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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 "induction_var_range.h"
#include <limits>
#include "optimizing/nodes.h"
namespace art HIDDEN {
/** 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));
}
/** Computes a * b for a,b > 0 (at least until first overflow happens). */
static int64_t SafeMul(int64_t a, int64_t b, /*out*/ bool* overflow) {
if (a > 0 && b > 0 && a > (std::numeric_limits<int64_t>::max() / b)) {
*overflow = true;
}
return a * b;
}
/** Returns b^e for b,e > 0. Sets overflow if arithmetic wrap-around occurred. */
static int64_t IntPow(int64_t b, int64_t e, /*out*/ bool* overflow) {
DCHECK_LT(0, b);
DCHECK_LT(0, e);
int64_t pow = 1;
while (e) {
if (e & 1) {
pow = SafeMul(pow, b, overflow);
}
e >>= 1;
if (e) {
b = SafeMul(b, b, overflow);
}
}
return pow;
}
/** Hunts "under the hood" for a suitable instruction at the hint. */
static bool IsMaxAtHint(
HInstruction* instruction, HInstruction* hint, /*out*/HInstruction** suitable) {
if (instruction->IsMin()) {
// For MIN(x, y), return most suitable x or y as maximum.
return IsMaxAtHint(instruction->InputAt(0), hint, suitable) ||
IsMaxAtHint(instruction->InputAt(1), hint, suitable);
} else {
*suitable = instruction;
return HuntForDeclaration(instruction) == hint;
}
}
/** Post-analysis simplification of a minimum value that makes the bound more useful to clients. */
static InductionVarRange::Value SimplifyMin(InductionVarRange::Value v) {
if (v.is_known && v.a_constant == 1 && v.b_constant <= 0) {
// If a == 1, instruction >= 0 and b <= 0, just return the constant b.
// No arithmetic wrap-around can occur.
if (IsGEZero(v.instruction)) {
return InductionVarRange::Value(v.b_constant);
}
}
return v;
}
/** Post-analysis simplification of a maximum value that makes the bound more useful to clients. */
static InductionVarRange::Value SimplifyMax(InductionVarRange::Value v, HInstruction* hint) {
if (v.is_known && v.a_constant >= 1) {
// An upper bound a * (length / a) + b, where a >= 1, can be conservatively rewritten as
// length + b because length >= 0 is true.
int64_t value;
if (v.instruction->IsDiv() &&
v.instruction->InputAt(0)->IsArrayLength() &&
IsInt64AndGet(v.instruction->InputAt(1), &value) && v.a_constant == value) {
return InductionVarRange::Value(v.instruction->InputAt(0), 1, v.b_constant);
}
// If a == 1, the most suitable one suffices as maximum value.
HInstruction* suitable = nullptr;
if (v.a_constant == 1 && IsMaxAtHint(v.instruction, hint, &suitable)) {
return InductionVarRange::Value(suitable, 1, v.b_constant);
}
}
return v;
}
/** Tests for a constant value. */
static bool IsConstantValue(InductionVarRange::Value v) {
return v.is_known && v.a_constant == 0;
}
/** Corrects a value for type to account for arithmetic wrap-around in lower precision. */
static InductionVarRange::Value CorrectForType(InductionVarRange::Value v, DataType::Type type) {
switch (type) {
case DataType::Type::kUint8:
case DataType::Type::kInt8:
case DataType::Type::kUint16:
case DataType::Type::kInt16: {
// Constants within range only.
// TODO: maybe some room for improvement, like allowing widening conversions
int32_t min = DataType::MinValueOfIntegralType(type);
int32_t max = DataType::MaxValueOfIntegralType(type);
return (IsConstantValue(v) && min <= v.b_constant && v.b_constant <= max)
? v
: InductionVarRange::Value();
}
default:
return v;
}
}
/** Inserts 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;
}
/** Obtains loop's control instruction. */
static HInstruction* GetLoopControl(const HLoopInformation* loop) {
DCHECK(loop != nullptr);
return loop->GetHeader()->GetLastInstruction();
}
/** Determines whether the `context` is in the body of the `loop`. */
static bool IsContextInBody(const HBasicBlock* context, const HLoopInformation* loop) {
DCHECK(loop != nullptr);
// We're currently classifying trip count only for the exit condition from loop header.
// All other blocks in the loop are considered loop body.
return context != loop->GetHeader() && loop->Contains(*context);
}
/** Determines whether to use the full trip count for given `context`, `loop` and `is_min`. */
bool UseFullTripCount(const HBasicBlock* context, const HLoopInformation* loop, bool is_min) {
// We're currently classifying trip count only for the exit condition from loop header.
// So, we should call this helper function only if the loop control is an `HIf` with
// one edge leaving the loop. The loop header is the only block that's both inside
// the loop and not in the loop body.
DCHECK(GetLoopControl(loop)->IsIf());
DCHECK_NE(loop->Contains(*GetLoopControl(loop)->AsIf()->IfTrueSuccessor()),
loop->Contains(*GetLoopControl(loop)->AsIf()->IfFalseSuccessor()));
if (loop->Contains(*context)) {
// Use the full trip count if determining the maximum and context is not in the loop body.
DCHECK_NE(context == loop->GetHeader(), IsContextInBody(context, loop));
return !is_min && context == loop->GetHeader();
} else {
// Trip count after the loop is always the maximum (ignoring `is_min`),
// as long as the `context` is dominated by the loop control exit block.
// If there are additional exit edges, the value is unknown on those paths.
HInstruction* loop_control = GetLoopControl(loop);
HBasicBlock* then_block = loop_control->AsIf()->IfTrueSuccessor();
HBasicBlock* else_block = loop_control->AsIf()->IfFalseSuccessor();
HBasicBlock* loop_exit_block = loop->Contains(*then_block) ? else_block : then_block;
return loop_exit_block->Dominates(context);
}
}
//
// Public class methods.
