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llvm-project/llvm/lib/Analysis/BlockFrequencyInfoImpl.cpp

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//===- BlockFrequencyImplInfo.cpp - Block Frequency Info Implementation ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Loops should be simplified before this analysis.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/Support/raw_ostream.h"
#include <deque>
using namespace llvm;
#define DEBUG_TYPE "block-freq"
//===----------------------------------------------------------------------===//
//
// UnsignedFloat implementation.
//
//===----------------------------------------------------------------------===//
#ifndef _MSC_VER
const int32_t UnsignedFloatBase::MaxExponent;
const int32_t UnsignedFloatBase::MinExponent;
#endif
static void appendDigit(std::string &Str, unsigned D) {
assert(D < 10);
Str += '0' + D % 10;
}
static void appendNumber(std::string &Str, uint64_t N) {
while (N) {
appendDigit(Str, N % 10);
N /= 10;
}
}
static bool doesRoundUp(char Digit) {
switch (Digit) {
case '5':
case '6':
case '7':
case '8':
case '9':
return true;
default:
return false;
}
}
static std::string toStringAPFloat(uint64_t D, int E, unsigned Precision) {
assert(E >= UnsignedFloatBase::MinExponent);
assert(E <= UnsignedFloatBase::MaxExponent);
// Find a new E, but don't let it increase past MaxExponent.
int LeadingZeros = UnsignedFloatBase::countLeadingZeros64(D);
int NewE = std::min(UnsignedFloatBase::MaxExponent, E + 63 - LeadingZeros);
int Shift = 63 - (NewE - E);
assert(Shift <= LeadingZeros);
assert(Shift == LeadingZeros || NewE == UnsignedFloatBase::MaxExponent);
D <<= Shift;
E = NewE;
// Check for a denormal.
unsigned AdjustedE = E + 16383;
if (!(D >> 63)) {
assert(E == UnsignedFloatBase::MaxExponent);
AdjustedE = 0;
}
// Build the float and print it.
uint64_t RawBits[2] = {D, AdjustedE};
APFloat Float(APFloat::x87DoubleExtended, APInt(80, RawBits));
SmallVector<char, 24> Chars;
Float.toString(Chars, Precision, 0);
return std::string(Chars.begin(), Chars.end());
}
static std::string stripTrailingZeros(const std::string &Float) {
size_t NonZero = Float.find_last_not_of('0');
assert(NonZero != std::string::npos && "no . in floating point string");
if (Float[NonZero] == '.')
++NonZero;
return Float.substr(0, NonZero + 1);
}
std::string UnsignedFloatBase::toString(uint64_t D, int16_t E, int Width,
unsigned Precision) {
if (!D)
return "0.0";
// Canonicalize exponent and digits.
uint64_t Above0 = 0;
uint64_t Below0 = 0;
uint64_t Extra = 0;
int ExtraShift = 0;
if (E == 0) {
Above0 = D;
} else if (E > 0) {
if (int Shift = std::min(int16_t(countLeadingZeros64(D)), E)) {
D <<= Shift;
E -= Shift;
if (!E)
Above0 = D;
}
} else if (E > -64) {
Above0 = D >> -E;
Below0 = D << (64 + E);
} else if (E > -120) {
Below0 = D >> (-E - 64);
Extra = D << (128 + E);
ExtraShift = -64 - E;
}
// Fall back on APFloat for very small and very large numbers.
if (!Above0 && !Below0)
return toStringAPFloat(D, E, Precision);
// Append the digits before the decimal.
std::string Str;
size_t DigitsOut = 0;
if (Above0) {
appendNumber(Str, Above0);
DigitsOut = Str.size();
} else
appendDigit(Str, 0);
std::reverse(Str.begin(), Str.end());
// Return early if there's nothing after the decimal.
if (!Below0)
return Str + ".0";
// Append the decimal and beyond.
Str += '.';
uint64_t Error = UINT64_C(1) << (64 - Width);
// We need to shift Below0 to the right to make space for calculating
// digits. Save the precision we're losing in Extra.
