge in the RHS then the LHS.  If so, we win.
     ExtAddrMode BackupAddrMode = AddrMode;
     unsigned OldSize = AddrModeInsts.size();
+    // Start a transaction at this point.
+    // The LHS may match but not the RHS.
+    // Therefore, we need a higher level restoration point to undo partially
+    // matched operation.
+    TypePromotionTransaction::ConstRestorationPt LastKnownGood =
+        TPT.getRestorationPoint();
+
     if (MatchAddr(AddrInst->getOperand(1), Depth+1) &&
         MatchAddr(AddrInst->getOperand(0), Depth+1))
       return true;
@@ -1062,6 +1788,7 @@ bool AddressingModeMatcher::MatchOperati
     // Restore the old addr mode info.
     AddrMode = BackupAddrMode;
     AddrModeInsts.resize(OldSize);
+    TPT.rollback(LastKnownGood);
 
     // Otherwise this was over-aggressive.  Try merging in the LHS then the RHS.
     if (MatchAddr(AddrInst->getOperand(0), Depth+1) &&
@@ -1071,6 +1798,7 @@ bool AddressingModeMatcher::MatchOperati
     // Otherwise we definitely can't merge the ADD in.
     AddrMode = BackupAddrMode;
     AddrModeInsts.resize(OldSize);
+    TPT.rollback(LastKnownGood);
     break;
   }
   //case Instruction::Or:
@@ -1173,6 +1901,51 @@ bool AddressingModeMatcher::MatchOperati
 
     return true;
   }
+  case Instruction::SExt: {
+    // Try to move this sext out of the way of the addressing mode.
+    Instruction *SExt = cast<Instruction>(AddrInst);
+    // Ask for a method for doing so.
+    TypePromotionHelper::Action TPH = TypePromotionHelper::getAction(
+        SExt, InsertedTruncs, TLI, PromotedInsts);
+    if (!TPH)
+      return false;
+
+    TypePromotionTransaction::ConstRestorationPt LastKnownGood =
+        TPT.getRestorationPoint();
+    unsigned CreatedInsts = 0;
+    Value *PromotedOperand = TPH(SExt, TPT, PromotedInsts, CreatedInsts);
+    // SExt has been moved away.
+    // Thus either it will be rematched later in the recursive calls or it is
+    // gone. Anyway, we must not fold it into the addressing mode at this point.
+    // E.g.,
+    // op = add opnd, 1
+    // idx = sext op
+    // addr = gep base, idx
+    // is now:
+    // promotedOpnd = sext opnd           <- no match here
+    // op = promoted_add promotedOpnd, 1  <- match (later in recursive calls)
+    // addr = gep base, op                <- match
+    if (MovedAway)
+      *MovedAway = true;
+
+    assert(PromotedOperand &&
+           "TypePromotionHelper should have filtered out those cases");
+
+    ExtAddrMode BackupAddrMode = AddrMode;
+    unsigned OldSize = AddrModeInsts.size();
+
+    if (!MatchAddr(PromotedOperand, Depth) ||
+        // We fold less instructions than what we created.
+        // Undo at this point.
+        (OldSize + CreatedInsts > AddrModeInsts.size())) {
+      AddrMode = BackupAddrMode;
+      AddrModeInsts.resize(OldSize);
+      DEBUG(dbgs() << "Sign extension does not pay off: rollback\n");
+      TPT.rollback(LastKnownGood);
+      return false;
+    }
+    return true;
+  }
   }
   return false;
 }
@@ -1183,6 +1956,10 @@ bool AddressingModeMatcher::MatchOperati
 /// or intptr_t for the target.
 ///
 bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) {
+  // Start a transaction at this point that we will rollback if the matching
+  // fails.
+  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
+      TPT.getRestorationPoint();
   if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
     // Fold in immediates if legal for the target.
     AddrMode.BaseOffs += CI->getSExtValue();
@@ -1202,7 +1979,12 @@ bool AddressingModeMatcher::MatchAddr(Va
     unsigned OldSize = AddrModeInsts.size();
 