//
InductionVarRange::InductionVarRange(HInductionVarAnalysis* induction_analysis)
: induction_analysis_(induction_analysis),
chase_hint_(nullptr) {
DCHECK(induction_analysis != nullptr);
}
bool InductionVarRange::GetInductionRange(const HBasicBlock* context,
HInstruction* instruction,
HInstruction* chase_hint,
/*out*/Value* min_val,
/*out*/Value* max_val,
/*out*/bool* needs_finite_test) {
const HLoopInformation* loop = nullptr;
HInductionVarAnalysis::InductionInfo* info = nullptr;
HInductionVarAnalysis::InductionInfo* trip = nullptr;
if (!HasInductionInfo(context, instruction, &loop, &info, &trip)) {
return false;
}
// 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 DataType::Type::kUint8:
case DataType::Type::kInt8:
case DataType::Type::kUint16:
case DataType::Type::kInt16:
case DataType::Type::kInt32:
break;
default:
return false;
}
// Find range.
chase_hint_ = chase_hint;
int64_t stride_value = 0;
*min_val = SimplifyMin(GetVal(context, loop, info, trip, /*is_min=*/ true));
*max_val = SimplifyMax(GetVal(context, loop, info, trip, /*is_min=*/ false), chase_hint);
*needs_finite_test =
NeedsTripCount(context, loop, info, &stride_value) && IsUnsafeTripCount(trip);
chase_hint_ = nullptr;
// Retry chasing constants for wrap-around (merge sensitive).
if (!min_val->is_known && info->induction_class == HInductionVarAnalysis::kWrapAround) {
*min_val = SimplifyMin(GetVal(context, loop, info, trip, /*is_min=*/ true));
}
return true;
}
bool InductionVarRange::CanGenerateRange(const HBasicBlock* context,
HInstruction* instruction,
/*out*/bool* needs_finite_test,
/*out*/bool* needs_taken_test) {
bool is_last_value = false;
int64_t stride_value = 0;
return GenerateRangeOrLastValue(context,
instruction,
is_last_value,
nullptr,
nullptr,
nullptr,
nullptr,
nullptr, // nothing generated yet
&stride_value,
needs_finite_test,
needs_taken_test)
&& (stride_value == -1 ||
stride_value == 0 ||
stride_value == 1); // avoid arithmetic wrap-around anomalies.
}
void InductionVarRange::GenerateRange(const HBasicBlock* context,
HInstruction* instruction,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** lower,
/*out*/HInstruction** upper) {
bool is_last_value = false;
int64_t stride_value = 0;
bool b1, b2; // unused
if (!GenerateRangeOrLastValue(context,
instruction,
is_last_value,
graph,
block,
lower,
upper,
nullptr,
&stride_value,
&b1,
&b2)) {
LOG(FATAL) << "Failed precondition: CanGenerateRange()";
}
}
HInstruction* InductionVarRange::GenerateTakenTest(HInstruction* loop_control,
HGraph* graph,
HBasicBlock* block) {
const HBasicBlock* context = loop_control->GetBlock();
HInstruction* taken_test = nullptr;
bool is_last_value = false;
int64_t stride_value = 0;
bool b1, b2; // unused
if (!GenerateRangeOrLastValue(context,
loop_control,
is_last_value,
graph,
block,
nullptr,
nullptr,
&taken_test,
&stride_value,
&b1,
&b2)) {
LOG(FATAL) << "Failed precondition: CanGenerateRange()";
}
return taken_test;
}
bool InductionVarRange::CanGenerateLastValue(HInstruction* instruction) {
const HBasicBlock* context = instruction->GetBlock();
bool is_last_value = true;
int64_t stride_value = 0;
bool needs_finite_test = false;
bool needs_taken_test = false;
return GenerateRangeOrLastValue(context,
instruction,
is_last_value,
nullptr,
nullptr,
nullptr,
nullptr,
nullptr, // nothing generated yet
&stride_value,
&needs_finite_test,
&needs_taken_test)
&& !needs_finite_test && !needs_taken_test;
}
HInstruction* InductionVarRange::GenerateLastValue(HInstruction* instruction,
HGraph* graph,
HBasicBlock* block) {
const HBasicBlock* context = instruction->GetBlock();
HInstruction* last_value = nullptr;
bool is_last_value = true;
int64_t stride_value = 0;
bool b1, b2; // unused
if (!GenerateRangeOrLastValue(context,
instruction,
is_last_value,
graph,
block,
&last_value,
&last_value,
nullptr,
&stride_value,
&b1,
&b2)) {
LOG(FATAL) << "Failed precondition: CanGenerateLastValue()";
}
return last_value;
}
void InductionVarRange::Replace(HInstruction* instruction,
HInstruction* fetch,
HInstruction* replacement) {
for (HLoopInformation* lp = instruction->GetBlock()->GetLoopInformation(); // closest enveloping loop
lp != nullptr;
lp = lp->GetPreHeader()->GetLoopInformation()) {
// Update instruction's information.
ReplaceInduction(induction_analysis_->LookupInfo(lp, instruction), fetch, replacement);
// Update loop's trip-count information.