Extra = (Below0 & 0xf) << 56 | (Extra >> 8);
Below0 >>= 4;
size_t SinceDot = 0;
size_t AfterDot = Str.size();
do {
if (ExtraShift) {
--ExtraShift;
Error *= 5;
} else
Error *= 10;
Below0 *= 10;
Extra *= 10;
Below0 += (Extra >> 60);
Extra = Extra & (UINT64_MAX >> 4);
appendDigit(Str, Below0 >> 60);
Below0 = Below0 & (UINT64_MAX >> 4);
if (DigitsOut || Str.back() != '0')
++DigitsOut;
++SinceDot;
} while (Error && (Below0 << 4 | Extra >> 60) >= Error / 2 &&
(!Precision || DigitsOut <= Precision || SinceDot < 2));
// Return early for maximum precision.
if (!Precision || DigitsOut <= Precision)
return stripTrailingZeros(Str);
// Find where to truncate.
size_t Truncate =
std::max(Str.size() - (DigitsOut - Precision), AfterDot + 1);
// Check if there's anything to truncate.
if (Truncate >= Str.size())
return stripTrailingZeros(Str);
bool Carry = doesRoundUp(Str[Truncate]);
if (!Carry)
return stripTrailingZeros(Str.substr(0, Truncate));
// Round with the first truncated digit.
for (std::string::reverse_iterator I(Str.begin() + Truncate), E = Str.rend();
I != E; ++I) {
if (*I == '.')
continue;
if (*I == '9') {
*I = '0';
continue;
}
++*I;
Carry = false;
break;
}
// Add "1" in front if we still need to carry.
return stripTrailingZeros(std::string(Carry, '1') + Str.substr(0, Truncate));
}
raw_ostream &UnsignedFloatBase::print(raw_ostream &OS, uint64_t D, int16_t E,
int Width, unsigned Precision) {
return OS << toString(D, E, Width, Precision);
}
void UnsignedFloatBase::dump(uint64_t D, int16_t E, int Width) {
print(dbgs(), D, E, Width, 0) << "[" << Width << ":" << D << "*2^" << E
<< "]";
}
static std::pair<uint64_t, int16_t>
getRoundedFloat(uint64_t N, bool ShouldRound, int64_t Shift) {
if (ShouldRound)
if (!++N)
// Rounding caused an overflow.
return std::make_pair(UINT64_C(1), Shift + 64);
return std::make_pair(N, Shift);
}
std::pair<uint64_t, int16_t> UnsignedFloatBase::divide64(uint64_t Dividend,
uint64_t Divisor) {
// Input should be sanitized.
assert(Divisor);
assert(Dividend);
// Minimize size of divisor.
int16_t Shift = 0;
if (int Zeros = countTrailingZeros(Divisor)) {
Shift -= Zeros;
Divisor >>= Zeros;
}
// Check for powers of two.
if (Divisor == 1)
return std::make_pair(Dividend, Shift);
// Maximize size of dividend.
if (int Zeros = countLeadingZeros64(Dividend)) {
Shift -= Zeros;
Dividend <<= Zeros;
}
// Start with the result of a divide.
uint64_t Quotient = Dividend / Divisor;
Dividend %= Divisor;
// Continue building the quotient with long division.
//
// TODO: continue with largers digits.
while (!(Quotient >> 63) && Dividend) {
// Shift Dividend, and check for overflow.
bool IsOverflow = Dividend >> 63;
Dividend <<= 1;
--Shift;
// Divide.
bool DoesDivide = IsOverflow || Divisor <= Dividend;
Quotient = (Quotient << 1) | uint64_t(DoesDivide);
Dividend -= DoesDivide ? Divisor : 0;
}
// Round.
if (Dividend >= getHalf(Divisor))
if (!++Quotient)
// Rounding caused an overflow in Quotient.
