/*
* 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 "induction_var_range.h"
#include <limits>
namespace art {
/** Returns true if 64-bit constant fits in 32-bit constant. */
static bool CanLongValueFitIntoInt(int64_t c) {
return std::numeric_limits<int32_t>::min() <= c && c <= std::numeric_limits<int32_t>::max();
}
/** Returns true if 32-bit addition can be done safely. */
static bool IsSafeAdd(int32_t c1, int32_t c2) {
return CanLongValueFitIntoInt(static_cast<int64_t>(c1) + static_cast<int64_t>(c2));
}
/** Returns true if 32-bit subtraction can be done safely. */
static bool IsSafeSub(int32_t c1, int32_t c2) {
return CanLongValueFitIntoInt(static_cast<int64_t>(c1) - static_cast<int64_t>(c2));
}
/** Returns true if 32-bit multiplication can be done safely. */
static bool IsSafeMul(int32_t c1, int32_t c2) {
return CanLongValueFitIntoInt(static_cast<int64_t>(c1) * static_cast<int64_t>(c2));
}
/** Returns true if 32-bit division can be done safely. */
static bool IsSafeDiv(int32_t c1, int32_t c2) {
return c2 != 0 && CanLongValueFitIntoInt(static_cast<int64_t>(c1) / static_cast<int64_t>(c2));
}
/** Returns true for 32/64-bit constant instruction. */
static bool IsIntAndGet(HInstruction* instruction, int64_t* value) {
if (instruction->IsIntConstant()) {
*value = instruction->AsIntConstant()->GetValue();
return true;
} else if (instruction->IsLongConstant()) {
*value = instruction->AsLongConstant()->GetValue();
return true;
}
return false;
}
/**
* An upper bound a * (length / a) + b, where a >= 1, can be conservatively rewritten as length + b
* because length >= 0 is true. This makes it more likely the bound is useful to clients.
*/
static InductionVarRange::Value SimplifyMax(InductionVarRange::Value v) {
int64_t value;
if (v.is_known &&
v.a_constant >= 1 &&
v.instruction->IsDiv() &&
v.instruction->InputAt(0)->IsArrayLength() &&
IsIntAndGet(v.instruction->InputAt(1), &value) && v.a_constant == value) {
return InductionVarRange::Value(v.instruction->InputAt(0), 1, v.b_constant);
}
return v;
}
/**
* Corrects a value for type to account for arithmetic wrap-around in lower precision.
*/
static InductionVarRange::Value CorrectForType(InductionVarRange::Value v, Primitive::Type type) {
switch (type) {
case Primitive::kPrimShort:
case Primitive::kPrimChar:
case Primitive::kPrimByte: {
// Constants within range only.
// TODO: maybe some room for improvement, like allowing widening conversions
const int32_t min = Primitive::MinValueOfIntegralType(type);
const int32_t max = Primitive::MaxValueOfIntegralType(type);
return (v.is_known && v.a_constant == 0 && min <= v.b_constant && v.b_constant <= max)
? v
: InductionVarRange::Value();
}
default:
// At int or higher.
return v;
}
}
/** Helper method to test for a constant value. */
static bool IsConstantValue(InductionVarRange::Value v) {
return v.is_known && v.a_constant == 0;
}
/** Helper method to test for same constant value. */
static bool IsSameConstantValue(InductionVarRange::Value v1, InductionVarRange::Value v2) {
return IsConstantValue(v1) && IsConstantValue(v2) && v1.b_constant == v2.b_constant;
}
/** Helper method to insert an instruction. */
static HInstruction* Insert(HBasicBlock* block, HInstruction* instruction) {
DCHECK(block != nullptr);
DCHECK(block->GetLastInstruction() != nullptr) << block->GetBlockId();
DCHECK(instruction != nullptr);
block->InsertInstructionBefore(instruction, block->GetLastInstruction());
return instruction;
}
//
// Public class methods.
