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…nkov

A big options clean-up

Lots of improvements here.

r? @Centril
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bors committed Apr 20, 2020
2 parents 4ca5fd2 + 3e3fd73 commit 8ce3f84
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172 changes: 89 additions & 83 deletions src/doc/rustc/src/codegen-options/index.md
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Expand Up @@ -9,10 +9,10 @@ This option is deprecated and does nothing.

## linker

This flag lets you control which linker `rustc` invokes to link your code. It
takes a path to the linker executable. If this flag is not specified, the
linker will be inferred based on the target. See also the
[linker-flavor](#linker-flavor) flag for another way to specify the linker.
This flag controls which linker `rustc` invokes to link your code. It takes a
path to the linker executable. If this flag is not specified, the linker will
be inferred based on the target. See also the [linker-flavor](#linker-flavor)
flag for another way to specify the linker.

## link-arg

Expand All @@ -27,49 +27,52 @@ options should be separated by spaces.

## linker-flavor

This flag lets you control the linker flavor used by `rustc`. If a linker is given with the
[`-C linker` flag](#linker), then the linker flavor is inferred from the value provided. If no
linker is given then the linker flavor is used to determine the linker to use. Every `rustc` target
defaults to some linker flavor. Valid options are:

* `em`: Uses [Emscripten `emcc`](https://emscripten.org/docs/tools_reference/emcc.html).
* `gcc`: Uses the `cc` executable, which is typically gcc or clang on many systems.
* `ld`: Uses the `ld` executable.
* `msvc`: Uses the `link.exe` executable from Microsoft Visual Studio MSVC.
* `ptx-linker`: Uses
This flag controls the linker flavor used by `rustc`. If a linker is given with
the [`-C linker` flag](#linker), then the linker flavor is inferred from the
value provided. If no linker is given then the linker flavor is used to
determine the linker to use. Every `rustc` target defaults to some linker
flavor. Valid options are:

* `em`: use [Emscripten `emcc`](https://emscripten.org/docs/tools_reference/emcc.html).
* `gcc`: use the `cc` executable, which is typically gcc or clang on many systems.
* `ld`: use the `ld` executable.
* `msvc`: use the `link.exe` executable from Microsoft Visual Studio MSVC.
* `ptx-linker`: use
[`rust-ptx-linker`](https://github.com/denzp/rust-ptx-linker) for Nvidia
NVPTX GPGPU support.
* `wasm-ld`: Uses the [`wasm-ld`](https://lld.llvm.org/WebAssembly.html)
* `wasm-ld`: use the [`wasm-ld`](https://lld.llvm.org/WebAssembly.html)
executable, a port of LLVM `lld` for WebAssembly.
* `ld64.lld`: Uses the LLVM `lld` executable with the [`-flavor darwin`
* `ld64.lld`: use the LLVM `lld` executable with the [`-flavor darwin`
flag][lld-flavor] for Apple's `ld`.
* `ld.lld`: Uses the LLVM `lld` executable with the [`-flavor gnu`
* `ld.lld`: use the LLVM `lld` executable with the [`-flavor gnu`
flag][lld-flavor] for GNU binutils' `ld`.
* `lld-link`: Uses the LLVM `lld` executable with the [`-flavor link`
* `lld-link`: use the LLVM `lld` executable with the [`-flavor link`
flag][lld-flavor] for Microsoft's `link.exe`.

[lld-flavor]: https://lld.llvm.org/Driver.html

## link-dead-code

Normally, the linker will remove dead code. This flag disables this behavior.
This flag controls whether the linker will keep dead code. It takes one of
the following values:

* `y`, `yes`, `on`, or no value: keep dead code.
* `n`, `no`, or `off`: remove dead code (the default).

An example of when this flag might be useful is when trying to construct code coverage
metrics.

