From 892b0c41816fca4eeea42ca03a43aac473311837 Mon Sep 17 00:00:00 2001
From: buggymcbugfix <4444-buggymcbugfix@users.noreply.gitlab.haskell.org>
Date: Mon, 18 May 2020 22:55:23 +0300
Subject: [PATCH] Document INLINE(ABLE) pragmas that enable fusion
---
libraries/base/GHC/Enum.hs | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/libraries/base/GHC/Enum.hs b/libraries/base/GHC/Enum.hs
index cb43c1b8ddc..70a964f6d33 100644
--- a/libraries/base/GHC/Enum.hs
+++ b/libraries/base/GHC/Enum.hs
@@ -368,16 +368,20 @@ instance Enum Char where
toEnum = chr
fromEnum = ord
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFrom #-}
enumFrom (C# x) = eftChar (ord# x) 0x10FFFF#
-- Blarg: technically I guess enumFrom isn't strict!
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromTo #-}
enumFromTo (C# x) (C# y) = eftChar (ord# x) (ord# y)
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromThen #-}
enumFromThen (C# x1) (C# x2) = efdChar (ord# x1) (ord# x2)
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromThenTo #-}
enumFromThenTo (C# x1) (C# x2) (C# y) = efdtChar (ord# x1) (ord# x2) (ord# y)
@@ -497,17 +501,21 @@ instance Enum Int where
toEnum x = x
fromEnum x = x
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFrom #-}
enumFrom (I# x) = eftInt x maxInt#
where !(I# maxInt#) = maxInt
-- Blarg: technically I guess enumFrom isn't strict!
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromTo #-}
enumFromTo (I# x) (I# y) = eftInt x y
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromThen #-}
enumFromThen (I# x1) (I# x2) = efdInt x1 x2
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromThenTo #-}
enumFromThenTo (I# x1) (I# x2) (I# y) = efdtInt x1 x2 y
@@ -837,13 +845,20 @@ instance Enum Integer where
toEnum (I# n) = smallInteger n
fromEnum n = I# (integerToInt n)
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFrom #-}
+ enumFrom x = enumDeltaInteger x 1
+
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromThen #-}
+ enumFromThen x y = enumDeltaInteger x (y-x)
+
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromTo #-}
+ enumFromTo x lim = enumDeltaToInteger x 1 lim
+
+ -- See Note [Stable Unfolding for list producers]
{-# INLINE enumFromThenTo #-}
- enumFrom x = enumDeltaInteger x 1
- enumFromThen x y = enumDeltaInteger x (y-x)
- enumFromTo x lim = enumDeltaToInteger x 1 lim
enumFromThenTo x y lim = enumDeltaToInteger x (y-x) lim
-- See Note [How the Enum rules work]
@@ -952,6 +967,7 @@ instance Enum Natural where
toEnum = intToNatural
#if defined(MIN_VERSION_integer_gmp)
+ -- This is the integer-gmp special case. The general case is after the endif.
fromEnum (NatS# w)
| i >= 0 = i
| otherwise = errorWithoutStackTrace "fromEnum: out of Int range"
@@ -961,11 +977,13 @@ instance Enum Natural where
fromEnum n = fromEnum (naturalToInteger n)
enumFrom x = enumDeltaNatural x (wordToNaturalBase 1##)
+
enumFromThen x y
| x <= y = enumDeltaNatural x (y-x)
| otherwise = enumNegDeltaToNatural x (x-y) (wordToNaturalBase 0##)
enumFromTo x lim = enumDeltaToNatural x (wordToNaturalBase 1##) lim
+
enumFromThenTo x y lim
| x <= y = enumDeltaToNatural x (y-x) lim
| otherwise = enumNegDeltaToNatural x (x-y) lim
--
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