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gerrit-public.fairphone.software / platform / art / 467d94a3d926620b01b034eff68fdcaf2b5fb579 / . / compiler / optimizing / instruction_simplifier.cc
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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "instruction_simplifier.h"
#include "escape.h"
#include "intrinsics.h"
#include "mirror/class-inl.h"
#include "scoped_thread_state_change-inl.h"
namespace art {
class InstructionSimplifierVisitor : public HGraphDelegateVisitor {
public:
InstructionSimplifierVisitor(HGraph* graph, OptimizingCompilerStats* stats)
: HGraphDelegateVisitor(graph),
stats_(stats) {}
void Run();
private:
void RecordSimplification() {
simplification_occurred_ = true;
simplifications_at_current_position_++;
MaybeRecordStat(kInstructionSimplifications);
}
void MaybeRecordStat(MethodCompilationStat stat) {
if (stats_ != nullptr) {
stats_->RecordStat(stat);
}
}
bool ReplaceRotateWithRor(HBinaryOperation* op, HUShr* ushr, HShl* shl);
bool TryReplaceWithRotate(HBinaryOperation* instruction);
bool TryReplaceWithRotateConstantPattern(HBinaryOperation* op, HUShr* ushr, HShl* shl);
bool TryReplaceWithRotateRegisterNegPattern(HBinaryOperation* op, HUShr* ushr, HShl* shl);
bool TryReplaceWithRotateRegisterSubPattern(HBinaryOperation* op, HUShr* ushr, HShl* shl);
bool TryMoveNegOnInputsAfterBinop(HBinaryOperation* binop);
// `op` should be either HOr or HAnd.
// De Morgan's laws:
// ~a & ~b = ~(a | b) and ~a | ~b = ~(a & b)
bool TryDeMorganNegationFactoring(HBinaryOperation* op);
bool TryHandleAssociativeAndCommutativeOperation(HBinaryOperation* instruction);
bool TrySubtractionChainSimplification(HBinaryOperation* instruction);
void VisitShift(HBinaryOperation* shift);
void VisitEqual(HEqual* equal) OVERRIDE;
void VisitNotEqual(HNotEqual* equal) OVERRIDE;
void VisitBooleanNot(HBooleanNot* bool_not) OVERRIDE;
void VisitInstanceFieldSet(HInstanceFieldSet* equal) OVERRIDE;
void VisitStaticFieldSet(HStaticFieldSet* equal) OVERRIDE;
void VisitArraySet(HArraySet* equal) OVERRIDE;
void VisitTypeConversion(HTypeConversion* instruction) OVERRIDE;
void VisitNullCheck(HNullCheck* instruction) OVERRIDE;
void VisitArrayLength(HArrayLength* instruction) OVERRIDE;
void VisitCheckCast(HCheckCast* instruction) OVERRIDE;
void VisitAdd(HAdd* instruction) OVERRIDE;
void VisitAnd(HAnd* instruction) OVERRIDE;
void VisitCondition(HCondition* instruction) OVERRIDE;
void VisitGreaterThan(HGreaterThan* condition) OVERRIDE;
void VisitGreaterThanOrEqual(HGreaterThanOrEqual* condition) OVERRIDE;
void VisitLessThan(HLessThan* condition) OVERRIDE;
void VisitLessThanOrEqual(HLessThanOrEqual* condition) OVERRIDE;
void VisitBelow(HBelow* condition) OVERRIDE;
void VisitBelowOrEqual(HBelowOrEqual* condition) OVERRIDE;
void VisitAbove(HAbove* condition) OVERRIDE;
void VisitAboveOrEqual(HAboveOrEqual* condition) OVERRIDE;
void VisitDiv(HDiv* instruction) OVERRIDE;
void VisitMul(HMul* instruction) OVERRIDE;
void VisitNeg(HNeg* instruction) OVERRIDE;
void VisitNot(HNot* instruction) OVERRIDE;
void VisitOr(HOr* instruction) OVERRIDE;
void VisitShl(HShl* instruction) OVERRIDE;
void VisitShr(HShr* instruction) OVERRIDE;
void VisitSub(HSub* instruction) OVERRIDE;
void VisitUShr(HUShr* instruction) OVERRIDE;
void VisitXor(HXor* instruction) OVERRIDE;
void VisitSelect(HSelect* select) OVERRIDE;
void VisitIf(HIf* instruction) OVERRIDE;
void VisitInstanceOf(HInstanceOf* instruction) OVERRIDE;
void VisitInvoke(HInvoke* invoke) OVERRIDE;
void VisitDeoptimize(HDeoptimize* deoptimize) OVERRIDE;
bool CanEnsureNotNullAt(HInstruction* instr, HInstruction* at) const;
void SimplifyRotate(HInvoke* invoke, bool is_left, Primitive::Type type);
void SimplifySystemArrayCopy(HInvoke* invoke);
void SimplifyStringEquals(HInvoke* invoke);
void SimplifyCompare(HInvoke* invoke, bool is_signum, Primitive::Type type);
void SimplifyIsNaN(HInvoke* invoke);
void SimplifyFP2Int(HInvoke* invoke);
void SimplifyStringCharAt(HInvoke* invoke);
void SimplifyStringIsEmptyOrLength(HInvoke* invoke);
void SimplifyNPEOnArgN(HInvoke* invoke, size_t);
void SimplifyReturnThis(HInvoke* invoke);
void SimplifyAllocationIntrinsic(HInvoke* invoke);
void SimplifyMemBarrier(HInvoke* invoke, MemBarrierKind barrier_kind);
OptimizingCompilerStats* stats_;
bool simplification_occurred_ = false;
int simplifications_at_current_position_ = 0;
// We ensure we do not loop infinitely. The value should not be too high, since that
// would allow looping around the same basic block too many times. The value should
// not be too low either, however, since we want to allow revisiting a basic block
// with many statements and simplifications at least once.
static constexpr int kMaxSamePositionSimplifications = 50;
};
void InstructionSimplifier::Run() {
InstructionSimplifierVisitor visitor(graph_, stats_);
visitor.Run();
}
void InstructionSimplifierVisitor::Run() {
// Iterate in reverse post order to open up more simplifications to users
// of instructions that got simplified.
for (HBasicBlock* block : GetGraph()->GetReversePostOrder()) {
// The simplification of an instruction to another instruction may yield
// possibilities for other simplifications. So although we perform a reverse
// post order visit, we sometimes need to revisit an instruction index.
do {
simplification_occurred_ = false;
VisitBasicBlock(block);
} while (simplification_occurred_ &&
(simplifications_at_current_position_ < kMaxSamePositionSimplifications));
simplifications_at_current_position_ = 0;
}
}
namespace {
bool AreAllBitsSet(HConstant* constant) {
return Int64FromConstant(constant) == -1;
}
} // namespace
// Returns true if the code was simplified to use only one negation operation
// after the binary operation instead of one on each of the inputs.
bool InstructionSimplifierVisitor::TryMoveNegOnInputsAfterBinop(HBinaryOperation* binop) {
DCHECK(binop->IsAdd() || binop->IsSub());
DCHECK(binop->GetLeft()->IsNeg() && binop->GetRight()->IsNeg());
HNeg* left_neg = binop->GetLeft()->AsNeg();
HNeg* right_neg = binop->GetRight()->AsNeg();
if (!left_neg->HasOnlyOneNonEnvironmentUse() ||
!right_neg->HasOnlyOneNonEnvironmentUse()) {
return false;
}
// Replace code looking like
// NEG tmp1, a
// NEG tmp2, b
// ADD dst, tmp1, tmp2
// with
// ADD tmp, a, b
// NEG dst, tmp
// Note that we cannot optimize `(-a) + (-b)` to `-(a + b)` for floating-point.
// When `a` is `-0.0` and `b` is `0.0`, the former expression yields `0.0`,
// while the later yields `-0.0`.
if (!Primitive::IsIntegralType(binop->GetType())) {
return false;
}
binop->ReplaceInput(left_neg->GetInput(), 0);
binop->ReplaceInput(right_neg->GetInput(), 1);
left_neg->GetBlock()->RemoveInstruction(left_neg);
right_neg->GetBlock()->RemoveInstruction(right_neg);
HNeg* neg = new (GetGraph()->GetArena()) HNeg(binop->GetType(), binop);
binop->GetBlock()->InsertInstructionBefore(neg, binop->GetNext());
binop->ReplaceWithExceptInReplacementAtIndex(neg, 0);
RecordSimplification();
return true;
}
bool InstructionSimplifierVisitor::TryDeMorganNegationFactoring(HBinaryOperation* op) {
DCHECK(op->IsAnd() || op->IsOr()) << op->DebugName();
Primitive::Type type = op->GetType();
HInstruction* left = op->GetLeft();
HInstruction* right = op->GetRight();
// We can apply De Morgan's laws if both inputs are Not's and are only used
// by `op`.
if (((left->IsNot() && right->IsNot()) ||
(left->IsBooleanNot() && right->IsBooleanNot())) &&
left->HasOnlyOneNonEnvironmentUse() &&
right->HasOnlyOneNonEnvironmentUse()) {
// Replace code looking like
// NOT nota, a
// NOT notb, b
// AND dst, nota, notb (respectively OR)
// with
// OR or, a, b (respectively AND)
// NOT dest, or
HInstruction* src_left = left->InputAt(0);
HInstruction* src_right = right->InputAt(0);
uint32_t dex_pc = op->GetDexPc();
// Remove the negations on the inputs.
left->ReplaceWith(src_left);
right->ReplaceWith(src_right);
left->GetBlock()->RemoveInstruction(left);
right->GetBlock()->RemoveInstruction(right);
// Replace the `HAnd` or `HOr`.
HBinaryOperation* hbin;
if (op->IsAnd()) {
hbin = new (GetGraph()->GetArena()) HOr(type, src_left, src_right, dex_pc);
} else {
hbin = new (GetGraph()->GetArena()) HAnd(type, src_left, src_right, dex_pc);
}
HInstruction* hnot;
if (left->IsBooleanNot()) {
hnot = new (GetGraph()->GetArena()) HBooleanNot(hbin, dex_pc);
} else {
hnot = new (GetGraph()->GetArena()) HNot(type, hbin, dex_pc);
}
op->GetBlock()->InsertInstructionBefore(hbin, op);
op->GetBlock()->ReplaceAndRemoveInstructionWith(op, hnot);
RecordSimplification();
return true;
}
return false;
}
void InstructionSimplifierVisitor::VisitShift(HBinaryOperation* instruction) {
DCHECK(instruction->IsShl() || instruction->IsShr() || instruction->IsUShr());
HInstruction* shift_amount = instruction->GetRight();
HInstruction* value = instruction->GetLeft();
int64_t implicit_mask = (value->GetType() == Primitive::kPrimLong)
? kMaxLongShiftDistance
: kMaxIntShiftDistance;
if (shift_amount->IsConstant()) {
int64_t cst = Int64FromConstant(shift_amount->AsConstant());
if ((cst & implicit_mask) == 0) {
// Replace code looking like
// SHL dst, value, 0
// with
// value
instruction->ReplaceWith(value);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
}
// Shift operations implicitly mask the shift amount according to the type width. Get rid of
// unnecessary explicit masking operations on the shift amount.
// Replace code looking like
// AND masked_shift, shift, <superset of implicit mask>
// SHL dst, value, masked_shift
// with
// SHL dst, value, shift
if (shift_amount->IsAnd()) {
HAnd* and_insn = shift_amount->AsAnd();
HConstant* mask = and_insn->GetConstantRight();
if ((mask != nullptr) && ((Int64FromConstant(mask) & implicit_mask) == implicit_mask)) {
instruction->ReplaceInput(and_insn->GetLeastConstantLeft(), 1);
RecordSimplification();
}
}
}
static bool IsSubRegBitsMinusOther(HSub* sub, size_t reg_bits, HInstruction* other) {
return (sub->GetRight() == other &&
sub->GetLeft()->IsConstant() &&
(Int64FromConstant(sub->GetLeft()->AsConstant()) & (reg_bits - 1)) == 0);
}
bool InstructionSimplifierVisitor::ReplaceRotateWithRor(HBinaryOperation* op,
HUShr* ushr,
HShl* shl) {
DCHECK(op->IsAdd() || op->IsXor() || op->IsOr()) << op->DebugName();
HRor* ror = new (GetGraph()->GetArena()) HRor(ushr->GetType(), ushr->GetLeft(), ushr->GetRight());
op->GetBlock()->ReplaceAndRemoveInstructionWith(op, ror);
if (!ushr->HasUses()) {
ushr->GetBlock()->RemoveInstruction(ushr);
}
if (!ushr->GetRight()->HasUses()) {
ushr->GetRight()->GetBlock()->RemoveInstruction(ushr->GetRight());
}
if (!shl->HasUses()) {
shl->GetBlock()->RemoveInstruction(shl);
}
if (!shl->GetRight()->HasUses()) {
shl->GetRight()->GetBlock()->RemoveInstruction(shl->GetRight());
}
RecordSimplification();
return true;
}
// Try to replace a binary operation flanked by one UShr and one Shl with a bitfield rotation.
bool InstructionSimplifierVisitor::TryReplaceWithRotate(HBinaryOperation* op) {
DCHECK(op->IsAdd() || op->IsXor() || op->IsOr());
HInstruction* left = op->GetLeft();
HInstruction* right = op->GetRight();
// If we have an UShr and a Shl (in either order).
if ((left->IsUShr() && right->IsShl()) || (left->IsShl() && right->IsUShr())) {
HUShr* ushr = left->IsUShr() ? left->AsUShr() : right->AsUShr();
HShl* shl = left->IsShl() ? left->AsShl() : right->AsShl();
DCHECK(Primitive::IsIntOrLongType(ushr->GetType()));
if (ushr->GetType() == shl->GetType() &&
ushr->GetLeft() == shl->GetLeft()) {
if (ushr->GetRight()->IsConstant() && shl->GetRight()->IsConstant()) {
// Shift distances are both constant, try replacing with Ror if they
// add up to the register size.
return TryReplaceWithRotateConstantPattern(op, ushr, shl);
} else if (ushr->GetRight()->IsSub() || shl->GetRight()->IsSub()) {
// Shift distances are potentially of the form x and (reg_size - x).
return TryReplaceWithRotateRegisterSubPattern(op, ushr, shl);
} else if (ushr->GetRight()->IsNeg() || shl->GetRight()->IsNeg()) {
// Shift distances are potentially of the form d and -d.
return TryReplaceWithRotateRegisterNegPattern(op, ushr, shl);
}
}
}
return false;
}
// Try replacing code looking like (x >>> #rdist OP x << #ldist):
// UShr dst, x, #rdist
// Shl tmp, x, #ldist
// OP dst, dst, tmp
// or like (x >>> #rdist OP x << #-ldist):
// UShr dst, x, #rdist
// Shl tmp, x, #-ldist
// OP dst, dst, tmp
// with
// Ror dst, x, #rdist
bool InstructionSimplifierVisitor::TryReplaceWithRotateConstantPattern(HBinaryOperation* op,
HUShr* ushr,
HShl* shl) {
DCHECK(op->IsAdd() || op->IsXor() || op->IsOr());
size_t reg_bits = Primitive::ComponentSize(ushr->GetType()) * kBitsPerByte;
size_t rdist = Int64FromConstant(ushr->GetRight()->AsConstant());
size_t ldist = Int64FromConstant(shl->GetRight()->AsConstant());
if (((ldist + rdist) & (reg_bits - 1)) == 0) {
ReplaceRotateWithRor(op, ushr, shl);
return true;
}
return false;
}
// Replace code looking like (x >>> -d OP x << d):
// Neg neg, d
// UShr dst, x, neg
// Shl tmp, x, d
// OP dst, dst, tmp
// with
// Neg neg, d
// Ror dst, x, neg
// *** OR ***
// Replace code looking like (x >>> d OP x << -d):
// UShr dst, x, d
// Neg neg, d
// Shl tmp, x, neg
// OP dst, dst, tmp
// with
// Ror dst, x, d
bool InstructionSimplifierVisitor::TryReplaceWithRotateRegisterNegPattern(HBinaryOperation* op,
HUShr* ushr,
HShl* shl) {
DCHECK(op->IsAdd() || op->IsXor() || op->IsOr());
DCHECK(ushr->GetRight()->IsNeg() || shl->GetRight()->IsNeg());
bool neg_is_left = shl->GetRight()->IsNeg();
HNeg* neg = neg_is_left ? shl->GetRight()->AsNeg() : ushr->GetRight()->AsNeg();
// And the shift distance being negated is the distance being shifted the other way.
if (neg->InputAt(0) == (neg_is_left ? ushr->GetRight() : shl->GetRight())) {
ReplaceRotateWithRor(op, ushr, shl);
}
return false;
}
// Try replacing code looking like (x >>> d OP x << (#bits - d)):
// UShr dst, x, d
// Sub ld, #bits, d
// Shl tmp, x, ld
// OP dst, dst, tmp
// with
// Ror dst, x, d
// *** OR ***
// Replace code looking like (x >>> (#bits - d) OP x << d):
// Sub rd, #bits, d
// UShr dst, x, rd
// Shl tmp, x, d
// OP dst, dst, tmp
// with
// Neg neg, d
// Ror dst, x, neg
bool InstructionSimplifierVisitor::TryReplaceWithRotateRegisterSubPattern(HBinaryOperation* op,
HUShr* ushr,
HShl* shl) {
DCHECK(op->IsAdd() || op->IsXor() || op->IsOr());
DCHECK(ushr->GetRight()->IsSub() || shl->GetRight()->IsSub());
size_t reg_bits = Primitive::ComponentSize(ushr->GetType()) * kBitsPerByte;
HInstruction* shl_shift = shl->GetRight();
HInstruction* ushr_shift = ushr->GetRight();
if ((shl_shift->IsSub() && IsSubRegBitsMinusOther(shl_shift->AsSub(), reg_bits, ushr_shift)) ||
(ushr_shift->IsSub() && IsSubRegBitsMinusOther(ushr_shift->AsSub(), reg_bits, shl_shift))) {
return ReplaceRotateWithRor(op, ushr, shl);
}
return false;
}
void InstructionSimplifierVisitor::VisitNullCheck(HNullCheck* null_check) {
HInstruction* obj = null_check->InputAt(0);
if (!obj->CanBeNull()) {
null_check->ReplaceWith(obj);
null_check->GetBlock()->RemoveInstruction(null_check);
if (stats_ != nullptr) {
stats_->RecordStat(MethodCompilationStat::kRemovedNullCheck);
}
}
}
bool InstructionSimplifierVisitor::CanEnsureNotNullAt(HInstruction* input, HInstruction* at) const {
if (!input->CanBeNull()) {
return true;
}
for (const HUseListNode<HInstruction*>& use : input->GetUses()) {
HInstruction* user = use.GetUser();
if (user->IsNullCheck() && user->StrictlyDominates(at)) {
return true;
}
}
return false;
}
// Returns whether doing a type test between the class of `object` against `klass` has
// a statically known outcome. The result of the test is stored in `outcome`.
static bool TypeCheckHasKnownOutcome(HLoadClass* klass, HInstruction* object, bool* outcome) {
DCHECK(!object->IsNullConstant()) << "Null constants should be special cased";
ReferenceTypeInfo obj_rti = object->GetReferenceTypeInfo();
ScopedObjectAccess soa(Thread::Current());
if (!obj_rti.IsValid()) {
// We run the simplifier before the reference type propagation so type info might not be
// available.
return false;
}
ReferenceTypeInfo class_rti = klass->GetLoadedClassRTI();
if (!class_rti.IsValid()) {
// Happens when the loaded class is unresolved.
return false;
}
DCHECK(class_rti.IsExact());
if (class_rti.IsSupertypeOf(obj_rti)) {
*outcome = true;
return true;
} else if (obj_rti.IsExact()) {
// The test failed at compile time so will also fail at runtime.
*outcome = false;
return true;
} else if (!class_rti.IsInterface()
&& !obj_rti.IsInterface()
&& !obj_rti.IsSupertypeOf(class_rti)) {
// Different type hierarchy. The test will fail.
*outcome = false;
return true;
}
return false;
}
void InstructionSimplifierVisitor::VisitCheckCast(HCheckCast* check_cast) {
HInstruction* object = check_cast->InputAt(0);
HLoadClass* load_class = check_cast->InputAt(1)->AsLoadClass();
if (load_class->NeedsAccessCheck()) {
// If we need to perform an access check we cannot remove the instruction.
return;
}
if (CanEnsureNotNullAt(object, check_cast)) {
check_cast->ClearMustDoNullCheck();
}
if (object->IsNullConstant()) {
check_cast->GetBlock()->RemoveInstruction(check_cast);
MaybeRecordStat(MethodCompilationStat::kRemovedCheckedCast);
return;
}
// Note: The `outcome` is initialized to please valgrind - the compiler can reorder
// the return value check with the `outcome` check, b/27651442 .
bool outcome = false;
if (TypeCheckHasKnownOutcome(load_class, object, &outcome)) {
if (outcome) {
check_cast->GetBlock()->RemoveInstruction(check_cast);
MaybeRecordStat(MethodCompilationStat::kRemovedCheckedCast);
if (!load_class->HasUses()) {
// We cannot rely on DCE to remove the class because the `HLoadClass` thinks it can throw.
