Revert "ARM: Use the shifter operand to merge in previous shift instructions."

This reverts r 22017

Reason: broke Nexus 7 GPU bots (see crbug.com/389198)

BUG=389198
LOG=n
TBR=machenbach@chromium.org, ulan@chromium.org

Review URL: https://codereview.chromium.org/359713004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22050 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/assembler-arm.cc

@@ -281,7 +281,6 @@ Operand::Operand(Handle<Object> handle) {
 
 Operand::Operand(Register rm, ShiftOp shift_op, int shift_imm) {
   ASSERT(is_uint5(shift_imm));
-  ASSERT(shift_op != NO_SHIFT);
 
   rm_ = rm;
   rs_ = no_reg;
@@ -302,7 +301,7 @@ Operand::Operand(Register rm, ShiftOp shift_op, int shift_imm) {
 
 
 Operand::Operand(Register rm, ShiftOp shift_op, Register rs) {
-  ASSERT((shift_op != RRX) && (shift_op != NO_SHIFT));
+  ASSERT(shift_op != RRX);
   rm_ = rm;
   rs_ = no_reg;
   shift_op_ = shift_op;
@@ -958,16 +957,16 @@ void Assembler::next(Label* L) {
 // If this returns true then you have to use the rotate_imm and immed_8
 // that it returns, because it may have already changed the instruction
 // to match them!
-bool fits_shifter(uint32_t imm32,
-                  uint32_t* rotate_imm,
-                  uint32_t* immed_8,
-                  Instr* instr) {
+static bool fits_shifter(uint32_t imm32,
+                         uint32_t* rotate_imm,
+                         uint32_t* immed_8,
+                         Instr* instr) {
   // imm32 must be unsigned.
   for (int rot = 0; rot < 16; rot++) {
     uint32_t imm8 = (imm32 << 2*rot) | (imm32 >> (32 - 2*rot));
     if ((imm8 <= 0xff)) {
-      if (rotate_imm != NULL) *rotate_imm = rot;
-      if (immed_8 != NULL) *immed_8 = imm8;
+      *rotate_imm = rot;
+      *immed_8 = imm8;
       return true;
     }
   }
@@ -983,8 +982,7 @@ bool fits_shifter(uint32_t imm32,
           if (imm32 < 0x10000) {
             *instr ^= kMovwLeaveCCFlip;
             *instr |= EncodeMovwImmediate(imm32);
-            if (rotate_imm != NULL) *rotate_imm = 0;  // Not used for movw.
-            if (immed_8 != NULL) *immed_8 = 0;  // Not used for movw.
+            *rotate_imm = *immed_8 = 0;  // Not used for movw.
             return true;
           }
         }

src/arm/assembler-arm.h

@@ -1598,10 +1598,6 @@ class Assembler : public AssemblerBase {
 };
 
 
-bool fits_shifter(uint32_t imm32, uint32_t* rotate_imm,
-                  uint32_t* immed_8, Instr* instr);
-
-
 class EnsureSpace BASE_EMBEDDED {
  public:
   explicit EnsureSpace(Assembler* assembler) {

src/arm/constants-arm.h

@@ -236,7 +236,6 @@ enum ShiftOp {
   // as an argument, and will never actually be encoded. The Assembler will
   // detect it and emit the correct ROR shift operand with shift_imm == 0.
   RRX = -1,
-  NO_SHIFT = -2,
   kNumberOfShifts = 4
 };
 

src/arm/lithium-arm.cc

@@ -676,127 +676,11 @@ LInstruction* LChunkBuilder::DoDeoptimize(HDeoptimize* instr) {
 }
 
