| //===-------------- lib/Support/BranchProbability.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 Branch Probability class. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #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"); |
| |
| // Fast path for multiplying by 1.0. |
| if (!Num || D == N) |
| return Num; |
| |
| // Split Num into upper and lower parts to multiply, then recombine. |
| uint64_t ProductHigh = (Num >> 32) * N; |
| uint64_t ProductLow = (Num & UINT32_MAX) * N; |
| |
| // Split into 32-bit digits. |
| uint32_t Upper32 = ProductHigh >> 32; |
| uint32_t Lower32 = ProductLow & UINT32_MAX; |
| uint32_t Mid32Partial = ProductHigh & UINT32_MAX; |
| uint32_t Mid32 = Mid32Partial + (ProductLow >> 32); |
| |
| // Carry. |
| Upper32 += Mid32 < Mid32Partial; |
| |
| // Check for overflow. |
| if (Upper32 >= D) |
| return UINT64_MAX; |
| |
| uint64_t Rem = (uint64_t(Upper32) << 32) | Mid32; |
| uint64_t UpperQ = Rem / D; |
| |
| // Check for overflow. |
| if (UpperQ > UINT32_MAX) |
| return UINT64_MAX; |
| |
| Rem = ((Rem % D) << 32) | Lower32; |
| uint64_t LowerQ = Rem / D; |
| uint64_t Q = (UpperQ << 32) + LowerQ; |
| |
| // Check for overflow. |
| 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); |
| } |