// However, here we know that it cannot because the checkcast was successfull, hence
// the class was already loaded.
load_class->GetBlock()->RemoveInstruction(load_class);
}
} else {
// Don't do anything for exceptional cases for now. Ideally we should remove
// all instructions and blocks this instruction dominates.
}
}
}
void InstructionSimplifierVisitor::VisitInstanceOf(HInstanceOf* instruction) {
HInstruction* object = instruction->InputAt(0);
HLoadClass* load_class = instruction->InputAt(1)->AsLoadClass();
if (load_class->NeedsAccessCheck()) {
// If we need to perform an access check we cannot remove the instruction.
return;
}
bool can_be_null = true;
if (CanEnsureNotNullAt(object, instruction)) {
can_be_null = false;
instruction->ClearMustDoNullCheck();
}
HGraph* graph = GetGraph();
if (object->IsNullConstant()) {
MaybeRecordStat(kRemovedInstanceOf);
instruction->ReplaceWith(graph->GetIntConstant(0));
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
// Note: The `outcome` is initialized to please valgrind - the compiler can reorder
// the return value check with the `outcome` check, b/27651442 .
bool outcome = false;
if (TypeCheckHasKnownOutcome(load_class, object, &outcome)) {
MaybeRecordStat(kRemovedInstanceOf);
if (outcome && can_be_null) {
// Type test will succeed, we just need a null test.
HNotEqual* test = new (graph->GetArena()) HNotEqual(graph->GetNullConstant(), object);
instruction->GetBlock()->InsertInstructionBefore(test, instruction);
instruction->ReplaceWith(test);
} else {
// We've statically determined the result of the instanceof.
instruction->ReplaceWith(graph->GetIntConstant(outcome));
}
RecordSimplification();
instruction->GetBlock()->RemoveInstruction(instruction);
if (outcome && !load_class->HasUses()) {
// We cannot rely on DCE to remove the class because the `HLoadClass` thinks it can throw.
// However, here we know that it cannot because the instanceof check was successfull, hence
// the class was already loaded.
load_class->GetBlock()->RemoveInstruction(load_class);
}
}
}
void InstructionSimplifierVisitor::VisitInstanceFieldSet(HInstanceFieldSet* instruction) {
if ((instruction->GetValue()->GetType() == Primitive::kPrimNot)
&& CanEnsureNotNullAt(instruction->GetValue(), instruction)) {
instruction->ClearValueCanBeNull();
}
}
void InstructionSimplifierVisitor::VisitStaticFieldSet(HStaticFieldSet* instruction) {
if ((instruction->GetValue()->GetType() == Primitive::kPrimNot)
&& CanEnsureNotNullAt(instruction->GetValue(), instruction)) {
instruction->ClearValueCanBeNull();
}
}
static HCondition* GetOppositeConditionSwapOps(ArenaAllocator* arena, HInstruction* cond) {
HInstruction *lhs = cond->InputAt(0);
HInstruction *rhs = cond->InputAt(1);
switch (cond->GetKind()) {
case HInstruction::kEqual:
return new (arena) HEqual(rhs, lhs);
case HInstruction::kNotEqual:
return new (arena) HNotEqual(rhs, lhs);
case HInstruction::kLessThan:
return new (arena) HGreaterThan(rhs, lhs);
case HInstruction::kLessThanOrEqual:
return new (arena) HGreaterThanOrEqual(rhs, lhs);
case HInstruction::kGreaterThan:
return new (arena) HLessThan(rhs, lhs);
case HInstruction::kGreaterThanOrEqual:
return new (arena) HLessThanOrEqual(rhs, lhs);
case HInstruction::kBelow:
return new (arena) HAbove(rhs, lhs);
case HInstruction::kBelowOrEqual:
return new (arena) HAboveOrEqual(rhs, lhs);
case HInstruction::kAbove:
return new (arena) HBelow(rhs, lhs);
case HInstruction::kAboveOrEqual:
return new (arena) HBelowOrEqual(rhs, lhs);
default:
LOG(FATAL) << "Unknown ConditionType " << cond->GetKind();
}
return nullptr;
}
static bool CmpHasBoolType(HInstruction* input, HInstruction* cmp) {
if (input->GetType() == Primitive::kPrimBoolean) {
return true; // input has direct boolean type
} else if (cmp->GetUses().HasExactlyOneElement()) {
// Comparison also has boolean type if both its input and the instruction
// itself feed into the same phi node.
HInstruction* user = cmp->GetUses().front().GetUser();
return user->IsPhi() && user->HasInput(input) && user->HasInput(cmp);
}
return false;
}
void InstructionSimplifierVisitor::VisitEqual(HEqual* equal) {
HInstruction* input_const = equal->GetConstantRight();
if (input_const != nullptr) {
HInstruction* input_value = equal->GetLeastConstantLeft();
if (CmpHasBoolType(input_value, equal) && input_const->IsIntConstant()) {
HBasicBlock* block = equal->GetBlock();
// We are comparing the boolean to a constant which is of type int and can
// be any constant.
if (input_const->AsIntConstant()->IsTrue()) {
// Replace (bool_value == true) with bool_value
equal->ReplaceWith(input_value);
block->RemoveInstruction(equal);
RecordSimplification();
} else if (input_const->AsIntConstant()->IsFalse()) {
// Replace (bool_value == false) with !bool_value
equal->ReplaceWith(GetGraph()->InsertOppositeCondition(input_value, equal));
block->RemoveInstruction(equal);
RecordSimplification();
} else {
// Replace (bool_value == integer_not_zero_nor_one_constant) with false
equal->ReplaceWith(GetGraph()->GetIntConstant(0));
block->RemoveInstruction(equal);
RecordSimplification();
}
} else {
VisitCondition(equal);
}
} else {
VisitCondition(equal);
}
}
void InstructionSimplifierVisitor::VisitNotEqual(HNotEqual* not_equal) {
HInstruction* input_const = not_equal->GetConstantRight();
if (input_const != nullptr) {
HInstruction* input_value = not_equal->GetLeastConstantLeft();
if (CmpHasBoolType(input_value, not_equal) && input_const->IsIntConstant()) {
HBasicBlock* block = not_equal->GetBlock();
// We are comparing the boolean to a constant which is of type int and can
// be any constant.
if (input_const->AsIntConstant()->IsTrue()) {
// Replace (bool_value != true) with !bool_value
not_equal->ReplaceWith(GetGraph()->InsertOppositeCondition(input_value, not_equal));
block->RemoveInstruction(not_equal);
RecordSimplification();
} else if (input_const->AsIntConstant()->IsFalse()) {
// Replace (bool_value != false) with bool_value
not_equal->ReplaceWith(input_value);
block->RemoveInstruction(not_equal);
RecordSimplification();
} else {
// Replace (bool_value != integer_not_zero_nor_one_constant) with true
not_equal->ReplaceWith(GetGraph()->GetIntConstant(1));
block->RemoveInstruction(not_equal);
RecordSimplification();
}
} else {
VisitCondition(not_equal);
}
} else {
VisitCondition(not_equal);
}
}
void InstructionSimplifierVisitor::VisitBooleanNot(HBooleanNot* bool_not) {
HInstruction* input = bool_not->InputAt(0);
HInstruction* replace_with = nullptr;
if (input->IsIntConstant()) {
// Replace !(true/false) with false/true.
if (input->AsIntConstant()->IsTrue()) {
replace_with = GetGraph()->GetIntConstant(0);
} else {
DCHECK(input->AsIntConstant()->IsFalse()) << input->AsIntConstant()->GetValue();
replace_with = GetGraph()->GetIntConstant(1);
}
} else if (input->IsBooleanNot()) {
// Replace (!(!bool_value)) with bool_value.
replace_with = input->InputAt(0);
} else if (input->IsCondition() &&
// Don't change FP compares. The definition of compares involving
// NaNs forces the compares to be done as written by the user.
!Primitive::IsFloatingPointType(input->InputAt(0)->GetType())) {
// Replace condition with its opposite.
replace_with = GetGraph()->InsertOppositeCondition(input->AsCondition(), bool_not);
}
if (replace_with != nullptr) {
bool_not->ReplaceWith(replace_with);
bool_not->GetBlock()->RemoveInstruction(bool_not);
RecordSimplification();
}
}
void InstructionSimplifierVisitor::VisitSelect(HSelect* select) {
HInstruction* replace_with = nullptr;
HInstruction* condition = select->GetCondition();
HInstruction* true_value = select->GetTrueValue();
HInstruction* false_value = select->GetFalseValue();
if (condition->IsBooleanNot()) {
// Change ((!cond) ? x : y) to (cond ? y : x).
condition = condition->InputAt(0);
std::swap(true_value, false_value);
select->ReplaceInput(false_value, 0);
select->ReplaceInput(true_value, 1);
select->ReplaceInput(condition, 2);
RecordSimplification();
}
if (true_value == false_value) {
// Replace (cond ? x : x) with (x).
replace_with = true_value;
} else if (condition->IsIntConstant()) {
if (condition->AsIntConstant()->IsTrue()) {
// Replace (true ? x : y) with (x).
replace_with = true_value;
} else {
// Replace (false ? x : y) with (y).
