Rollup merge of #54811 - pnkfelix:issue-24840-separate-bootstrap-default-for-optimize-from-debug-setting, r=nikomatsakis

During rustc bootstrap, make default for `optimize` independent of `debug`

It may have taken me three and a half years, but I'm following through on my ["threat"](https://github.com/rust-lang/rust/issues/24840#issuecomment-97911700)

Fix #24840
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kennytm 2018-10-12 22:04:01 +08:00 committed by GitHub
commit e03db2301e
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2 changed files with 29 additions and 10 deletions

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@ -243,19 +243,36 @@
# =============================================================================
[rust]
# Indicates that the build should be optimized for debugging Rust. Note that
# this is typically not what you want as it takes an incredibly large amount of
# time to have a debug-mode rustc compile any code (notably libstd). If this
# value is set to `true` it will affect a number of configuration options below
# as well, if unconfigured.
#debug = false
# Whether or not to optimize the compiler and standard library
# Whether or not to optimize the compiler and standard library.
#
# Note: the slowness of the non optimized compiler compiling itself usually
# outweighs the time gains in not doing optimizations, therefore a
# full bootstrap takes much more time with optimize set to false.
# full bootstrap takes much more time with `optimize` set to false.
#optimize = true
# Indicates that the build should be configured for debugging Rust. A
# `debug`-enabled compiler and standard library will be somewhat
# slower (due to e.g. checking of debug assertions) but should remain
# usable.
#
# Note: If this value is set to `true`, it will affect a number of
# configuration options below as well, if they have been left
# unconfigured in this file.
#
# Note: changes to the `debug` setting do *not* affect `optimize`
# above. In theory, a "maximally debuggable" environment would
# set `optimize` to `false` above to assist the introspection
# facilities of debuggers like lldb and gdb. To recreate such an
# environment, explicitly set `optimize` to `false` and `debug`
# to `true`. In practice, everyone leaves `optimize` set to
# `true`, because an unoptimized rustc with debugging
# enabled becomes *unusably slow* (e.g. rust-lang/rust#24840
# reported a 25x slowdown) and bootstrapping the supposed
# "maximally debuggable" environment (notably libstd) takes
# hours to build.
#
#debug = false
# Number of codegen units to use for each compiler invocation. A value of 0
# means "the number of cores on this machine", and 1+ is passed through to the
# compiler.

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@ -628,6 +628,9 @@ impl Config {
let default = false;
config.llvm_assertions = llvm_assertions.unwrap_or(default);
let default = true;
config.rust_optimize = optimize.unwrap_or(default);
let default = match &config.channel[..] {
"stable" | "beta" | "nightly" => true,
_ => false,
@ -640,7 +643,6 @@ impl Config {
config.debug_jemalloc = debug_jemalloc.unwrap_or(default);
config.rust_debuginfo = debuginfo.unwrap_or(default);
config.rust_debug_assertions = debug_assertions.unwrap_or(default);
config.rust_optimize = optimize.unwrap_or(!default);
let default = config.channel == "dev";
config.ignore_git = ignore_git.unwrap_or(default);