     // Check to see if it is possible to fold this operation.
-    if (MatchOperationAddr(I, I->getOpcode(), Depth)) {
+    bool MovedAway = false;
+    if (MatchOperationAddr(I, I->getOpcode(), Depth, &MovedAway)) {
+      // This instruction may have been move away. If so, there is nothing
+      // to check here.
+      if (MovedAway)
+        return true;
       // Okay, it's possible to fold this.  Check to see if it is actually
       // *profitable* to do so.  We use a simple cost model to avoid increasing
       // register pressure too much.
@@ -1216,10 +1998,12 @@ bool AddressingModeMatcher::MatchAddr(Va
       //cerr << "NOT FOLDING: " << *I;
       AddrMode = BackupAddrMode;
       AddrModeInsts.resize(OldSize);
+      TPT.rollback(LastKnownGood);
     }
   } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
     if (MatchOperationAddr(CE, CE->getOpcode(), Depth))
       return true;
+    TPT.rollback(LastKnownGood);
   } else if (isa<ConstantPointerNull>(Addr)) {
     // Null pointer gets folded without affecting the addressing mode.
     return true;
@@ -1246,6 +2030,7 @@ bool AddressingModeMatcher::MatchAddr(Va
     AddrMode.ScaledReg = 0;
   }
   // Couldn't match.
+  TPT.rollback(LastKnownGood);
   return false;
 }
 
@@ -1427,7 +2212,8 @@ IsProfitableToFoldIntoAddressingMode(Ins
     // *actually* cover the shared instruction.
     ExtAddrMode Result;
     AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy,
-                                  MemoryInst, Result);
+                                  MemoryInst, Result, InsertedTruncs,
+                                  PromotedInsts, TPT);
     Matcher.IgnoreProfitability = true;
     bool Success = Matcher.MatchAddr(Address, 0);
     (void)Success; assert(Success && "Couldn't select *anything*?");
@@ -1480,6 +2266,9 @@ bool CodeGenPrepare::OptimizeMemoryInst(
   bool IsNumUsesConsensusValid = false;
   SmallVector<Instruction*, 16> AddrModeInsts;
   ExtAddrMode AddrMode;
+  TypePromotionTransaction TPT;
+  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
+      TPT.getRestorationPoint();
   while (!worklist.empty()) {
     Value *V = worklist.back();
     worklist.pop_back();
@@ -1499,9 +2288,9 @@ bool CodeGenPrepare::OptimizeMemoryInst(
 
     // For non-PHIs, determine the addressing mode being computed.
     SmallVector<Instruction*, 16> NewAddrModeInsts;
-    ExtAddrMode NewAddrMode =
-      AddressingModeMatcher::Match(V, AccessTy, MemoryInst,
-                                   NewAddrModeInsts, *TLI);
+    ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
+        V, AccessTy, MemoryInst, NewAddrModeInsts, *TLI, InsertedTruncsSet,
+        PromotedInsts, TPT);
 
     // This check is broken into two cases with very similar code to avoid using
     // getNumUses() as much as possible. Some values have a lot of uses, so
@@ -1538,7 +2327,11 @@ bool CodeGenPrepare::OptimizeMemoryInst(
 
   // If the addressing mode couldn't be determined, or if multiple different
   // ones were determined, bail out now.
-  if (!Consensus) return false;
+  if (!Consensus) {
+    TPT.rollback(LastKnownGood);
+    return false;
+  }
+  TPT.commit();
 
   // Check to see if any of the instructions supersumed by this addr mode are
   // non-local to I's BB.
@@ -1789,6 +2582,7 @@ bool CodeGenPrepare::OptimizeExtUses(Ins
     if (!InsertedTrunc) {
       BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
       InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
+      InsertedTruncsSet.insert(InsertedTrunc);
     }
 
     // Replace a use of the {s|z}ext source with a use of the result.