DCHECK(condition->AsIntConstant()->IsFalse()) << condition->AsIntConstant()->GetValue();
replace_with = false_value;
}
} else if (true_value->IsIntConstant() && false_value->IsIntConstant()) {
if (true_value->AsIntConstant()->IsTrue() && false_value->AsIntConstant()->IsFalse()) {
// Replace (cond ? true : false) with (cond).
replace_with = condition;
} else if (true_value->AsIntConstant()->IsFalse() && false_value->AsIntConstant()->IsTrue()) {
// Replace (cond ? false : true) with (!cond).
replace_with = GetGraph()->InsertOppositeCondition(condition, select);
}
}
if (replace_with != nullptr) {
select->ReplaceWith(replace_with);
select->GetBlock()->RemoveInstruction(select);
RecordSimplification();
}
}
void InstructionSimplifierVisitor::VisitIf(HIf* instruction) {
HInstruction* condition = instruction->InputAt(0);
if (condition->IsBooleanNot()) {
// Swap successors if input is negated.
instruction->ReplaceInput(condition->InputAt(0), 0);
instruction->GetBlock()->SwapSuccessors();
RecordSimplification();
}
}
void InstructionSimplifierVisitor::VisitArrayLength(HArrayLength* instruction) {
HInstruction* input = instruction->InputAt(0);
// If the array is a NewArray with constant size, replace the array length
// with the constant instruction. This helps the bounds check elimination phase.
if (input->IsNewArray()) {
input = input->AsNewArray()->GetLength();
if (input->IsIntConstant()) {
instruction->ReplaceWith(input);
}
}
}
void InstructionSimplifierVisitor::VisitArraySet(HArraySet* instruction) {
HInstruction* value = instruction->GetValue();
if (value->GetType() != Primitive::kPrimNot) return;
if (CanEnsureNotNullAt(value, instruction)) {
instruction->ClearValueCanBeNull();
}
if (value->IsArrayGet()) {
if (value->AsArrayGet()->GetArray() == instruction->GetArray()) {
// If the code is just swapping elements in the array, no need for a type check.
instruction->ClearNeedsTypeCheck();
return;
}
}
if (value->IsNullConstant()) {
instruction->ClearNeedsTypeCheck();
return;
}
ScopedObjectAccess soa(Thread::Current());
ReferenceTypeInfo array_rti = instruction->GetArray()->GetReferenceTypeInfo();
ReferenceTypeInfo value_rti = value->GetReferenceTypeInfo();
if (!array_rti.IsValid()) {
return;
}
if (value_rti.IsValid() && array_rti.CanArrayHold(value_rti)) {
instruction->ClearNeedsTypeCheck();
return;
}
if (array_rti.IsObjectArray()) {
if (array_rti.IsExact()) {
instruction->ClearNeedsTypeCheck();
return;
}
instruction->SetStaticTypeOfArrayIsObjectArray();
}
}
static bool IsTypeConversionImplicit(Primitive::Type input_type, Primitive::Type result_type) {
// Invariant: We should never generate a conversion to a Boolean value.
DCHECK_NE(Primitive::kPrimBoolean, result_type);
// Besides conversion to the same type, widening integral conversions are implicit,
// excluding conversions to long and the byte->char conversion where we need to
// clear the high 16 bits of the 32-bit sign-extended representation of byte.
return result_type == input_type ||
(result_type == Primitive::kPrimInt && (input_type == Primitive::kPrimBoolean ||
input_type == Primitive::kPrimByte ||
input_type == Primitive::kPrimShort ||
input_type == Primitive::kPrimChar)) ||
(result_type == Primitive::kPrimChar && input_type == Primitive::kPrimBoolean) ||
(result_type == Primitive::kPrimShort && (input_type == Primitive::kPrimBoolean ||
input_type == Primitive::kPrimByte)) ||
(result_type == Primitive::kPrimByte && input_type == Primitive::kPrimBoolean);
}
static bool IsTypeConversionLossless(Primitive::Type input_type, Primitive::Type result_type) {
// The conversion to a larger type is loss-less with the exception of two cases,
// - conversion to char, the only unsigned type, where we may lose some bits, and
// - conversion from float to long, the only FP to integral conversion with smaller FP type.
// For integral to FP conversions this holds because the FP mantissa is large enough.
DCHECK_NE(input_type, result_type);
return Primitive::ComponentSize(result_type) > Primitive::ComponentSize(input_type) &&
result_type != Primitive::kPrimChar &&
!(result_type == Primitive::kPrimLong && input_type == Primitive::kPrimFloat);
}
void InstructionSimplifierVisitor::VisitTypeConversion(HTypeConversion* instruction) {
HInstruction* input = instruction->GetInput();
Primitive::Type input_type = input->GetType();
Primitive::Type result_type = instruction->GetResultType();
if (IsTypeConversionImplicit(input_type, result_type)) {
// Remove the implicit conversion; this includes conversion to the same type.
instruction->ReplaceWith(input);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
if (input->IsTypeConversion()) {
HTypeConversion* input_conversion = input->AsTypeConversion();
HInstruction* original_input = input_conversion->GetInput();
Primitive::Type original_type = original_input->GetType();
// When the first conversion is lossless, a direct conversion from the original type
// to the final type yields the same result, even for a lossy second conversion, for
// example float->double->int or int->double->float.
bool is_first_conversion_lossless = IsTypeConversionLossless(original_type, input_type);
// For integral conversions, see if the first conversion loses only bits that the second
// doesn't need, i.e. the final type is no wider than the intermediate. If so, direct
// conversion yields the same result, for example long->int->short or int->char->short.
bool integral_conversions_with_non_widening_second =
Primitive::IsIntegralType(input_type) &&
Primitive::IsIntegralType(original_type) &&
Primitive::IsIntegralType(result_type) &&
Primitive::ComponentSize(result_type) <= Primitive::ComponentSize(input_type);
if (is_first_conversion_lossless || integral_conversions_with_non_widening_second) {
// If the merged conversion is implicit, do the simplification unconditionally.
if (IsTypeConversionImplicit(original_type, result_type)) {
instruction->ReplaceWith(original_input);
instruction->GetBlock()->RemoveInstruction(instruction);
if (!input_conversion->HasUses()) {
// Don't wait for DCE.
input_conversion->GetBlock()->RemoveInstruction(input_conversion);
}
RecordSimplification();
return;
}
// Otherwise simplify only if the first conversion has no other use.
if (input_conversion->HasOnlyOneNonEnvironmentUse()) {
input_conversion->ReplaceWith(original_input);
input_conversion->GetBlock()->RemoveInstruction(input_conversion);
RecordSimplification();
return;
}
}
} else if (input->IsAnd() && Primitive::IsIntegralType(result_type)) {
DCHECK(Primitive::IsIntegralType(input_type));
HAnd* input_and = input->AsAnd();
HConstant* constant = input_and->GetConstantRight();
if (constant != nullptr) {
int64_t value = Int64FromConstant(constant);
DCHECK_NE(value, -1); // "& -1" would have been optimized away in VisitAnd().
size_t trailing_ones = CTZ(~static_cast<uint64_t>(value));
if (trailing_ones >= kBitsPerByte * Primitive::ComponentSize(result_type)) {
// The `HAnd` is useless, for example in `(byte) (x & 0xff)`, get rid of it.
HInstruction* original_input = input_and->GetLeastConstantLeft();
if (IsTypeConversionImplicit(original_input->GetType(), result_type)) {
instruction->ReplaceWith(original_input);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
} else if (input->HasOnlyOneNonEnvironmentUse()) {
input_and->ReplaceWith(original_input);
input_and->GetBlock()->RemoveInstruction(input_and);
RecordSimplification();
return;
}
}
}
}
}
void InstructionSimplifierVisitor::VisitAdd(HAdd* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
bool integral_type = Primitive::IsIntegralType(instruction->GetType());
if ((input_cst != nullptr) && input_cst->IsArithmeticZero()) {
// Replace code looking like
// ADD dst, src, 0
// with
// src
// Note that we cannot optimize `x + 0.0` to `x` for floating-point. When
// `x` is `-0.0`, the former expression yields `0.0`, while the later
// yields `-0.0`.
if (integral_type) {
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
}
HInstruction* left = instruction->GetLeft();
HInstruction* right = instruction->GetRight();
bool left_is_neg = left->IsNeg();
bool right_is_neg = right->IsNeg();
if (left_is_neg && right_is_neg) {
if (TryMoveNegOnInputsAfterBinop(instruction)) {
return;
}
}
HNeg* neg = left_is_neg ? left->AsNeg() : right->AsNeg();
if ((left_is_neg ^ right_is_neg) && neg->HasOnlyOneNonEnvironmentUse()) {
// Replace code looking like
// NEG tmp, b
// ADD dst, a, tmp
// with
// SUB dst, a, b
// We do not perform the optimization if the input negation has environment
// uses or multiple non-environment uses as it could lead to worse code. In
// particular, we do not want the live range of `b` to be extended if we are
// not sure the initial 'NEG' instruction can be removed.
HInstruction* other = left_is_neg ? right : left;
HSub* sub = new(GetGraph()->GetArena()) HSub(instruction->GetType(), other, neg->GetInput());
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, sub);
RecordSimplification();
neg->GetBlock()->RemoveInstruction(neg);
return;
}
if (TryReplaceWithRotate(instruction)) {
return;
}
// TryHandleAssociativeAndCommutativeOperation() does not remove its input,
// so no need to return.
TryHandleAssociativeAndCommutativeOperation(instruction);
if ((left->IsSub() || right->IsSub()) &&
TrySubtractionChainSimplification(instruction)) {
return;
}
if (integral_type) {
// Replace code patterns looking like
// SUB dst1, x, y SUB dst1, x, y
// ADD dst2, dst1, y ADD dst2, y, dst1
// with
// SUB dst1, x, y
// ADD instruction is not needed in this case, we may use
// one of inputs of SUB instead.
if (left->IsSub() && left->InputAt(1) == right) {
instruction->ReplaceWith(left->InputAt(0));
RecordSimplification();
instruction->GetBlock()->RemoveInstruction(instruction);
return;
} else if (right->IsSub() && right->InputAt(1) == left) {
instruction->ReplaceWith(right->InputAt(0));
RecordSimplification();
instruction->GetBlock()->RemoveInstruction(instruction);
return;
}
}
}
void InstructionSimplifierVisitor::VisitAnd(HAnd* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
if (input_cst != nullptr) {
int64_t value = Int64FromConstant(input_cst);
if (value == -1) {
// Replace code looking like
// AND dst, src, 0xFFF...FF
// with
// src
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
// Eliminate And from UShr+And if the And-mask contains all the bits that
// can be non-zero after UShr. Transform Shr+And to UShr if the And-mask
// precisely clears the shifted-in sign bits.
if ((input_other->IsUShr() || input_other->IsShr()) && input_other->InputAt(1)->IsConstant()) {
size_t reg_bits = (instruction->GetResultType() == Primitive::kPrimLong) ? 64 : 32;
size_t shift = Int64FromConstant(input_other->InputAt(1)->AsConstant()) & (reg_bits - 1);
size_t num_tail_bits_set = CTZ(value + 1);
if ((num_tail_bits_set >= reg_bits - shift) && input_other->IsUShr()) {
// This AND clears only bits known to be clear, for example "(x >>> 24) & 0xff".
