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/*
* Copyright (C) 2015 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_shared.h"
namespace art {
namespace {
bool TrySimpleMultiplyAccumulatePatterns(HMul* mul,
HBinaryOperation* input_binop,
HInstruction* input_other) {
DCHECK(Primitive::IsIntOrLongType(mul->GetType()));
DCHECK(input_binop->IsAdd() || input_binop->IsSub());
DCHECK_NE(input_binop, input_other);
if (!input_binop->HasOnlyOneNonEnvironmentUse()) {
return false;
}
// Try to interpret patterns like
// a * (b <+/-> 1)
// as
// (a * b) <+/-> a
HInstruction* input_a = input_other;
HInstruction* input_b = nullptr; // Set to a non-null value if we found a pattern to optimize.
HInstruction::InstructionKind op_kind;
if (input_binop->IsAdd()) {
if ((input_binop->GetConstantRight() != nullptr) && input_binop->GetConstantRight()->IsOne()) {
// Interpret
// a * (b + 1)
// as
// (a * b) + a
input_b = input_binop->GetLeastConstantLeft();
op_kind = HInstruction::kAdd;
}
} else {
DCHECK(input_binop->IsSub());
if (input_binop->GetRight()->IsConstant() &&
input_binop->GetRight()->AsConstant()->IsMinusOne()) {
// Interpret
// a * (b - (-1))
// as
// a + (a * b)
input_b = input_binop->GetLeft();
op_kind = HInstruction::kAdd;
} else if (input_binop->GetLeft()->IsConstant() &&
input_binop->GetLeft()->AsConstant()->IsOne()) {
// Interpret
// a * (1 - b)
// as
// a - (a * b)
input_b = input_binop->GetRight();
op_kind = HInstruction::kSub;
}
}
if (input_b == nullptr) {
// We did not find a pattern we can optimize.
return false;
}
ArenaAllocator* arena = mul->GetBlock()->GetGraph()->GetArena();
HMultiplyAccumulate* mulacc = new(arena) HMultiplyAccumulate(
mul->GetType(), op_kind, input_a, input_a, input_b, mul->GetDexPc());
mul->GetBlock()->ReplaceAndRemoveInstructionWith(mul, mulacc);
input_binop->GetBlock()->RemoveInstruction(input_binop);
return true;
}
} // namespace
bool TryCombineMultiplyAccumulate(HMul* mul, InstructionSet isa) {
Primitive::Type type = mul->GetType();
switch (isa) {
case kArm:
case kThumb2:
if (type != Primitive::kPrimInt) {
return false;
}
break;
case kArm64:
if (!Primitive::IsIntOrLongType(type)) {
return false;
}
break;
default:
return false;
}
HInstruction* use = mul->HasNonEnvironmentUses()
? mul->GetUses().GetFirst()->GetUser()
: nullptr;
ArenaAllocator* arena = mul->GetBlock()->GetGraph()->GetArena();
if (mul->HasOnlyOneNonEnvironmentUse()) {
if (use->IsAdd() || use->IsSub()) {
// Replace code looking like
// MUL tmp, x, y
// SUB dst, acc, tmp
// with
// MULSUB dst, acc, x, y
// Note that we do not want to (unconditionally) perform the merge when the
// multiplication has multiple uses and it can be merged in all of them.
// Multiple uses could happen on the same control-flow path, and we would
// then increase the amount of work. In the future we could try to evaluate
// whether all uses are on different control-flow paths (using dominance and
// reverse-dominance information) and only perform the merge when they are.
HInstruction* accumulator = nullptr;
HBinaryOperation* binop = use->AsBinaryOperation();
HInstruction* binop_left = binop->GetLeft();
HInstruction* binop_right = binop->GetRight();
// Be careful after GVN. This should not happen since the `HMul` has only
// one use.
DCHECK_NE(binop_left, binop_right);
if (binop_right == mul) {
accumulator = binop_left;
} else if (use->IsAdd()) {
DCHECK_EQ(binop_left, mul);
accumulator = binop_right;
}
if (accumulator != nullptr) {
HMultiplyAccumulate* mulacc =
new (arena) HMultiplyAccumulate(type,
binop->GetKind(),
accumulator,
mul->GetLeft(),
mul->GetRight());
binop->GetBlock()->ReplaceAndRemoveInstructionWith(binop, mulacc);
DCHECK(!mul->HasUses());
mul->GetBlock()->RemoveInstruction(mul);
return true;
}
} else if (use->IsNeg() && isa != kArm) {
HMultiplyAccumulate* mulacc =
new (arena) HMultiplyAccumulate(type,
HInstruction::kSub,
mul->GetBlock()->GetGraph()->GetConstant(type, 0),
mul->GetLeft(),
mul->GetRight());
use->GetBlock()->ReplaceAndRemoveInstructionWith(use, mulacc);
DCHECK(!mul->HasUses());
mul->GetBlock()->RemoveInstruction(mul);
return true;
}
}
// Use multiply accumulate instruction for a few simple patterns.
// We prefer not applying the following transformations if the left and
// right inputs perform the same operation.
// We rely on GVN having squashed the inputs if appropriate. However the
// results are still correct even if that did not happen.
if (mul->GetLeft() == mul->GetRight()) {
return false;
}
HInstruction* left = mul->GetLeft();
HInstruction* right = mul->GetRight();
if ((right->IsAdd() || right->IsSub()) &&
TrySimpleMultiplyAccumulatePatterns(mul, right->AsBinaryOperation(), left)) {
return true;
}
if ((left->IsAdd() || left->IsSub()) &&
TrySimpleMultiplyAccumulatePatterns(mul, left->AsBinaryOperation(), right)) {
return true;
}
return false;
}
bool TryMergeNegatedInput(HBinaryOperation* op) {
DCHECK(op->IsAnd() || op->IsOr() || op->IsXor()) << op->DebugName();
HInstruction* left = op->GetLeft();
HInstruction* right = op->GetRight();
// Only consider the case where there is exactly one Not, with 2 Not's De
// Morgan's laws should be applied instead.
if (left->IsNot() ^ right->IsNot()) {
HInstruction* hnot = (left->IsNot() ? left : right);
HInstruction* hother = (left->IsNot() ? right : left);
// Only do the simplification if the Not has only one use and can thus be
// safely removed. Even though ARM64 negated bitwise operations do not have
// an immediate variant (only register), we still do the simplification when
// `hother` is a constant, because it removes an instruction if the constant
// cannot be encoded as an immediate:
// mov r0, #large_constant
// neg r2, r1
// and r0, r0, r2
// becomes:
// mov r0, #large_constant
// bic r0, r0, r1
if (hnot->HasOnlyOneNonEnvironmentUse()) {
// Replace code looking like
// NOT tmp, mask
// AND dst, src, tmp (respectively ORR, EOR)
// with
// BIC dst, src, mask (respectively ORN, EON)
HInstruction* src = hnot->AsNot()->GetInput();
HBitwiseNegatedRight* neg_op = new (hnot->GetBlock()->GetGraph()->GetArena())
HBitwiseNegatedRight(op->GetType(), op->GetKind(), hother, src, op->GetDexPc());
op->GetBlock()->ReplaceAndRemoveInstructionWith(op, neg_op);
hnot->GetBlock()->RemoveInstruction(hnot);
return true;
}
}
return false;
}
} // namespace art
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