 
-HBitwiseBinaryOperation* LChunkBuilder::CanTransformToShiftedOp(HValue* val,
-                                                                HValue** left) {
-  if (!val->representation().IsInteger32()) return NULL;
-  if (!(val->IsBitwise() || val->IsAdd() || val->IsSub())) return NULL;
-
-  HBinaryOperation* hinstr = HBinaryOperation::cast(val);
-  HValue* hleft = hinstr->left();
-  HValue* hright = hinstr->right();
-  ASSERT(hleft->representation().Equals(hinstr->representation()));
-  ASSERT(hright->representation().Equals(hinstr->representation()));
-
-  if ((hright->IsConstant() &&
-       LikelyFitsImmField(hinstr, HConstant::cast(hright)->Integer32Value())) ||
-      (hinstr->IsCommutative() && hleft->IsConstant() &&
-       LikelyFitsImmField(hinstr, HConstant::cast(hleft)->Integer32Value()))) {
-    // The constant operand will likely fit in the immediate field. We are
-    // better off with
-    //     mov r1, r2 LSL #imm
-    //     add r0, r1, #imm2
-    // than with
-    //     mov r5, #imm2
-    //     add r0, r5, r2 LSL #imm
-    return NULL;
-  }
-
-  HBitwiseBinaryOperation* shift = NULL;
-  // TODO(aleram): We will miss situations where a shift operation is used by
-  // different instructions both as a left and right operands.
-  if (hright->IsBitwiseBinaryShift() &&
-      HBitwiseBinaryOperation::cast(hright)->right()->IsConstant()) {
-    shift = HBitwiseBinaryOperation::cast(hright);
-    if (left != NULL) {
-      *left = hleft;
-    }
-  } else if (hinstr->IsCommutative() &&
-             hleft->IsBitwiseBinaryShift() &&
-             HBitwiseBinaryOperation::cast(hleft)->right()->IsConstant()) {
-    shift = HBitwiseBinaryOperation::cast(hleft);
-    if (left != NULL) {
-      *left = hright;
-    }
-  } else {
-    return NULL;
-  }
-
-  if ((JSShiftAmountFromHConstant(shift->right()) == 0) && shift->IsShr()) {
-    // Logical shifts right by zero can deoptimize.
-    return NULL;
-  }
-
-  return shift;
-}
-
-
-bool LChunkBuilder::ShiftCanBeOptimizedAway(HBitwiseBinaryOperation* shift) {
-  if (!shift->representation().IsInteger32()) {
-    return false;
-  }
-  for (HUseIterator it(shift->uses()); !it.Done(); it.Advance()) {
-    if (shift != CanTransformToShiftedOp(it.value())) {
-      return false;
-    }
-  }
-  return true;
-}
-
-
-LInstruction* LChunkBuilder::TryDoOpWithShiftedRightOperand(
-    HBinaryOperation* instr) {
-  HValue* left;
-  HBitwiseBinaryOperation* shift = CanTransformToShiftedOp(instr, &left);
-
-  if ((shift != NULL) && ShiftCanBeOptimizedAway(shift)) {
-    return DoShiftedBinaryOp(instr, left, shift);
-  }
-  return NULL;
-}
-
-
-LInstruction* LChunkBuilder::DoShiftedBinaryOp(
-    HBinaryOperation* hinstr, HValue* hleft, HBitwiseBinaryOperation* hshift) {
-  ASSERT(hshift->IsBitwiseBinaryShift());
-  ASSERT(!hshift->IsShr() || (JSShiftAmountFromHConstant(hshift->right()) > 0));
-
-  LTemplateResultInstruction<1>* res;
-  LOperand* left = UseRegisterAtStart(hleft);
-  LOperand* right = UseRegisterAtStart(hshift->left());
-  LOperand* shift_amount = UseConstant(hshift->right());
-  ShiftOp shift_op;
-  switch (hshift->opcode()) {
-    case HValue::kShl: shift_op = LSL; break;
-    case HValue::kShr: shift_op = LSR; break;
-    case HValue::kSar: shift_op = ASR; break;
-    default: UNREACHABLE(); shift_op = NO_SHIFT;
-  }
-
-  if (hinstr->IsBitwise()) {
-    res = new(zone()) LBitI(left, right, shift_op, shift_amount);
-  } else if (hinstr->IsAdd()) {
-    res = new(zone()) LAddI(left, right, shift_op, shift_amount);
-  } else {
-    ASSERT(hinstr->IsSub());
-    res = new(zone()) LSubI(left, right, shift_op, shift_amount);
-  }
-  if (hinstr->CheckFlag(HValue::kCanOverflow)) {
-    AssignEnvironment(res);
-  }
-  return DefineAsRegister(res);
-}
-
-
 LInstruction* LChunkBuilder::DoShift(Token::Value op,
                                      HBitwiseBinaryOperation* instr) {
   if (instr->representation().IsSmiOrInteger32()) {
     ASSERT(instr->left()->representation().Equals(instr->representation()));
     ASSERT(instr->right()->representation().Equals(instr->representation()));
-
-    if (ShiftCanBeOptimizedAway(instr)) {
-      return NULL;
-    }
-
     LOperand* left = UseRegisterAtStart(instr->left());
 