return std::make_pair(UINT64_C(1), Shift + 64);
return getRoundedFloat(Quotient, Dividend >= getHalf(Divisor), Shift);
}
std::pair<uint64_t, int16_t> UnsignedFloatBase::multiply64(uint64_t L,
uint64_t R) {
// Separate into two 32-bit digits (U.L).
uint64_t UL = L >> 32, LL = L & UINT32_MAX, UR = R >> 32, LR = R & UINT32_MAX;
// Compute cross products.
uint64_t P1 = UL * UR, P2 = UL * LR, P3 = LL * UR, P4 = LL * LR;
// Sum into two 64-bit digits.
uint64_t Upper = P1, Lower = P4;
auto addWithCarry = [&](uint64_t N) {
uint64_t NewLower = Lower + (N << 32);
Upper += (N >> 32) + (NewLower < Lower);
Lower = NewLower;
};
addWithCarry(P2);
addWithCarry(P3);
// Check whether the upper digit is empty.
if (!Upper)
return std::make_pair(Lower, 0);
// Shift as little as possible to maximize precision.
unsigned LeadingZeros = countLeadingZeros64(Upper);
int16_t Shift = 64 - LeadingZeros;
if (LeadingZeros)
Upper = Upper << LeadingZeros | Lower >> Shift;
bool ShouldRound = Shift && (Lower & UINT64_C(1) << (Shift - 1));
return getRoundedFloat(Upper, ShouldRound, Shift);
}
//===----------------------------------------------------------------------===//
//
// BlockMass implementation.
//
//===----------------------------------------------------------------------===//
BlockMass &BlockMass::operator*=(const BranchProbability &P) {
uint32_t N = P.getNumerator(), D = P.getDenominator();
assert(D && "divide by 0");
assert(N <= D && "fraction greater than 1");
// Fast path for multiplying by 1.0.
if (!Mass || N == D)
return *this;
// Get as much precision as we can.
int Shift = countLeadingZeros(Mass);
uint64_t ShiftedQuotient = (Mass << Shift) / D;
uint64_t Product = ShiftedQuotient * N >> Shift;
// Now check for what's lost.
uint64_t Left = ShiftedQuotient * (D - N) >> Shift;
uint64_t Lost = Mass - Product - Left;
// TODO: prove this assertion.
assert(Lost <= UINT32_MAX);
// Take the product plus a portion of the spoils.
Mass = Product + Lost * N / D;
return *this;
}
UnsignedFloat<uint64_t> BlockMass::toFloat() const {
if (isFull())
return UnsignedFloat<uint64_t>(1, 0);
return UnsignedFloat<uint64_t>(getMass() + 1, -64);
}
void BlockMass::dump() const { print(dbgs()); }
static char getHexDigit(int N) {
assert(N < 16);
if (N < 10)
return '0' + N;
return 'a' + N - 10;
}
raw_ostream &BlockMass::print(raw_ostream &OS) const {
for (int Digits = 0; Digits < 16; ++Digits)
OS << getHexDigit(Mass >> (60 - Digits * 4) & 0xf);
return OS;
}
//===----------------------------------------------------------------------===//
//
// BlockFrequencyInfoImpl implementation.
//
//===----------------------------------------------------------------------===//
namespace {
typedef BlockFrequencyInfoImplBase::BlockNode BlockNode;
typedef BlockFrequencyInfoImplBase::Distribution Distribution;
typedef BlockFrequencyInfoImplBase::Distribution::WeightList WeightList;
typedef BlockFrequencyInfoImplBase::Float Float;
typedef BlockFrequencyInfoImplBase::PackagedLoopData PackagedLoopData;
typedef BlockFrequencyInfoImplBase::Weight Weight;
typedef BlockFrequencyInfoImplBase::FrequencyData FrequencyData;
/// \brief Dithering mass distributer.
///
/// This class splits up a single mass into portions by weight, dithering to
/// spread out error. No mass is lost. The dithering precision depends on the
/// precision of the product of \a BlockMass and \a BranchProbability.
///
/// The distribution algorithm follows.