## lto

This flag instructs LLVM to use [link time
This flag controls whether LLVM uses [link time
optimizations](https://llvm.org/docs/LinkTimeOptimization.html) to produce
better optimized code, using whole-program analysis, at the cost of longer
linking time.
linking time. It takes one of the following values:

This flag may take one of the following values:

* `y`, `yes`, `on`, `fat`, or no value: Performs "fat" LTO which attempts to
* `y`, `yes`, `on`, `fat`, or no value: perform "fat" LTO which attempts to
perform optimizations across all crates within the dependency graph.
* `n`, `no`, `off`: Disables LTO.
* `thin`: Performs ["thin"
* `n`, `no`, `off`: disables LTO.
* `thin`: perform ["thin"
LTO](http://blog.llvm.org/2016/06/thinlto-scalable-and-incremental-lto.html).
This is similar to "fat", but takes substantially less time to run while
still achieving performance gains similar to "fat".
Expand All @@ -81,22 +84,22 @@ disabled if codegen units is 1 or optimizations are disabled ([`-C
opt-level=0`](#opt-level)). That is:

* When `-C lto` is not specified:
* `codegen-units=1`: Disables LTO.
* `opt-level=0`: Disables LTO.
* `codegen-units=1`: disable LTO.
* `opt-level=0`: disable LTO.
* When `-C lto=true`:
* `lto=true`: 16 codegen units, performs fat LTO across crates.
* `lto=true`: 16 codegen units, perform fat LTO across crates.
* `codegen-units=1` + `lto=true`: 1 codegen unit, fat LTO across crates.

See also [linker-plugin-lto](#linker-plugin-lto) for cross-language LTO.

## linker-plugin-lto

Defers LTO optimizations to the linker. See
[linkger-plugin-LTO](../linker-plugin-lto.md) for more details. Takes one of
This flag defers LTO optimizations to the linker. See
[linker-plugin-LTO](../linker-plugin-lto.md) for more details. It takes one of
the following values:

* `y`, `yes`, `on`, or no value: Enabled.
* `n`, `no`, or `off`: Disabled (default).
* `y`, `yes`, `on`, or no value: enable linker plugin LTO.
* `n`, `no`, or `off`: disable linker plugin LTO (the default).
* A path to the linker plugin.

## target-cpu
Expand Down Expand Up @@ -148,14 +151,19 @@ Pass `--help` to see a list of options.

## save-temps

`rustc` will generate temporary files during compilation; normally it will
delete them after it's done with its work. This option will cause them to be
preserved instead of removed.
This flag controls whether temporary files generated during compilation are
deleted once compilation finishes. It takes one of the following values:

* `y`, `yes`, `on`, or no value: save temporary files.
* `n`, `no`, or `off`: delete temporary files (the default).

## rpath

This option allows you to enable
[`rpath`](https://en.wikipedia.org/wiki/Rpath).
This flag controls whether [`rpath`](https://en.wikipedia.org/wiki/Rpath) is
enabled. It takes one of the following values:

* `y`, `yes`, `on`, or no value: enable rpath.
* `n`, `no`, or `off`: disable rpath (the default).

## overflow-checks

Expand All @@ -164,35 +172,35 @@ overflow](../../reference/expressions/operator-expr.md#overflow). When
overflow-checks are enabled, a panic will occur on overflow. This flag takes
one of the following values:

* `y`, `yes`, `on`, or no value: Enable overflow checks.
* `n`, `no`, or `off`: Disable overflow checks.
* `y`, `yes`, `on`, or no value: enable overflow checks.
* `n`, `no`, or `off`: disable overflow checks.

If not specified, overflow checks are enabled if
[debug-assertions](#debug-assertions) are enabled, disabled otherwise.

## no-prepopulate-passes

The pass manager comes pre-populated with a list of passes; this flag
ensures that list is empty.
This flag tells the pass manager to use an empty list of passes, instead of the
usual pre-populated list of passes.

## no-vectorize-loops

By default, `rustc` will attempt to [vectorize
loops](https://llvm.org/docs/Vectorizers.html#the-loop-vectorizer). This
flag will turn that behavior off.
This flag disables [loop
vectorization](https://llvm.org/docs/Vectorizers.html#the-loop-vectorizer).

## no-vectorize-slp

By default, `rustc` will attempt to vectorize code using [superword-level
parallelism](https://llvm.org/docs/Vectorizers.html#the-slp-vectorizer). This
flag will turn that behavior off.
This flag disables vectorization using
[superword-level
parallelism](https://llvm.org/docs/Vectorizers.html#the-slp-vectorizer).

## soft-float

This option will make `rustc` generate code using "soft floats." By default,
a lot of hardware supports floating point instructions, and so the code generated
will take advantage of this. "soft floats" emulate floating point instructions
in software.
This option controls whether `rustc` generates code that emulates floating
point instructions in software. It takes one of the following values:

* `y`, `yes`, `on`, or no value: use soft floats.
* `n`, `no`, or `off`: use hardware floats (the default).

## prefer-dynamic

Expand All @@ -201,24 +209,21 @@ indicate that dynamic linking should be used if possible if both a static and
dynamic versions of a library are available. There is an internal algorithm
for determining whether or not it is possible to statically or dynamically
link with a dependency. For example, `cdylib` crate types may only use static
linkage.
linkage. This flag takes one of the following values:

## no-integrated-as

`rustc` normally uses the LLVM internal assembler to create object code. This
flag will disable the internal assembler and emit assembly code to be
translated using an external assembler, currently the linker such as `cc`.
* `y`, `yes`, `on`, or no value: use dynamic linking.
* `n`, `no`, or `off`: use static linking (the default).

## no-redzone

This flag allows you to disable [the
red zone](https://en.wikipedia.org/wiki/Red_zone_\(computing\)). This flag can
be passed one of the following options:
red zone](https://en.wikipedia.org/wiki/Red_zone_\(computing\)). It takes one
of the following values:

* `y`, `yes`, `on`, or no value: Disables the red zone.
* `n`, `no`, or `off`: Enables the red zone.
* `y`, `yes`, `on`, or no value: disable the red zone.
* `n`, `no`, or `off`: enable the red zone.

The default if not specified depends on the target.
The default behaviour, if the flag is not specified, depends on the target.

## relocation-model

Expand Down Expand Up @@ -257,7 +262,7 @@ them in parallel. Increasing parallelism may speed up compile times, but may
also produce slower code. Setting this to 1 may improve the performance of
generated code, but may be slower to compile.

The default, if not specified, is 16 for non-incremental builds. For
The default value, if not specified, is 16 for non-incremental builds. For
incremental builds the default is 256 which allows caching to be more granular.

## remark
Expand All @@ -274,23 +279,25 @@ This option is deprecated and does nothing.

## debuginfo

This flag lets you control debug information:
This flag controls the generation of debug information. It takes one of the
following values:

* `0`: no debug info at all (default)
* `1`: line tables only
* `2`: full debug info
* `0`: no debug info at all (the default).
* `1`: line tables only.
* `2`: full debug info.

Note: The [`-g` flag][option-g-debug] is an alias for `-C debuginfo=2`.

## opt-level

This flag lets you control the optimization level.
This flag controls the optimization level.

* `0`: no optimizations, also turns on [`cfg(debug_assertions)`](#debug-assertions).
* `1`: basic optimizations
* `2`: some optimizations
* `3`: all optimizations
* `s`: optimize for binary size
* `0`: no optimizations, also turns on
[`cfg(debug_assertions)`](#debug-assertions) (the default).
* `1`: basic optimizations.
* `2`: some optimizations.
* `3`: all optimizations.
* `s`: optimize for binary size.
* `z`: optimize for binary size, but also turn off loop vectorization.

Note: The [`-O` flag][option-o-optimize] is an alias for `-C opt-level=2`.
Expand All @@ -303,8 +310,8 @@ This flag lets you turn `cfg(debug_assertions)` [conditional
compilation](../../reference/conditional-compilation.md#debug_assertions) on
or off. It takes one of the following values:

* `y`, `yes`, `on`, or no value: Enable debug-assertions.
* `n`, `no`, or `off`: Disable debug-assertions.
* `y`, `yes`, `on`, or no value: enable debug-assertions.
* `n`, `no`, or `off`: disable debug-assertions.

If not specified, debug assertions are automatically enabled only if the
[opt-level](#opt-level) is 0.
Expand Down Expand Up @@ -362,25 +369,24 @@ to a valid `.profdata` file. See the chapter on
This flag forces the use of frame pointers. It takes one of the following
values:

* `y`, `yes`, `on`, or no value: Frame pointers are forced to be enabled.
* `n`, `no`, or `off`: Frame pointers are not forced to be enabled. This does
* `y`, `yes`, `on`, or no value: force-enable frame pointers.
* `n`, `no`, or `off`: do not force-enable frame pointers. This does
not necessarily mean frame pointers will be removed.

