Revision: 22017
Author: [email protected]
Date: Wed Jun 25 15:11:00 2014 UTC
Log: ARM: Use the shifter operand to merge in previous shift
instructions.
When possible, we transform sequences of code of the form
lsl r1, r2, #imm
add r0, r5, r1
into
add r0, r5, r2 LSL #imm
This is an adaptation of r21161.
[email protected]
Review URL: https://codereview.chromium.org/312173002
http://code.google.com/p/v8/source/detail?r=22017
Modified:
/branches/bleeding_edge/src/arm/assembler-arm.cc
/branches/bleeding_edge/src/arm/assembler-arm.h
/branches/bleeding_edge/src/arm/constants-arm.h
/branches/bleeding_edge/src/arm/lithium-arm.cc
/branches/bleeding_edge/src/arm/lithium-arm.h
/branches/bleeding_edge/src/arm/lithium-codegen-arm.cc
/branches/bleeding_edge/src/arm/lithium-codegen-arm.h
=======================================
--- /branches/bleeding_edge/src/arm/assembler-arm.cc Tue Jun 24 12:20:12
2014 UTC
+++ /branches/bleeding_edge/src/arm/assembler-arm.cc Wed Jun 25 15:11:00
2014 UTC
@@ -281,6 +281,7 @@
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;
@@ -301,7 +302,7 @@
Operand::Operand(Register rm, ShiftOp shift_op, Register rs) {
- ASSERT(shift_op != RRX);
+ ASSERT((shift_op != RRX) && (shift_op != NO_SHIFT));
rm_ = rm;
rs_ = no_reg;
shift_op_ = shift_op;
@@ -957,16 +958,16 @@
// 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!
-static bool fits_shifter(uint32_t imm32,
- uint32_t* rotate_imm,
- uint32_t* immed_8,
- Instr* instr) {
+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)) {
- *rotate_imm = rot;
- *immed_8 = imm8;
+ if (rotate_imm != NULL) *rotate_imm = rot;
+ if (immed_8 != NULL) *immed_8 = imm8;
return true;
}
}
@@ -982,7 +983,8 @@
if (imm32 < 0x10000) {
*instr ^= kMovwLeaveCCFlip;
*instr |= EncodeMovwImmediate(imm32);
- *rotate_imm = *immed_8 = 0; // Not used for movw.
+ if (rotate_imm != NULL) *rotate_imm = 0; // Not used for movw.
+ if (immed_8 != NULL) *immed_8 = 0; // Not used for movw.
return true;
}
}
=======================================
--- /branches/bleeding_edge/src/arm/assembler-arm.h Mon Jun 23 11:27:24
2014 UTC
+++ /branches/bleeding_edge/src/arm/assembler-arm.h Wed Jun 25 15:11:00
2014 UTC
@@ -1598,6 +1598,10 @@
};
+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) {
=======================================
--- /branches/bleeding_edge/src/arm/constants-arm.h Mon Jun 23 11:27:24
2014 UTC
+++ /branches/bleeding_edge/src/arm/constants-arm.h Wed Jun 25 15:11:00
2014 UTC
@@ -236,6 +236,7 @@
// 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
};
=======================================
--- /branches/bleeding_edge/src/arm/lithium-arm.cc Tue Jun 24 12:54:59 2014
UTC
+++ /branches/bleeding_edge/src/arm/lithium-arm.cc Wed Jun 25 15:11:00 2014
UTC
@@ -674,6 +674,117 @@
LInstruction* LChunkBuilder::DoDeoptimize(HDeoptimize* instr) {
return AssignEnvironment(new(zone()) LDeoptimize);
}
+
+
+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,
@@ -681,6 +792,11 @@
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();
@@ -690,7 +806,7 @@
if (right_value->IsConstant()) {
HConstant* constant = HConstant::cast(right_value);
right = chunk_->DefineConstantOperand(constant);
- constant_value = constant->Integer32Value() & 0x1f;
+ constant_value = JSShiftAmountFromHConstant(constant);
// Left shifts can deoptimize if we shift by > 0 and the result
cannot be
// truncated to smi.
if (instr->representation().IsSmi() && constant_value > 0) {
@@ -1249,6 +1365,11 @@
ASSERT(instr->left()->representation().Equals(instr->representation()));
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());
@@ -1532,6 +1653,11 @@
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;
+ }
if (instr->left()->IsConstant()) {
// If lhs is constant, do reverse subtraction instead.
@@ -1600,6 +1726,12 @@
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);
=======================================
--- /branches/bleeding_edge/src/arm/lithium-arm.h Fri Jun 20 08:40:11 2014
UTC
+++ /branches/bleeding_edge/src/arm/lithium-arm.h Wed Jun 25 15:11:00 2014
UTC
@@ -1239,18 +1239,32 @@
class LBitI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
public:
- LBitI(LOperand* left, LOperand* right) {
+ 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) {
+ inputs_[0] = left;
+ inputs_[1] = right;
+ }
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_;
};
@@ -1277,16 +1291,30 @@
class LSubI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
public:
- LSubI(LOperand* left, LOperand* right) {
+ 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) {
+ 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_;
};
@@ -1455,16 +1483,30 @@
class LAddI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
public:
- LAddI(LOperand* left, LOperand* right) {
+ 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) {
inputs_[0] = left;
inputs_[1] = right;
}
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_;
};
@@ -2855,6 +2897,49 @@
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);
=======================================
--- /branches/bleeding_edge/src/arm/lithium-codegen-arm.cc Tue Jun 24
12:54:59 2014 UTC
+++ /branches/bleeding_edge/src/arm/lithium-codegen-arm.cc Wed Jun 25
15:11:00 2014 UTC
@@ -478,6 +478,19 @@
bool LCodeGen::IsInteger32(LConstantOperand* op) const {
return chunk_->LookupLiteralRepresentation(op).IsSmiOrInteger32();
}
+
+
+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 {
@@ -1712,11 +1725,13 @@
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 = ToOperand(right_op);
+ right = ToShiftedRightOperand(right_op, instr);
}
switch (instr->op()) {
@@ -1773,9 +1788,7 @@
break;
}
} else {
- // Mask the right_op operand.
- int value = ToInteger32(LConstantOperand::cast(right_op));
- uint8_t shift_count = static_cast<uint8_t>(value & 0x1F);
+ int shift_count = JSShiftAmountFromLConstant(right_op);
switch (instr->op()) {
case Token::ROR:
if (shift_count != 0) {
@@ -1835,12 +1848,15 @@
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), ToOperand(right),
set_cond);
+ __ sub(ToRegister(result), ToRegister(left),
+ ToShiftedRightOperand(right, instr), set_cond);
}
if (can_overflow) {
@@ -2029,12 +2045,15 @@
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), ToOperand(right),
set_cond);
+ __ add(ToRegister(result), ToRegister(left),
+ ToShiftedRightOperand(right, instr), set_cond);
}
if (can_overflow) {
=======================================
--- /branches/bleeding_edge/src/arm/lithium-codegen-arm.h Tue Jun 3
08:12:43 2014 UTC
+++ /branches/bleeding_edge/src/arm/lithium-codegen-arm.h Wed Jun 25
15:11:00 2014 UTC
@@ -85,6 +85,13 @@
MemOperand ToMemOperand(LOperand* op) const;
// 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;
--
--
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