//
InductionVarRange::InductionVarRange(HInductionVarAnalysis* induction_analysis)
: induction_analysis_(induction_analysis) {
DCHECK(induction_analysis != nullptr);
}
bool InductionVarRange::GetInductionRange(HInstruction* context,
HInstruction* instruction,
/*out*/Value* min_val,
/*out*/Value* max_val,
/*out*/bool* needs_finite_test) {
HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop
if (loop == nullptr) {
return false; // no loop
}
HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, instruction);
if (info == nullptr) {
return false; // no induction information
}
// Type int or lower (this is not too restrictive since intended clients, like
// bounds check elimination, will have truncated higher precision induction
// at their use point already).
switch (info->type) {
case Primitive::kPrimInt:
case Primitive::kPrimShort:
case Primitive::kPrimChar:
case Primitive::kPrimByte:
break;
default:
return false;
}
// Set up loop information.
HBasicBlock* header = loop->GetHeader();
bool in_body = context->GetBlock() != header;
HInductionVarAnalysis::InductionInfo* trip =
induction_analysis_->LookupInfo(loop, header->GetLastInstruction());
// Find range.
*min_val = GetVal(info, trip, in_body, /* is_min */ true);
*max_val = SimplifyMax(GetVal(info, trip, in_body, /* is_min */ false));
*needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip);
return true;
}
bool InductionVarRange::RefineOuter(/*in-out*/ Value* min_val,
/*in-out*/ Value* max_val) const {
if (min_val->instruction != nullptr || max_val->instruction != nullptr) {
Value v1_min = RefineOuter(*min_val, /* is_min */ true);
Value v2_max = RefineOuter(*max_val, /* is_min */ false);
// The refined range is safe if both sides refine the same instruction. Otherwise, since two
// different ranges are combined, the new refined range is safe to pass back to the client if
// the extremes of the computed ranges ensure no arithmetic wrap-around anomalies occur.
if (min_val->instruction != max_val->instruction) {
Value v1_max = RefineOuter(*min_val, /* is_min */ false);
Value v2_min = RefineOuter(*max_val, /* is_min */ true);
if (!IsConstantValue(v1_max) ||
!IsConstantValue(v2_min) ||
v1_max.b_constant > v2_min.b_constant) {
return false;
}
}
// Did something change?
if (v1_min.instruction != min_val->instruction || v2_max.instruction != max_val->instruction) {
*min_val = v1_min;
*max_val = v2_max;
return true;
}
}
return false;
}
bool InductionVarRange::CanGenerateCode(HInstruction* context,
HInstruction* instruction,
/*out*/bool* needs_finite_test,
/*out*/bool* needs_taken_test) {
return GenerateCode(context,
instruction,
nullptr, nullptr, nullptr, nullptr, nullptr, // nothing generated yet
needs_finite_test,
needs_taken_test);
}
void InductionVarRange::GenerateRangeCode(HInstruction* context,
HInstruction* instruction,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** lower,
/*out*/HInstruction** upper) {
bool b1, b2; // unused
if (!GenerateCode(context, instruction, graph, block, lower, upper, nullptr, &b1, &b2)) {
LOG(FATAL) << "Failed precondition: GenerateCode()";
}
}
void InductionVarRange::GenerateTakenTest(HInstruction* context,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** taken_test) {
bool b1, b2; // unused
if (!GenerateCode(context, context, graph, block, nullptr, nullptr, taken_test, &b1, &b2)) {
LOG(FATAL) << "Failed precondition: GenerateCode()";
}
}
//
// Private class methods.
//
bool InductionVarRange::IsConstant(HInductionVarAnalysis::InductionInfo* info,
ConstantRequest request,
/*out*/ int64_t *value) const {
if (info != nullptr) {
// A direct 32-bit or 64-bit constant fetch. This immediately satisfies
// any of the three requests (kExact, kAtMost, and KAtLeast).
if (info->induction_class == HInductionVarAnalysis::kInvariant &&
info->operation == HInductionVarAnalysis::kFetch) {
if (IsIntAndGet(info->fetch, value)) {
return true;
}
}
// Try range analysis while traversing outward on loops.
