Martin Huschenbett d75afebb8a damlc: Avoid immediately invoked closures (#6274) ... * damlc: Avoid immediately invoked closures We add rules to the simplifier which rewrite expressions of the form ``` (\x1 ... xn -> E) A1 ... An ``` into ``` let x1 = A1 in ... let xn = An in E ``` provided that `xi` is not free in `Aj` for any `i < j`. In cases where `E` is _not_ a lambda, this rewriting is beneficial since it removes a costly closure allocation and the immediate entering of the closure. If `E` is a closure itself, this rewriting is not detrimental since the only difference it makes is that the values for `A1, ..., An` end up in the list of captured variables rather than in the list of already applied variables. Even though users might not write expressions like the one we're simplifying here themselves, various desugarings produce them nevertheless. A common pattern is to define multiple auxiliary functions that a only used once in a where cluase. For instance, with the help these new rewriting rules the function ```haskell f: Int -> Int -> Int f x y = g (h x) y where g x y = x+y h x = 2*x ``` gets translated to ``` def f : Int64 -> Int64 -> Int64 = \(x : Int64) (y : Int64). let x2 : Int64 = let x2 : Int64 = x in MUL_INT64 2 x2 y2 : Int64 = y in ADD_INT64 x2 y2 ``` Without the simplification, `g` and `h` would each allocate a closure: ``` def f : Int64 -> Int64 -> Int64 = \(x : Int64) (y : Int64). (\(x2 : Int64) (y2 : Int64). ADD_INT64 x2 y2) ((\(x2 : Int64). MUL_INT64 2 x2) x) y ``` The `collect-authority` benchmarck is sped up by 1.03x by this change. This is not a huge improvement but the change is simple enough to merge it nevertheless. CHANGELOG_BEGIN CHANGELOG_END * Let code speak not comments CHANGELOG_BEGIN CHANGELOG_END * Improve explanations CHANGELOG_BEGIN CHANGELOG_END		2020-06-09 18:07:33 +00:00
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src/DA/Daml/LF	damlc: Avoid immediately invoked closures (#6274)	2020-06-09 18:07:33 +00:00
BUILD.bazel	replace DAML Authors with DA in copyright headers (#5228)	2020-03-27 01:26:10 +01:00