1 //===-------------- lib/Support/BranchProbability.cpp -----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements Branch Probability class.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Support/BranchProbability.h"
15 #include "llvm/Support/Debug.h"
16 #include "llvm/Support/Format.h"
17 #include "llvm/Support/raw_ostream.h"
21 void BranchProbability::print(raw_ostream &OS) const {
22 OS << N << " / " << D << " = " << format("%g%%", ((double)N / D) * 100.0);
25 void BranchProbability::dump() const {
26 dbgs() << *this << '\n';
29 static uint64_t scale(uint64_t Num, uint32_t N, uint32_t D) {
30 assert(D && "divide by 0");
32 // Fast path for multiplying by 1.0.
36 // Split Num into upper and lower parts to multiply, then recombine.
37 uint64_t ProductHigh = (Num >> 32) * N;
38 uint64_t ProductLow = (Num & UINT32_MAX) * N;
40 // Split into 32-bit digits.
41 uint32_t Upper32 = ProductHigh >> 32;
42 uint32_t Lower32 = ProductLow & UINT32_MAX;
43 uint32_t Mid32Partial = ProductHigh & UINT32_MAX;
44 uint32_t Mid32 = Mid32Partial + (ProductLow >> 32);
47 Upper32 += Mid32 < Mid32Partial;
49 // Check for overflow.
53 uint64_t Rem = (uint64_t(Upper32) << 32) | Mid32;
54 uint64_t UpperQ = Rem / D;
56 // Check for overflow.
57 if (UpperQ > UINT32_MAX)
60 Rem = ((Rem % D) << 32) | Lower32;
61 uint64_t LowerQ = Rem / D;
62 uint64_t Q = (UpperQ << 32) + LowerQ;
64 // Check for overflow.
65 return Q < LowerQ ? UINT64_MAX : Q;
68 uint64_t BranchProbability::scale(uint64_t Num) const {
69 return ::scale(Num, N, D);
72 uint64_t BranchProbability::scaleByInverse(uint64_t Num) const {
73 return ::scale(Num, D, N);
78 raw_ostream &operator<<(raw_ostream &OS, const BranchProbability &Prob) {