///
/// 1. Initialize by saving the sum of the weights in \a RemWeight and the
/// mass to distribute in \a RemMass.
///
/// 2. For each portion:
///
/// 1. Construct a branch probability, P, as the portion's weight divided
/// by the current value of \a RemWeight.
/// 2. Calculate the portion's mass as \a RemMass times P.
/// 3. Update \a RemWeight and \a RemMass at each portion by subtracting
/// the current portion's weight and mass.
///
/// Mass is distributed in two ways: full distribution and forward
/// distribution. The latter ignores backedges, and uses the parallel fields
/// \a RemForwardWeight and \a RemForwardMass.
struct DitheringDistributer {
uint32_t RemWeight;
uint32_t RemForwardWeight;
BlockMass RemMass;
BlockMass RemForwardMass;
DitheringDistributer(Distribution &Dist, const BlockMass &Mass);
BlockMass takeLocalMass(uint32_t Weight) {
(void)takeMass(Weight);
return takeForwardMass(Weight);
}
BlockMass takeExitMass(uint32_t Weight) {
(void)takeForwardMass(Weight);
return takeMass(Weight);
}
BlockMass takeBackedgeMass(uint32_t Weight) { return takeMass(Weight); }
private:
BlockMass takeForwardMass(uint32_t Weight);
BlockMass takeMass(uint32_t Weight);
};
}
DitheringDistributer::DitheringDistributer(Distribution &Dist,
const BlockMass &Mass) {
Dist.normalize();
RemWeight = Dist.Total;
RemForwardWeight = Dist.ForwardTotal;
RemMass = Mass;
RemForwardMass = Dist.ForwardTotal ? Mass : BlockMass();
}
BlockMass DitheringDistributer::takeForwardMass(uint32_t Weight) {
// Compute the amount of mass to take.
assert(Weight && "invalid weight");
assert(Weight <= RemForwardWeight);
BlockMass Mass = RemForwardMass * BranchProbability(Weight, RemForwardWeight);
// Decrement totals (dither).
RemForwardWeight -= Weight;
RemForwardMass -= Mass;
return Mass;
}
BlockMass DitheringDistributer::takeMass(uint32_t Weight) {
assert(Weight && "invalid weight");
assert(Weight <= RemWeight);
BlockMass Mass = RemMass * BranchProbability(Weight, RemWeight);
// Decrement totals (dither).
RemWeight -= Weight;
RemMass -= Mass;
return Mass;
}
void Distribution::add(const BlockNode &Node, uint64_t Amount,
Weight::DistType Type) {
assert(Amount && "invalid weight of 0");
uint64_t NewTotal = Total + Amount;
// Check for overflow. It should be impossible to overflow twice.
bool IsOverflow = NewTotal < Total;
assert(!(DidOverflow && IsOverflow) && "unexpected repeated overflow");
DidOverflow |= IsOverflow;
// Update the total.
Total = NewTotal;
// Save the weight.
Weight W;
W.TargetNode = Node;
W.Amount = Amount;
W.Type = Type;
Weights.push_back(W);
if (Type == Weight::Backedge)
return;
// Update forward total. Don't worry about overflow here, since then Total
// will exceed 32-bits and they'll both be recomputed in normalize().
ForwardTotal += Amount;
}
static void combineWeight(Weight &W, const Weight &OtherW) {
assert(OtherW.TargetNode.isValid());
if (!W.Amount) {
W = OtherW;
return;
}
assert(W.Type == OtherW.Type);
assert(W.TargetNode == OtherW.TargetNode);
assert(W.Amount < W.Amount + OtherW.Amount);
W.Amount += OtherW.Amount;
}
static void combineWeightsBySorting(WeightList &Weights) {
// Sort so edges to the same node are adjacent.
std::sort(Weights.begin(), Weights.end(),
[](const Weight &L,
const Weight &R) { return L.TargetNode < R.TargetNode; });
// Combine adjacent edges.