Added: llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll?rev=200947&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll (added)
+++ llvm/trunk/test/CodeGen/X86/codegen-prepare-addrmode-sext.ll Thu Feb  6 15:44:56 2014
@@ -0,0 +1,254 @@
+; RUN: opt -S -codegenprepare %s -o - | FileCheck %s
+; This file tests the different cases what are involved when codegen prepare
+; tries to get sign extension out of the way of addressing mode.
+; This tests require an actual target as addressing mode decisions depends
+; on the target.
+
+target datalayout = "e-i64:64-f80:128-s:64-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx"
+
+
+; Check that we correctly promote both operands of the promotable add.
+; CHECK-LABEL: @twoArgsPromotion
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i32 %arg1 to i64
+; CHECK: [[ARG2SEXT:%[a-zA-Z_0-9-]+]] = sext i32 %arg2 to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], [[ARG2SEXT]]
+; CHECK: inttoptr i64 [[PROMOTED]] to i8*
+; CHECK: ret
+define i8 @twoArgsPromotion(i32 %arg1, i32 %arg2) {
+  %add = add nsw i32 %arg1, %arg2 
+  %sextadd = sext i32 %add to i64
+  %base = inttoptr i64 %sextadd to i8*
+  %res = load i8* %base
+  ret i8 %res
+}
+
+; Check that we do not promote both operands of the promotable add when
+; the instruction will not be folded into the addressing mode.
+; Otherwise, we will increase the number of instruction executed.
+; (This is a heuristic of course, because the new sext could have been
+; merged with something else.)
+; CHECK-LABEL: @twoArgsNoPromotion
+; CHECK: add nsw i32 %arg1, %arg2
+; CHECK: ret
+define i8 @twoArgsNoPromotion(i32 %arg1, i32 %arg2, i8* %base) {
+  %add = add nsw i32 %arg1, %arg2 
+  %sextadd = sext i32 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; Check that we do not promote when the related instruction does not have
+; the nsw flag.
+; CHECK-LABEL: @noPromotion
+; CHECK-NOT: add i64
+; CHECK: ret
+define i8 @noPromotion(i32 %arg1, i32 %arg2, i8* %base) {
+  %add = add i32 %arg1, %arg2 
+  %sextadd = sext i32 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; Check that we correctly promote constant arguments.
+; CHECK-LABEL: @oneArgPromotion
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i32 %arg1 to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], 1
+; CHECK: getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: ret
+define i8 @oneArgPromotion(i32 %arg1, i8* %base) {
+  %add = add nsw i32 %arg1, 1 
+  %sextadd = sext i32 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; Check that we do not promote truncate when we cannot determine the
+; bits that are dropped.
+; CHECK-LABEL: @oneArgPromotionBlockTrunc1
+; CHECK: [[ARG1TRUNC:%[a-zA-Z_0-9-]+]] = trunc i32 %arg1 to i8
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i8 [[ARG1TRUNC]] to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], 1
+; CHECK: getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: ret
+define i8 @oneArgPromotionBlockTrunc1(i32 %arg1, i8* %base) {
+  %trunc = trunc i32 %arg1 to i8
+  %add = add nsw i8 %trunc, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; Check that we do not promote truncate when we cannot determine all the
+; bits that are dropped.
+; CHECK-LABEL: @oneArgPromotionBlockTrunc2
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i16 %arg1 to i32