ReplaceInduction(induction_analysis_->LookupInfo(lp, GetLoopControl(lp)), fetch, replacement);
}
}
bool InductionVarRange::IsFinite(const HLoopInformation* loop, /*out*/ int64_t* trip_count) const {
bool is_constant_unused = false;
return CheckForFiniteAndConstantProps(loop, &is_constant_unused, trip_count);
}
bool InductionVarRange::HasKnownTripCount(const HLoopInformation* loop,
/*out*/ int64_t* trip_count) const {
bool is_constant = false;
CheckForFiniteAndConstantProps(loop, &is_constant, trip_count);
return is_constant;
}
bool InductionVarRange::IsUnitStride(const HBasicBlock* context,
HInstruction* instruction,
HGraph* graph,
/*out*/ HInstruction** offset) const {
const HLoopInformation* loop = nullptr;
HInductionVarAnalysis::InductionInfo* info = nullptr;
HInductionVarAnalysis::InductionInfo* trip = nullptr;
if (HasInductionInfo(context, instruction, &loop, &info, &trip)) {
if (info->induction_class == HInductionVarAnalysis::kLinear &&
!HInductionVarAnalysis::IsNarrowingLinear(info)) {
int64_t stride_value = 0;
if (IsConstant(context, loop, info->op_a, kExact, &stride_value) && stride_value == 1) {
int64_t off_value = 0;
if (IsConstant(context, loop, info->op_b, kExact, &off_value)) {
*offset = graph->GetConstant(info->op_b->type, off_value);
} else if (info->op_b->operation == HInductionVarAnalysis::kFetch) {
*offset = info->op_b->fetch;
} else {
return false;
}
return true;
}
}
}
return false;
}
HInstruction* InductionVarRange::GenerateTripCount(const HLoopInformation* loop,
HGraph* graph,
HBasicBlock* block) {
HInstruction* loop_control = GetLoopControl(loop);
HInductionVarAnalysis::InductionInfo *trip = induction_analysis_->LookupInfo(loop, loop_control);
if (trip != nullptr && !IsUnsafeTripCount(trip)) {
const HBasicBlock* context = loop_control->GetBlock();
HInstruction* taken_test = nullptr;
HInstruction* trip_expr = nullptr;
if (IsBodyTripCount(trip)) {
if (!GenerateCode(context,
loop,
trip->op_b,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
&taken_test)) {
return nullptr;
}
}
if (GenerateCode(context,
loop,
trip->op_a,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
&trip_expr)) {
if (taken_test != nullptr) {
HInstruction* zero = graph->GetConstant(trip->type, 0);
ArenaAllocator* allocator = graph->GetAllocator();
trip_expr = Insert(block, new (allocator) HSelect(taken_test, trip_expr, zero, kNoDexPc));
}
return trip_expr;
}
}
return nullptr;
}
//
// Private class methods.
//
bool InductionVarRange::CheckForFiniteAndConstantProps(const HLoopInformation* loop,
/*out*/ bool* is_constant,
/*out*/ int64_t* trip_count) const {
HInstruction* loop_control = GetLoopControl(loop);
HInductionVarAnalysis::InductionInfo *trip = induction_analysis_->LookupInfo(loop, loop_control);
if (trip != nullptr && !IsUnsafeTripCount(trip)) {
const HBasicBlock* context = loop_control->GetBlock();
*is_constant = IsConstant(context, loop, trip->op_a, kExact, trip_count);
return true;
}
return false;
}
bool InductionVarRange::IsConstant(const HBasicBlock* context,
const HLoopInformation* loop,
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 (IsInt64AndGet(info->fetch, value)) {
return true;
}
}
// Try range analysis on the invariant, only accept a proper range
// to avoid arithmetic wrap-around anomalies.
Value min_val = GetVal(context, loop, info, /*trip=*/ nullptr, /*is_min=*/ true);
Value max_val = GetVal(context, loop, info, /*trip=*/ nullptr, /*is_min=*/ false);
if (IsConstantValue(min_val) &&
IsConstantValue(max_val) && min_val.b_constant <= max_val.b_constant) {
if ((request == kExact && min_val.b_constant == max_val.b_constant) || request == kAtMost) {
*value = max_val.b_constant;
return true;
} else if (request == kAtLeast) {
*value = min_val.b_constant;
return true;
}
}
}
return false;
}
bool InductionVarRange::HasInductionInfo(
const HBasicBlock* context,
HInstruction* instruction,
/*out*/ const HLoopInformation** loop,
/*out*/ HInductionVarAnalysis::InductionInfo** info,
/*out*/ HInductionVarAnalysis::InductionInfo** trip) const {
DCHECK(context != nullptr);
HLoopInformation* lp = context->GetLoopInformation(); // closest enveloping loop
if (lp != nullptr) {
HInductionVarAnalysis::InductionInfo* i = induction_analysis_->LookupInfo(lp, instruction);
if (i != nullptr) {
*loop = lp;
*info = i;
*trip = induction_analysis_->LookupInfo(lp, GetLoopControl(lp));
return true;
}
}
return false;
}
bool InductionVarRange::IsWellBehavedTripCount(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* trip) const {
if (trip != nullptr) {
// Both bounds that define a trip-count are well-behaved if they either are not defined
// in any loop, or are contained in a proper interval. This allows finding the min/max
// of an expression by chasing outward.
InductionVarRange range(induction_analysis_);
HInductionVarAnalysis::InductionInfo* lower = trip->op_b->op_a;
HInductionVarAnalysis::InductionInfo* upper = trip->op_b->op_b;
int64_t not_used = 0;
return
(!HasFetchInLoop(lower) || range.IsConstant(context, loop, lower, kAtLeast, &not_used)) &&
(!HasFetchInLoop(upper) || range.IsConstant(context, loop, upper, kAtLeast, &not_used));
}
return true;
}
bool InductionVarRange::HasFetchInLoop(HInductionVarAnalysis::InductionInfo* info) const {
if (info != nullptr) {
if (info->induction_class == HInductionVarAnalysis::kInvariant &&
info->operation == HInductionVarAnalysis::kFetch) {
return info->fetch->GetBlock()->GetLoopInformation() != nullptr;
}
return HasFetchInLoop(info->op_a) || HasFetchInLoop(info->op_b);
}
return false;
}
bool InductionVarRange::NeedsTripCount(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
int64_t* stride_value) const {
if (info != nullptr) {
if (info->induction_class == HInductionVarAnalysis::kLinear) {
return IsConstant(context, loop, info->op_a, kExact, stride_value);
} else if (info->induction_class == HInductionVarAnalysis::kPolynomial) {
return NeedsTripCount(context, loop, info->op_a, stride_value);
} else if (info->induction_class == HInductionVarAnalysis::kWrapAround) {
return NeedsTripCount(context, loop, info->op_b, stride_value);
}
}
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(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kLinear);
// 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->type == info->type && trip_expr->operation == HInductionVarAnalysis::kSub) {
int64_t stride_value = 0;
if (IsConstant(context, loop, 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(context, loop, &cancelled_trip, trip, 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(context, loop, &cancelled_trip, trip, !is_min));
}
}
}
}
}
// General rule of linear induction a * i + b, for normalized 0 <= i < TC.