bool in_body = true; // no known trip count
Value v_min = GetVal(info, nullptr, in_body, /* is_min */ true);
Value v_max = GetVal(info, nullptr, in_body, /* is_min */ false);
do {
// Make sure *both* extremes are known to avoid arithmetic wrap-around anomalies.
if (IsConstantValue(v_min) && IsConstantValue(v_max) && v_min.b_constant <= v_max.b_constant) {
if ((request == kExact && v_min.b_constant == v_max.b_constant) || request == kAtMost) {
*value = v_max.b_constant;
return true;
} else if (request == kAtLeast) {
*value = v_min.b_constant;
return true;
}
}
} while (RefineOuter(&v_min, &v_max));
// Exploit array length + c >= c, with c <= 0 to avoid arithmetic wrap-around anomalies
// (e.g. array length == maxint and c == 1 would yield minint).
if (request == kAtLeast) {
if (v_min.a_constant == 1 && v_min.b_constant <= 0 && v_min.instruction->IsArrayLength()) {
*value = v_min.b_constant;
return true;
}
}
}
return false;
}
bool InductionVarRange::NeedsTripCount(HInductionVarAnalysis::InductionInfo* info) const {
if (info != nullptr) {
if (info->induction_class == HInductionVarAnalysis::kLinear) {
return true;
} else if (info->induction_class == HInductionVarAnalysis::kWrapAround) {
return NeedsTripCount(info->op_b);
}
}
return false;
}
bool InductionVarRange::IsBodyTripCount(HInductionVarAnalysis::InductionInfo* trip) const {
if (trip != nullptr) {
if (trip->induction_class == HInductionVarAnalysis::kInvariant) {
return trip->operation == HInductionVarAnalysis::kTripCountInBody ||
trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe;
}
}
return false;
}
bool InductionVarRange::IsUnsafeTripCount(HInductionVarAnalysis::InductionInfo* trip) const {
if (trip != nullptr) {
if (trip->induction_class == HInductionVarAnalysis::kInvariant) {
return trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe ||
trip->operation == HInductionVarAnalysis::kTripCountInLoopUnsafe;
}
}
return false;
}
InductionVarRange::Value InductionVarRange::GetLinear(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) const {
// Detect common situation where an offset inside the trip count cancels out during range
// analysis (finding max a * (TC - 1) + OFFSET for a == 1 and TC = UPPER - OFFSET or finding
// min a * (TC - 1) + OFFSET for a == -1 and TC = OFFSET - UPPER) to avoid losing information
// with intermediate results that only incorporate single instructions.
if (trip != nullptr) {
HInductionVarAnalysis::InductionInfo* trip_expr = trip->op_a;
if (trip_expr->operation == HInductionVarAnalysis::kSub) {
int64_t stride_value = 0;
if (IsConstant(info->op_a, kExact, &stride_value)) {
if (!is_min && stride_value == 1) {
// Test original trip's negative operand (trip_expr->op_b) against offset of induction.
if (HInductionVarAnalysis::InductionEqual(trip_expr->op_b, info->op_b)) {
// Analyze cancelled trip with just the positive operand (trip_expr->op_a).
HInductionVarAnalysis::InductionInfo cancelled_trip(
trip->induction_class,
trip->operation,
trip_expr->op_a,
trip->op_b,
nullptr,
trip->type);
return GetVal(&cancelled_trip, trip, in_body, is_min);
}
} else if (is_min && stride_value == -1) {
// Test original trip's positive operand (trip_expr->op_a) against offset of induction.
if (HInductionVarAnalysis::InductionEqual(trip_expr->op_a, info->op_b)) {
// Analyze cancelled trip with just the negative operand (trip_expr->op_b).
