From a10ed3e64336e272137e1743c36970b36f7076c7 Mon Sep 17 00:00:00 2001
From: Simon Peyton Jones <simonpj@microsoft.com>
Date: Thu, 6 Mar 2014 11:54:33 +0000
Subject: [PATCH] Comments only
---
compiler/coreSyn/CoreArity.lhs | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/compiler/coreSyn/CoreArity.lhs b/compiler/coreSyn/CoreArity.lhs
index 080a6fd7674c..12d427422310 100644
--- a/compiler/coreSyn/CoreArity.lhs
+++ b/compiler/coreSyn/CoreArity.lhs
@@ -323,10 +323,10 @@ this transformation. So we try to limit it as much as possible:
going to diverge eventually anyway then getting the best arity
isn't an issue, so we might as well play safe
- (3) Do NOT move a lambda outside a case unless
+ (3) Do NOT move a lambda outside a case unless
(a) The scrutinee is ok-for-speculation, or
- (b) more liberally: the scrutinee is cheap and -fpedantic-bottoms is not
- enforced
+ (b) more liberally: the scrutinee is cheap (e.g. a variable), and
+ -fpedantic-bottoms is not enforced (see Trac #2915 for an example)
Of course both (1) and (2) are readily defeated by disguising the bottoms.
@@ -753,10 +753,10 @@ arityType env (Case scrut _ _ alts)
| otherwise -> ABot 0 -- if RHS is bottomming
-- See Note [Dealing with bottom (2)]
- ATop as | not (ae_ped_bot env) -- Check -fpedantic-bottoms
+ ATop as | not (ae_ped_bot env) -- See Note [Dealing with bottom (3)]
, ae_cheap_fn env scrut Nothing -> ATop as
- | exprOkForSpeculation scrut -> ATop as
- | otherwise -> ATop (takeWhile isOneShotInfo as)
+ | exprOkForSpeculation scrut -> ATop as
+ | otherwise -> ATop (takeWhile isOneShotInfo as)
where
alts_type = foldr1 andArityType [arityType env rhs | (_,_,rhs) <- alts]
--
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