return AddValue(GetMul(context, loop, info->op_a, trip, trip, is_min),
GetVal(context, loop, info->op_b, trip, is_min));
}
InductionVarRange::Value InductionVarRange::GetPolynomial(
const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kPolynomial);
int64_t a = 0;
int64_t b = 0;
if (IsConstant(context, loop, info->op_a->op_a, kExact, &a) &&
CanLongValueFitIntoInt(a) &&
a >= 0 &&
IsConstant(context, loop, info->op_a->op_b, kExact, &b) &&
CanLongValueFitIntoInt(b) &&
b >= 0) {
// Evaluate bounds on sum_i=0^m-1(a * i + b) + c with a,b >= 0 for
// maximum index value m as a * (m * (m-1)) / 2 + b * m + c.
// Do not simply return `c` as minimum because the trip count may be non-zero
// if the `context` is after the `loop` (and therefore ignoring `is_min`).
Value c = GetVal(context, loop, info->op_b, trip, is_min);
Value m = GetVal(context, loop, trip, trip, is_min);
Value t = DivValue(MulValue(m, SubValue(m, Value(1))), Value(2));
Value x = MulValue(Value(a), t);
Value y = MulValue(Value(b), m);
return AddValue(AddValue(x, y), c);
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetGeometric(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kGeometric);
int64_t a = 0;
int64_t f = 0;
if (IsConstant(context, loop, info->op_a, kExact, &a) &&
CanLongValueFitIntoInt(a) &&
IsInt64AndGet(info->fetch, &f) && f >= 1) {
// Conservative bounds on a * f^-i + b with f >= 1 can be computed without
// trip count. Other forms would require a much more elaborate evaluation.
const bool is_min_a = a >= 0 ? is_min : !is_min;
if (info->operation == HInductionVarAnalysis::kDiv) {
Value b = GetVal(context, loop, info->op_b, trip, is_min);
return is_min_a ? b : AddValue(Value(a), b);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetFetch(const HBasicBlock* context,
const HLoopInformation* loop,
HInstruction* instruction,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
// Special case when chasing constants: single instruction that denotes trip count in the
// loop-body is minimal 1 and maximal, with safe trip-count, max int,
if (chase_hint_ == nullptr &&
IsContextInBody(context, loop) &&
trip != nullptr &&
instruction == trip->op_a->fetch) {
if (is_min) {
return Value(1);
} else if (!instruction->IsConstant() && !IsUnsafeTripCount(trip)) {
return Value(std::numeric_limits<int32_t>::max());
}
}
// Unless at a constant or hint, chase the instruction 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 (IsInt64AndGet(instruction, &value) && CanLongValueFitIntoInt(value)) {
// Proper constant reveals best information.
return Value(static_cast<int32_t>(value));
} else if (instruction == chase_hint_) {
// At hint, fetch is represented by itself.
return Value(instruction, 1, 0);
} else if (instruction->IsAdd()) {
// Incorporate suitable constants in the chased value.
if (IsInt64AndGet(instruction->InputAt(0), &value) && CanLongValueFitIntoInt(value)) {
return AddValue(Value(static_cast<int32_t>(value)),
GetFetch(context, loop, instruction->InputAt(1), trip, is_min));
} else if (IsInt64AndGet(instruction->InputAt(1), &value) && CanLongValueFitIntoInt(value)) {
return AddValue(GetFetch(context, loop, instruction->InputAt(0), trip, is_min),
Value(static_cast<int32_t>(value)));
}
} else if (instruction->IsSub()) {
// Incorporate suitable constants in the chased value.
if (IsInt64AndGet(instruction->InputAt(0), &value) && CanLongValueFitIntoInt(value)) {
return SubValue(Value(static_cast<int32_t>(value)),
GetFetch(context, loop, instruction->InputAt(1), trip, !is_min));
} else if (IsInt64AndGet(instruction->InputAt(1), &value) && CanLongValueFitIntoInt(value)) {
return SubValue(GetFetch(context, loop, instruction->InputAt(0), trip, is_min),
Value(static_cast<int32_t>(value)));
}
} else if (instruction->IsArrayLength()) {
// Exploit length properties when chasing constants or chase into a new array declaration.
if (chase_hint_ == nullptr) {
return is_min ? Value(0) : Value(std::numeric_limits<int32_t>::max());
} else if (instruction->InputAt(0)->IsNewArray()) {
return GetFetch(
context, loop, instruction->InputAt(0)->AsNewArray()->GetLength(), trip, is_min);
}
} else if (instruction->IsTypeConversion()) {
// Since analysis is 32-bit (or narrower), chase beyond widening along the path.
// For example, this discovers the length in: for (long i = 0; i < a.length; i++);
if (instruction->AsTypeConversion()->GetInputType() == DataType::Type::kInt32 &&
instruction->AsTypeConversion()->GetResultType() == DataType::Type::kInt64) {
return GetFetch(context, loop, instruction->InputAt(0), trip, is_min);
}
}
// Chase an invariant fetch that is defined by another loop if the trip-count used
// so far is well-behaved in both bounds and the next trip-count is safe.
// Example:
// for (int i = 0; i <= 100; i++) // safe
// for (int j = 0; j <= i; j++) // well-behaved
// j is in range [0, i ] (if i is chase hint)
// or in range [0, 100] (otherwise)
// Example:
// for (i = 0; i < 100; ++i)
// <some-code>
// for (j = 0; j < 10; ++j)
// sum += i; // The `i` is a "fetch" of a loop Phi from the previous loop.
const HLoopInformation* next_loop = nullptr;
HInductionVarAnalysis::InductionInfo* next_info = nullptr;
HInductionVarAnalysis::InductionInfo* next_trip = nullptr;
if (HasInductionInfo(instruction->GetBlock(), instruction, &next_loop, &next_info, &next_trip) &&
IsWellBehavedTripCount(context, next_loop, trip) &&
!IsUnsafeTripCount(next_trip)) {
return GetVal(context, next_loop, next_info, next_trip, is_min);
}
// Fetch is represented by itself.
return Value(instruction, 1, 0);
}
InductionVarRange::Value InductionVarRange::GetVal(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
if (info != nullptr) {
switch (info->induction_class) {
case HInductionVarAnalysis::kInvariant:
// Invariants.