WeightList::iterator O = Weights.begin();
for (WeightList::const_iterator I = O, L = O, E = Weights.end(); I != E;
++O, (I = L)) {
*O = *I;
// Find the adjacent weights to the same node.
for (++L; L != E && I->TargetNode == L->TargetNode; ++L)
combineWeight(*O, *L);
}
// Erase extra entries.
Weights.erase(O, Weights.end());
return;
}
static void combineWeightsByHashing(WeightList &Weights) {
// Collect weights into a DenseMap.
typedef DenseMap<BlockNode::IndexType, Weight> HashTable;
HashTable Combined(NextPowerOf2(2 * Weights.size()));
for (const Weight &W : Weights)
combineWeight(Combined[W.TargetNode.Index], W);
// Check whether anything changed.
if (Weights.size() == Combined.size())
return;
// Fill in the new weights.
Weights.clear();
Weights.reserve(Combined.size());
for (const auto &I : Combined)
Weights.push_back(I.second);
}
static void combineWeights(WeightList &Weights) {
// Use a hash table for many successors to keep this linear.
if (Weights.size() > 128) {
combineWeightsByHashing(Weights);
return;
}
combineWeightsBySorting(Weights);
}
static uint64_t shiftRightAndRound(uint64_t N, int Shift) {
assert(Shift >= 0);
assert(Shift < 64);
if (!Shift)
return N;
return (N >> Shift) + (UINT64_C(1) & N >> (Shift - 1));
}
void Distribution::normalize() {
// Early exit for termination nodes.
if (Weights.empty())
return;
// Only bother if there are multiple successors.
if (Weights.size() > 1)
combineWeights(Weights);
// Early exit when combined into a single successor.
if (Weights.size() == 1) {
Total = 1;
ForwardTotal = Weights.front().Type != Weight::Backedge;
Weights.front().Amount = 1;
return;
}
// Determine how much to shift right so that the total fits into 32-bits.
//
// If we shift at all, shift by 1 extra. Otherwise, the lower limit of 1
// for each weight can cause a 32-bit overflow.
int Shift = 0;
if (DidOverflow)
Shift = 33;
else if (Total > UINT32_MAX)
Shift = 33 - countLeadingZeros(Total);
// Early exit if nothing needs to be scaled.
if (!Shift)
return;
// Recompute the total through accumulation (rather than shifting it) so that
// it's accurate after shifting. ForwardTotal is dirty here anyway.
Total = 0;
ForwardTotal = 0;
// Sum the weights to each node and shift right if necessary.
for (Weight &W : Weights) {
// Scale down below UINT32_MAX. Since Shift is larger than necessary, we
// can round here without concern about overflow.
assert(W.TargetNode.isValid());
W.Amount = std::max(UINT64_C(1), shiftRightAndRound(W.Amount, Shift));
assert(W.Amount <= UINT32_MAX);
// Update the total.
Total += W.Amount;
if (W.Type == Weight::Backedge)
continue;
// Update the forward total.
ForwardTotal += W.Amount;
}
assert(Total <= UINT32_MAX);
}
void BlockFrequencyInfoImplBase::clear() {
*this = BlockFrequencyInfoImplBase();
}
/// \brief Clear all memory not needed downstream.
///
/// Releases all memory not used downstream. In particular, saves Freqs.
static void cleanup(BlockFrequencyInfoImplBase &BFI) {
std::vector<FrequencyData> SavedFreqs(std::move(BFI.Freqs));
BFI.clear();
BFI.Freqs = std::move(SavedFreqs);
}
/// \brief Get a possibly packaged node.
///
/// Get the node currently representing Node, which could be a containing
/// loop.
///
/// This function should only be called when distributing mass. As long as
/// there are no irreducilbe edges to Node, then it will have complexity O(1)
/// in this context.
