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more expression simplification

This commit is contained in:
Zachary Snow 2019-04-08 21:57:50 -04:00
parent 9a38225b1d
commit 9b51d7566b
1 changed files with 13 additions and 0 deletions
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13
src/Language/SystemVerilog/AST/Expr.hs
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@ -101,9 +101,18 @@ showRanges l = " " ++ (concatMap showRange l)
showRange :: Range -> String
showRange (h, l) = printf "[%s:%s]" (show h) (show l)
clog2Help :: Int -> Int -> Int
clog2Help p n = if p >= n then 0 else 1 + clog2Help (p*2) n
clog2 :: Int -> Int
clog2 n = if n < 2 then 0 else clog2Help 1 n
-- basic expression simplfication utility to help us generate nicer code in the
-- common case of ranges like `[FOO-1:0]`
simplify :: Expr -> Expr
simplify (orig @ (Call "$clog2" (Args [Just (Number n)] []))) =
case readMaybe n :: Maybe Int of
Nothing -> orig
Just x -> Number $ show $ clog2 x
simplify (Mux (BinOp Ge c1 c2) e1 e2) =
case (c1', c2') of
(Number a, Number b) ->
@ -124,6 +133,10 @@ simplify (BinOp op e1 e2) =
case (op, e1', e2') of
(Add, Number "0", e) -> e
(Add, e, Number "0") -> e
(Mul, _, Number "0") -> Number "0"
(Mul, Number "0", _) -> Number "0"
(Mul, e, Number "1") -> e
(Mul, Number "1", e) -> e
(Sub, e, Number "0") -> e
(Add, BinOp Sub e (Number "1"), Number "1") -> e
(Add, e, BinOp Sub (Number "0") (Number "1")) -> BinOp Sub e (Number "1")