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
return AddValue(GetVal(context, loop, info->op_a, trip, is_min),
GetVal(context, loop, info->op_b, trip, is_min));
case HInductionVarAnalysis::kSub: // second reversed!
return SubValue(GetVal(context, loop, info->op_a, trip, is_min),
GetVal(context, loop, info->op_b, trip, !is_min));
case HInductionVarAnalysis::kNeg: // second reversed!
return SubValue(Value(0),
GetVal(context, loop, info->op_b, trip, !is_min));
case HInductionVarAnalysis::kMul:
return GetMul(context, loop, info->op_a, info->op_b, trip, is_min);
case HInductionVarAnalysis::kDiv:
return GetDiv(context, loop, info->op_a, info->op_b, trip, is_min);
case HInductionVarAnalysis::kRem:
return GetRem(context, loop, info->op_a, info->op_b);
case HInductionVarAnalysis::kXor:
return GetXor(context, loop, info->op_a, info->op_b);
case HInductionVarAnalysis::kFetch:
return GetFetch(context, loop, info->fetch, trip, is_min);
case HInductionVarAnalysis::kTripCountInLoop:
case HInductionVarAnalysis::kTripCountInLoopUnsafe:
if (UseFullTripCount(context, loop, is_min)) {
// Return the full trip count (do not subtract 1 as we do in loop body).
return GetVal(context, loop, info->op_a, trip, /*is_min=*/ false);
}
FALLTHROUGH_INTENDED;
case HInductionVarAnalysis::kTripCountInBody:
case HInductionVarAnalysis::kTripCountInBodyUnsafe:
if (is_min) {
return Value(0);
} else if (IsContextInBody(context, loop)) {
return SubValue(GetVal(context, loop, info->op_a, trip, is_min), Value(1));
}
break;
default:
break;
}
break;
case HInductionVarAnalysis::kLinear:
return CorrectForType(GetLinear(context, loop, info, trip, is_min), info->type);
case HInductionVarAnalysis::kPolynomial:
return GetPolynomial(context, loop, info, trip, is_min);
case HInductionVarAnalysis::kGeometric:
return GetGeometric(context, loop, info, trip, is_min);
case HInductionVarAnalysis::kWrapAround:
case HInductionVarAnalysis::kPeriodic:
return MergeVal(GetVal(context, loop, info->op_a, trip, is_min),
GetVal(context, loop, info->op_b, trip, is_min),
is_min);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetMul(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
// Constant times range.
int64_t value = 0;
if (IsConstant(context, loop, info1, kExact, &value)) {
return MulRangeAndConstant(context, loop, value, info2, trip, is_min);
} else if (IsConstant(context, loop, info2, kExact, &value)) {
return MulRangeAndConstant(context, loop, value, info1, trip, is_min);
}
// Interval ranges.
Value v1_min = GetVal(context, loop, info1, trip, /*is_min=*/ true);
Value v1_max = GetVal(context, loop, info1, trip, /*is_min=*/ false);
Value v2_min = GetVal(context, loop, info2, trip, /*is_min=*/ true);
Value v2_max = GetVal(context, loop, info2, trip, /*is_min=*/ false);
// 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(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
// Range divided by constant.
int64_t value = 0;
if (IsConstant(context, loop, info2, kExact, &value)) {
return DivRangeAndConstant(context, loop, value, info1, trip, is_min);
}
// Interval ranges.
Value v1_min = GetVal(context, loop, info1, trip, /*is_min=*/ true);
Value v1_max = GetVal(context, loop, info1, trip, /*is_min=*/ false);
Value v2_min = GetVal(context, loop, info2, trip, /*is_min=*/ true);
Value v2_max = GetVal(context, loop, info2, trip, /*is_min=*/ false);
// 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::GetRem(
const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2) const {
int64_t v1 = 0;
int64_t v2 = 0;
// Only accept exact values.
if (IsConstant(context, loop, info1, kExact, &v1) &&
IsConstant(context, loop, info2, kExact, &v2) &&
v2 != 0) {
int64_t value = v1 % v2;
if (CanLongValueFitIntoInt(value)) {
return Value(static_cast<int32_t>(value));
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetXor(
const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2) const {
int64_t v1 = 0;
int64_t v2 = 0;
// Only accept exact values.
if (IsConstant(context, loop, info1, kExact, &v1) &&
IsConstant(context, loop, info2, kExact, &v2)) {
int64_t value = v1 ^ v2;
if (CanLongValueFitIntoInt(value)) {
return Value(static_cast<int32_t>(value));
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::MulRangeAndConstant(
const HBasicBlock* context,
const HLoopInformation* loop,
int64_t value,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
if (CanLongValueFitIntoInt(value)) {
Value c(static_cast<int32_t>(value));
return MulValue(GetVal(context, loop, info, trip, is_min == value >= 0), c);
}
return Value();
}
InductionVarRange::Value InductionVarRange::DivRangeAndConstant(
const HBasicBlock* context,
const HLoopInformation* loop,
int64_t value,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool is_min) const {
if (CanLongValueFitIntoInt(value)) {
Value c(static_cast<int32_t>(value));
return DivValue(GetVal(context, loop, info, trip, is_min == value >= 0), c);
}
return Value();
}
InductionVarRange::Value InductionVarRange::AddValue(Value v1, Value v2) const {
if (v1.is_known && v2.is_known && IsSafeAdd(v1.b_constant, v2.b_constant)) {
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)) {
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();
}
bool InductionVarRange::GenerateRangeOrLastValue(const HBasicBlock* context,
HInstruction* instruction,
bool is_last_value,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** lower,
/*out*/HInstruction** upper,
/*out*/HInstruction** taken_test,
/*out*/int64_t* stride_value,
/*out*/bool* needs_finite_test,
/*out*/bool* needs_taken_test) const {
const HLoopInformation* loop = nullptr;
HInductionVarAnalysis::InductionInfo* info = nullptr;
HInductionVarAnalysis::InductionInfo* trip = nullptr;
if (!HasInductionInfo(context, instruction, &loop, &info, &trip) || trip == nullptr) {
return false; // codegen needs all information, including tripcount
}
// 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).