///
/// In general, the complexity is O(L), where L is the number of loop headers
/// Node has been packaged into. Since this method is called in the context
/// of distributing mass, L will be the number of loop headers an early exit
/// edge jumps out of.
static BlockNode getPackagedNode(const BlockFrequencyInfoImplBase &BFI,
const BlockNode &Node) {
assert(Node.isValid());
if (!BFI.Working[Node.Index].IsPackaged)
return Node;
if (!BFI.Working[Node.Index].ContainingLoop.isValid())
return Node;
return getPackagedNode(BFI, BFI.Working[Node.Index].ContainingLoop);
}
/// \brief Get the appropriate mass for a possible pseudo-node loop package.
///
/// Get appropriate mass for Node. If Node is a loop-header (whose loop has
/// been packaged), returns the mass of its pseudo-node. If it's a node inside
/// a packaged loop, it returns the loop's pseudo-node.
static BlockMass &getPackageMass(BlockFrequencyInfoImplBase &BFI,
const BlockNode &Node) {
assert(Node.isValid());
assert(!BFI.Working[Node.Index].IsPackaged);
if (!BFI.Working[Node.Index].IsAPackage)
return BFI.Working[Node.Index].Mass;
return BFI.getLoopPackage(Node).Mass;
}
void BlockFrequencyInfoImplBase::addToDist(Distribution &Dist,
const BlockNode &LoopHead,
const BlockNode &Pred,
const BlockNode &Succ,
uint64_t Weight) {
if (!Weight)
Weight = 1;
#ifndef NDEBUG
auto debugSuccessor = [&](const char *Type, const BlockNode &Resolved) {
dbgs() << " =>"
<< " [" << Type << "] weight = " << Weight;
if (Succ != LoopHead)
dbgs() << ", succ = " << getBlockName(Succ);
if (Resolved != Succ)
dbgs() << ", resolved = " << getBlockName(Resolved);
dbgs() << "\n";
};
(void)debugSuccessor;
#endif
if (Succ == LoopHead) {
DEBUG(debugSuccessor("backedge", Succ));
Dist.addBackedge(LoopHead, Weight);
return;
}
BlockNode Resolved = getPackagedNode(*this, Succ);
assert(Resolved != LoopHead);
if (Working[Resolved.Index].ContainingLoop != LoopHead) {
DEBUG(debugSuccessor(" exit ", Resolved));
Dist.addExit(Resolved, Weight);
return;
}
if (!LoopHead.isValid() && Resolved < Pred) {
// Irreducible backedge. Skip this edge in the distribution.
DEBUG(debugSuccessor("skipped ", Resolved));
return;
}
DEBUG(debugSuccessor(" local ", Resolved));
Dist.addLocal(Resolved, Weight);
}
void BlockFrequencyInfoImplBase::addLoopSuccessorsToDist(
const BlockNode &LoopHead, const BlockNode &LocalLoopHead,
Distribution &Dist) {
PackagedLoopData &LoopPackage = getLoopPackage(LocalLoopHead);
const PackagedLoopData::ExitMap &Exits = LoopPackage.Exits;
// Copy the exit map into Dist.
for (const auto &I : Exits)
addToDist(Dist, LoopHead, LocalLoopHead, I.first, I.second.getMass());
// We don't need this map any more. Clear it to prevent quadratic memory
// usage in deeply nested loops with irreducible control flow.
LoopPackage.Exits.clear();
}
/// \brief Get the maximum allowed loop scale.
///
/// Gives the maximum number of estimated iterations allowed for a loop. Very
/// large numbers cause problems downstream (even within 64-bits).
static Float getMaxLoopScale() { return Float(1, 12); }
/// \brief Compute the loop scale for a loop.
void BlockFrequencyInfoImplBase::computeLoopScale(const BlockNode &LoopHead) {
// Compute loop scale.
DEBUG(dbgs() << "compute-loop-scale: " << getBlockName(LoopHead) << "\n");
// LoopScale == 1 / ExitMass
// ExitMass == HeadMass - BackedgeMass
PackagedLoopData &LoopPackage = getLoopPackage(LoopHead);
BlockMass ExitMass = BlockMass::getFull() - LoopPackage.BackedgeMass;
// Block scale stores the inverse of the scale.
