Expose cseExpr from CSE
Expose cseExpr from CSE

for the benefit of GHC API users who want to CSE single expressions.

Differential Revision: https://phabricator.haskell.org/D3069

shlevy/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc