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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185226 91177308-0d34-0410-b5e6-96231b3b80d8
151 lines
3.7 KiB
C++
151 lines
3.7 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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/// Multiply FREQ by N and store result in W array.
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static 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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/// Divide 96-bit value stored in W array by D.
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/// Return 64-bit quotient, saturated to UINT64_MAX on overflow.
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static 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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unsigned i;
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assert(x != 0 && "This is really a 64-bit division");
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// This long division algorithm automatically saturates on overflow.
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for (i = 0; i < 64 && x; ++i) {
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uint32_t t = -((x >> 31) & 1); // Splat bit 31 to bits 0-31.
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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);
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}
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void BlockFrequency::scale(uint32_t N, uint32_t D) {
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assert(D != 0 && "Division by zero");
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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 the product fits in 64 bits, just use built-in division.
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if (MulHi <= UINT32_MAX && MulRes >= MulLo) {
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Frequency = MulRes / D;
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return;
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}
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// Product overflowed, use 96-bit operations.
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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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mult96bit(Frequency, N, W);
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Frequency = div96bit(W, D);
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return;
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}
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BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
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scale(Prob.getNumerator(), Prob.getDenominator());
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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 BranchProbability &Prob) {
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scale(Prob.getDenominator(), Prob.getNumerator());
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return *this;
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}
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BlockFrequency 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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// Convert fixed-point number to decimal.
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OS << Frequency / getEntryFrequency() << ".";
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uint64_t Rem = Frequency % getEntryFrequency();
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uint64_t Eps = 1;
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do {
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Rem *= 10;
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Eps *= 10;
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OS << Rem / getEntryFrequency();
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Rem = Rem % getEntryFrequency();
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} while (Rem >= Eps/2);
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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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