HInductionVarAnalysis::InductionInfo neg(
HInductionVarAnalysis::kInvariant,
HInductionVarAnalysis::kNeg,
nullptr,
trip_expr->op_b,
nullptr,
trip->type);
HInductionVarAnalysis::InductionInfo cancelled_trip(
trip->induction_class, trip->operation, &neg, trip->op_b, nullptr, trip->type);
return SubValue(Value(0), GetVal(&cancelled_trip, trip, in_body, !is_min));
}
}
}
}
}
// General rule of linear induction a * i + b, for normalized 0 <= i < TC.
return AddValue(GetMul(info->op_a, trip, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, is_min));
}
InductionVarRange::Value InductionVarRange::GetFetch(HInstruction* instruction,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) const {
// Detect constants and chase the fetch a bit deeper into the HIR tree, so that it becomes
// more likely range analysis will compare the same instructions as terminal nodes.
int64_t value;
if (IsIntAndGet(instruction, &value) && CanLongValueFitIntoInt(value)) {
return Value(static_cast<int32_t>(value));
} else if (instruction->IsAdd()) {
if (IsIntAndGet(instruction->InputAt(0), &value) && CanLongValueFitIntoInt(value)) {
return AddValue(Value(static_cast<int32_t>(value)),
GetFetch(instruction->InputAt(1), trip, in_body, is_min));
} else if (IsIntAndGet(instruction->InputAt(1), &value) && CanLongValueFitIntoInt(value)) {
return AddValue(GetFetch(instruction->InputAt(0), trip, in_body, is_min),
Value(static_cast<int32_t>(value)));
}
} else if (instruction->IsArrayLength() && instruction->InputAt(0)->IsNewArray()) {
return GetFetch(instruction->InputAt(0)->InputAt(0), trip, in_body, is_min);
} else if (instruction->IsTypeConversion()) {
// Since analysis is 32-bit (or narrower) we allow a widening along the path.
if (instruction->AsTypeConversion()->GetInputType() == Primitive::kPrimInt &&
instruction->AsTypeConversion()->GetResultType() == Primitive::kPrimLong) {
return GetFetch(instruction->InputAt(0), trip, in_body, is_min);
}
} else if (is_min) {
// Special case for finding minimum: minimum of trip-count in loop-body is 1.
if (trip != nullptr && in_body && instruction == trip->op_a->fetch) {
return Value(1);
}
}
return Value(instruction, 1, 0);
}
InductionVarRange::Value InductionVarRange::GetVal(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) const {
if (info != nullptr) {
switch (info->induction_class) {
case HInductionVarAnalysis::kInvariant:
// Invariants.
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
return AddValue(GetVal(info->op_a, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, is_min));
case HInductionVarAnalysis::kSub: // second reversed!
return SubValue(GetVal(info->op_a, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, !is_min));
case HInductionVarAnalysis::kNeg: // second reversed!
return SubValue(Value(0),
GetVal(info->op_b, trip, in_body, !is_min));
case HInductionVarAnalysis::kMul:
return GetMul(info->op_a, info->op_b, trip, in_body, is_min);
case HInductionVarAnalysis::kDiv:
return GetDiv(info->op_a, info->op_b, trip, in_body, is_min);
case HInductionVarAnalysis::kFetch:
return GetFetch(info->fetch, trip, in_body, is_min);
case HInductionVarAnalysis::kTripCountInLoop:
case HInductionVarAnalysis::kTripCountInLoopUnsafe:
if (!in_body && !is_min) { // one extra!
return GetVal(info->op_a, trip, in_body, is_min);
}
FALLTHROUGH_INTENDED;
case HInductionVarAnalysis::kTripCountInBody:
case HInductionVarAnalysis::kTripCountInBodyUnsafe:
if (is_min) {
return Value(0);
} else if (in_body) {
return SubValue(GetVal(info->op_a, trip, in_body, is_min), Value(1));
}
break;
default:
break;
}
break;
case HInductionVarAnalysis::kLinear: {
return CorrectForType(GetLinear(info, trip, in_body, is_min), info->type);
}
case HInductionVarAnalysis::kWrapAround:
case HInductionVarAnalysis::kPeriodic:
return MergeVal(GetVal(info->op_a, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, is_min), is_min);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetMul(HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) const {
Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true);
Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false);
Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true);
Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false);
// Try to refine first operand.
if (!IsConstantValue(v1_min) && !IsConstantValue(v1_max)) {
RefineOuter(&v1_min, &v1_max);
}
// Constant times range.