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
} else if ((num_tail_bits_set == reg_bits - shift) && IsPowerOfTwo(value + 1) &&
input_other->HasOnlyOneNonEnvironmentUse()) {
DCHECK(input_other->IsShr()); // For UShr, we would have taken the branch above.
// Replace SHR+AND with USHR, for example "(x >> 24) & 0xff" -> "x >>> 24".
HUShr* ushr = new (GetGraph()->GetArena()) HUShr(instruction->GetType(),
input_other->InputAt(0),
input_other->InputAt(1),
input_other->GetDexPc());
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, ushr);
input_other->GetBlock()->RemoveInstruction(input_other);
RecordSimplification();
return;
}
}
}
// We assume that GVN has run before, so we only perform a pointer comparison.
// If for some reason the values are equal but the pointers are different, we
// are still correct and only miss an optimization opportunity.
if (instruction->GetLeft() == instruction->GetRight()) {
// Replace code looking like
// AND dst, src, src
// with
// src
instruction->ReplaceWith(instruction->GetLeft());
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
if (TryDeMorganNegationFactoring(instruction)) {
return;
}
// TryHandleAssociativeAndCommutativeOperation() does not remove its input,
// so no need to return.
TryHandleAssociativeAndCommutativeOperation(instruction);
}
void InstructionSimplifierVisitor::VisitGreaterThan(HGreaterThan* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitGreaterThanOrEqual(HGreaterThanOrEqual* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitLessThan(HLessThan* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitLessThanOrEqual(HLessThanOrEqual* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitBelow(HBelow* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitBelowOrEqual(HBelowOrEqual* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitAbove(HAbove* condition) {
VisitCondition(condition);
}
void InstructionSimplifierVisitor::VisitAboveOrEqual(HAboveOrEqual* condition) {
VisitCondition(condition);
}
// Recognize the following pattern:
// obj.getClass() ==/!= Foo.class
// And replace it with a constant value if the type of `obj` is statically known.
static bool RecognizeAndSimplifyClassCheck(HCondition* condition) {
HInstruction* input_one = condition->InputAt(0);
HInstruction* input_two = condition->InputAt(1);
HLoadClass* load_class = input_one->IsLoadClass()
? input_one->AsLoadClass()
: input_two->AsLoadClass();
if (load_class == nullptr) {
return false;
}
ReferenceTypeInfo class_rti = load_class->GetLoadedClassRTI();
if (!class_rti.IsValid()) {
// Unresolved class.
return false;
}
HInstanceFieldGet* field_get = (load_class == input_one)
? input_two->AsInstanceFieldGet()
: input_one->AsInstanceFieldGet();
if (field_get == nullptr) {
return false;
}
HInstruction* receiver = field_get->InputAt(0);
ReferenceTypeInfo receiver_type = receiver->GetReferenceTypeInfo();
if (!receiver_type.IsExact()) {
return false;
}
{
ScopedObjectAccess soa(Thread::Current());
ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
ArtField* field = class_linker->GetClassRoot(ClassLinker::kJavaLangObject)->GetInstanceField(0);
DCHECK_EQ(std::string(field->GetName()), "shadow$_klass_");
if (field_get->GetFieldInfo().GetField() != field) {
return false;
}
// We can replace the compare.
int value = 0;
if (receiver_type.IsEqual(class_rti)) {
value = condition->IsEqual() ? 1 : 0;
} else {
value = condition->IsNotEqual() ? 1 : 0;
}
condition->ReplaceWith(condition->GetBlock()->GetGraph()->GetIntConstant(value));
return true;
}
}
void InstructionSimplifierVisitor::VisitCondition(HCondition* condition) {
if (condition->IsEqual() || condition->IsNotEqual()) {
if (RecognizeAndSimplifyClassCheck(condition)) {
return;
}
}
// Reverse condition if left is constant. Our code generators prefer constant
// on the right hand side.
if (condition->GetLeft()->IsConstant() && !condition->GetRight()->IsConstant()) {
HBasicBlock* block = condition->GetBlock();
HCondition* replacement = GetOppositeConditionSwapOps(block->GetGraph()->GetArena(), condition);
// If it is a fp we must set the opposite bias.
if (replacement != nullptr) {
if (condition->IsLtBias()) {
replacement->SetBias(ComparisonBias::kGtBias);
} else if (condition->IsGtBias()) {
replacement->SetBias(ComparisonBias::kLtBias);
}
block->ReplaceAndRemoveInstructionWith(condition, replacement);
RecordSimplification();
condition = replacement;
}
}
HInstruction* left = condition->GetLeft();
HInstruction* right = condition->GetRight();
// Try to fold an HCompare into this HCondition.
// We can only replace an HCondition which compares a Compare to 0.
// Both 'dx' and 'jack' generate a compare to 0 when compiling a
// condition with a long, float or double comparison as input.
if (!left->IsCompare() || !right->IsConstant() || right->AsIntConstant()->GetValue() != 0) {
// Conversion is not possible.
return;
}
// Is the Compare only used for this purpose?
if (!left->GetUses().HasExactlyOneElement()) {
// Someone else also wants the result of the compare.
return;
}
if (!left->GetEnvUses().empty()) {
// There is a reference to the compare result in an environment. Do we really need it?
if (GetGraph()->IsDebuggable()) {
return;
}
// We have to ensure that there are no deopt points in the sequence.
if (left->HasAnyEnvironmentUseBefore(condition)) {
return;
}
}
// Clean up any environment uses from the HCompare, if any.
left->RemoveEnvironmentUsers();
// We have decided to fold the HCompare into the HCondition. Transfer the information.
condition->SetBias(left->AsCompare()->GetBias());
// Replace the operands of the HCondition.
condition->ReplaceInput(left->InputAt(0), 0);
condition->ReplaceInput(left->InputAt(1), 1);
// Remove the HCompare.
left->GetBlock()->RemoveInstruction(left);
RecordSimplification();
}
// Return whether x / divisor == x * (1.0f / divisor), for every float x.
static constexpr bool CanDivideByReciprocalMultiplyFloat(int32_t divisor) {
// True, if the most significant bits of divisor are 0.
return ((divisor & 0x7fffff) == 0);
}
// Return whether x / divisor == x * (1.0 / divisor), for every double x.
static constexpr bool CanDivideByReciprocalMultiplyDouble(int64_t divisor) {
// True, if the most significant bits of divisor are 0.
return ((divisor & ((UINT64_C(1) << 52) - 1)) == 0);
}
void InstructionSimplifierVisitor::VisitDiv(HDiv* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
Primitive::Type type = instruction->GetType();
if ((input_cst != nullptr) && input_cst->IsOne()) {
// Replace code looking like
// DIV dst, src, 1
// with
// src
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
if ((input_cst != nullptr) && input_cst->IsMinusOne()) {
// Replace code looking like
// DIV dst, src, -1
// with
// NEG dst, src
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(
instruction, new (GetGraph()->GetArena()) HNeg(type, input_other));
RecordSimplification();
return;
}
if ((input_cst != nullptr) && Primitive::IsFloatingPointType(type)) {
// Try replacing code looking like
// DIV dst, src, constant
// with
// MUL dst, src, 1 / constant
HConstant* reciprocal = nullptr;
if (type == Primitive::Primitive::kPrimDouble) {
double value = input_cst->AsDoubleConstant()->GetValue();
if (CanDivideByReciprocalMultiplyDouble(bit_cast<int64_t, double>(value))) {
reciprocal = GetGraph()->GetDoubleConstant(1.0 / value);
}
} else {
DCHECK_EQ(type, Primitive::kPrimFloat);
float value = input_cst->AsFloatConstant()->GetValue();
if (CanDivideByReciprocalMultiplyFloat(bit_cast<int32_t, float>(value))) {
reciprocal = GetGraph()->GetFloatConstant(1.0f / value);
}
}
if (reciprocal != nullptr) {
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(
instruction, new (GetGraph()->GetArena()) HMul(type, input_other, reciprocal));
RecordSimplification();
return;
}
}
}
void InstructionSimplifierVisitor::VisitMul(HMul* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
Primitive::Type type = instruction->GetType();
HBasicBlock* block = instruction->GetBlock();
ArenaAllocator* allocator = GetGraph()->GetArena();
if (input_cst == nullptr) {
return;
}
if (input_cst->IsOne()) {
// Replace code looking like
// MUL dst, src, 1
// with
// src
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
if (input_cst->IsMinusOne() &&
(Primitive::IsFloatingPointType(type) || Primitive::IsIntOrLongType(type))) {
// Replace code looking like
// MUL dst, src, -1
// with
// NEG dst, src
HNeg* neg = new (allocator) HNeg(type, input_other);
block->ReplaceAndRemoveInstructionWith(instruction, neg);
RecordSimplification();
return;
}
if (Primitive::IsFloatingPointType(type) &&
((input_cst->IsFloatConstant() && input_cst->AsFloatConstant()->GetValue() == 2.0f) ||
(input_cst->IsDoubleConstant() && input_cst->AsDoubleConstant()->GetValue() == 2.0))) {
// Replace code looking like
// FP_MUL dst, src, 2.0
// with
// FP_ADD dst, src, src
// The 'int' and 'long' cases are handled below.
block->ReplaceAndRemoveInstructionWith(instruction,
new (allocator) HAdd(type, input_other, input_other));
RecordSimplification();
return;
}
if (Primitive::IsIntOrLongType(type)) {
int64_t factor = Int64FromConstant(input_cst);
// Even though constant propagation also takes care of the zero case, other
// optimizations can lead to having a zero multiplication.
if (factor == 0) {
// Replace code looking like
// MUL dst, src, 0
// with
// 0
instruction->ReplaceWith(input_cst);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
} else if (IsPowerOfTwo(factor)) {
// Replace code looking like
// MUL dst, src, pow_of_2
// with
// SHL dst, src, log2(pow_of_2)
HIntConstant* shift = GetGraph()->GetIntConstant(WhichPowerOf2(factor));
HShl* shl = new (allocator) HShl(type, input_other, shift);
block->ReplaceAndRemoveInstructionWith(instruction, shl);
RecordSimplification();
return;
} else if (IsPowerOfTwo(factor - 1)) {
// Transform code looking like
// MUL dst, src, (2^n + 1)
// into
// SHL tmp, src, n
// ADD dst, src, tmp
HShl* shl = new (allocator) HShl(type,
input_other,
GetGraph()->GetIntConstant(WhichPowerOf2(factor - 1)));
HAdd* add = new (allocator) HAdd(type, input_other, shl);
block->InsertInstructionBefore(shl, instruction);
block->ReplaceAndRemoveInstructionWith(instruction, add);
RecordSimplification();
return;
} else if (IsPowerOfTwo(factor + 1)) {
// Transform code looking like
// MUL dst, src, (2^n - 1)
// into
// SHL tmp, src, n
// SUB dst, tmp, src
HShl* shl = new (allocator) HShl(type,
input_other,
GetGraph()->GetIntConstant(WhichPowerOf2(factor + 1)));
HSub* sub = new (allocator) HSub(type, shl, input_other);
block->InsertInstructionBefore(shl, instruction);
block->ReplaceAndRemoveInstructionWith(instruction, sub);
RecordSimplification();
return;
}
}
// TryHandleAssociativeAndCommutativeOperation() does not remove its input,
// so no need to return.
