3 files changed, 26 insertions, 23 deletions

diff --git a/src/mongo/platform/atomic_word.h b/src/mongo/platform/atomic_word.h
index c277497b15c..5a7d38ccca7 100644
--- a/src/mongo/platform/atomic_word.h
+++ b/src/mongo/platform/atomic_word.h
@@ -87,9 +87,7 @@ public:
     }
 
     /**
-     * Gets the current value of this AtomicWord.
-     *
-     * Has relaxed semantics.
+     * Gets the current value of this AtomicWord using relaxed memory order.
      */
     WordType loadRelaxed() const {
         return _value.load(std::memory_order_relaxed);
@@ -103,6 +101,13 @@ public:
     }
 
     /**
+     * Sets the value of this AtomicWord to "newValue" using relaxed memory order.
+     */
+    void storeRelaxed(WordType newValue) {
+        _value.store(newValue, std::memory_order_relaxed);
+    }
+
+    /**
      * Atomically swaps the current value of this with "newValue".
      *
      * Returns the old value.
diff --git a/src/mongo/platform/decimal128.cpp b/src/mongo/platform/decimal128.cpp
index 0d12479f70a..ef785025b17 100644
--- a/src/mongo/platform/decimal128.cpp
+++ b/src/mongo/platform/decimal128.cpp
@@ -827,36 +827,33 @@ Decimal128 Decimal128::exponential(std::uint32_t* signalingFlags, RoundingMode r
     return Decimal128{libraryTypeToValue(current)};
 }
 
-Decimal128 Decimal128::logarithm(RoundingMode roundMode) const {
+Decimal128 Decimal128::naturalLogarithm(RoundingMode roundMode) const {
     std::uint32_t throwAwayFlag = 0;
-    return logarithm(&throwAwayFlag, roundMode);
+    return naturalLogarithm(&throwAwayFlag, roundMode);
 }
 
-Decimal128 Decimal128::logarithm(std::uint32_t* signalingFlags, RoundingMode roundMode) const {
+Decimal128 Decimal128::naturalLogarithm(std::uint32_t* signalingFlags,
+                                        RoundingMode roundMode) const {
     BID_UINT128 current = decimal128ToLibraryType(_value);
     current = bid128_log(current, roundMode, signalingFlags);
     return Decimal128{libraryTypeToValue(current)};
 }
 
-Decimal128 Decimal128::logarithm(const Decimal128& other, RoundingMode roundMode) const {
+Decimal128 Decimal128::logarithm(const Decimal128& base, RoundingMode roundMode) const {
     std::uint32_t throwAwayFlag = 0;
-    if (other.isEqual(Decimal128(2))) {
+    if (base.isEqual(Decimal128(2))) {
         BID_UINT128 current = decimal128ToLibraryType(_value);
         current = bid128_log2(current, roundMode, &throwAwayFlag);
         return Decimal128{libraryTypeToValue(current)};
     }
-    if (other.isEqual(Decimal128(10))) {
+    if (base.isEqual(Decimal128(10))) {
         BID_UINT128 current = decimal128ToLibraryType(_value);
         current = bid128_log10(current, roundMode, &throwAwayFlag);
         return Decimal128{libraryTypeToValue(current)};
     }
-    return logarithm(other, &throwAwayFlag);
-}
-
-Decimal128 Decimal128::logarithm(const Decimal128& other,
-                                 std::uint32_t* signalingFlags,
-                                 RoundingMode roundMode) const {
-    return logarithm(signalingFlags, roundMode).divide(other);
+    // Logarithm with a generic base is equivalent to `ln(input) / ln(base)`.
+    return naturalLogarithm(&throwAwayFlag, roundMode)
+        .divide(base.naturalLogarithm(&throwAwayFlag, roundMode));
 }
 
 Decimal128 Decimal128::modulo(const Decimal128& other) const {
diff --git a/src/mongo/platform/decimal128.h b/src/mongo/platform/decimal128.h
index 64306df0e0c..06a78352546 100644
--- a/src/mongo/platform/decimal128.h
+++ b/src/mongo/platform/decimal128.h
@@ -467,13 +467,14 @@ public:
     Decimal128 exponential(RoundingMode roundMode = kRoundTiesToEven) const;
     Decimal128 exponential(std::uint32_t* signalingFlags,
                            RoundingMode roundMode = kRoundTiesToEven) const;
-    Decimal128 logarithm(RoundingMode roundMode = kRoundTiesToEven) const;
-    Decimal128 logarithm(std::uint32_t* signalingFlags,
-                         RoundingMode roundMode = kRoundTiesToEven) const;
-    Decimal128 logarithm(const Decimal128& other, RoundingMode roundMode = kRoundTiesToEven) const;
-    Decimal128 logarithm(const Decimal128& other,
-                         std::uint32_t* signalingFlags,
-                         RoundingMode roundMode = kRoundTiesToEven) const;
+    Decimal128 naturalLogarithm(RoundingMode roundMode = kRoundTiesToEven) const;
+    Decimal128 naturalLogarithm(std::uint32_t* signalingFlags,
+                                RoundingMode roundMode = kRoundTiesToEven) const;
+    // Calculate the logarithm with the given `base`, using this number as input. Uses fast paths
+    // for base 2 and 10.
+    // TODO SERVER-91935 convert `logarithm` and others to static methods for a more clear
+    // interface.
+    Decimal128 logarithm(const Decimal128& base, RoundingMode roundMode = kRoundTiesToEven) const;
     Decimal128 modulo(const Decimal128& other) const;
     Decimal128 modulo(const Decimal128& other, std::uint32_t* signalingFlags) const;