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"
using namespace llvm;
raw_ostream &BranchProbability::print(raw_ostream &OS) const {
return OS << N << " / " << D << " = "
<< format("%g%%", ((double)N / D) * 100.0);
}
void BranchProbability::dump() const { print(dbgs()) << '\n'; }
static uint64_t scale(uint64_t Num, uint32_t N, uint32_t D) {
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(Num, N, D);
}
uint64_t BranchProbability::scaleByInverse(uint64_t Num) const {
return ::scale(Num, D, N);
}