Consider the following GHC code: module Main where import GHC.Word import GHC.Base import GHC.Prim import Random a `shiftRLT` b | b >=# 32# = int2Word# 0# | otherwise = a `uncheckedShiftRL#` b (W32# x#) `shift` (I# i#) | i# >=# 0# = W32# (narrow32Word# (x# `shiftL#` i#)) | otherwise = W32# (x# `shiftRLT` negateInt# i#) x `shiftR` i = x `shift` (-i) shift7 x = x `shiftR` 7 shift6 (W32# x) = (W32# (x `uncheckedShiftRL#` 6#)) main = do xs <- sequence (replicate 1000000 (fmap (shift7 . fromIntegral) (randomIO::IO Int))) print (sum xs) I have copied the definition of `shiftR` for Word32 into this file. Suppose we want to shift a series of numbers by 7 bits. One would expect GHC's inliner to notice that (-7) is indeed not greater than 0, and eliminate the branch in the definition of `shift`. Further one would expect GHC to notice that 7 is indeed not gtreater than 32, and eliminate the branch in shiftRLT. Thus one would expect the code generated by using shift7 to be identical to that being generated by shfit6 (with 7 replaced by 6). But this appears not to be the case. The code generated for shift7 (if I can read the C code correctly) is: Sp[-1] = (-0x7U); Sp[-2] = R1.p[1]; *Sp = (W_)&s2za_info; Sp=Sp-2; JMP_((W_)&Main_zdwshift_info); while the code generated for shift6 is the lovely: Hp=Hp+2; if ((W_)Hp > (W_)HpLim) goto _c2Aa; _s2xq = (R1.p[1]) >> 0x6U; Hp[-1] = (W_)&GHCziWord_W32zh_con_info; *Hp = _s2xq; R1.p=Hp-1; Sp=Sp+1; JMP_(*Sp); _c2Aa: HpAlloc = 0x8U; JMP_(stg_gc_enter_1); My question is, why the discrepency? -- Russell O'Connor <http://r6.ca/> ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.''