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This adds INLINABLE pragmas to most exported combinators, which enables cross-module specialization of the Stream constraint (which can in turn enable further optimizations). This improves performance of these combinators in scenarios where GHC chooses not to inline them, since they may still be specialized instead. This change is primarily in response to a performance regression discovered by the GHC performance test suite when running haddock (since haddock uses parsec). The full discussion is available here: ghc/ghc!3041 The gist is that, without these pragmas, performance relies too heavily on inlining heuristics working out in our favor, and subtle changes in the optimizer can cause regressions. The GHC performance tests suggest this patch reliably reduces runtime of haddock on base by 7–9% and allocation by 3–5%. Pretty good for doing something so simple!
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