mirror of
https://github.com/c64scene-ar/llvm-6502.git
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bc1430a0a0
This trades one 64 bit div for one 64 bit mul and some arithmetic. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143106 91177308-0d34-0410-b5e6-96231b3b80d8
131 lines
3.0 KiB
C++
131 lines
3.0 KiB
C++
//====--------------- lib/Support/BlockFrequency.cpp -----------*- C++ -*-====//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements Block Frequency class.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/BranchProbability.h"
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#include "llvm/Support/BlockFrequency.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cassert>
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using namespace llvm;
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namespace {
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/// mult96bit - Multiply FREQ by N and store result in W array.
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void mult96bit(uint64_t freq, uint32_t N, uint64_t W[2]) {
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uint64_t u0 = freq & UINT32_MAX;
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uint64_t u1 = freq >> 32;
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// Represent 96-bit value as w[2]:w[1]:w[0];
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uint32_t w[3] = { 0, 0, 0 };
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uint64_t t = u0 * N;
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uint64_t k = t >> 32;
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w[0] = t;
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t = u1 * N + k;
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w[1] = t;
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w[2] = t >> 32;
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// W[1] - higher bits.
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// W[0] - lower bits.
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W[0] = w[0] + ((uint64_t) w[1] << 32);
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W[1] = w[2];
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}
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/// div96bit - Divide 96-bit value stored in W array by D. Return 64-bit frequency.
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uint64_t div96bit(uint64_t W[2], uint32_t D) {
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uint64_t y = W[0];
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uint64_t x = W[1];
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int i;
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for (i = 1; i <= 64 && x; ++i) {
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uint32_t t = (int)x >> 31;
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x = (x << 1) | (y >> 63);
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y = y << 1;
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if ((x | t) >= D) {
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x -= D;
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++y;
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}
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}
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return y << (64 - i + 1);
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}
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}
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BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
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uint32_t n = Prob.getNumerator();
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uint32_t d = Prob.getDenominator();
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assert(n <= d && "Probability must be less or equal to 1.");
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// Calculate Frequency * n.
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uint64_t mulLo = (Frequency & UINT32_MAX) * n;
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uint64_t mulHi = (Frequency >> 32) * n;
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uint64_t mulRes = (mulHi << 32) + mulLo;
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// If there was overflow use 96-bit operations.
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if (mulHi > UINT32_MAX || mulRes < mulLo) {
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// 96-bit value represented as W[1]:W[0].
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uint64_t W[2];
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// Probability is less or equal to 1 which means that results must fit
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// 64-bit.
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mult96bit(Frequency, n, W);
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Frequency = div96bit(W, d);
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return *this;
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}
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Frequency = mulRes / d;
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return *this;
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}
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const BlockFrequency
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BlockFrequency::operator*(const BranchProbability &Prob) const {
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BlockFrequency Freq(Frequency);
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Freq *= Prob;
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return Freq;
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}
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BlockFrequency &BlockFrequency::operator+=(const BlockFrequency &Freq) {
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uint64_t Before = Freq.Frequency;
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Frequency += Freq.Frequency;
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// If overflow, set frequency to the maximum value.
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if (Frequency < Before)
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Frequency = UINT64_MAX;
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return *this;
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}
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const BlockFrequency
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BlockFrequency::operator+(const BlockFrequency &Prob) const {
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BlockFrequency Freq(Frequency);
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Freq += Prob;
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return Freq;
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}
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void BlockFrequency::print(raw_ostream &OS) const {
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OS << Frequency;
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}
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namespace llvm {
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raw_ostream &operator<<(raw_ostream &OS, const BlockFrequency &Freq) {
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Freq.print(OS);
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return OS;
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}
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}
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