     HValue* right_value = instr->right();
@@ -806,7 +690,7 @@ LInstruction* LChunkBuilder::DoShift(Token::Value op,
     if (right_value->IsConstant()) {
       HConstant* constant = HConstant::cast(right_value);
       right = chunk_->DefineConstantOperand(constant);
-      constant_value = JSShiftAmountFromHConstant(constant);
+      constant_value = constant->Integer32Value() & 0x1f;
       // Left shifts can deoptimize if we shift by > 0 and the result cannot be
       // truncated to smi.
       if (instr->representation().IsSmi() && constant_value > 0) {
@@ -1366,11 +1250,6 @@ LInstruction* LChunkBuilder::DoBitwise(HBitwise* instr) {
     ASSERT(instr->right()->representation().Equals(instr->representation()));
     ASSERT(instr->CheckFlag(HValue::kTruncatingToInt32));
 
-    LInstruction* shifted_operation = TryDoOpWithShiftedRightOperand(instr);
-    if (shifted_operation != NULL) {
-      return shifted_operation;
-    }
-
     LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
     LOperand* right = UseOrConstantAtStart(instr->BetterRightOperand());
     return DefineAsRegister(new(zone()) LBitI(left, right));
@@ -1654,11 +1533,6 @@ LInstruction* LChunkBuilder::DoSub(HSub* instr) {
     ASSERT(instr->left()->representation().Equals(instr->representation()));
     ASSERT(instr->right()->representation().Equals(instr->representation()));
 
-    LInstruction* shifted_operation = TryDoOpWithShiftedRightOperand(instr);
-    if (shifted_operation != NULL) {
-      return shifted_operation;
-    }
-
     if (instr->left()->IsConstant()) {
       // If lhs is constant, do reverse subtraction instead.
       return DoRSub(instr);
@@ -1726,12 +1600,6 @@ LInstruction* LChunkBuilder::DoAdd(HAdd* instr) {
   if (instr->representation().IsSmiOrInteger32()) {
     ASSERT(instr->left()->representation().Equals(instr->representation()));
     ASSERT(instr->right()->representation().Equals(instr->representation()));
-
-    LInstruction* shifted_operation = TryDoOpWithShiftedRightOperand(instr);
-    if (shifted_operation != NULL) {
-      return shifted_operation;
-    }
-
     LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
     LOperand* right = UseOrConstantAtStart(instr->BetterRightOperand());
     LAddI* add = new(zone()) LAddI(left, right);

src/arm/lithium-arm.h

@@ -1239,14 +1239,7 @@ class LBoundsCheck V8_FINAL : public LTemplateInstruction<0, 2, 0> {
 
 class LBitI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
  public:
-  LBitI(LOperand* left, LOperand* right)
-      : shift_(NO_SHIFT), shift_amount_(0)  {
-    inputs_[0] = left;
-    inputs_[1] = right;
-  }
-
-  LBitI(LOperand* left, LOperand* right, ShiftOp shift, LOperand* shift_amount)
-      : shift_(shift), shift_amount_(shift_amount)  {
+  LBitI(LOperand* left, LOperand* right) {
     inputs_[0] = left;
     inputs_[1] = right;
   }
@@ -1254,17 +1247,10 @@ class LBitI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
   LOperand* left() { return inputs_[0]; }
   LOperand* right() { return inputs_[1]; }
 
-  ShiftOp shift() const { return shift_; }
-  LOperand* shift_amount() const { return shift_amount_; }
-
   Token::Value op() const { return hydrogen()->op(); }
 
   DECLARE_CONCRETE_INSTRUCTION(BitI, "bit-i")
   DECLARE_HYDROGEN_ACCESSOR(Bitwise)
-
- protected:
-  ShiftOp shift_;
-  LOperand* shift_amount_;
 };
 
 
@@ -1291,30 +1277,16 @@ class LShiftI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
 
 class LSubI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
  public:
-  LSubI(LOperand* left, LOperand* right)
-      : shift_(NO_SHIFT), shift_amount_(0)  {
-    inputs_[0] = left;
-    inputs_[1] = right;
-  }
-
-  LSubI(LOperand* left, LOperand* right, ShiftOp shift, LOperand* shift_amount)
-      : shift_(shift), shift_amount_(shift_amount)  {
+  LSubI(LOperand* left, LOperand* right) {
     inputs_[0] = left;
     inputs_[1] = right;
   }
 
