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Hello, The "validate" script against GHC HEAD freezes on FreeBSD 9.1. After sync-all, I did as follow: ---------------------------------------------------------------- % config_args="--with-iconv-includes=/usr/local/include --with-iconv-libraries=/usr/local/lib --with-gmp-includes=/usr/local/include --with-gmp-libraries=/usr/local/lib --with-gcc=/usr/local/bin/gcc47" CPUS=10 sh validate ---------------------------------------------------------------- This stopped quickly due to this problem: http://hackage.haskell.org/trac/ghc/ticket/7592 Then I executed "validate" with "--no-clean" again. ---------------------------------------------------------------- % config_args="--with-iconv-includes=/usr/local/include --with-iconv-libraries=/usr/local/lib --with-gmp-includes=/usr/local/include --with-gmp-libraries=/usr/local/lib --with-gcc=/usr/local/bin/gcc47" CPUS=10 sh validate --no-clean ---------------------------------------------------------------- GHC could be compiled and tests started. But this result

I'm curious about global constant propagation in GHC.  It's a fairly basic optimization in the CFG-based compiler domain, and it's similar to constructor specialization, but it doesn't seem to be in GHC's repertoire.  Perhaps it's usually subsumed by other optimizations or it's more complicated than I am thinking.  Is this optimization worth implementing? This optimization can help when a case expression returns a product, some fields of which are the same in all branches.  The following program is a minimal example of an optimizable situation that GHC doesn't exploit. {-# OPTIONS_GHC -O3 -funbox-strict-fields #-} data D = D !Int !Int foo n = if n > 0         then D 0 0         else D 0 n main =   case foo $ read "7"   of D x y -> if x == 0 then return () else print y >> putStrLn "A" After inlining and case-of-case transformation, GHC produces main = let n = read "7"            k x y = case x of {0 -> return (); _ -> print y >> putStrLn "A"}        in if n > 0

Thanks to John Lato and Duncan Coutts for the latest bugfix release! The latest packages should be buildable on GHC 7.6, and the cairo package should behave a bit nicer in ghci on Windows. Thanks to all!

~d