1 files changed, 8 insertions, 0 deletions
diff --git a/libraries/base/Data/Bits.hs b/libraries/base/Data/Bits.hs
index 000e663b83..69446f9adc 100644
--- a/libraries/base/Data/Bits.hs
+++ b/libraries/base/Data/Bits.hs
@@ -438,6 +438,9 @@ instance Bits Int where
     {-# INLINE shift #-}
     {-# INLINE bit #-}
     {-# INLINE testBit #-}
+    -- We want popCnt# to be inlined in user code so that `ghc -msse4.2`
+    -- can compile it down to a popcnt instruction without an extra function call
+    {-# INLINE popCount #-}
 
     zeroBits = 0
 
@@ -478,13 +481,16 @@ instance Bits Int where
 instance FiniteBits Int where
     finiteBitSize _ = WORD_SIZE_IN_BITS
     countLeadingZeros  (I# x#) = I# (word2Int# (clz# (int2Word# x#)))
+    {-# INLINE countLeadingZeros #-}
     countTrailingZeros (I# x#) = I# (word2Int# (ctz# (int2Word# x#)))
+    {-# INLINE countTrailingZeros #-}
 
 -- | @since 2.01
 instance Bits Word where
     {-# INLINE shift #-}
     {-# INLINE bit #-}
     {-# INLINE testBit #-}
+    {-# INLINE popCount #-}
 
     (W# x#) .&.   (W# y#)    = W# (x# `and#` y#)
     (W# x#) .|.   (W# y#)    = W# (x# `or#`  y#)
@@ -519,7 +525,9 @@ instance Bits Word where
 instance FiniteBits Word where
     finiteBitSize _ = WORD_SIZE_IN_BITS
     countLeadingZeros  (W# x#) = I# (word2Int# (clz# x#))
+    {-# INLINE countLeadingZeros #-}
     countTrailingZeros (W# x#) = I# (word2Int# (ctz# x#))
+    {-# INLINE countTrailingZeros #-}
 
 -- | @since 2.01
 instance Bits Integer where