diff options
Diffstat (limited to 'testsuite/tests/haddock/should_compile_noflag_haddock/haddockSimplUtilsBug.hs')
| -rw-r--r-- | testsuite/tests/haddock/should_compile_noflag_haddock/haddockSimplUtilsBug.hs | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/testsuite/tests/haddock/should_compile_noflag_haddock/haddockSimplUtilsBug.hs b/testsuite/tests/haddock/should_compile_noflag_haddock/haddockSimplUtilsBug.hs new file mode 100644 index 0000000000..a62020f508 --- /dev/null +++ b/testsuite/tests/haddock/should_compile_noflag_haddock/haddockSimplUtilsBug.hs @@ -0,0 +1,44 @@ +module ShouldCompile where + +postInlineUnconditionally + = case Just "Hey" of + -- The point of examining occ_info here is that for *non-values* + -- that occur outside a lambda, the call-site inliner won't have + -- a chance (becuase it doesn't know that the thing + -- only occurs once). The pre-inliner won't have gotten + -- it either, if the thing occurs in more than one branch + -- So the main target is things like + -- let x = f y in + -- case v of + -- True -> case x of ... + -- False -> case x of ... + -- I'm not sure how important this is in practice + Just a -- OneOcc => no work-duplication issue + -> True -- Small enough to dup + -- ToDo: consider discount on smallEnoughToInline if int_cxt is true + -- + -- NB: Do NOT inline arbitrarily big things, even if one_br is True + -- Reason: doing so risks exponential behaviour. We simplify a big + -- expression, inline it, and simplify it again. But if the + -- very same thing happens in the big expression, we get + -- exponential cost! + -- PRINCIPLE: when we've already simplified an expression once, + -- make sure that we only inline it if it's reasonably small. + + _ -> False + +-- Here's an example that we don't handle well: +-- let f = if b then Left (\x.BIG) else Right (\y.BIG) +-- in \y. ....case f of {...} .... +-- Here f is used just once, and duplicating the case work is fine (exprIsCheap). +-- But +-- * We can't preInlineUnconditionally because that woud invalidate +-- the occ info for b. +-- * We can't postInlineUnconditionally because the RHS is big, and +-- that risks exponential behaviour +-- * We can't call-site inline, because the rhs is big +-- Alas! + + where + x = id + |