Add BlockFrequency class.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135992 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 120 insertions, 0 deletions

diff --git a/lib/Support/BlockFrequency.cpp b/lib/Support/BlockFrequency.cpp
new file mode 100644
index 0000000000..87e1b2dba0
--- /dev/null
+++ b/lib/Support/BlockFrequency.cpp
@@ -0,0 +1,120 @@
+//====--------------- lib/Support/BlockFrequency.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 Block Frequency class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/BranchProbability.h"
+#include "llvm/Support/BlockFrequency.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+
+using namespace llvm;
+
+/// mult96bit - Multiply FREQ by N and store result in W array.
+void BlockFrequency::mult96bit(uint64_t freq, uint32_t N, uint64_t W[2]) {
+  uint64_t u0 = freq & UINT32_MAX;
+  uint64_t u1 = freq >> 32;
+
+  // Represent 96-bit value as w[2]:w[1]:w[0];
+  uint32_t w[3] = { 0, 0, 0 };
+
+  uint64_t t = u0 * N;
+  uint64_t k = t >> 32;
+  w[0] = t;
+  t = u1 * N + k;
+  w[1] = t;
+  w[2] = t >> 32;
+
+  // W[1] - higher bits.
+  // W[0] - lower bits.
+  W[0] = w[0] + ((uint64_t) w[1] << 32);
+  W[1] = w[2];
+}
+
+
+/// div96bit - Divide 96-bit value stored in W array by D. Return 64-bit frequency.
+uint64_t BlockFrequency::div96bit(uint64_t W[2], uint32_t D) {
+  uint64_t y = W[0];
+  uint64_t x = W[1];
+
+  for (int i = 1; i <= 64; ++i) {
+    uint32_t t = (int)x >> 31;
+    x = (x << 1) | (y >> 63);
+    y = y << 1;
+    if ((x | t) >= D) {
+      x -= D;
+      ++y;
+    }
+  }
+
+  return y;
+}
+
+BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
+  uint32_t n = Prob.getNumerator();
+  uint32_t d = Prob.getDenominator();
+
+  assert(n <= d && "Probability must be less or equal to 1.");
+
+  // If we can overflow use 96-bit operations.
+  if (n > 0 && Frequency > UINT64_MAX / n) {
+    // 96-bit value represented as W[1]:W[0].
+    uint64_t W[2];
+
+    // Probability is less or equal to 1 which means that results must fit
+    // 64-bit.
+    mult96bit(Frequency, n, W);
+    Frequency = div96bit(W, d);
+    return *this;
+  }
+
+  Frequency *= n;
+  Frequency /= d;
+  return *this;
+}
+
+const BlockFrequency
+BlockFrequency::operator*(const BranchProbability &Prob) const {
+  BlockFrequency Freq(Frequency);
+  Freq *= Prob;
+  return Freq;
+}
+
+BlockFrequency &BlockFrequency::operator+=(const BlockFrequency &Freq) {
+  uint64_t Before = Freq.Frequency;
+  Frequency += Freq.Frequency;
+
+  // If overflow, set frequency to the maximum value.
+  if (Frequency < Before)
+    Frequency = UINT64_MAX;
+
+  return *this;
+}
+
+const BlockFrequency
+BlockFrequency::operator+(const BlockFrequency &Prob) const {
+  BlockFrequency Freq(Frequency);
+  Freq += Prob;
+  return Freq;
+}
+
+void BlockFrequency::print(raw_ostream &OS) const {
+  OS << Frequency;
+}
+
+namespace llvm {
+
+raw_ostream &operator<<(raw_ostream &OS, const BlockFrequency &Freq) {
+  Freq.print(OS);
+  return OS;
+}
+
+}