*stride_value = 0;
*needs_finite_test = NeedsTripCount(context, loop, info, stride_value) && IsUnsafeTripCount(trip);
*needs_taken_test = IsBodyTripCount(trip);
// Handle last value request.
if (is_last_value) {
DCHECK(!IsContextInBody(context, loop));
switch (info->induction_class) {
case HInductionVarAnalysis::kLinear:
if (*stride_value > 0) {
lower = nullptr;
return GenerateLastValueLinear(
context, loop, info, trip, graph, block, /*is_min=*/false, upper);
} else {
upper = nullptr;
return GenerateLastValueLinear(
context, loop, info, trip, graph, block, /*is_min=*/true, lower);
}
case HInductionVarAnalysis::kPolynomial:
return GenerateLastValuePolynomial(context, loop, info, trip, graph, block, lower);
case HInductionVarAnalysis::kGeometric:
return GenerateLastValueGeometric(context, loop, info, trip, graph, block, lower);
case HInductionVarAnalysis::kWrapAround:
return GenerateLastValueWrapAround(context, loop, info, trip, graph, block, lower);
case HInductionVarAnalysis::kPeriodic:
return GenerateLastValuePeriodic(
context, loop, info, trip, graph, block, lower, needs_taken_test);
default:
return false;
}
}
// 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(context,
loop,
trip->op_b,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
taken_test);
} else if (*needs_taken_test) {
if (!GenerateCode(context,
loop,
trip->op_b,
/*trip=*/ nullptr,
/*graph=*/ nullptr,
/*block=*/ nullptr,
/*is_min=*/ false,
/*result=*/ nullptr)) {
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(context, loop, info, trip, graph, block, /*is_min=*/ true, lower)) &&
// And success on upper.
GenerateCode(context, loop, info, trip, graph, block, /*is_min=*/ false, upper);
}
bool InductionVarRange::GenerateLastValueLinear(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph,
HBasicBlock* block,
bool is_min,
/*out*/ HInstruction** result) const {
DataType::Type type = info->type;
// Avoid any narrowing linear induction or any type mismatch between the linear induction and the
// trip count expression.
if (HInductionVarAnalysis::IsNarrowingLinear(info) || trip->type != type) {
return false;
}
// Stride value must be a known constant that fits into int32.
int64_t stride_value = 0;
if (!IsConstant(context, loop, info->op_a, kExact, &stride_value) ||
!CanLongValueFitIntoInt(stride_value)) {
return false;
}
// We require `a` to be a constant value that didn't overflow.
const bool is_min_a = stride_value >= 0 ? is_min : !is_min;
Value val_a = GetVal(context, loop, trip, trip, is_min_a);
HInstruction* opb;
if (!IsConstantValue(val_a) ||
!GenerateCode(context, loop, info->op_b, trip, graph, block, is_min, &opb)) {
return false;
}
if (graph != nullptr) {
ArenaAllocator* allocator = graph->GetAllocator();
HInstruction* oper;
HInstruction* opa = graph->GetConstant(type, val_a.b_constant);
if (stride_value == 1) {
oper = new (allocator) HAdd(type, opa, opb);
} else if (stride_value == -1) {
oper = new (graph->GetAllocator()) HSub(type, opb, opa);
} else {
HInstruction* mul = new (allocator) HMul(type, graph->GetConstant(type, stride_value), opa);
oper = new (allocator) HAdd(type, Insert(block, mul), opb);
}
*result = Insert(block, oper);
}
return true;
}
bool InductionVarRange::GenerateLastValuePolynomial(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** result) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kPolynomial);
// Detect known coefficients and trip count (always taken).
int64_t a = 0;
int64_t b = 0;
int64_t m = 0;
if (IsConstant(context, loop, info->op_a->op_a, kExact, &a) &&
IsConstant(context, loop, info->op_a->op_b, kExact, &b) &&
IsConstant(context, loop, trip->op_a, kExact, &m) &&
m >= 1) {
// Evaluate bounds on sum_i=0^m-1(a * i + b) + c for known
// maximum index value m as a * (m * (m-1)) / 2 + b * m + c.
HInstruction* c = nullptr;
if (GenerateCode(context,
loop,
info->op_b,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
graph ? &c : nullptr)) {
if (graph != nullptr) {
DataType::Type type = info->type;
int64_t sum = a * ((m * (m - 1)) / 2) + b * m;
if (type != DataType::Type::kInt64) {
sum = static_cast<int32_t>(sum); // okay to truncate
}
*result =
Insert(block, new (graph->GetAllocator()) HAdd(type, graph->GetConstant(type, sum), c));
}
return true;
}
}
return false;
}
bool InductionVarRange::GenerateLastValueGeometric(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** result) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kGeometric);
// Detect known base and trip count (always taken).
int64_t f = 0;
int64_t m = 0;
if (IsInt64AndGet(info->fetch, &f) &&
f >= 1 &&
IsConstant(context, loop, trip->op_a, kExact, &m) &&
m >= 1) {
HInstruction* opa = nullptr;
HInstruction* opb = nullptr;
if (GenerateCode(
context, loop, info->op_a, /*trip=*/ nullptr, graph, block, /*is_min=*/ false, &opa) &&
GenerateCode(
context, loop, info->op_b, /*trip=*/ nullptr, graph, block, /*is_min=*/ false, &opb)) {
if (graph != nullptr) {
DataType::Type type = info->type;
// Compute f ^ m for known maximum index value m.
bool overflow = false;
int64_t fpow = IntPow(f, m, &overflow);
if (info->operation == HInductionVarAnalysis::kDiv) {
// For division, any overflow truncates to zero.
if (overflow || (type != DataType::Type::kInt64 && !CanLongValueFitIntoInt(fpow))) {
fpow = 0;
}
} else if (type != DataType::Type::kInt64) {
// For multiplication, okay to truncate to required precision.
