c4ee44b7b9
Currently we always create context objects for closures that capture variables. However, it is completely unnecessary for direct calls of closures (whether it is func()(), defer func()() or go func()()). This change transforms any OCALLFUNC(OCLOSURE) to normal function call. Closed variables become function arguments. This transformation is especially beneficial for go func(), because we do not need to allocate context object on heap. But it makes direct closure calls a bit faster as well (see BenchmarkClosureCall). On implementation level it required to introduce yet another compiler pass. However, the pass iterates only over xtop, so it should not be an issue. Transformation consists of two parts: closure transformation and call site transformation. We can't run these parts on different sides of escape analysis, because tree state is inconsistent. We can do both parts during typecheck, we don't know how to capture variables and don't have call site. We can't do both parts during walk of OCALLFUNC, because we can walk OCLOSURE body earlier. So now capturevars pass only decides how to capture variables (this info is required for escape analysis). New transformclosure pass, that runs just before order/walk, does all transformations of a closure. And later walk of OCALLFUNC(OCLOSURE) transforms call site. benchmark old ns/op new ns/op delta BenchmarkClosureCall 4.89 3.09 -36.81% BenchmarkCreateGoroutinesCapture 1634 1294 -20.81% benchmark old allocs new allocs delta BenchmarkCreateGoroutinesCapture 6 2 -66.67% benchmark old bytes new bytes delta BenchmarkCreateGoroutinesCapture 176 48 -72.73% Change-Id: Ic85e1706e18c3235cc45b3c0c031a9c1cdb7a40e Reviewed-on: https://go-review.googlesource.com/4050 Reviewed-by: Russ Cox <rsc@golang.org> |
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