TryHandleAssociativeAndCommutativeOperation(instruction);
}
void InstructionSimplifierVisitor::VisitNeg(HNeg* instruction) {
HInstruction* input = instruction->GetInput();
if (input->IsNeg()) {
// Replace code looking like
// NEG tmp, src
// NEG dst, tmp
// with
// src
HNeg* previous_neg = input->AsNeg();
instruction->ReplaceWith(previous_neg->GetInput());
instruction->GetBlock()->RemoveInstruction(instruction);
// We perform the optimization even if the input negation has environment
// uses since it allows removing the current instruction. But we only delete
// the input negation only if it is does not have any uses left.
if (!previous_neg->HasUses()) {
previous_neg->GetBlock()->RemoveInstruction(previous_neg);
}
RecordSimplification();
return;
}
if (input->IsSub() && input->HasOnlyOneNonEnvironmentUse() &&
!Primitive::IsFloatingPointType(input->GetType())) {
// Replace code looking like
// SUB tmp, a, b
// NEG dst, tmp
// with
// SUB dst, b, a
// We do not perform the optimization if the input subtraction has
// environment uses or multiple non-environment uses as it could lead to
// worse code. In particular, we do not want the live ranges of `a` and `b`
// to be extended if we are not sure the initial 'SUB' instruction can be
// removed.
// We do not perform optimization for fp because we could lose the sign of zero.
HSub* sub = input->AsSub();
HSub* new_sub =
new (GetGraph()->GetArena()) HSub(instruction->GetType(), sub->GetRight(), sub->GetLeft());
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, new_sub);
if (!sub->HasUses()) {
sub->GetBlock()->RemoveInstruction(sub);
}
RecordSimplification();
}
}
void InstructionSimplifierVisitor::VisitNot(HNot* instruction) {
HInstruction* input = instruction->GetInput();
if (input->IsNot()) {
// Replace code looking like
// NOT tmp, src
// NOT dst, tmp
// with
// src
// We perform the optimization even if the input negation has environment
// uses since it allows removing the current instruction. But we only delete
// the input negation only if it is does not have any uses left.
HNot* previous_not = input->AsNot();
instruction->ReplaceWith(previous_not->GetInput());
instruction->GetBlock()->RemoveInstruction(instruction);
if (!previous_not->HasUses()) {
previous_not->GetBlock()->RemoveInstruction(previous_not);
}
RecordSimplification();
}
}
void InstructionSimplifierVisitor::VisitOr(HOr* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
if ((input_cst != nullptr) && input_cst->IsZeroBitPattern()) {
// Replace code looking like
// OR dst, src, 0
// with
// src
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
// We assume that GVN has run before, so we only perform a pointer comparison.
// If for some reason the values are equal but the pointers are different, we
// are still correct and only miss an optimization opportunity.
if (instruction->GetLeft() == instruction->GetRight()) {
// Replace code looking like
// OR dst, src, src
// with
// src
instruction->ReplaceWith(instruction->GetLeft());
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
if (TryDeMorganNegationFactoring(instruction)) return;
if (TryReplaceWithRotate(instruction)) {
return;
}
// TryHandleAssociativeAndCommutativeOperation() does not remove its input,
// so no need to return.
TryHandleAssociativeAndCommutativeOperation(instruction);
}
void InstructionSimplifierVisitor::VisitShl(HShl* instruction) {
VisitShift(instruction);
}
void InstructionSimplifierVisitor::VisitShr(HShr* instruction) {
VisitShift(instruction);
}
void InstructionSimplifierVisitor::VisitSub(HSub* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
Primitive::Type type = instruction->GetType();
if (Primitive::IsFloatingPointType(type)) {
return;
}
if ((input_cst != nullptr) && input_cst->IsArithmeticZero()) {
// Replace code looking like
// SUB dst, src, 0
// with
// src
// Note that we cannot optimize `x - 0.0` to `x` for floating-point. When
// `x` is `-0.0`, the former expression yields `0.0`, while the later
// yields `-0.0`.
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
HBasicBlock* block = instruction->GetBlock();
ArenaAllocator* allocator = GetGraph()->GetArena();
HInstruction* left = instruction->GetLeft();
HInstruction* right = instruction->GetRight();
if (left->IsConstant()) {
if (Int64FromConstant(left->AsConstant()) == 0) {
// Replace code looking like
// SUB dst, 0, src
// with
// NEG dst, src
// Note that we cannot optimize `0.0 - x` to `-x` for floating-point. When
// `x` is `0.0`, the former expression yields `0.0`, while the later
// yields `-0.0`.
HNeg* neg = new (allocator) HNeg(type, right);
block->ReplaceAndRemoveInstructionWith(instruction, neg);
RecordSimplification();
return;
}
}
if (left->IsNeg() && right->IsNeg()) {
if (TryMoveNegOnInputsAfterBinop(instruction)) {
return;
}
}
if (right->IsNeg() && right->HasOnlyOneNonEnvironmentUse()) {
// Replace code looking like
// NEG tmp, b
// SUB dst, a, tmp
// with
// ADD dst, a, b
HAdd* add = new(GetGraph()->GetArena()) HAdd(type, left, right->AsNeg()->GetInput());
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, add);
RecordSimplification();
right->GetBlock()->RemoveInstruction(right);
return;
}
if (left->IsNeg() && left->HasOnlyOneNonEnvironmentUse()) {
// Replace code looking like
// NEG tmp, a
// SUB dst, tmp, b
// with
// ADD tmp, a, b
// NEG dst, tmp
// The second version is not intrinsically better, but enables more
// transformations.
HAdd* add = new(GetGraph()->GetArena()) HAdd(type, left->AsNeg()->GetInput(), right);
instruction->GetBlock()->InsertInstructionBefore(add, instruction);
HNeg* neg = new (GetGraph()->GetArena()) HNeg(instruction->GetType(), add);
instruction->GetBlock()->InsertInstructionBefore(neg, instruction);
instruction->ReplaceWith(neg);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
left->GetBlock()->RemoveInstruction(left);
return;
}
if (TrySubtractionChainSimplification(instruction)) {
return;
}
if (left->IsAdd()) {
// Replace code patterns looking like
// ADD dst1, x, y ADD dst1, x, y
// SUB dst2, dst1, y SUB dst2, dst1, x
// with
// ADD dst1, x, y
// SUB instruction is not needed in this case, we may use
// one of inputs of ADD instead.
// It is applicable to integral types only.
DCHECK(Primitive::IsIntegralType(type));
if (left->InputAt(1) == right) {
instruction->ReplaceWith(left->InputAt(0));
RecordSimplification();
instruction->GetBlock()->RemoveInstruction(instruction);
return;
} else if (left->InputAt(0) == right) {
instruction->ReplaceWith(left->InputAt(1));
RecordSimplification();
instruction->GetBlock()->RemoveInstruction(instruction);
return;
}
}
}
void InstructionSimplifierVisitor::VisitUShr(HUShr* instruction) {
VisitShift(instruction);
}
void InstructionSimplifierVisitor::VisitXor(HXor* instruction) {
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
if ((input_cst != nullptr) && input_cst->IsZeroBitPattern()) {
// Replace code looking like
// XOR dst, src, 0
// with
// src
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
RecordSimplification();
return;
}
if ((input_cst != nullptr) && input_cst->IsOne()
&& input_other->GetType() == Primitive::kPrimBoolean) {
// Replace code looking like
// XOR dst, src, 1
// with
// BOOLEAN_NOT dst, src
HBooleanNot* boolean_not = new (GetGraph()->GetArena()) HBooleanNot(input_other);
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, boolean_not);
RecordSimplification();
return;
}
if ((input_cst != nullptr) && AreAllBitsSet(input_cst)) {
// Replace code looking like
// XOR dst, src, 0xFFF...FF
// with
// NOT dst, src
HNot* bitwise_not = new (GetGraph()->GetArena()) HNot(instruction->GetType(), input_other);
instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, bitwise_not);
RecordSimplification();
return;
}
HInstruction* left = instruction->GetLeft();
HInstruction* right = instruction->GetRight();
if (((left->IsNot() && right->IsNot()) ||
(left->IsBooleanNot() && right->IsBooleanNot())) &&
left->HasOnlyOneNonEnvironmentUse() &&
right->HasOnlyOneNonEnvironmentUse()) {
// Replace code looking like
// NOT nota, a
// NOT notb, b
// XOR dst, nota, notb
// with
// XOR dst, a, b
instruction->ReplaceInput(left->InputAt(0), 0);
instruction->ReplaceInput(right->InputAt(0), 1);
left->GetBlock()->RemoveInstruction(left);
right->GetBlock()->RemoveInstruction(right);
RecordSimplification();
return;
}
if (TryReplaceWithRotate(instruction)) {
return;
}
// TryHandleAssociativeAndCommutativeOperation() does not remove its input,
// so no need to return.
TryHandleAssociativeAndCommutativeOperation(instruction);
}
void InstructionSimplifierVisitor::SimplifyStringEquals(HInvoke* instruction) {
HInstruction* argument = instruction->InputAt(1);
HInstruction* receiver = instruction->InputAt(0);
if (receiver == argument) {
// Because String.equals is an instance call, the receiver is
// a null check if we don't know it's null. The argument however, will
// be the actual object. So we cannot end up in a situation where both
// are equal but could be null.
