Revert r254348: "Replace all weight-based interfaces in MBB with probability-based...

[oota-llvm.git] / lib / Support / BranchProbability.cpp

diff --git a/lib/Support/BranchProbability.cpp b/lib/Support/BranchProbability.cpp
index e8b83e59802d167ef45f0d80d612786803e7c1fe..3b0f6e6f06e42c48157190dac6b3887047e951f1 100644 (file)
--- a/lib/Support/BranchProbability.cpp
+++ b/lib/Support/BranchProbability.cpp
@@ -15,22 +15,84 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
 
 using namespace llvm;
 
-void BranchProbability::print(raw_ostream &OS) const {
-  OS << N << " / " << D << " = " << format("%g%%", ((double)N / D) * 100.0);
+const uint32_t BranchProbability::D;
+
+raw_ostream &BranchProbability::print(raw_ostream &OS) const {
+  // 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;
+  OS << format("0x%08" PRIx32 " / 0x%08" PRIx32 " = %.2f%%", N, D, Percent);
+  return OS;
 }
 
-void BranchProbability::dump() const {
-  dbgs() << *this << '\n';
+void BranchProbability::dump() const { print(dbgs()) << '\n'; }
+
+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);
+  }
 }
 
-namespace llvm {
+// 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;
 
-raw_ostream &operator<<(raw_ostream &OS, const BranchProbability &Prob) {
-  Prob.print(OS);
-  return OS;
+  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;
+
+  // Check for overflow.
+  if (Upper32 >= D)
+    return UINT64_MAX;
+
+  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);
 }