LoopPackage.Scale = ExitMass.toFloat().inverse();
DEBUG(dbgs() << " - exit-mass = " << ExitMass << " (" << BlockMass::getFull()
<< " - " << LoopPackage.BackedgeMass << ")\n"
<< " - scale = " << LoopPackage.Scale << "\n");
if (LoopPackage.Scale > getMaxLoopScale()) {
LoopPackage.Scale = getMaxLoopScale();
DEBUG(dbgs() << " - reduced-to-max-scale: " << getMaxLoopScale() << "\n");
}
}
/// \brief Package up a loop.
void BlockFrequencyInfoImplBase::packageLoop(const BlockNode &LoopHead) {
DEBUG(dbgs() << "packaging-loop: " << getBlockName(LoopHead) << "\n");
Working[LoopHead.Index].IsAPackage = true;
for (const BlockNode &M : getLoopPackage(LoopHead).Members) {
DEBUG(dbgs() << " - node: " << getBlockName(M.Index) << "\n");
Working[M.Index].IsPackaged = true;
}
}
void BlockFrequencyInfoImplBase::distributeMass(const BlockNode &Source,
const BlockNode &LoopHead,
Distribution &Dist) {
BlockMass Mass = getPackageMass(*this, Source);
DEBUG(dbgs() << " => mass: " << Mass
<< " ( general | forward )\n");
// Distribute mass to successors as laid out in Dist.
DitheringDistributer D(Dist, Mass);
#ifndef NDEBUG
auto debugAssign = [&](const BlockNode &T, const BlockMass &M,
const char *Desc) {
dbgs() << " => assign " << M << " (" << D.RemMass << "|"
<< D.RemForwardMass << ")";
if (Desc)
dbgs() << " [" << Desc << "]";
if (T.isValid())
dbgs() << " to " << getBlockName(T);
dbgs() << "\n";
};
(void)debugAssign;
#endif
PackagedLoopData *LoopPackage = 0;
if (LoopHead.isValid())
LoopPackage = &getLoopPackage(LoopHead);
for (const Weight &W : Dist.Weights) {
// Check for a local edge (forward and non-exit).
if (W.Type == Weight::Local) {
BlockMass Local = D.takeLocalMass(W.Amount);
getPackageMass(*this, W.TargetNode) += Local;
DEBUG(debugAssign(W.TargetNode, Local, nullptr));
continue;
}
// Backedges and exits only make sense if we're processing a loop.
assert(LoopPackage && "backedge or exit outside of loop");
// Check for a backedge.
if (W.Type == Weight::Backedge) {
BlockMass Back = D.takeBackedgeMass(W.Amount);
LoopPackage->BackedgeMass += Back;
DEBUG(debugAssign(BlockNode(), Back, "back"));
continue;
}
// This must be an exit.
assert(W.Type == Weight::Exit);
BlockMass Exit = D.takeExitMass(W.Amount);
LoopPackage->Exits.push_back(std::make_pair(W.TargetNode, Exit));
DEBUG(debugAssign(W.TargetNode, Exit, "exit"));
}
}
static void convertFloatingToInteger(BlockFrequencyInfoImplBase &BFI,
const Float &Min, const Float &Max) {
// Scale the Factor to a size that creates integers. Ideally, integers would
// be scaled so that Max == UINT64_MAX so that they can be best
// differentiated. However, the register allocator currently deals poorly
// with large numbers. Instead, push Min up a little from 1 to give some
// room to differentiate small, unequal numbers.
//
// TODO: fix issues downstream so that ScalingFactor can be Float(1,64)/Max.
Float ScalingFactor = Min.inverse();
if ((Max / Min).lg() < 60)
ScalingFactor <<= 3;
// Translate the floats to integers.
