Re: [GHC] #9136: Constant folding in Core could be better

#9136: Constant folding in Core could be better -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: infoneeded Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2858 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"fea04defa64871caab6339ff3fc5511a272f37c7/ghc" fea04de/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="fea04defa64871caab6339ff3fc5511a272f37c7" Enhanced constant folding Until now GHC only supported basic constant folding (lit op lit, expr op 0, etc.). This patch uses laws of +/-/* (associativity, commutativity, distributivity) to support some constant folding into nested expressions. Examples of new transformations: - simple nesting: (10 + x) + 10 becomes 20 + x - deep nesting: 5 + x + (y + (z + (t + 5))) becomes 10 + (x + (y + (z + t))) - distribution: (5 + x) * 6 becomes 30 + 6*x - simple factorization: 5 + x + (x + (x + (x + 5))) becomes 10 + (4 *x) - siblings: (5 + 4*x) - (3*x + 2) becomes 3 + x Test Plan: validate Reviewers: simonpj, austin, bgamari Reviewed By: bgamari Subscribers: thomie GHC Trac Issues: #9136 Differential Revision: https://phabricator.haskell.org/D2858 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9136#comment:24 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler