1 // Copyright 2021 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package goexperiment implements support for toolchain experiments. 6 // 7 // Toolchain experiments are controlled by the GOEXPERIMENT 8 // environment variable. GOEXPERIMENT is a comma-separated list of 9 // experiment names. GOEXPERIMENT can be set at make.bash time, which 10 // sets the default experiments for binaries built with the tool 11 // chain; or it can be set at build time. GOEXPERIMENT can also be set 12 // to "none", which disables any experiments that were enabled at 13 // make.bash time. 14 // 15 // Experiments are exposed to the build in the following ways: 16 // 17 // - Build tag goexperiment.x is set if experiment x (lower case) is 18 // enabled. 19 // 20 // - For each experiment x (in camel case), this package contains a 21 // boolean constant x and an integer constant xInt. 22 // 23 // - In runtime assembly, the macro GOEXPERIMENT_x is defined if 24 // experiment x (lower case) is enabled. 25 // 26 // In the toolchain, the set of experiments enabled for the current 27 // build should be accessed via objabi.Experiment. 28 // 29 // The set of experiments is included in the output of runtime.Version() 30 // and "go version <binary>" if it differs from the default experiments. 31 // 32 // For the set of experiments supported by the current toolchain, see 33 // "go doc goexperiment.Flags". 34 // 35 // Note that this package defines the set of experiments (in Flags) 36 // and records the experiments that were enabled when the package 37 // was compiled (as boolean and integer constants). 38 // 39 // Note especially that this package does not itself change behavior 40 // at run time based on the GOEXPERIMENT variable. 41 // The code used in builds to interpret the GOEXPERIMENT variable 42 // is in the separate package internal/buildcfg. 43 package goexperiment 44 45 //go:generate go run mkconsts.go 46 47 // Flags is the set of experiments that can be enabled or disabled in 48 // the current toolchain. 49 // 50 // When specified in the GOEXPERIMENT environment variable or as build 51 // tags, experiments use the strings.ToLower of their field name. 52 // 53 // For the baseline experimental configuration, see 54 // objabi.experimentBaseline. 55 // 56 // If you change this struct definition, run "go generate". 57 type Flags struct { 58 FieldTrack bool 59 PreemptibleLoops bool 60 StaticLockRanking bool 61 BoringCrypto bool 62 63 // Regabi is split into several sub-experiments that can be 64 // enabled individually. Not all combinations work. 65 // The "regabi" GOEXPERIMENT is an alias for all "working" 66 // subexperiments. 67 68 // RegabiWrappers enables ABI wrappers for calling between 69 // ABI0 and ABIInternal functions. Without this, the ABIs are 70 // assumed to be identical so cross-ABI calls are direct. 71 RegabiWrappers bool 72 // RegabiArgs enables register arguments/results in all 73 // compiled Go functions. 74 // 75 // Requires wrappers (to do ABI translation), and reflect (so 76 // reflection calls use registers). 77 RegabiArgs bool 78 79 // HeapMinimum512KiB reduces the minimum heap size to 512 KiB. 80 // 81 // This was originally reduced as part of PacerRedesign, but 82 // has been broken out to its own experiment that is disabled 83 // by default. 84 HeapMinimum512KiB bool 85 86 // CoverageRedesign enables the new compiler-based code coverage 87 // tooling. 88 CoverageRedesign bool 89 90 // Arenas causes the "arena" standard library package to be visible 91 // to the outside world. 92 Arenas bool 93 94 // CgoCheck2 enables an expensive cgo rule checker. 95 // When this experiment is enabled, cgo rule checks occur regardless 96 // of the GODEBUG=cgocheck setting provided at runtime. 97 CgoCheck2 bool 98 99 // LoopVar changes loop semantics so that each iteration gets its own 100 // copy of the iteration variable. 101 LoopVar bool 102 103 // CacheProg adds support to cmd/go to use a child process to implement 104 // the build cache; see https://github.com/golang/go/issues/59719. 105 CacheProg bool 106 107 // NewInliner enables a new+improved version of the function 108 // inlining phase within the Go compiler. 109 NewInliner bool 110 111 // RangeFunc enables range over func. 112 RangeFunc bool 113 114 // AliasTypeParams enables type parameters for alias types. 115 // Requires that gotypesalias=1 is set with GODEBUG. 116 // This flag will be removed with Go 1.24. 117 AliasTypeParams bool 118 } 119