#define LLVM_SUPPORT_BRANCHPROBABILITY_H
#include "llvm/Support/DataTypes.h"
+#include <algorithm>
#include <cassert>
+#include <climits>
+#include <numeric>
namespace llvm {
template <class ProbabilityList>
static void normalizeProbabilities(ProbabilityList &Probs);
+ // Normalize a list of weights by scaling them down so that the sum of them
+ // doesn't exceed UINT32_MAX.
+ template <class WeightListIter>
+ static void normalizeEdgeWeights(WeightListIter Begin, WeightListIter End);
+
uint32_t getNumerator() const { return N; }
static uint32_t getDenominator() { return D; }
Prob.N = (Prob.N * uint64_t(D) + Sum / 2) / Sum;
}
+template <class WeightListIter>
+void BranchProbability::normalizeEdgeWeights(WeightListIter Begin,
+ WeightListIter End) {
+ // First we compute the sum with 64-bits of precision.
+ uint64_t Sum = std::accumulate(Begin, End, uint64_t(0));
+
+ if (Sum > UINT32_MAX) {
+ // Compute the scale necessary to cause the weights to fit, and re-sum with
+ // that scale applied.
+ assert(Sum / UINT32_MAX < UINT32_MAX &&
+ "The sum of weights exceeds UINT32_MAX^2!");
+ uint32_t Scale = Sum / UINT32_MAX + 1;
+ for (auto I = Begin; I != End; ++I)
+ *I /= Scale;
+ Sum = std::accumulate(Begin, End, uint64_t(0));
+ }
+
+ // Eliminate zero weights.
+ auto ZeroWeightNum = std::count(Begin, End, 0u);
+ if (ZeroWeightNum > 0) {
+ // If all weights are zeros, replace them by 1.
+ if (Sum == 0)
+ std::fill(Begin, End, 1u);
+ else {
+ // We are converting zeros into ones, and here we need to make sure that
+ // after this the sum won't exceed UINT32_MAX.
+ if (Sum + ZeroWeightNum > UINT32_MAX) {
+ for (auto I = Begin; I != End; ++I)
+ *I /= 2;
+ ZeroWeightNum = std::count(Begin, End, 0u);
+ Sum = std::accumulate(Begin, End, uint64_t(0));
+ }
+ // Scale up non-zero weights and turn zero weights into ones.
+ uint64_t ScalingFactor = (UINT32_MAX - ZeroWeightNum) / Sum;
+ assert(ScalingFactor >= 1);
+ if (ScalingFactor > 1)
+ for (auto I = Begin; I != End; ++I)
+ *I *= ScalingFactor;
+ std::replace(Begin, End, 0u, 1u);
+ }
+ }
+}
+
}
#endif