+; CHECK: [[ARG1TRUNC:%[a-zA-Z_0-9-]+]] = trunc i32 [[ARG1SEXT]] to i8
+; CHECK: [[ARG1SEXT64:%[a-zA-Z_0-9-]+]] = sext i8 [[ARG1TRUNC]] to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT64]], 1
+; CHECK: getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: ret
+define i8 @oneArgPromotionBlockTrunc2(i16 %arg1, i8* %base) {
+  %sextarg1 = sext i16 %arg1 to i32
+  %trunc = trunc i32 %sextarg1 to i8
+  %add = add nsw i8 %trunc, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; Check that we are able to promote truncate when we know all the bits
+; that are dropped.
+; CHECK-LABEL: @oneArgPromotionPassTruncKeepSExt
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i1 %arg1 to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], 1
+; CHECK: getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: ret
+define i8 @oneArgPromotionPassTruncKeepSExt(i1 %arg1, i8* %base) {
+  %sextarg1 = sext i1 %arg1 to i32
+  %trunc = trunc i32 %sextarg1 to i8
+  %add = add nsw i8 %trunc, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; On X86 truncate are free. Check that we are able to promote the add
+; to be used as addressing mode and that we insert a truncate for the other
+; use. 
+; CHECK-LABEL: @oneArgPromotionTruncInsert
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i8 %arg1 to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], 1
+; CHECK: [[TRUNC:%[a-zA-Z_0-9-]+]] = trunc i64 [[PROMOTED]] to i8
+; CHECK: [[GEP:%[a-zA-Z_0-9-]+]] = getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: [[LOAD:%[a-zA-Z_0-9-]+]] = load i8* [[GEP]]
+; CHECK: add i8 [[LOAD]], [[TRUNC]]
+; CHECK: ret
+define i8 @oneArgPromotionTruncInsert(i8 %arg1, i8* %base) {
+  %add = add nsw i8 %arg1, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  %finalres = add i8 %res, %add
+  ret i8 %finalres
+}
+
+; Cannot sext from a larger type than the promoted type.
+; CHECK-LABEL: @oneArgPromotionLargerType
+; CHECK: [[ARG1TRUNC:%[a-zA-Z_0-9-]+]] = trunc i128 %arg1 to i8
+; CHECK: [[ARG1SEXT64:%[a-zA-Z_0-9-]+]] = sext i8 [[ARG1TRUNC]] to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT64]], 1
+; CHECK: getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: ret
+define i8 @oneArgPromotionLargerType(i128 %arg1, i8* %base) {
+  %trunc = trunc i128 %arg1 to i8
+  %add = add nsw i8 %trunc, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  %finalres = add i8 %res, %add
+  ret i8 %finalres
+}
+
+; Use same inserted trunc
+; On X86 truncate are free. Check that we are able to promote the add
+; to be used as addressing mode and that we insert a truncate for
+; *all* the other uses. 
+; CHECK-LABEL: @oneArgPromotionTruncInsertSeveralUse
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i8 %arg1 to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], 1
+; CHECK: [[TRUNC:%[a-zA-Z_0-9-]+]] = trunc i64 [[PROMOTED]] to i8
+; CHECK: [[GEP:%[a-zA-Z_0-9-]+]] = getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: [[LOAD:%[a-zA-Z_0-9-]+]] = load i8* [[GEP]]
+; CHECK: [[ADDRES:%[a-zA-Z_0-9-]+]] = add i8 [[LOAD]], [[TRUNC]]
+; CHECK: add i8 [[ADDRES]], [[TRUNC]]
+; CHECK: ret
+define i8 @oneArgPromotionTruncInsertSeveralUse(i8 %arg1, i8* %base) {
+  %add = add nsw i8 %arg1, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  %almostfinalres = add i8 %res, %add