DCHECK(info->operation == HInductionVarAnalysis::kMul);
fpow = static_cast<int32_t>(fpow);
}
// Generate code.
if (fpow == 0) {
// Special case: repeated mul/div always yields zero.
*result = graph->GetConstant(type, 0);
} else {
// Last value: a * f ^ m + b or a * f ^ -m + b.
HInstruction* e = nullptr;
ArenaAllocator* allocator = graph->GetAllocator();
if (info->operation == HInductionVarAnalysis::kMul) {
e = new (allocator) HMul(type, opa, graph->GetConstant(type, fpow));
} else {
e = new (allocator) HDiv(type, opa, graph->GetConstant(type, fpow), kNoDexPc);
}
*result = Insert(block, new (allocator) HAdd(type, Insert(block, e), opb));
}
}
return true;
}
}
return false;
}
bool InductionVarRange::GenerateLastValueWrapAround(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** result) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kWrapAround);
// Count depth.
int32_t depth = 0;
for (; info->induction_class == HInductionVarAnalysis::kWrapAround;
info = info->op_b, ++depth) {}
// Handle wrap(x, wrap(.., y)) if trip count reaches an invariant at end.
// TODO: generalize, but be careful to adjust the terminal.
int64_t m = 0;
if (info->induction_class == HInductionVarAnalysis::kInvariant &&
IsConstant(context, loop, trip->op_a, kExact, &m) &&
m >= depth) {
return GenerateCode(
context, loop, info, /*trip=*/ nullptr, graph, block, /*is_min=*/ false, result);
}
return false;
}
bool InductionVarRange::GenerateLastValuePeriodic(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** result,
/*out*/bool* needs_taken_test) const {
DCHECK(info != nullptr);
DCHECK_EQ(info->induction_class, HInductionVarAnalysis::kPeriodic);
// Count period and detect all-invariants.
int64_t period = 1;
bool all_invariants = true;
HInductionVarAnalysis::InductionInfo* p = info;
for (; p->induction_class == HInductionVarAnalysis::kPeriodic; p = p->op_b, ++period) {
DCHECK_EQ(p->op_a->induction_class, HInductionVarAnalysis::kInvariant);
if (p->op_a->operation != HInductionVarAnalysis::kFetch) {
all_invariants = false;
}
}
DCHECK_EQ(p->induction_class, HInductionVarAnalysis::kInvariant);
if (p->operation != HInductionVarAnalysis::kFetch) {
all_invariants = false;
}
// Don't rely on FP arithmetic to be precise, unless the full period
// consist of pre-computed expressions only.
if (info->type == DataType::Type::kFloat32 || info->type == DataType::Type::kFloat64) {
if (!all_invariants) {
return false;
}
}
// Handle any periodic(x, periodic(.., y)) for known maximum index value m.
int64_t m = 0;
if (IsConstant(context, loop, trip->op_a, kExact, &m) && m >= 1) {
int64_t li = m % period;
for (int64_t i = 0; i < li; info = info->op_b, i++) {}
if (info->induction_class == HInductionVarAnalysis::kPeriodic) {
info = info->op_a;
}
return GenerateCode(
context, loop, info, /*trip=*/ nullptr, graph, block, /*is_min=*/ false, result);
}
// Handle periodic(x, y) using even/odd-select on trip count. Enter trip count expression
// directly to obtain the maximum index value t even if taken test is needed.
HInstruction* x = nullptr;
HInstruction* y = nullptr;
HInstruction* t = nullptr;
if (period == 2 &&
GenerateCode(context,
loop,
info->op_a,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
graph ? &x : nullptr) &&
GenerateCode(context,
loop,
info->op_b,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
graph ? &y : nullptr) &&
GenerateCode(context,
loop,
trip->op_a,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
graph ? &t : nullptr)) {
// During actual code generation (graph != nullptr), generate is_even ? x : y.
if (graph != nullptr) {
DataType::Type type = trip->type;
ArenaAllocator* allocator = graph->GetAllocator();
HInstruction* msk =
Insert(block, new (allocator) HAnd(type, t, graph->GetConstant(type, 1)));
HInstruction* is_even =
Insert(block, new (allocator) HEqual(msk, graph->GetConstant(type, 0), kNoDexPc));
*result = Insert(block, new (graph->GetAllocator()) HSelect(is_even, x, y, kNoDexPc));
}
// Guard select with taken test if needed.
if (*needs_taken_test) {
HInstruction* is_taken = nullptr;
if (GenerateCode(context,
loop,
trip->op_b,
/*trip=*/ nullptr,
graph,
block,
/*is_min=*/ false,
graph ? &is_taken : nullptr)) {
if (graph != nullptr) {
ArenaAllocator* allocator = graph->GetAllocator();
*result = Insert(block, new (allocator) HSelect(is_taken, *result, x, kNoDexPc));
}
*needs_taken_test = false; // taken care of
} else {
return false;
}
}
return true;
}
return false;
}
bool InductionVarRange::GenerateCode(const HBasicBlock* context,
const HLoopInformation* loop,
HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph, // when set, code is generated
HBasicBlock* block,
bool is_min,
/*out*/HInstruction** result) const {
if (info != nullptr) {
// If during codegen, the result is not needed (nullptr), simply return success.
if (graph != nullptr && result == nullptr) {
return true;
}
// Handle current operation.
