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@@ -395,26 +395,28 @@ cmmMachOpFoldM platform mop [x, (CmmLit (CmmInt 1 rep))] |
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one = CmmLit (CmmInt 1 (wordWidth platform))
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-- Now look for multiplication/division by powers of 2 (integers).
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-
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-cmmMachOpFoldM platform mop [x, (CmmLit (CmmInt n w))]
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+--
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+-- ToDo: See #25664 (comment 605821) describing a change to the Cmm literal representation.
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+-- When/If this is completed, this code must be refactored to account for the explicit width sizes.
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+cmmMachOpFoldM platform mop [x, (CmmLit (CmmInt n _))]
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= case mop of
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MO_Mul rep
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- | Just p <- widthBoundedExactLog2 False w n ->
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+ | Just p <- exactLog2 (narrowU rep n) ->
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Just $! (cmmMachOpFold platform (MO_Shl rep) [x, CmmLit (CmmInt p $ wordWidth platform)])
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MO_U_Quot rep
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- | Just p <- widthBoundedExactLog2 False w n ->
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+ | Just p <- exactLog2 (narrowU rep n) ->
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Just $! (cmmMachOpFold platform (MO_U_Shr rep) [x, CmmLit (CmmInt p $ wordWidth platform)])
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MO_U_Rem rep
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- | Just _ <- widthBoundedExactLog2 False w n ->
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+ | Just _ <- exactLog2 (narrowU rep n) ->
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Just $! (cmmMachOpFold platform (MO_And rep) [x, CmmLit (CmmInt (n - 1) rep)])
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MO_S_Quot rep
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- | Just p <- widthBoundedExactLog2 True w n,
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+ | Just p <- exactLog2 (narrowS rep n),
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CmmReg _ <- x -> -- We duplicate x in signedQuotRemHelper, hence require
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-- it is a reg. FIXME: remove this restriction.
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Just $! (cmmMachOpFold platform (MO_S_Shr rep)
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[signedQuotRemHelper rep p, CmmLit (CmmInt p $ wordWidth platform)])
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MO_S_Rem rep
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- | Just p <- widthBoundedExactLog2 True w n,
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+ | Just p <- exactLog2 (narrowS rep n),
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CmmReg _ <- x -> -- We duplicate x in signedQuotRemHelper, hence require
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-- it is a reg. FIXME: remove this restriction.
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-- We replace (x `rem` 2^p) by (x - (x `quot` 2^p) * 2^p).
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@@ -449,14 +451,6 @@ cmmMachOpFoldM platform mop [x, (CmmLit (CmmInt n w))] |
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x1 = CmmMachOp shr [x, CmmLit (CmmInt bits $ wordWidth platform)]
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x2 = if p == 1 then x1 else
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CmmMachOp (MO_And rep) [x1, CmmLit (CmmInt (n-1) rep)]
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- -- Determine if the input is an exact power of 2 AND within the logical range
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- -- of values permited by the bit-width. Without this check, the bit shifting
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- -- operations to multiply/divide by oowers of 2 may be unsound and result in
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- -- incorrect runtime results.
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- widthBoundedExactLog2 :: Bool -> Width -> Integer -> Maybe Integer
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- widthBoundedExactLog2 signed rep v = case exactLog2 v of
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- Just p | p >= fromIntegral (widthInBits rep - fromEnum signed) -> Nothing
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- m -> m
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-- ToDo (#7116): optimise floating-point multiplication, e.g. x*2.0 -> x+x
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-- Unfortunately this needs a unique supply because x might not be a
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