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//====--------------- lib/Support/BlockFrequency.cpp -----------*- C++ -*-====//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements Block Frequency class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
using namespace llvm;
namespace {
/// mult96bit - Multiply FREQ by N and store result in W array.
void mult96bit(uint64_t freq, uint32_t N, uint64_t W[2]) {
uint64_t u0 = freq & UINT32_MAX;
uint64_t u1 = freq >> 32;
// Represent 96-bit value as w[2]:w[1]:w[0];
uint32_t w[3] = { 0, 0, 0 };
uint64_t t = u0 * N;
uint64_t k = t >> 32;
w[0] = t;
t = u1 * N + k;
w[1] = t;
w[2] = t >> 32;
// W[1] - higher bits.
// W[0] - lower bits.
W[0] = w[0] + ((uint64_t) w[1] << 32);
W[1] = w[2];
}
/// div96bit - Divide 96-bit value stored in W array by D. Return 64-bit frequency.
uint64_t div96bit(uint64_t W[2], uint32_t D) {
uint64_t y = W[0];
uint64_t x = W[1];
int i;
for (i = 1; i <= 64 && x; ++i) {
uint32_t t = (int)x >> 31;
x = (x << 1) | (y >> 63);
y = y << 1;
if ((x | t) >= D) {
x -= D;
++y;
}
}
return y << (64 - i + 1);
}
}
BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
uint32_t n = Prob.getNumerator();
uint32_t d = Prob.getDenominator();
assert(n <= d && "Probability must be less or equal to 1.");
// Calculate Frequency * n.
uint64_t mulLo = (Frequency & UINT32_MAX) * n;
uint64_t mulHi = (Frequency >> 32) * n;
uint64_t mulRes = (mulHi << 32) + mulLo;
// If there was overflow use 96-bit operations.
if (mulHi > UINT32_MAX || mulRes < mulLo) {
// 96-bit value represented as W[1]:W[0].
uint64_t W[2];
// Probability is less or equal to 1 which means that results must fit
// 64-bit.
mult96bit(Frequency, n, W);
Frequency = div96bit(W, d);
return *this;
}
Frequency = mulRes / d;
return *this;
}
const BlockFrequency
BlockFrequency::operator*(const BranchProbability &Prob) const {
BlockFrequency Freq(Frequency);
Freq *= Prob;
return Freq;
}
BlockFrequency &BlockFrequency::operator+=(const BlockFrequency &Freq) {
uint64_t Before = Freq.Frequency;
Frequency += Freq.Frequency;
// If overflow, set frequency to the maximum value.
if (Frequency < Before)
Frequency = UINT64_MAX;
return *this;
}
const BlockFrequency
BlockFrequency::operator+(const BlockFrequency &Prob) const {
BlockFrequency Freq(Frequency);
Freq += Prob;
return Freq;
}
void BlockFrequency::print(raw_ostream &OS) const {
OS << Frequency;
}
namespace llvm {
raw_ostream &operator<<(raw_ostream &OS, const BlockFrequency &Freq) {
Freq.print(OS);
return OS;
}
}
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