From 2cc4616d6b4a93c3deba68812f57b2c1c77e6e41 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?R=C3=A9mi=20Verschelde?= Date: Tue, 8 Feb 2022 15:35:13 +0100 Subject: [PATCH] SCons: Add `fast_unsafe` option for faster rebuilds This reverts #53828 which had caused a significant drop in incremental rebuild time for debug builds (from 10s to 23s on my laptop). The "faster but unsafe" options are re-added, as well as adding `max_drift=60` which we didn't use previously. These options speed up SCons' own processing of the codebase to decide what to build/rebuild (i.e. the first step before actually calling the compiler). This will therefore not make much difference for scratch builds, and is mostly useful for incremental rebuilds (including "null" rebuilds with no change). These options are enabled automatically for `debug` builds, unless `fast_unsafe=no` is passed. They are disabled by default for `release` and `release_debug` builds, unless `fast_unsafe=yes` is passed. (cherry picked from commit d4553c51262e347b8c877d57ca251d94faf4dc30) --- SConstruct | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/SConstruct b/SConstruct index 0635b57cf2e..24ecbe774e1 100644 --- a/SConstruct +++ b/SConstruct @@ -132,8 +132,9 @@ opts.Add(BoolVariable("custom_modules_recursive", "Detect custom modules recursi # Advanced options opts.Add(BoolVariable("dev", "If yes, alias for verbose=yes warnings=extra werror=yes", False)) -opts.Add(BoolVariable("progress", "Show a progress indicator during compilation", True)) +opts.Add(BoolVariable("fast_unsafe", "Enable unsafe options for faster rebuilds", False)) opts.Add(BoolVariable("verbose", "Enable verbose output for the compilation", False)) +opts.Add(BoolVariable("progress", "Show a progress indicator during compilation", True)) opts.Add(EnumVariable("warnings", "Level of compilation warnings", "all", ("extra", "all", "moderate", "no"))) opts.Add(BoolVariable("werror", "Treat compiler warnings as errors", False)) opts.Add("extra_suffix", "Custom extra suffix added to the base filename of all generated binary files", "") @@ -308,6 +309,17 @@ if env_base["target"] == "debug": # working on the engine itself. env_base.Append(CPPDEFINES=["DEV_ENABLED"]) +# SCons speed optimization controlled by the `fast_unsafe` option, which provide +# more than 10 s speed up for incremental rebuilds. +# Unsafe as they reduce the certainty of rebuilding all changed files, so it's +# enabled by default for `debug` builds, and can be overridden from command line. +# Ref: https://github.com/SCons/scons/wiki/GoFastButton +if methods.get_cmdline_bool("fast_unsafe", env_base["target"] == "debug"): + # Renamed to `content-timestamp` in SCons >= 4.2, keeping MD5 for compat. + env_base.Decider("MD5-timestamp") + env_base.SetOption("implicit_cache", 1) + env_base.SetOption("max_drift", 60) + if env_base["use_precise_math_checks"]: env_base.Append(CPPDEFINES=["PRECISE_MATH_CHECKS"])