The default if not specified depends on the target.
The default behaviour, if frame pointers are not force-enabled, depends on the
target.

## default-linker-libraries

This flag controls whether or not the linker includes its default libraries.
It takes one of the following values:

* `y`, `yes`, `on`, or no value: Default libraries are included.
* `n`, `no`, or `off`: Default libraries are **not** included.
* `y`, `yes`, `on`, or no value: include default libraries (the default).
* `n`, `no`, or `off`: exclude default libraries.

For example, for gcc flavor linkers, this issues the `-nodefaultlibs` flag to
the linker.

The default is `yes` if not specified.

[option-emit]: ../command-line-arguments.md#option-emit
[option-o-optimize]: ../command-line-arguments.md#option-o-optimize
[profile-guided optimization]: ../profile-guided-optimization.md
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_codegen_llvm/back/write.rs
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Expand Up @@ -347,7 +347,7 @@ pub(crate) fn should_use_new_llvm_pass_manager(config: &ModuleConfig) -> bool {
}

// The new pass manager is disabled by default.
config.new_llvm_pass_manager.unwrap_or(false)
config.new_llvm_pass_manager
}

pub(crate) unsafe fn optimize_with_new_llvm_pass_manager(
Expand Down
21 changes: 4 additions & 17 deletions src/librustc_codegen_ssa/back/link.rs
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Expand Up @@ -858,18 +858,7 @@ fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
// *not* running dsymutil then the object files are the only source of truth
// for debug information, so we must preserve them.
if sess.target.target.options.is_like_osx {
match sess.opts.debugging_opts.run_dsymutil {
// dsymutil is not being run, preserve objects
Some(false) => return true,

// dsymutil is being run, no need to preserve the objects
Some(true) => return false,

// The default historical behavior was to always run dsymutil, so
// we're preserving that temporarily, but we're likely to switch the
// default soon.
None => return false,
}
return !sess.opts.debugging_opts.run_dsymutil;
}

false
Expand Down Expand Up @@ -1324,11 +1313,11 @@ fn link_local_crate_native_libs_and_dependent_crate_libs<'a, B: ArchiveBuilder<'
// If -Zlink-native-libraries=false is set, then the assumption is that an
// external build system already has the native dependencies defined, and it
// will provide them to the linker itself.
if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
if sess.opts.debugging_opts.link_native_libraries {
add_local_native_libraries(cmd, sess, codegen_results);
}
add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
if sess.opts.debugging_opts.link_native_libraries {
add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
}
}
Expand Down Expand Up @@ -1534,9 +1523,7 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
// OBJECT-FILES-NO, AUDIT-ORDER
// We want to prevent the compiler from accidentally leaking in any system libraries,
// so by default we tell linkers not to link to any default libraries.
if !sess.opts.cg.default_linker_libraries.unwrap_or(false)
&& sess.target.target.options.no_default_libraries
{
if !sess.opts.cg.default_linker_libraries && sess.target.target.options.no_default_libraries {
cmd.no_default_libraries();
}

Expand Down
2 changes: 1 addition & 1 deletion src/librustc_codegen_ssa/back/linker.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -384,7 +384,7 @@ impl<'a> Linker for GccLinker<'a> {
// If we are building without debuginfo enabled and we were called with
// `-Zstrip-debuginfo-if-disabled=yes`, tell the linker to strip any debuginfo
// found when linking to get rid of symbols from libstd.
if let Some(true) = self.sess.opts.debugging_opts.strip_debuginfo_if_disabled {
if self.sess.opts.debugging_opts.strip_debuginfo_if_disabled {
self.linker_arg("-S");
}
};
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_codegen_ssa/back/write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -115,7 +115,7 @@ pub struct ModuleConfig {
pub vectorize_slp: bool,
pub merge_functions: bool,
pub inline_threshold: Option<usize>,
pub new_llvm_pass_manager: Option<bool>,
pub new_llvm_pass_manager: bool,
}

impl ModuleConfig {
Expand Down
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