if (IsSameConstantValue(v1_min, v1_max)) {
return MulRangeAndConstant(v2_min, v2_max, v1_min, is_min);
} else if (IsSameConstantValue(v2_min, v2_max)) {
return MulRangeAndConstant(v1_min, v1_max, v2_min, is_min);
}
// Positive range vs. positive or negative range.
if (IsConstantValue(v1_min) && v1_min.b_constant >= 0) {
if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) {
return is_min ? MulValue(v1_min, v2_min) : MulValue(v1_max, v2_max);
} else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) {
return is_min ? MulValue(v1_max, v2_min) : MulValue(v1_min, v2_max);
}
}
// Negative range vs. positive or negative range.
if (IsConstantValue(v1_max) && v1_max.b_constant <= 0) {
if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) {
return is_min ? MulValue(v1_min, v2_max) : MulValue(v1_max, v2_min);
} else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) {
return is_min ? MulValue(v1_max, v2_max) : MulValue(v1_min, v2_min);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetDiv(HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) const {
Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true);
Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false);
Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true);
Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false);
// Range divided by constant.
if (IsSameConstantValue(v2_min, v2_max)) {
return DivRangeAndConstant(v1_min, v1_max, v2_min, is_min);
}
// Positive range vs. positive or negative range.
if (IsConstantValue(v1_min) && v1_min.b_constant >= 0) {
if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) {
return is_min ? DivValue(v1_min, v2_max) : DivValue(v1_max, v2_min);
} else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) {
return is_min ? DivValue(v1_max, v2_max) : DivValue(v1_min, v2_min);
}
}
// Negative range vs. positive or negative range.
if (IsConstantValue(v1_max) && v1_max.b_constant <= 0) {
if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) {
return is_min ? DivValue(v1_min, v2_min) : DivValue(v1_max, v2_max);
} else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) {
return is_min ? DivValue(v1_max, v2_min) : DivValue(v1_min, v2_max);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::MulRangeAndConstant(Value v_min,
Value v_max,
Value c,
bool is_min) const {
return is_min == (c.b_constant >= 0) ? MulValue(v_min, c) : MulValue(v_max, c);
}
InductionVarRange::Value InductionVarRange::DivRangeAndConstant(Value v_min,
Value v_max,
Value c,
bool is_min) const {
return is_min == (c.b_constant >= 0) ? DivValue(v_min, c) : DivValue(v_max, c);
}
InductionVarRange::Value InductionVarRange::AddValue(Value v1, Value v2) const {
if (v1.is_known && v2.is_known && IsSafeAdd(v1.b_constant, v2.b_constant)) {
const int32_t b = v1.b_constant + v2.b_constant;
if (v1.a_constant == 0) {
return Value(v2.instruction, v2.a_constant, b);
} else if (v2.a_constant == 0) {
return Value(v1.instruction, v1.a_constant, b);
} else if (v1.instruction == v2.instruction && IsSafeAdd(v1.a_constant, v2.a_constant)) {
return Value(v1.instruction, v1.a_constant + v2.a_constant, b);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::SubValue(Value v1, Value v2) const {
if (v1.is_known && v2.is_known && IsSafeSub(v1.b_constant, v2.b_constant)) {
const int32_t b = v1.b_constant - v2.b_constant;
if (v1.a_constant == 0 && IsSafeSub(0, v2.a_constant)) {
return Value(v2.instruction, -v2.a_constant, b);
} else if (v2.a_constant == 0) {
return Value(v1.instruction, v1.a_constant, b);
} else if (v1.instruction == v2.instruction && IsSafeSub(v1.a_constant, v2.a_constant)) {
return Value(v1.instruction, v1.a_constant - v2.a_constant, b);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::MulValue(Value v1, Value v2) const {
if (v1.is_known && v2.is_known) {
if (v1.a_constant == 0) {
if (IsSafeMul(v1.b_constant, v2.a_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) {
return Value(v2.instruction, v1.b_constant * v2.a_constant, v1.b_constant * v2.b_constant);
}
} else if (v2.a_constant == 0) {
if (IsSafeMul(v1.a_constant, v2.b_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) {
