llvm/unittests/Support/BranchProbabilityTest.cpp
Cong Hou fed6bd8617 Use fixed-point representation for BranchProbability.
BranchProbability now is represented by its numerator and denominator in uint32_t type. This patch changes this representation into a fixed point that is represented by the numerator in uint32_t type and a constant denominator 1<<31. This is quite similar to the representation of BlockMass in BlockFrequencyInfoImpl.h. There are several pros and cons of this change:

Pros:

1. It uses only a half space of the current one.
2. Some operations are much faster like plus, subtraction, comparison, and scaling by an integer.

Cons:

1. Constructing a probability using arbitrary numerator and denominator needs additional calculations.
2. It is a little less precise than before as we use a fixed denominator. For example, 1 - 1/3 may not be exactly identical to 1 / 3 (this will lead to many BranchProbability unit test failures). This should not matter when we only use it for branch probability. If we use it like a rational value for some precise calculations we may need another construct like ValueRatio.

One important reason for this change is that we propose to store branch probabilities instead of edge weights in MachineBasicBlock. We also want clients to use probability instead of weight when adding successors to a MBB. The current BranchProbability has more space which may be a concern.

Differential revision: http://reviews.llvm.org/D12603



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248633 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 23:09:59 +00:00

291 lines
12 KiB
C++

//===- unittest/Support/BranchProbabilityTest.cpp - BranchProbability tests -=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/raw_ostream.h"
#include "gtest/gtest.h"
using namespace llvm;
namespace llvm {
void PrintTo(BranchProbability P, ::std::ostream *os) {
*os << P.getNumerator() << "/" << P.getDenominator();
}
}
namespace {
typedef BranchProbability BP;
TEST(BranchProbabilityTest, Accessors) {
EXPECT_EQ(306783378u, BP(1, 7).getNumerator());
EXPECT_EQ(1u << 31, BP(1, 7).getDenominator());
EXPECT_EQ(0u, BP::getZero().getNumerator());
EXPECT_EQ(1u << 31, BP::getZero().getDenominator());
EXPECT_EQ(1u << 31, BP::getOne().getNumerator());
EXPECT_EQ(1u << 31, BP::getOne().getDenominator());
}
TEST(BranchProbabilityTest, Operators) {
EXPECT_TRUE(BP(1, 7) < BP(2, 7));
EXPECT_TRUE(BP(1, 7) < BP(1, 4));
EXPECT_TRUE(BP(5, 7) < BP(3, 4));
EXPECT_FALSE(BP(1, 7) < BP(1, 7));
EXPECT_FALSE(BP(1, 7) < BP(2, 14));
EXPECT_FALSE(BP(4, 7) < BP(1, 2));
EXPECT_FALSE(BP(4, 7) < BP(3, 7));
EXPECT_FALSE(BP(1, 7) > BP(2, 7));
