Thu Jan 17 07:03:25 PST 2008 [EMAIL PROTECTED]
* Add -fspec-inline-join-points to SpecConstr
This patch addresses a problem that Roman found in SpecConstr. Consider:
foo :: Maybe Int -> Maybe Int -> Int
foo a b = let j b = foo a b
in
case b of
Nothing -> ...
Just n -> case a of
Just m -> ... j (Just (n+1)) ...
Nothing -> ... j (Just (n-1)) ...
We want to make specialised versions for 'foo' for the patterns
Nothing (Just v)
(Just a) (Just b)
Two problems, caused by the join point j. First, j does not
scrutinise b, so j won't be specialised f for the (Just v) pattern.
Second, j is defined where the free var 'a' is not evaluated.
Both are solved by brutally inlining j at its call sites. This risks
major code bloat, but it's relatively quick to implement. The flag
-fspec-inline-join-points
causes brutal inlining for a
non-recursive binding
of a function
whose RHS contains calls
of a recursive function
The (experimental) flag is static for now, and I have not even
documented it properly.
M ./compiler/main/StaticFlags.hs +3
M ./compiler/specialise/SpecConstr.lhs -93 +128
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