+  %finalres = add i8 %almostfinalres, %add
+  ret i8 %finalres
+}
+
+; Check that the promoted instruction is used for all uses of the original
+; sign extension.
+; CHECK-LABEL: @oneArgPromotionSExtSeveralUse
+; CHECK: [[ARG1SEXT:%[a-zA-Z_0-9-]+]] = sext i8 %arg1 to i64
+; CHECK: [[PROMOTED:%[a-zA-Z_0-9-]+]] = add nsw i64 [[ARG1SEXT]], 1
+; CHECK: [[GEP:%[a-zA-Z_0-9-]+]] = getelementptr inbounds i8* %base, i64 [[PROMOTED]]
+; CHECK: [[LOAD:%[a-zA-Z_0-9-]+]] = load i8* [[GEP]]
+; CHECK: [[ADDRES:%[a-zA-Z_0-9-]+]] = zext i8 [[LOAD]] to i64
+; CHECK: add i64 [[ADDRES]], [[PROMOTED]]
+; CHECK: ret
+define i64 @oneArgPromotionSExtSeveralUse(i8 %arg1, i8* %base) {
+  %add = add nsw i8 %arg1, 1 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  %almostfinalres = zext i8 %res to i64
+  %finalres = add i64 %almostfinalres, %sextadd
+  ret i64 %finalres
+}
+
+; Check all types of rollback mechanism.
+; For this test, the sign extension stays in place.
+; However, the matching process goes until promoting both the operands
+; of the first promotable add implies.
+; At this point the rollback mechanism kicks in and restores the states
+; until the addressing mode matcher is able to match something: in that
+; case promote nothing.
+; Along the way, the promotion mechanism involves:
+; - Mutating the type of %promotableadd1 and %promotableadd2.
+; - Creating a sext for %arg1 and %arg2.
+; - Creating a trunc for a use of %promotableadd1.
+; - Replacing a bunch of uses.
+; - Setting the operands of the promoted instruction with the promoted values.
+; - Moving instruction around (mainly sext when promoting instruction).
+; Each type of those promotions has to be undo at least once during this
+; specific test. 
+; CHECK-LABEL: @twoArgsPromotionNest
+; CHECK: [[ORIG:%[a-zA-Z_0-9-]+]] = add nsw i32 %arg1, %arg2
+; CHECK: [[ADD:%[a-zA-Z_0-9-]+]] = add nsw i32 [[ORIG]], [[ORIG]]
+; CHECK: [[SEXT:%[a-zA-Z_0-9-]+]] = sext i32 [[ADD]] to i64
+; CHECK: getelementptr inbounds i8* %base, i64 [[SEXT]]
+; CHECK: ret
+define i8 @twoArgsPromotionNest(i32 %arg1, i32 %arg2, i8* %base) {
+  %promotableadd1 = add nsw i32 %arg1, %arg2
+  %promotableadd2 = add nsw i32 %promotableadd1, %promotableadd1 
+  %sextadd = sext i32 %promotableadd2 to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}
+
+; Test the InstructionRemover undo, which was the only one not
+; kicked in the previous test.
+; The matcher first promotes the add, removes the trunc and promotes
+; the sext of arg1.
+; Then, the matcher cannot use an addressing mode r + r + r, thus it
+; rolls back. 
+; CHECK-LABEL: @twoArgsNoPromotionRemove
+; CHECK: [[SEXTARG1:%[a-zA-Z_0-9-]+]] = sext i1 %arg1 to i32
+; CHECK: [[TRUNC:%[a-zA-Z_0-9-]+]] = trunc i32 [[SEXTARG1]] to i8
+; CHECK: [[ADD:%[a-zA-Z_0-9-]+]] = add nsw i8 [[TRUNC]], %arg2
+; CHECK: [[SEXT:%[a-zA-Z_0-9-]+]] = sext i8 [[ADD]] to i64
+; CHECK: getelementptr inbounds i8* %base, i64 [[SEXT]]
+; CHECK: ret
+define i8 @twoArgsNoPromotionRemove(i1 %arg1, i8 %arg2, i8* %base) {
+  %sextarg1 = sext i1 %arg1 to i32
+  %trunc = trunc i32 %sextarg1 to i8
+  %add = add nsw i8 %trunc, %arg2 
+  %sextadd = sext i8 %add to i64
+  %arrayidx = getelementptr inbounds i8* %base, i64 %sextadd
+  %res = load i8* %arrayidx
+  ret i8 %res
+}





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