EXPECT_FALSE(BP(1, 7) > BP(1, 4));
EXPECT_FALSE(BP(5, 7) > BP(3, 4));
EXPECT_FALSE(BP(1, 7) > BP(1, 7));
EXPECT_FALSE(BP(1, 7) > BP(2, 14));
EXPECT_TRUE(BP(4, 7) > BP(1, 2));
EXPECT_TRUE(BP(4, 7) > BP(3, 7));
EXPECT_TRUE(BP(1, 7) <= BP(2, 7));
EXPECT_TRUE(BP(1, 7) <= BP(1, 4));
EXPECT_TRUE(BP(5, 7) <= BP(3, 4));
EXPECT_TRUE(BP(1, 7) <= BP(1, 7));
EXPECT_TRUE(BP(1, 7) <= BP(2, 14));
EXPECT_FALSE(BP(4, 7) <= BP(1, 2));
EXPECT_FALSE(BP(4, 7) <= BP(3, 7));
EXPECT_FALSE(BP(1, 7) >= BP(2, 7));
EXPECT_FALSE(BP(1, 7) >= BP(1, 4));
EXPECT_FALSE(BP(5, 7) >= BP(3, 4));
EXPECT_TRUE(BP(1, 7) >= BP(1, 7));
EXPECT_TRUE(BP(1, 7) >= BP(2, 14));
EXPECT_TRUE(BP(4, 7) >= BP(1, 2));
EXPECT_TRUE(BP(4, 7) >= BP(3, 7));
EXPECT_FALSE(BP(1, 7) == BP(2, 7));
EXPECT_FALSE(BP(1, 7) == BP(1, 4));
EXPECT_FALSE(BP(5, 7) == BP(3, 4));
EXPECT_TRUE(BP(1, 7) == BP(1, 7));
EXPECT_TRUE(BP(1, 7) == BP(2, 14));
EXPECT_FALSE(BP(4, 7) == BP(1, 2));
EXPECT_FALSE(BP(4, 7) == BP(3, 7));
EXPECT_TRUE(BP(1, 7) != BP(2, 7));
EXPECT_TRUE(BP(1, 7) != BP(1, 4));
EXPECT_TRUE(BP(5, 7) != BP(3, 4));
EXPECT_FALSE(BP(1, 7) != BP(1, 7));
EXPECT_FALSE(BP(1, 7) != BP(2, 14));
EXPECT_TRUE(BP(4, 7) != BP(1, 2));
EXPECT_TRUE(BP(4, 7) != BP(3, 7));
EXPECT_TRUE(BP(1, 7) == BP(2, 14));
EXPECT_TRUE(BP(1, 7) == BP(3, 21));
EXPECT_TRUE(BP(5, 7) == BP(25, 35));
EXPECT_TRUE(BP(99999998, 100000000) < BP(99999999, 100000000));
EXPECT_TRUE(BP(4, 8) == BP(400000000, 800000000));
}
TEST(BranchProbabilityTest, MoreOperators) {
BP A(4, 5);
BP B(4U << 29, 5U << 29);
BP C(3, 4);
EXPECT_TRUE(A == B);
EXPECT_FALSE(A != B);
EXPECT_FALSE(A < B);
EXPECT_FALSE(A > B);
EXPECT_TRUE(A <= B);
EXPECT_TRUE(A >= B);
EXPECT_FALSE(B == C);
EXPECT_TRUE(B != C);
EXPECT_FALSE(B < C);
EXPECT_TRUE(B > C);
EXPECT_FALSE(B <= C);
EXPECT_TRUE(B >= C);
BP BigZero(0, UINT32_MAX);
BP BigOne(UINT32_MAX, UINT32_MAX);
EXPECT_FALSE(BigZero == BigOne);
EXPECT_TRUE(BigZero != BigOne);
EXPECT_TRUE(BigZero < BigOne);
EXPECT_FALSE(BigZero > BigOne);
EXPECT_TRUE(BigZero <= BigOne);
EXPECT_FALSE(BigZero >= BigOne);
}
TEST(BranchProbabilityTest, getCompl) {
EXPECT_EQ(BP(5, 7), BP(2, 7).getCompl());
EXPECT_EQ(BP(2, 7), BP(5, 7).getCompl());
EXPECT_EQ(BP::getZero(), BP(7, 7).getCompl());
EXPECT_EQ(BP::getOne(), BP(0, 7).getCompl());
}
TEST(BranchProbabilityTest, scale) {
// Multiply by 1.0.
EXPECT_EQ(UINT64_MAX, BP(1, 1).scale(UINT64_MAX));
EXPECT_EQ(UINT64_MAX, BP(7, 7).scale(UINT64_MAX));
EXPECT_EQ(UINT32_MAX, BP(1, 1).scale(UINT32_MAX));
EXPECT_EQ(UINT32_MAX, BP(7, 7).scale(UINT32_MAX));
EXPECT_EQ(0u, BP(1, 1).scale(0));
EXPECT_EQ(0u, BP(7, 7).scale(0));
// Multiply by 0.0.
EXPECT_EQ(0u, BP(0, 1).scale(UINT64_MAX));
EXPECT_EQ(0u, BP(0, 1).scale(UINT64_MAX));
