BranchProbability.cpp [plain text]
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
using namespace llvm;
const uint32_t BranchProbability::D;
raw_ostream &BranchProbability::print(raw_ostream &OS) const {
double Percent = rint(((double)N / D) * 100.0 * 100.0) / 100.0;
OS << format("0x%08" PRIx32 " / 0x%08" PRIx32 " = %.2f%%", N, D, Percent);
return OS;
}
void BranchProbability::dump() const { print(dbgs()) << '\n'; }
BranchProbability::BranchProbability(uint32_t Numerator, uint32_t Denominator) {
assert(Denominator > 0 && "Denominator cannot be 0!");
assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
if (Denominator == D)
N = Numerator;
else {
uint64_t Prob64 =
(Numerator * static_cast<uint64_t>(D) + Denominator / 2) / Denominator;
N = static_cast<uint32_t>(Prob64);
}
}
template <uint32_t ConstD>
static uint64_t scale(uint64_t Num, uint32_t N, uint32_t D) {
if (ConstD > 0)
D = ConstD;
assert(D && "divide by 0");
if (!Num || D == N)
return Num;
uint64_t ProductHigh = (Num >> 32) * N;
uint64_t ProductLow = (Num & UINT32_MAX) * N;
uint32_t Upper32 = ProductHigh >> 32;
uint32_t Lower32 = ProductLow & UINT32_MAX;
uint32_t Mid32Partial = ProductHigh & UINT32_MAX;
uint32_t Mid32 = Mid32Partial + (ProductLow >> 32);
Upper32 += Mid32 < Mid32Partial;
if (Upper32 >= D)
return UINT64_MAX;
uint64_t Rem = (uint64_t(Upper32) << 32) | Mid32;
uint64_t UpperQ = Rem / D;
if (UpperQ > UINT32_MAX)
return UINT64_MAX;
Rem = ((Rem % D) << 32) | Lower32;
uint64_t LowerQ = Rem / D;
uint64_t Q = (UpperQ << 32) + LowerQ;
return Q < LowerQ ? UINT64_MAX : Q;
}
uint64_t BranchProbability::scale(uint64_t Num) const {
return ::scale<D>(Num, N, D);
}
uint64_t BranchProbability::scaleByInverse(uint64_t Num) const {
return ::scale<0>(Num, D, N);
}