DCHECK(CanEnsureNotNullAt(argument, instruction));
instruction->ReplaceWith(GetGraph()->GetIntConstant(1));
instruction->GetBlock()->RemoveInstruction(instruction);
} else {
StringEqualsOptimizations optimizations(instruction);
if (CanEnsureNotNullAt(argument, instruction)) {
optimizations.SetArgumentNotNull();
}
ScopedObjectAccess soa(Thread::Current());
ReferenceTypeInfo argument_rti = argument->GetReferenceTypeInfo();
if (argument_rti.IsValid() && argument_rti.IsStringClass()) {
optimizations.SetArgumentIsString();
}
}
}
void InstructionSimplifierVisitor::SimplifyRotate(HInvoke* invoke,
bool is_left,
Primitive::Type type) {
DCHECK(invoke->IsInvokeStaticOrDirect());
DCHECK_EQ(invoke->GetInvokeType(), InvokeType::kStatic);
HInstruction* value = invoke->InputAt(0);
HInstruction* distance = invoke->InputAt(1);
// Replace the invoke with an HRor.
if (is_left) {
// Unconditionally set the type of the negated distance to `int`,
// as shift and rotate operations expect a 32-bit (or narrower)
// value for their distance input.
distance = new (GetGraph()->GetArena()) HNeg(Primitive::kPrimInt, distance);
invoke->GetBlock()->InsertInstructionBefore(distance, invoke);
}
HRor* ror = new (GetGraph()->GetArena()) HRor(type, value, distance);
invoke->GetBlock()->ReplaceAndRemoveInstructionWith(invoke, ror);
// Remove ClinitCheck and LoadClass, if possible.
HInstruction* clinit = invoke->GetInputs().back();
if (clinit->IsClinitCheck() && !clinit->HasUses()) {
clinit->GetBlock()->RemoveInstruction(clinit);
HInstruction* ldclass = clinit->InputAt(0);
if (ldclass->IsLoadClass() && !ldclass->HasUses()) {
ldclass->GetBlock()->RemoveInstruction(ldclass);
}
}
}
static bool IsArrayLengthOf(HInstruction* potential_length, HInstruction* potential_array) {
if (potential_length->IsArrayLength()) {
return potential_length->InputAt(0) == potential_array;
}
if (potential_array->IsNewArray()) {
return potential_array->AsNewArray()->GetLength() == potential_length;
}
return false;
}
void InstructionSimplifierVisitor::SimplifySystemArrayCopy(HInvoke* instruction) {
HInstruction* source = instruction->InputAt(0);
HInstruction* destination = instruction->InputAt(2);
HInstruction* count = instruction->InputAt(4);
SystemArrayCopyOptimizations optimizations(instruction);
if (CanEnsureNotNullAt(source, instruction)) {
optimizations.SetSourceIsNotNull();
}
if (CanEnsureNotNullAt(destination, instruction)) {
optimizations.SetDestinationIsNotNull();
}
if (destination == source) {
optimizations.SetDestinationIsSource();
}
if (IsArrayLengthOf(count, source)) {
optimizations.SetCountIsSourceLength();
}
if (IsArrayLengthOf(count, destination)) {
optimizations.SetCountIsDestinationLength();
}
{
ScopedObjectAccess soa(Thread::Current());
ReferenceTypeInfo destination_rti = destination->GetReferenceTypeInfo();
if (destination_rti.IsValid()) {
if (destination_rti.IsObjectArray()) {
if (destination_rti.IsExact()) {
optimizations.SetDoesNotNeedTypeCheck();
}
optimizations.SetDestinationIsTypedObjectArray();
}
if (destination_rti.IsPrimitiveArrayClass()) {
optimizations.SetDestinationIsPrimitiveArray();
} else if (destination_rti.IsNonPrimitiveArrayClass()) {
optimizations.SetDestinationIsNonPrimitiveArray();
}
}
ReferenceTypeInfo source_rti = source->GetReferenceTypeInfo();
if (source_rti.IsValid()) {
if (destination_rti.IsValid() && destination_rti.CanArrayHoldValuesOf(source_rti)) {
optimizations.SetDoesNotNeedTypeCheck();
}
if (source_rti.IsPrimitiveArrayClass()) {
optimizations.SetSourceIsPrimitiveArray();
} else if (source_rti.IsNonPrimitiveArrayClass()) {
optimizations.SetSourceIsNonPrimitiveArray();
}
}
}
}
void InstructionSimplifierVisitor::SimplifyCompare(HInvoke* invoke,
bool is_signum,
Primitive::Type type) {
DCHECK(invoke->IsInvokeStaticOrDirect());
uint32_t dex_pc = invoke->GetDexPc();
HInstruction* left = invoke->InputAt(0);
HInstruction* right;
if (!is_signum) {
right = invoke->InputAt(1);
} else if (type == Primitive::kPrimLong) {
right = GetGraph()->GetLongConstant(0);
} else {
right = GetGraph()->GetIntConstant(0);
}
HCompare* compare = new (GetGraph()->GetArena())
HCompare(type, left, right, ComparisonBias::kNoBias, dex_pc);
invoke->GetBlock()->ReplaceAndRemoveInstructionWith(invoke, compare);
}
void InstructionSimplifierVisitor::SimplifyIsNaN(HInvoke* invoke) {
DCHECK(invoke->IsInvokeStaticOrDirect());
uint32_t dex_pc = invoke->GetDexPc();
// IsNaN(x) is the same as x != x.
HInstruction* x = invoke->InputAt(0);
HCondition* condition = new (GetGraph()->GetArena()) HNotEqual(x, x, dex_pc);
condition->SetBias(ComparisonBias::kLtBias);
invoke->GetBlock()->ReplaceAndRemoveInstructionWith(invoke, condition);
}
void InstructionSimplifierVisitor::SimplifyFP2Int(HInvoke* invoke) {
DCHECK(invoke->IsInvokeStaticOrDirect());
uint32_t dex_pc = invoke->GetDexPc();
HInstruction* x = invoke->InputAt(0);
Primitive::Type type = x->GetType();
// Set proper bit pattern for NaN and replace intrinsic with raw version.
HInstruction* nan;
if (type == Primitive::kPrimDouble) {
nan = GetGraph()->GetLongConstant(0x7ff8000000000000L);
invoke->SetIntrinsic(Intrinsics::kDoubleDoubleToRawLongBits,
kNeedsEnvironmentOrCache,
kNoSideEffects,
kNoThrow);
} else {
DCHECK_EQ(type, Primitive::kPrimFloat);
nan = GetGraph()->GetIntConstant(0x7fc00000);
invoke->SetIntrinsic(Intrinsics::kFloatFloatToRawIntBits,
kNeedsEnvironmentOrCache,
kNoSideEffects,
kNoThrow);
}
// Test IsNaN(x), which is the same as x != x.
HCondition* condition = new (GetGraph()->GetArena()) HNotEqual(x, x, dex_pc);
condition->SetBias(ComparisonBias::kLtBias);
invoke->GetBlock()->InsertInstructionBefore(condition, invoke->GetNext());
// Select between the two.
HInstruction* select = new (GetGraph()->GetArena()) HSelect(condition, nan, invoke, dex_pc);
invoke->GetBlock()->InsertInstructionBefore(select, condition->GetNext());
invoke->ReplaceWithExceptInReplacementAtIndex(select, 0); // false at index 0
}
void InstructionSimplifierVisitor::SimplifyStringCharAt(HInvoke* invoke) {
HInstruction* str = invoke->InputAt(0);
HInstruction* index = invoke->InputAt(1);
uint32_t dex_pc = invoke->GetDexPc();
ArenaAllocator* arena = GetGraph()->GetArena();
// We treat String as an array to allow DCE and BCE to seamlessly work on strings,
// so create the HArrayLength, HBoundsCheck and HArrayGet.
HArrayLength* length = new (arena) HArrayLength(str, dex_pc, /* is_string_length */ true);
invoke->GetBlock()->InsertInstructionBefore(length, invoke);
HBoundsCheck* bounds_check = new (arena) HBoundsCheck(
index, length, dex_pc, invoke->GetDexMethodIndex());
invoke->GetBlock()->InsertInstructionBefore(bounds_check, invoke);
HArrayGet* array_get = new (arena) HArrayGet(
str, bounds_check, Primitive::kPrimChar, dex_pc, /* is_string_char_at */ true);
invoke->GetBlock()->ReplaceAndRemoveInstructionWith(invoke, array_get);
bounds_check->CopyEnvironmentFrom(invoke->GetEnvironment());
GetGraph()->SetHasBoundsChecks(true);
}
void InstructionSimplifierVisitor::SimplifyStringIsEmptyOrLength(HInvoke* invoke) {
HInstruction* str = invoke->InputAt(0);
uint32_t dex_pc = invoke->GetDexPc();
// We treat String as an array to allow DCE and BCE to seamlessly work on strings,
// so create the HArrayLength.
HArrayLength* length =
new (GetGraph()->GetArena()) HArrayLength(str, dex_pc, /* is_string_length */ true);
HInstruction* replacement;
if (invoke->GetIntrinsic() == Intrinsics::kStringIsEmpty) {
// For String.isEmpty(), create the `HEqual` representing the `length == 0`.
invoke->GetBlock()->InsertInstructionBefore(length, invoke);
HIntConstant* zero = GetGraph()->GetIntConstant(0);
HEqual* equal = new (GetGraph()->GetArena()) HEqual(length, zero, dex_pc);
replacement = equal;
} else {
DCHECK_EQ(invoke->GetIntrinsic(), Intrinsics::kStringLength);
replacement = length;
}
invoke->GetBlock()->ReplaceAndRemoveInstructionWith(invoke, replacement);
}
// This method should only be used on intrinsics whose sole way of throwing an
// exception is raising a NPE when the nth argument is null. If that argument
// is provably non-null, we can clear the flag.
void InstructionSimplifierVisitor::SimplifyNPEOnArgN(HInvoke* invoke, size_t n) {
HInstruction* arg = invoke->InputAt(n);
if (invoke->CanThrow() && !arg->CanBeNull()) {
invoke->SetCanThrow(false);
}
}
// Methods that return "this" can replace the returned value with the receiver.
void InstructionSimplifierVisitor::SimplifyReturnThis(HInvoke* invoke) {
if (invoke->HasUses()) {
HInstruction* receiver = invoke->InputAt(0);
invoke->ReplaceWith(receiver);
RecordSimplification();
}
}
// Helper method for StringBuffer escape analysis.
static bool NoEscapeForStringBufferReference(HInstruction* reference, HInstruction* user) {
if (user->IsInvokeStaticOrDirect()) {
// Any constructor on StringBuffer is okay.
return user->AsInvokeStaticOrDirect()->GetResolvedMethod() != nullptr &&
user->AsInvokeStaticOrDirect()->GetResolvedMethod()->IsConstructor() &&
user->InputAt(0) == reference;
} else if (user->IsInvokeVirtual()) {
switch (user->AsInvokeVirtual()->GetIntrinsic()) {
case Intrinsics::kStringBufferLength:
case Intrinsics::kStringBufferToString:
DCHECK_EQ(user->InputAt(0), reference);
return true;
case Intrinsics::kStringBufferAppend:
// Returns "this", so only okay if no further uses.
DCHECK_EQ(user->InputAt(0), reference);
DCHECK_NE(user->InputAt(1), reference);
return !user->HasUses();
default:
break;
}
}
return false;
}
// Certain allocation intrinsics are not removed by dead code elimination
// because of potentially throwing an OOM exception or other side effects.
// This method removes such intrinsics when special circumstances allow.
void InstructionSimplifierVisitor::SimplifyAllocationIntrinsic(HInvoke* invoke) {
if (!invoke->HasUses()) {
// Instruction has no uses. If unsynchronized, we can remove right away, safely ignoring
// the potential OOM of course. Otherwise, we must ensure the receiver object of this
// call does not escape since only thread-local synchronization may be removed.
bool is_synchronized = invoke->GetIntrinsic() == Intrinsics::kStringBufferToString;
HInstruction* receiver = invoke->InputAt(0);
if (!is_synchronized || DoesNotEscape(receiver, NoEscapeForStringBufferReference)) {
invoke->GetBlock()->RemoveInstruction(invoke);
RecordSimplification();
}
}
}
void InstructionSimplifierVisitor::SimplifyMemBarrier(HInvoke* invoke, MemBarrierKind barrier_kind) {
uint32_t dex_pc = invoke->GetDexPc();
HMemoryBarrier* mem_barrier = new (GetGraph()->GetArena()) HMemoryBarrier(barrier_kind, dex_pc);
invoke->GetBlock()->ReplaceAndRemoveInstructionWith(invoke, mem_barrier);
}
void InstructionSimplifierVisitor::VisitInvoke(HInvoke* instruction) {
switch (instruction->GetIntrinsic()) {
case Intrinsics::kStringEquals:
SimplifyStringEquals(instruction);
break;
case Intrinsics::kSystemArrayCopy:
SimplifySystemArrayCopy(instruction);
break;
case Intrinsics::kIntegerRotateRight:
SimplifyRotate(instruction, /* is_left */ false, Primitive::kPrimInt);
break;
case Intrinsics::kLongRotateRight:
SimplifyRotate(instruction, /* is_left */ false, Primitive::kPrimLong);
break;
case Intrinsics::kIntegerRotateLeft:
SimplifyRotate(instruction, /* is_left */ true, Primitive::kPrimInt);
break;
case Intrinsics::kLongRotateLeft:
SimplifyRotate(instruction, /* is_left */ true, Primitive::kPrimLong);
break;
case Intrinsics::kIntegerCompare:
SimplifyCompare(instruction, /* is_signum */ false, Primitive::kPrimInt);
break;
case Intrinsics::kLongCompare:
SimplifyCompare(instruction, /* is_signum */ false, Primitive::kPrimLong);
break;
case Intrinsics::kIntegerSignum:
SimplifyCompare(instruction, /* is_signum */ true, Primitive::kPrimInt);
break;
case Intrinsics::kLongSignum:
SimplifyCompare(instruction, /* is_signum */ true, Primitive::kPrimLong);
break;
case Intrinsics::kFloatIsNaN:
case Intrinsics::kDoubleIsNaN:
SimplifyIsNaN(instruction);
break;
case Intrinsics::kFloatFloatToIntBits:
case Intrinsics::kDoubleDoubleToLongBits:
SimplifyFP2Int(instruction);
break;
case Intrinsics::kStringCharAt:
SimplifyStringCharAt(instruction);
break;
case Intrinsics::kStringIsEmpty:
case Intrinsics::kStringLength:
SimplifyStringIsEmptyOrLength(instruction);
break;
case Intrinsics::kStringStringIndexOf:
case Intrinsics::kStringStringIndexOfAfter:
SimplifyNPEOnArgN(instruction, 1); // 0th has own NullCheck
break;
case Intrinsics::kStringBufferAppend:
case Intrinsics::kStringBuilderAppend:
SimplifyReturnThis(instruction);
break;
case Intrinsics::kStringBufferToString:
case Intrinsics::kStringBuilderToString:
SimplifyAllocationIntrinsic(instruction);
break;
case Intrinsics::kUnsafeLoadFence:
SimplifyMemBarrier(instruction, MemBarrierKind::kLoadAny);
break;
case Intrinsics::kUnsafeStoreFence:
SimplifyMemBarrier(instruction, MemBarrierKind::kAnyStore);
break;
case Intrinsics::kUnsafeFullFence:
SimplifyMemBarrier(instruction, MemBarrierKind::kAnyAny);
break;
default:
break;
}
}
void InstructionSimplifierVisitor::VisitDeoptimize(HDeoptimize* deoptimize) {
HInstruction* cond = deoptimize->InputAt(0);
if (cond->IsConstant()) {
if (cond->AsIntConstant()->IsFalse()) {
// Never deopt: instruction can be removed.
deoptimize->GetBlock()->RemoveInstruction(deoptimize);
} else {
// Always deopt.
}
}
}
// Replace code looking like
// OP y, x, const1
// OP z, y, const2
// with
// OP z, x, const3
// where OP is both an associative and a commutative operation.
bool InstructionSimplifierVisitor::TryHandleAssociativeAndCommutativeOperation(
HBinaryOperation* instruction) {
DCHECK(instruction->IsCommutative());
if (!Primitive::IsIntegralType(instruction->GetType())) {
return false;
}
HInstruction* left = instruction->GetLeft();
HInstruction* right = instruction->GetRight();
// Variable names as described above.
HConstant* const2;
HBinaryOperation* y;
if (instruction->InstructionTypeEquals(left) && right->IsConstant()) {
const2 = right->AsConstant();
y = left->AsBinaryOperation();
} else if (left->IsConstant() && instruction->InstructionTypeEquals(right)) {
const2 = left->AsConstant();
y = right->AsBinaryOperation();
} else {
// The node does not match the pattern.
return false;
}
// If `y` has more than one use, we do not perform the optimization
// because it might increase code size (e.g. if the new constant is
// no longer encodable as an immediate operand in the target ISA).
if (!y->HasOnlyOneNonEnvironmentUse()) {
return false;
}
// GetConstantRight() can return both left and right constants
// for commutative operations.
HConstant* const1 = y->GetConstantRight();
if (const1 == nullptr) {
return false;
}
instruction->ReplaceInput(const1, 0);
instruction->ReplaceInput(const2, 1);
HConstant* const3 = instruction->TryStaticEvaluation();
DCHECK(const3 != nullptr);
instruction->ReplaceInput(y->GetLeastConstantLeft(), 0);
instruction->ReplaceInput(const3, 1);
RecordSimplification();
return true;
}
static HBinaryOperation* AsAddOrSub(HInstruction* binop) {
return (binop->IsAdd() || binop->IsSub()) ? binop->AsBinaryOperation() : nullptr;
}
// Helper function that performs addition statically, considering the result type.
static int64_t ComputeAddition(Primitive::Type type, int64_t x, int64_t y) {
// Use the Compute() method for consistency with TryStaticEvaluation().
if (type == Primitive::kPrimInt) {
return HAdd::Compute<int32_t>(x, y);
} else {
DCHECK_EQ(type, Primitive::kPrimLong);
return HAdd::Compute<int64_t>(x, y);
}
}
// Helper function that handles the child classes of HConstant
// and returns an integer with the appropriate sign.
static int64_t GetValue(HConstant* constant, bool is_negated) {
int64_t ret = Int64FromConstant(constant);
return is_negated ? -ret : ret;
}
// Replace code looking like
// OP1 y, x, const1
// OP2 z, y, const2
// with
// OP3 z, x, const3
// where OPx is either ADD or SUB, and at least one of OP{1,2} is SUB.
bool InstructionSimplifierVisitor::TrySubtractionChainSimplification(
HBinaryOperation* instruction) {
DCHECK(instruction->IsAdd() || instruction->IsSub()) << instruction->DebugName();
Primitive::Type type = instruction->GetType();
if (!Primitive::IsIntegralType(type)) {
return false;
}
HInstruction* left = instruction->GetLeft();
HInstruction* right = instruction->GetRight();
// Variable names as described above.
HConstant* const2 = right->IsConstant() ? right->AsConstant() : left->AsConstant();
if (const2 == nullptr) {
return false;
}
HBinaryOperation* y = (AsAddOrSub(left) != nullptr)
? left->AsBinaryOperation()
: AsAddOrSub(right);
// If y has more than one use, we do not perform the optimization because
// it might increase code size (e.g. if the new constant is no longer
// encodable as an immediate operand in the target ISA).
if ((y == nullptr) || !y->HasOnlyOneNonEnvironmentUse()) {
return false;
}
left = y->GetLeft();
HConstant* const1 = left->IsConstant() ? left->AsConstant() : y->GetRight()->AsConstant();
if (const1 == nullptr) {
return false;
}
HInstruction* x = (const1 == left) ? y->GetRight() : left;
// If both inputs are constants, let the constant folding pass deal with it.
if (x->IsConstant()) {
return false;
}
bool is_const2_negated = (const2 == right) && instruction->IsSub();
int64_t const2_val = GetValue(const2, is_const2_negated);
bool is_y_negated = (y == right) && instruction->IsSub();
right = y->GetRight();
bool is_const1_negated = is_y_negated ^ ((const1 == right) && y->IsSub());
int64_t const1_val = GetValue(const1, is_const1_negated);
bool is_x_negated = is_y_negated ^ ((x == right) && y->IsSub());
int64_t const3_val = ComputeAddition(type, const1_val, const2_val);
HBasicBlock* block = instruction->GetBlock();
HConstant* const3 = block->GetGraph()->GetConstant(type, const3_val);
ArenaAllocator* arena = instruction->GetArena();
HInstruction* z;
if (is_x_negated) {
z = new (arena) HSub(type, const3, x, instruction->GetDexPc());
} else {
z = new (arena) HAdd(type, x, const3, instruction->GetDexPc());
}
block->ReplaceAndRemoveInstructionWith(instruction, z);
RecordSimplification();
return true;
}
} // namespace art