EXPECT_EQ(0u, BP(0, 1).scale(0));
auto Two63 = UINT64_C(1) << 63;
auto Two31 = UINT64_C(1) << 31;
// Multiply by 0.5.
EXPECT_EQ(Two63 - 1, BP(1, 2).scale(UINT64_MAX));
// Big fractions.
EXPECT_EQ(1u, BP(Two31, UINT32_MAX).scale(2));
EXPECT_EQ(Two31, BP(Two31, UINT32_MAX).scale(Two31 * 2));
EXPECT_EQ(9223372036854775807ULL, BP(Two31, UINT32_MAX).scale(UINT64_MAX));
// High precision.
EXPECT_EQ(UINT64_C(9223372045444710399),
BP(Two31 + 1, UINT32_MAX - 2).scale(UINT64_MAX));
}
TEST(BranchProbabilityTest, scaleByInverse) {
// Divide by 1.0.
EXPECT_EQ(UINT64_MAX, BP(1, 1).scaleByInverse(UINT64_MAX));
EXPECT_EQ(UINT64_MAX, BP(7, 7).scaleByInverse(UINT64_MAX));
EXPECT_EQ(UINT32_MAX, BP(1, 1).scaleByInverse(UINT32_MAX));
EXPECT_EQ(UINT32_MAX, BP(7, 7).scaleByInverse(UINT32_MAX));
EXPECT_EQ(0u, BP(1, 1).scaleByInverse(0));
EXPECT_EQ(0u, BP(7, 7).scaleByInverse(0));
auto MAX_DENOMINATOR = BP::getDenominator();
// Divide by something very small.
EXPECT_EQ(UINT64_MAX, BP(1, UINT32_MAX).scaleByInverse(UINT64_MAX));
EXPECT_EQ(uint64_t(UINT32_MAX) * MAX_DENOMINATOR,
BP(1, MAX_DENOMINATOR).scaleByInverse(UINT32_MAX));
EXPECT_EQ(MAX_DENOMINATOR, BP(1, MAX_DENOMINATOR).scaleByInverse(1));
auto Two63 = UINT64_C(1) << 63;
auto Two31 = UINT64_C(1) << 31;
// Divide by 0.5.
EXPECT_EQ(UINT64_MAX - 1, BP(1, 2).scaleByInverse(Two63 - 1));
EXPECT_EQ(UINT64_MAX, BP(1, 2).scaleByInverse(Two63));
// Big fractions.
EXPECT_EQ(2u, BP(Two31, UINT32_MAX).scaleByInverse(1));
EXPECT_EQ(2u, BP(Two31 - 1, UINT32_MAX).scaleByInverse(1));
EXPECT_EQ(Two31 * 2, BP(Two31, UINT32_MAX).scaleByInverse(Two31));
EXPECT_EQ(Two31 * 2, BP(Two31 - 1, UINT32_MAX).scaleByInverse(Two31));
EXPECT_EQ(UINT64_MAX, BP(Two31, UINT32_MAX).scaleByInverse(Two63 + Two31));
// High precision. The exact answers to these are close to the successors of
// the floor. If we were rounding, these would round up.
EXPECT_EQ(UINT64_C(18446744060824649767),
BP(Two31 + 2, UINT32_MAX - 2)
.scaleByInverse(UINT64_C(9223372047592194056)));
EXPECT_EQ(UINT64_C(18446744060824649739),
BP(Two31 + 1, UINT32_MAX).scaleByInverse(Two63 + Two31));
}
TEST(BranchProbabilityTest, scaleBruteForce) {
struct {
uint64_t Num;
uint32_t Prob[2];
uint64_t Result;
} Tests[] = {
// Data for scaling that results in <= 64 bit division.
{ 0x1423e2a50ULL, { 0x64819521, 0x7765dd13 }, 0x10f418888ULL },
{ 0x35ef14ceULL, { 0x28ade3c7, 0x304532ae }, 0x2d73c33bULL },
{ 0xd03dbfbe24ULL, { 0x790079, 0xe419f3 }, 0x6e776fc2c4ULL },
{ 0x21d67410bULL, { 0x302a9dc2, 0x3ddb4442 }, 0x1a5948fd4ULL },
{ 0x8664aeadULL, { 0x3d523513, 0x403523b1 }, 0x805a04cfULL },
{ 0x201db0cf4ULL, { 0x35112a7b, 0x79fc0c74 }, 0xdf8b07f8ULL },