return Value(v1.instruction, v1.a_constant * v2.b_constant, v1.b_constant * v2.b_constant);
}
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::DivValue(Value v1, Value v2) const {
if (v1.is_known && v2.is_known && v1.a_constant == 0 && v2.a_constant == 0) {
if (IsSafeDiv(v1.b_constant, v2.b_constant)) {
return Value(v1.b_constant / v2.b_constant);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::MergeVal(Value v1, Value v2, bool is_min) const {
if (v1.is_known && v2.is_known) {
if (v1.instruction == v2.instruction && v1.a_constant == v2.a_constant) {
return Value(v1.instruction, v1.a_constant,
is_min ? std::min(v1.b_constant, v2.b_constant)
: std::max(v1.b_constant, v2.b_constant));
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::RefineOuter(Value v, bool is_min) const {
if (v.instruction == nullptr) {
return v; // nothing to refine
}
HLoopInformation* loop =
v.instruction->GetBlock()->GetLoopInformation(); // closest enveloping loop
if (loop == nullptr) {
return v; // no loop
}
HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, v.instruction);
if (info == nullptr) {
return v; // no induction information
}
// Set up loop information.
HBasicBlock* header = loop->GetHeader();
bool in_body = true; // inner always in more outer
HInductionVarAnalysis::InductionInfo* trip =
induction_analysis_->LookupInfo(loop, header->GetLastInstruction());
// Try to refine "a x instruction + b" with outer loop range information on instruction.
return AddValue(MulValue(Value(v.a_constant), GetVal(info, trip, in_body, is_min)), Value(v.b_constant));
}
bool InductionVarRange::GenerateCode(HInstruction* context,
HInstruction* instruction,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** lower,
/*out*/HInstruction** upper,
/*out*/HInstruction** taken_test,
/*out*/bool* needs_finite_test,
/*out*/bool* needs_taken_test) const {
HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop
if (loop == nullptr) {
return false; // no loop
}
HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, instruction);
if (info == nullptr) {
return false; // no induction information
}
// Set up loop information.
HBasicBlock* header = loop->GetHeader();
bool in_body = context->GetBlock() != header;
HInductionVarAnalysis::InductionInfo* trip =
induction_analysis_->LookupInfo(loop, header->GetLastInstruction());
if (trip == nullptr) {
return false; // codegen relies on trip count
}
// Determine what tests are needed. A finite test is needed if the evaluation code uses the
// trip-count and the loop maybe unsafe (because in such cases, the index could "overshoot"
// the computed range). A taken test is needed for any unknown trip-count, even if evaluation
// code does not use the trip-count explicitly (since there could be an implicit relation
// between e.g. an invariant subscript and a not-taken condition).
*needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip);
*needs_taken_test = IsBodyTripCount(trip);
// Code generation for taken test: generate the code when requested or otherwise analyze
// if code generation is feasible when taken test is needed.
if (taken_test != nullptr) {
return GenerateCode(trip->op_b, nullptr, graph, block, taken_test, in_body, /* is_min */ false);
} else if (*needs_taken_test) {
if (!GenerateCode(
trip->op_b, nullptr, nullptr, nullptr, nullptr, in_body, /* is_min */ false)) {
return false;
}
}
// Code generation for lower and upper.
return
// Success on lower if invariant (not set), or code can be generated.
((info->induction_class == HInductionVarAnalysis::kInvariant) ||
GenerateCode(info, trip, graph, block, lower, in_body, /* is_min */ true)) &&
// And success on upper.
GenerateCode(info, trip, graph, block, upper, in_body, /* is_min */ false);
}
bool InductionVarRange::GenerateCode(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph, // when set, code is generated
HBasicBlock* block,
/*out*/HInstruction** result,
bool in_body,
bool is_min) const {
if (info != nullptr) {
// Verify type safety.
Primitive::Type type = Primitive::kPrimInt;
if (info->type != type) {
return false;
}
// Handle current operation.