DEBUG(dbgs() << "float-to-int: min = " << Min << ", max = " << Max
<< ", factor = " << ScalingFactor << "\n");
for (size_t Index = 0; Index < BFI.Freqs.size(); ++Index) {
Float Scaled = BFI.Freqs[Index].Floating * ScalingFactor;
BFI.Freqs[Index].Integer = std::max(UINT64_C(1), Scaled.toInt<uint64_t>());
DEBUG(dbgs() << " - " << BFI.getBlockName(Index) << ": float = "
<< BFI.Freqs[Index].Floating << ", scaled = " << Scaled
<< ", int = " << BFI.Freqs[Index].Integer << "\n");
}
}
static void scaleBlockData(BlockFrequencyInfoImplBase &BFI,
const BlockNode &Node,
const PackagedLoopData &Loop) {
Float F = Loop.Mass.toFloat() * Loop.Scale;
Float &Current = BFI.Freqs[Node.Index].Floating;
Float Updated = Current * F;
DEBUG(dbgs() << " - " << BFI.getBlockName(Node) << ": " << Current << " => "
<< Updated << "\n");
Current = Updated;
}
/// \brief Unwrap a loop package.
///
/// Visits all the members of a loop, adjusting their BlockData according to
/// the loop's pseudo-node.
static void unwrapLoopPackage(BlockFrequencyInfoImplBase &BFI,
const BlockNode &Head) {
assert(Head.isValid());
PackagedLoopData &LoopPackage = BFI.getLoopPackage(Head);
DEBUG(dbgs() << "unwrap-loop-package: " << BFI.getBlockName(Head)
<< ": mass = " << LoopPackage.Mass
<< ", scale = " << LoopPackage.Scale << "\n");
scaleBlockData(BFI, Head, LoopPackage);
// Propagate the head scale through the loop. Since members are visited in
// RPO, the head scale will be updated by the loop scale first, and then the
// final head scale will be used for updated the rest of the members.
for (const BlockNode &M : LoopPackage.Members) {
const FrequencyData &HeadData = BFI.Freqs[Head.Index];
FrequencyData &Freqs = BFI.Freqs[M.Index];
Float NewFreq = Freqs.Floating * HeadData.Floating;
DEBUG(dbgs() << " - " << BFI.getBlockName(M) << ": " << Freqs.Floating
<< " => " << NewFreq << "\n");
Freqs.Floating = NewFreq;
}
}
void BlockFrequencyInfoImplBase::finalizeMetrics() {
// Set initial frequencies from loop-local masses.
for (size_t Index = 0; Index < Working.size(); ++Index)
Freqs[Index].Floating = Working[Index].Mass.toFloat();
// Unwrap loop packages in reverse post-order, tracking min and max
// frequencies.
auto Min = Float::getLargest();
auto Max = Float::getZero();
for (size_t Index = 0; Index < Working.size(); ++Index) {
if (Working[Index].isLoopHeader())
unwrapLoopPackage(*this, BlockNode(Index));
// Update max scale.
Min = std::min(Min, Freqs[Index].Floating);
Max = std::max(Max, Freqs[Index].Floating);
}
// Convert to integers.
convertFloatingToInteger(*this, Min, Max);
// Clean up data structures.
cleanup(*this);
// Print out the final stats.
DEBUG(dump());
}
BlockFrequency
BlockFrequencyInfoImplBase::getBlockFreq(const BlockNode &Node) const {
if (!Node.isValid())
return 0;
return Freqs[Node.Index].Integer;
}
Float
BlockFrequencyInfoImplBase::getFloatingBlockFreq(const BlockNode &Node) const {
if (!Node.isValid())
return Float::getZero();
return Freqs[Node.Index].Floating;
}
std::string
BlockFrequencyInfoImplBase::getBlockName(const BlockNode &Node) const {
return std::string();
}
raw_ostream &
BlockFrequencyInfoImplBase::printBlockFreq(raw_ostream &OS,
const BlockNode &Node) const {
return OS << getFloatingBlockFreq(Node);
}
raw_ostream &
BlockFrequencyInfoImplBase::printBlockFreq(raw_ostream &OS,
const BlockFrequency &Freq) const {
Float Block(Freq.getFrequency(), 0);
Float Entry(getEntryFreq(), 0);
return OS << Block / Entry;
}
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