1 files changed, 112 insertions, 0 deletions
diff --git a/llvm/lib/Support/BranchProbability.cpp b/llvm/lib/Support/BranchProbability.cpp
new file mode 100644
index 000000000000..195e2d58d8e1
--- /dev/null
+++ b/llvm/lib/Support/BranchProbability.cpp
@@ -0,0 +1,112 @@
+//===-------------- lib/Support/BranchProbability.cpp -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements Branch Probability class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/BranchProbability.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+
+using namespace llvm;
+
+const uint32_t BranchProbability::D;
+
+raw_ostream &BranchProbability::print(raw_ostream &OS) const {
+  if (isUnknown())
+    return OS << "?%";
+
+  // Get a percentage rounded to two decimal digits. This avoids
+  // implementation-defined rounding inside printf.
+  double Percent = rint(((double)N / D) * 100.0 * 100.0) / 100.0;
+  return OS << format("0x%08" PRIx32 " / 0x%08" PRIx32 " = %.2f%%", N, D,
+                      Percent);
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void BranchProbability::dump() const { print(dbgs()) << '\n'; }
+#endif
+
+BranchProbability::BranchProbability(uint32_t Numerator, uint32_t Denominator) {
+  assert(Denominator > 0 && "Denominator cannot be 0!");
+  assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
+  if (Denominator == D)
+    N = Numerator;
+  else {
+    uint64_t Prob64 =
+        (Numerator * static_cast<uint64_t>(D) + Denominator / 2) / Denominator;
+    N = static_cast<uint32_t>(Prob64);
+  }
+}
+
+BranchProbability
+BranchProbability::getBranchProbability(uint64_t Numerator,
+                                        uint64_t Denominator) {
+  assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
+  // Scale down Denominator to fit in a 32-bit integer.
+  int Scale = 0;
+  while (Denominator > UINT32_MAX) {
+    Denominator >>= 1;
+    Scale++;
+  }
+  return BranchProbability(Numerator >> Scale, Denominator);
+}
+
+// If ConstD is not zero, then replace D by ConstD so that division and modulo
+// operations by D can be optimized, in case this function is not inlined by the
+// compiler.
+template <uint32_t ConstD>
+static uint64_t scale(uint64_t Num, uint32_t N, uint32_t D) {
+  if (ConstD > 0)
+    D = ConstD;
+
+  assert(D && "divide by 0");
+
+  // Fast path for multiplying by 1.0.
+  if (!Num || D == N)
+    return Num;
+
+  // Split Num into upper and lower parts to multiply, then recombine.
+  uint64_t ProductHigh = (Num >> 32) * N;
+  uint64_t ProductLow = (Num & UINT32_MAX) * N;
+
+  // Split into 32-bit digits.
+  uint32_t Upper32 = ProductHigh >> 32;
+  uint32_t Lower32 = ProductLow & UINT32_MAX;
+  uint32_t Mid32Partial = ProductHigh & UINT32_MAX;
+  uint32_t Mid32 = Mid32Partial + (ProductLow >> 32);
+
+  // Carry.
+  Upper32 += Mid32 < Mid32Partial;
+
+  uint64_t Rem = (uint64_t(Upper32) << 32) | Mid32;
+  uint64_t UpperQ = Rem / D;
+
+  // Check for overflow.
+  if (UpperQ > UINT32_MAX)
+    return UINT64_MAX;
+
+  Rem = ((Rem % D) << 32) | Lower32;
+  uint64_t LowerQ = Rem / D;
+  uint64_t Q = (UpperQ << 32) + LowerQ;
+
+  // Check for overflow.
+  return Q < LowerQ ? UINT64_MAX : Q;
+}
+
+uint64_t BranchProbability::scale(uint64_t Num) const {
+  return ::scale<D>(Num, N, D);
+}
+
+uint64_t BranchProbability::scaleByInverse(uint64_t Num) const {
+  return ::scale<0>(Num, D, N);
+}