DataType::Type type = info->type;
HInstruction* opa = nullptr;
HInstruction* opb = nullptr;
switch (info->induction_class) {
case HInductionVarAnalysis::kInvariant:
// Invariants (note that since invariants only have other invariants as
// sub expressions, viz. no induction, there is no need to adjust is_min).
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
case HInductionVarAnalysis::kSub:
case HInductionVarAnalysis::kMul:
case HInductionVarAnalysis::kDiv:
case HInductionVarAnalysis::kRem:
case HInductionVarAnalysis::kXor:
case HInductionVarAnalysis::kLT:
case HInductionVarAnalysis::kLE:
case HInductionVarAnalysis::kGT:
case HInductionVarAnalysis::kGE:
if (GenerateCode(context, loop, info->op_a, trip, graph, block, is_min, &opa) &&
GenerateCode(context, loop, info->op_b, trip, graph, block, is_min, &opb)) {
if (graph != nullptr) {
HInstruction* operation = nullptr;
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
operation = new (graph->GetAllocator()) HAdd(type, opa, opb); break;
case HInductionVarAnalysis::kSub:
operation = new (graph->GetAllocator()) HSub(type, opa, opb); break;
case HInductionVarAnalysis::kMul:
operation = new (graph->GetAllocator()) HMul(type, opa, opb, kNoDexPc); break;
case HInductionVarAnalysis::kDiv:
operation = new (graph->GetAllocator()) HDiv(type, opa, opb, kNoDexPc); break;
case HInductionVarAnalysis::kRem:
operation = new (graph->GetAllocator()) HRem(type, opa, opb, kNoDexPc); break;
case HInductionVarAnalysis::kXor:
operation = new (graph->GetAllocator()) HXor(type, opa, opb); break;
case HInductionVarAnalysis::kLT:
operation = new (graph->GetAllocator()) HLessThan(opa, opb); break;
case HInductionVarAnalysis::kLE:
operation = new (graph->GetAllocator()) HLessThanOrEqual(opa, opb); break;
case HInductionVarAnalysis::kGT:
operation = new (graph->GetAllocator()) HGreaterThan(opa, opb); break;
case HInductionVarAnalysis::kGE:
operation = new (graph->GetAllocator()) HGreaterThanOrEqual(opa, opb); break;
default:
LOG(FATAL) << "unknown operation";
}
*result = Insert(block, operation);
}
return true;
}
break;
case HInductionVarAnalysis::kNeg:
if (GenerateCode(context, loop, info->op_b, trip, graph, block, !is_min, &opb)) {
if (graph != nullptr) {
*result = Insert(block, new (graph->GetAllocator()) 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 (UseFullTripCount(context, loop, is_min)) {
// Generate the full trip count (do not subtract 1 as we do in loop body).
return GenerateCode(
context, loop, info->op_a, trip, graph, block, /*is_min=*/ false, result);
}
FALLTHROUGH_INTENDED;
case HInductionVarAnalysis::kTripCountInBody:
case HInductionVarAnalysis::kTripCountInBodyUnsafe:
if (is_min) {
if (graph != nullptr) {
*result = graph->GetConstant(type, 0);
}
return true;
} else if (IsContextInBody(context, loop)) {
if (GenerateCode(context, loop, info->op_a, trip, graph, block, is_min, &opb)) {
if (graph != nullptr) {
ArenaAllocator* allocator = graph->GetAllocator();
*result =
Insert(block, new (allocator) HSub(type, opb, graph->GetConstant(type, 1)));
}
return true;
}
}
break;
case HInductionVarAnalysis::kNop:
LOG(FATAL) << "unexpected invariant nop";
} // switch invariant operation
break;
case HInductionVarAnalysis::kLinear: {
// Linear induction a * i + b, for normalized 0 <= i < TC. For ranges, this should
// be restricted to a unit stride to avoid arithmetic wrap-around situations that
// are harder to guard against. For a last value, requesting min/max based on any
// known stride yields right value. Always avoid any narrowing linear induction or
// any type mismatch between the linear induction and the trip count expression.
// TODO: careful runtime type conversions could generalize this latter restriction.
if (!HInductionVarAnalysis::IsNarrowingLinear(info) && trip->type == type) {
int64_t stride_value = 0;
if (IsConstant(context, loop, info->op_a, kExact, &stride_value) &&
CanLongValueFitIntoInt(stride_value)) {
const bool is_min_a = stride_value >= 0 ? is_min : !is_min;
if (GenerateCode(context, loop, trip, trip, graph, block, is_min_a, &opa) &&
GenerateCode(context, loop, info->op_b, trip, graph, block, is_min, &opb)) {
if (graph != nullptr) {
ArenaAllocator* allocator = graph->GetAllocator();
HInstruction* oper;
if (stride_value == 1) {
oper = new (allocator) HAdd(type, opa, opb);
} else if (stride_value == -1) {
oper = new (graph->GetAllocator()) HSub(type, opb, opa);
} else {
HInstruction* mul =
new (allocator) HMul(type, graph->GetConstant(type, stride_value), opa);
oper = new (allocator) HAdd(type, Insert(block, mul), opb);
}
*result = Insert(block, oper);
}
return true;
}
}
}
break;
}
case HInductionVarAnalysis::kPolynomial:
case HInductionVarAnalysis::kGeometric:
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(context, loop, info, trip, is_min);
if (IsConstantValue(extreme)) {
if (graph != nullptr) {
*result = graph->GetConstant(type, extreme.b_constant);
}
return true;
}
break;
}
} // switch induction class
}
return false;
}
void InductionVarRange::ReplaceInduction(HInductionVarAnalysis::InductionInfo* info,
HInstruction* fetch,
HInstruction* replacement) {
if (info != nullptr) {
if (info->induction_class == HInductionVarAnalysis::kInvariant &&
info->operation == HInductionVarAnalysis::kFetch &&
info->fetch == fetch) {
info->fetch = replacement;
}
ReplaceInduction(info->op_a, fetch, replacement);
ReplaceInduction(info->op_b, fetch, replacement);
}
}
} // namespace art