-  ShiftOp shift() const { return shift_; }
-  LOperand* shift_amount() const { return shift_amount_; }
-
   LOperand* left() { return inputs_[0]; }
   LOperand* right() { return inputs_[1]; }
 
   DECLARE_CONCRETE_INSTRUCTION(SubI, "sub-i")
   DECLARE_HYDROGEN_ACCESSOR(Sub)
-
- protected:
-  ShiftOp shift_;
-  LOperand* shift_amount_;
 };
 
 
@@ -1483,14 +1455,7 @@ class LSeqStringSetChar V8_FINAL : public LTemplateInstruction<1, 4, 0> {
 
 class LAddI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
  public:
-  LAddI(LOperand* left, LOperand* right)
-      : shift_(NO_SHIFT), shift_amount_(0)  {
-    inputs_[0] = left;
-    inputs_[1] = right;
-  }
-
-  LAddI(LOperand* left, LOperand* right, ShiftOp shift, LOperand* shift_amount)
-      : shift_(shift), shift_amount_(shift_amount)  {
+  LAddI(LOperand* left, LOperand* right) {
     inputs_[0] = left;
     inputs_[1] = right;
   }
@@ -1498,15 +1463,8 @@ class LAddI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
   LOperand* left() { return inputs_[0]; }
   LOperand* right() { return inputs_[1]; }
 
-  ShiftOp shift() const { return shift_; }
-  LOperand* shift_amount() const { return shift_amount_; }
-
   DECLARE_CONCRETE_INSTRUCTION(AddI, "add-i")
   DECLARE_HYDROGEN_ACCESSOR(Add)
-
- protected:
-  ShiftOp shift_;
-  LOperand* shift_amount_;
 };
 
 
@@ -2897,49 +2855,6 @@ class LChunkBuilder V8_FINAL : public LChunkBuilderBase {
   void AddInstruction(LInstruction* instr, HInstruction* current);
 
   void DoBasicBlock(HBasicBlock* block, HBasicBlock* next_block);
-
-  int JSShiftAmountFromHConstant(HValue* constant) {
-    return HConstant::cast(constant)->Integer32Value() & 0x1f;
-  }
-  bool LikelyFitsImmField(HInstruction* instr, int imm) {
-    Instr instr_bits;
-    // All arithmetic and logical operations accept the same range of
-    // immediates. In some cases though, the operation itself can be changed to
-    // get a wider effective range of immediates.
-    if (instr->IsAdd() || instr->IsSub()) {
-      // ADD and SUB can be exchanged with a negate immediate.
-      instr_bits = ADD;
-    } else if (HBitwise::cast(instr)->op() == Token::BIT_AND) {
-      ASSERT(instr->IsBitwise());
-      // AND and BIC can be exchanged with an inverted immediate.
-      instr_bits = AND;
-    } else {
-      ASSERT(instr->IsBitwise());
-      // Use ORR for all other operations, since fits_shifter() can't adapt ORR.
-      instr_bits = ORR;
-    }
-    return fits_shifter(imm, NULL, NULL, &instr_bits);
-  }
-
-  // Indicates if a sequence of the form
-  //   mov r1, r2 LSL #imm
-  //   add r0, r5, r1
-  // can be replaced with:
-  //   add r0, r5, r2 LSL #imm
-  // If this is not possible, the function returns NULL. Otherwise it returns a
-  // pointer to the shift instruction that would be optimized away.
-  HBitwiseBinaryOperation* CanTransformToShiftedOp(HValue* val,
-                                                   HValue** left = NULL);
-  // Checks if all uses of the shift operation can optimize it away.
-  bool ShiftCanBeOptimizedAway(HBitwiseBinaryOperation* shift);
-  // Attempts to merge the binary operation and a previous shift operation into
-  // a single operation. Returns the merged instruction on success, and NULL
-  // otherwise.
-  LInstruction* TryDoOpWithShiftedRightOperand(HBinaryOperation* op);
-  LInstruction* DoShiftedBinaryOp(HBinaryOperation* instr,
-                                  HValue* left,
-                                  HBitwiseBinaryOperation* shift);
-
   LInstruction* DoShift(Token::Value op, HBitwiseBinaryOperation* instr);
   LInstruction* DoArithmeticD(Token::Value op,
                               HArithmeticBinaryOperation* instr);

