Than McIntosh f8162a0e72 cmd/compile: allow more inlining of functions that construct closures ... [This is a roll-forward of CL 479095, which was reverted due to a bad interaction between inlining and escape analysis, then later fixed fist with an attempt in CL 482355, then again in 484859 .] Currently, when the inliner is determining if a function is inlineable, it descends into the bodies of closures constructed by that function. This has several unfortunate consequences: - If the closure contains a disallowed operation (e.g., a defer), then the outer function can't be inlined. It makes sense that the *closure* can't be inlined in this case, but it doesn't make sense to punish the function that constructs the closure. - The hairiness of the closure counts against the inlining budget of the outer function. Since we currently copy the closure body when inlining the outer function, this makes sense from the perspective of export data size and binary size, but ultimately doesn't make much sense from the perspective of what should be inlineable. - Since the inliner walks into every closure created by an outer function in addition to starting a walk at every closure, this adds an n^2 factor to inlinability analysis. This CL simply drops this behavior. In std, this makes 57 more functions inlinable, and disallows inlining for 10 (due to the basic instability of our bottom-up inlining approach), for an net increase of 47 inlinable functions (+0.6%). This will help significantly with the performance of the functions to be added for #56102, which have a somewhat complicated nesting of closures with a performance-critical fast path. The downside of this seems to be a potential increase in export data and text size, but the practical impact of this seems to be negligible: │ before │ after │ │ bytes │ bytes vs base │ Go/binary 15.12Mi ± 0% 15.14Mi ± 0% +0.16% (n=1) Go/text 5.220Mi ± 0% 5.237Mi ± 0% +0.32% (n=1) Compile/binary 22.92Mi ± 0% 22.94Mi ± 0% +0.07% (n=1) Compile/text 8.428Mi ± 0% 8.435Mi ± 0% +0.08% (n=1) Updates #56102. Change-Id: I6e938d596992ffb473cf51e7e598f372ce08deb0 Reviewed-on: https://go-review.googlesource.com/c/go/+/484860 Run-TryBot: Than McIntosh <thanm@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>		2023-04-17 14:52:41 +00:00
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main.go	cmd/compile: allow more inlining of functions that construct closures	2023-04-17 14:52:41 +00:00