{ 0x13f1e4430aULL, { 0x21c92bf, 0x21e63aae }, 0x13e0cba26ULL },
{ 0x16c83229ULL, { 0x3793f66f, 0x53180dea }, 0xf3ce7b6ULL },
{ 0xc62415be8ULL, { 0x9cc4a63, 0x4327ae9b }, 0x1ce8b71c1ULL },
{ 0x6fac5e434ULL, { 0xe5f9170, 0x1115e10b }, 0x5df23dd4cULL },
{ 0x1929375f2ULL, { 0x3a851375, 0x76c08456 }, 0xc662b083ULL },
{ 0x243c89db6ULL, { 0x354ebfc0, 0x450ef197 }, 0x1bf8c1663ULL },
{ 0x310e9b31aULL, { 0x1b1b8acf, 0x2d3629f0 }, 0x1d69c93f9ULL },
{ 0xa1fae921dULL, { 0xa7a098c, 0x10469f44 }, 0x684413d6eULL },
{ 0xc1582d957ULL, { 0x498e061, 0x59856bc }, 0x9edc5f4ecULL },
{ 0x57cfee75ULL, { 0x1d061dc3, 0x7c8bfc17 }, 0x1476a220ULL },
{ 0x139220080ULL, { 0x294a6c71, 0x2a2b07c9 }, 0x1329e1c75ULL },
{ 0x1665d353cULL, { 0x7080db5, 0xde0d75c }, 0xb590d9faULL },
{ 0xe8f14541ULL, { 0x5188e8b2, 0x736527ef }, 0xa4971be5ULL },
{ 0x2f4775f29ULL, { 0x254ef0fe, 0x435fcf50 }, 0x1a2e449c1ULL },
{ 0x27b85d8d7ULL, { 0x304c8220, 0x5de678f2 }, 0x146e3befbULL },
{ 0x1d362e36bULL, { 0x36c85b12, 0x37a66f55 }, 0x1cc19b8e7ULL },
{ 0x155fd48c7ULL, { 0xf5894d, 0x1256108 }, 0x11e383604ULL },
{ 0xb5db2d15ULL, { 0x39bb26c5, 0x5bdcda3e }, 0x72499259ULL },
{ 0x153990298ULL, { 0x48921c09, 0x706eb817 }, 0xdb3268e7ULL },
{ 0x28a7c3ed7ULL, { 0x1f776fd7, 0x349f7a70 }, 0x184f73ae2ULL },
{ 0x724dbeabULL, { 0x1bd149f5, 0x253a085e }, 0x5569c0b3ULL },
{ 0xd8f0c513ULL, { 0x18c8cc4c, 0x1b72bad0 }, 0xc3e30642ULL },
{ 0x17ce3dcbULL, { 0x1e4c6260, 0x233b359e }, 0x1478f4afULL },
{ 0x1ce036ce0ULL, { 0x29e3c8af, 0x5318dd4a }, 0xe8e76195ULL },
{ 0x1473ae2aULL, { 0x29b897ba, 0x2be29378 }, 0x13718185ULL },
{ 0x1dd41aa68ULL, { 0x3d0a4441, 0x5a0e8f12 }, 0x1437b6bbfULL },
{ 0x1b49e4a53ULL, { 0x3430c1fe, 0x5a204aed }, 0xfcd6852fULL },
{ 0x217941b19ULL, { 0x12ced2bd, 0x21b68310 }, 0x12aca65b1ULL },
{ 0xac6a4dc8ULL, { 0x3ed68da8, 0x6fdca34c }, 0x60da926dULL },
{ 0x1c503a4e7ULL, { 0xfcbbd32, 0x11e48d17 }, 0x18fec7d37ULL },
{ 0x1c885855ULL, { 0x213e919d, 0x25941897 }, 0x193de742ULL },
{ 0x29b9c168eULL, { 0x2b644aea, 0x45725ee7 }, 0x1a122e5d4ULL },
{ 0x806a33f2ULL, { 0x30a80a23, 0x5063733a }, 0x4db9a264ULL },
{ 0x282afc96bULL, { 0x143ae554, 0x1a9863ff }, 0x1e8de5204ULL },
// Data for scaling that results in > 64 bit division.
{ 0x23ca5f2f672ca41cULL, { 0xecbc641, 0x111373f7 }, 0x1f0301e5c76869c6ULL },
{ 0x5e4f2468142265e3ULL, { 0x1ddf5837, 0x32189233 }, 0x383ca7bad6053ac9ULL },
{ 0x277a1a6f6b266bf6ULL, { 0x415d81a8, 0x61eb5e1e }, 0x1a5a3e1d1c9e8540ULL },
{ 0x1bdbb49a237035cbULL, { 0xea5bf17, 0x1d25ffb3 }, 0xdffc51c5cb51cf1ULL },
{ 0x2bce6d29b64fb8ULL, { 0x3bfd5631, 0x7525c9bb }, 0x166ebedd9581fdULL },
{ 0x3a02116103df5013ULL, { 0x2ee18a83, 0x3299aea8 }, 0x35be89227276f105ULL },