src/arm/lithium-codegen-arm.cc

@@ -480,19 +480,6 @@ bool LCodeGen::IsInteger32(LConstantOperand* op) const {
 }
 
 
-template<class LI>
-Operand LCodeGen::ToShiftedRightOperand(LOperand* right, LI* shift_info) {
-  if (shift_info->shift() == NO_SHIFT) {
-    return ToOperand(right);
-  } else {
-    return Operand(
-        ToRegister(right),
-        shift_info->shift(),
-        JSShiftAmountFromLConstant(shift_info->shift_amount()));
-  }
-}
-
-
 bool LCodeGen::IsSmi(LConstantOperand* op) const {
   return chunk_->LookupLiteralRepresentation(op).IsSmi();
 }
@@ -1725,13 +1712,11 @@ void LCodeGen::DoBitI(LBitI* instr) {
   Register result = ToRegister(instr->result());
   Operand right(no_reg);
 
-  ASSERT(right_op->IsRegister() || (instr->shift() == NO_SHIFT));
-
   if (right_op->IsStackSlot()) {
     right = Operand(EmitLoadRegister(right_op, ip));
   } else {
     ASSERT(right_op->IsRegister() || right_op->IsConstantOperand());
-    right = ToShiftedRightOperand(right_op, instr);
+    right = ToOperand(right_op);
   }
 
   switch (instr->op()) {
@@ -1788,7 +1773,9 @@ void LCodeGen::DoShiftI(LShiftI* instr) {
         break;
     }
   } else {
-    int shift_count = JSShiftAmountFromLConstant(right_op);
+    // Mask the right_op operand.
+    int value = ToInteger32(LConstantOperand::cast(right_op));
+    uint8_t shift_count = static_cast<uint8_t>(value & 0x1F);
     switch (instr->op()) {
       case Token::ROR:
           if (shift_count != 0) {
@@ -1848,15 +1835,12 @@ void LCodeGen::DoSubI(LSubI* instr) {
   bool can_overflow = instr->hydrogen()->CheckFlag(HValue::kCanOverflow);
   SBit set_cond = can_overflow ? SetCC : LeaveCC;
 
-  ASSERT(right->IsRegister() || (instr->shift() == NO_SHIFT));
-
   if (right->IsStackSlot()) {
     Register right_reg = EmitLoadRegister(right, ip);
     __ sub(ToRegister(result), ToRegister(left), Operand(right_reg), set_cond);
   } else {
     ASSERT(right->IsRegister() || right->IsConstantOperand());
-    __ sub(ToRegister(result), ToRegister(left),
-           ToShiftedRightOperand(right, instr), set_cond);
+    __ sub(ToRegister(result), ToRegister(left), ToOperand(right), set_cond);
   }
 
   if (can_overflow) {
@@ -2045,15 +2029,12 @@ void LCodeGen::DoAddI(LAddI* instr) {
   bool can_overflow = instr->hydrogen()->CheckFlag(HValue::kCanOverflow);
   SBit set_cond = can_overflow ? SetCC : LeaveCC;
 
-  ASSERT(right->IsRegister() || (instr->shift() == NO_SHIFT));
-
   if (right->IsStackSlot()) {
     Register right_reg = EmitLoadRegister(right, ip);
     __ add(ToRegister(result), ToRegister(left), Operand(right_reg), set_cond);
   } else {
     ASSERT(right->IsRegister() || right->IsConstantOperand());
-    __ add(ToRegister(result), ToRegister(left),
-           ToShiftedRightOperand(right, instr), set_cond);
+    __ add(ToRegister(result), ToRegister(left), ToOperand(right), set_cond);
   }
 
   if (can_overflow) {

src/arm/lithium-codegen-arm.h

@@ -86,13 +86,6 @@ class LCodeGen: public LCodeGenBase {
   // Returns a MemOperand pointing to the high word of a DoubleStackSlot.
   MemOperand ToHighMemOperand(LOperand* op) const;
 
-  template<class LI>
-  Operand ToShiftedRightOperand(LOperand* right, LI* shift_info);
-
-  int JSShiftAmountFromLConstant(LOperand* constant) {
-    return ToInteger32(LConstantOperand::cast(constant)) & 0x1f;
-  }
-
   bool IsInteger32(LConstantOperand* op) const;
   bool IsSmi(LConstantOperand* op) const;
   Handle<Object> ToHandle(LConstantOperand* op) const;