HInstruction* opa = nullptr;
HInstruction* opb = nullptr;
switch (info->induction_class) {
case HInductionVarAnalysis::kInvariant:
// Invariants.
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
case HInductionVarAnalysis::kLT:
case HInductionVarAnalysis::kLE:
case HInductionVarAnalysis::kGT:
case HInductionVarAnalysis::kGE:
if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) &&
GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) {
if (graph != nullptr) {
HInstruction* operation = nullptr;
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
operation = new (graph->GetArena()) HAdd(type, opa, opb); break;
case HInductionVarAnalysis::kLT:
operation = new (graph->GetArena()) HLessThan(opa, opb); break;
case HInductionVarAnalysis::kLE:
operation = new (graph->GetArena()) HLessThanOrEqual(opa, opb); break;
case HInductionVarAnalysis::kGT:
operation = new (graph->GetArena()) HGreaterThan(opa, opb); break;
case HInductionVarAnalysis::kGE:
operation = new (graph->GetArena()) HGreaterThanOrEqual(opa, opb); break;
default:
LOG(FATAL) << "unknown operation";
}
*result = Insert(block, operation);
}
return true;
}
break;
case HInductionVarAnalysis::kSub: // second reversed!
if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) &&
GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) {
if (graph != nullptr) {
*result = Insert(block, new (graph->GetArena()) HSub(type, opa, opb));
}
return true;
}
break;
case HInductionVarAnalysis::kNeg: // reversed!
if (GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) {
if (graph != nullptr) {
*result = Insert(block, new (graph->GetArena()) HNeg(type, opb));
}
return true;
}
break;
case HInductionVarAnalysis::kFetch:
if (graph != nullptr) {
*result = info->fetch; // already in HIR
}
return true;
case HInductionVarAnalysis::kTripCountInLoop:
case HInductionVarAnalysis::kTripCountInLoopUnsafe:
if (!in_body && !is_min) { // one extra!
return GenerateCode(info->op_a, trip, graph, block, result, in_body, is_min);
}
FALLTHROUGH_INTENDED;
case HInductionVarAnalysis::kTripCountInBody:
case HInductionVarAnalysis::kTripCountInBodyUnsafe:
if (is_min) {
if (graph != nullptr) {
*result = graph->GetIntConstant(0);
}
return true;
} else if (in_body) {
if (GenerateCode(info->op_a, trip, graph, block, &opb, in_body, is_min)) {
if (graph != nullptr) {
*result = Insert(block,
new (graph->GetArena())
HSub(type, opb, graph->GetIntConstant(1)));
}
return true;
}
}
break;
default:
break;
}
break;
case HInductionVarAnalysis::kLinear: {
// Linear induction a * i + b, for normalized 0 <= i < TC. Restrict to unit stride only
// to avoid arithmetic wrap-around situations that are hard to guard against.
int64_t stride_value = 0;
if (IsConstant(info->op_a, kExact, &stride_value)) {
if (stride_value == 1 || stride_value == -1) {
const bool is_min_a = stride_value == 1 ? is_min : !is_min;
if (GenerateCode(trip, trip, graph, block, &opa, in_body, is_min_a) &&
GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) {
if (graph != nullptr) {
HInstruction* oper;
if (stride_value == 1) {
oper = new (graph->GetArena()) HAdd(type, opa, opb);
} else {
oper = new (graph->GetArena()) HSub(type, opb, opa);
}
*result = Insert(block, oper);
}
return true;
}
}
}
break;
}
case HInductionVarAnalysis::kWrapAround:
case HInductionVarAnalysis::kPeriodic: {
// Wrap-around and periodic inductions are restricted to constants only, so that extreme
// values are easy to test at runtime without complications of arithmetic wrap-around.
Value extreme = GetVal(info, trip, in_body, is_min);
if (IsConstantValue(extreme)) {
if (graph != nullptr) {
*result = graph->GetIntConstant(extreme.b_constant);
}
return true;
}
break;
}
default:
break;
}
}
return false;
}
} // namespace art