{ 0x7b5762390799b18cULL, { 0x12f8e5b9, 0x2563bcd4 }, 0x3e960077695655a3ULL },
{ 0x69cfd72537021579ULL, { 0x4c35f468, 0x6a40feee }, 0x4be4cb38695a4f30ULL },
{ 0x49dfdf835120f1c1ULL, { 0x8cb3759, 0x559eb891 }, 0x79663f6e3c8d8f6ULL },
{ 0x74b5be5c27676381ULL, { 0x47e4c5e0, 0x7c7b19ff }, 0x4367d2dfb22b3265ULL },
{ 0x4f50f97075e7f431ULL, { 0x9a50a17, 0x11cd1185 }, 0x2af952b30374f382ULL },
{ 0x2f8b0d712e393be4ULL, { 0x1487e386, 0x15aa356e }, 0x2d0df3649b2b19fcULL },
{ 0x224c1c75999d3deULL, { 0x3b2df0ea, 0x4523b100 }, 0x1d5b481d160dd8bULL },
{ 0x2bcbcea22a399a76ULL, { 0x28b58212, 0x48dd013e }, 0x187814d0610c8a56ULL },
{ 0x1dbfca91257cb2d1ULL, { 0x1a8c04d9, 0x5e92502c }, 0x859cf7d19e83ad0ULL },
{ 0x7f20039b57cda935ULL, { 0xeccf651, 0x323f476e }, 0x25720cd9054634bdULL },
{ 0x40512c6a586aa087ULL, { 0x113b0423, 0x398c9eab }, 0x1341c03dbb662054ULL },
{ 0x63d802693f050a11ULL, { 0xf50cdd6, 0xfce2a44 }, 0x60c0177b667a4feaULL },
{ 0x2d956b422838de77ULL, { 0xb2d345b, 0x1321e557 }, 0x1aa0ed16b094575cULL },
{ 0x5a1cdf0c1657bc91ULL, { 0x1d77bb0c, 0x1f991ff1 }, 0x54097ee9907290eaULL },
{ 0x3801b26d7e00176bULL, { 0xeed25da, 0x1a819d8b }, 0x1f89e96a616b9abeULL },
{ 0x37655e74338e1e45ULL, { 0x300e170a, 0x5a1595fe }, 0x1d8cfb55ff6a6dbcULL },
{ 0x7b38703f2a84e6ULL, { 0x66d9053, 0xc79b6b9 }, 0x3f7d4c91b9afb9ULL },
{ 0x2245063c0acb3215ULL, { 0x30ce2f5b, 0x610e7271 }, 0x113b916455fe2560ULL },
{ 0x6bc195877b7b8a7eULL, { 0x392004aa, 0x4a24e60c }, 0x530594fabfc81cc3ULL },
{ 0x40a3fde23c7b43dbULL, { 0x4e712195, 0x6553e56e }, 0x320a799bc205c78dULL },
{ 0x1d3dfc2866fbccbaULL, { 0x5075b517, 0x5fc42245 }, 0x18917f00745cb781ULL },
{ 0x19aeb14045a61121ULL, { 0x1bf6edec, 0x707e2f4b }, 0x6626672aa2ba10aULL },
{ 0x44ff90486c531e9fULL, { 0x66598a, 0x8a90dc }, 0x32f6f2b097001598ULL },
{ 0x3f3e7121092c5bcbULL, { 0x1c754df7, 0x5951a1b9 }, 0x14267f50d4971583ULL },
{ 0x60e2dafb7e50a67eULL, { 0x4d96c66e, 0x65bd878d }, 0x49e317155d75e883ULL },
{ 0x656286667e0e6e29ULL, { 0x9d971a2, 0xacda23b }, 0x5c6ee3159e1deac3ULL },
{ 0x1114e0974255d507ULL, { 0x1c693, 0x2d6ff }, 0xaae42e4be5f9f8dULL },
{ 0x508c8baf3a70ff5aULL, { 0x3b26b779, 0x6ad78745 }, 0x2c983876178ed5b1ULL },
{ 0x5b47bc666bf1f9cfULL, { 0x10a87ed6, 0x187d358a }, 0x3e1767153bea720aULL },
{ 0x50954e3744460395ULL, { 0x7a42263, 0xcdaa048 }, 0x2fe739f0944a023cULL },
{ 0x20020b406550dd8fULL, { 0x3318539, 0x42eead0 }, 0x186f326307c0d985ULL },
{ 0x5bcb0b872439ffd5ULL, { 0x6f61fb2, 0x9af7344 }, 0x41fa1e3c47f0f80dULL },
{ 0x7a670f365db87a53ULL, { 0x417e102, 0x3bb54c67 }, 0x8642a551d0f41b0ULL },
{ 0x1ef0db1e7bab1cd0ULL, { 0x2b60cf38, 0x4188f78f }, 0x147ae0d63fc0575aULL }
};
for (const auto &T : Tests) {
EXPECT_EQ(T.Result, BP(T.Prob[0], T.Prob[1]).scale(T.Num));
}
}
}