rust/compiler/rustc_codegen_llvm/src/llvm_util.rs
2022-08-14 13:46:51 -07:00

555 lines
22 KiB
Rust

use crate::back::write::create_informational_target_machine;
use crate::{llvm, llvm_util};
use libc::c_int;
use libloading::Library;
use rustc_codegen_ssa::target_features::{
supported_target_features, tied_target_features, RUSTC_SPECIFIC_FEATURES,
};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::small_c_str::SmallCStr;
use rustc_fs_util::path_to_c_string;
use rustc_middle::bug;
use rustc_session::config::PrintRequest;
use rustc_session::Session;
use rustc_span::symbol::Symbol;
use rustc_target::spec::{MergeFunctions, PanicStrategy};
use smallvec::{smallvec, SmallVec};
use std::ffi::{CStr, CString};
use tracing::debug;
use std::mem;
use std::path::Path;
use std::ptr;
use std::slice;
use std::str;
use std::sync::Once;
static INIT: Once = Once::new();
pub(crate) fn init(sess: &Session) {
unsafe {
// Before we touch LLVM, make sure that multithreading is enabled.
if llvm::LLVMIsMultithreaded() != 1 {
bug!("LLVM compiled without support for threads");
}
INIT.call_once(|| {
configure_llvm(sess);
});
}
}
fn require_inited() {
if !INIT.is_completed() {
bug!("LLVM is not initialized");
}
}
unsafe fn configure_llvm(sess: &Session) {
let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
let mut llvm_args = Vec::with_capacity(n_args + 1);
llvm::LLVMRustInstallFatalErrorHandler();
// On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
// box for the purpose of launching a debugger. However, on CI this will
// cause it to hang until it times out, which can take several hours.
if std::env::var_os("CI").is_some() {
llvm::LLVMRustDisableSystemDialogsOnCrash();
}
fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
}
let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref);
let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref);
let sess_args = cg_opts.chain(tg_opts);
let user_specified_args: FxHashSet<_> =
sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
{
// This adds the given argument to LLVM. Unless `force` is true
// user specified arguments are *not* overridden.
let mut add = |arg: &str, force: bool| {
if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
let s = CString::new(arg).unwrap();
llvm_args.push(s.as_ptr());
llvm_c_strs.push(s);
}
};
// Set the llvm "program name" to make usage and invalid argument messages more clear.
add("rustc -Cllvm-args=\"...\" with", true);
if sess.time_llvm_passes() {
add("-time-passes", false);
}
if sess.print_llvm_passes() {
add("-debug-pass=Structure", false);
}
if sess.target.generate_arange_section
&& !sess.opts.unstable_opts.no_generate_arange_section
{
add("-generate-arange-section", false);
}
match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
MergeFunctions::Aliases => {
add("-mergefunc-use-aliases", false);
}
}
if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
add("-enable-emscripten-cxx-exceptions", false);
}
// HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
// during inlining. Unfortunately these may block other optimizations.
add("-preserve-alignment-assumptions-during-inlining=false", false);
// Use non-zero `import-instr-limit` multiplier for cold callsites.
add("-import-cold-multiplier=0.1", false);
for arg in sess_args {
add(&(*arg), true);
}
}
if sess.opts.unstable_opts.llvm_time_trace {
llvm::LLVMTimeTraceProfilerInitialize();
}
llvm::LLVMInitializePasses();
// Use the legacy plugin registration if we don't use the new pass manager
if !should_use_new_llvm_pass_manager(
&sess.opts.unstable_opts.new_llvm_pass_manager,
&sess.target.arch,
) {
// Register LLVM plugins by loading them into the compiler process.
for plugin in &sess.opts.unstable_opts.llvm_plugins {
let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));
debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin);
// Intentionally leak the dynamic library. We can't ever unload it
// since the library can make things that will live arbitrarily long.
mem::forget(lib);
}
}
rustc_llvm::initialize_available_targets();
llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
}
pub fn time_trace_profiler_finish(file_name: &Path) {
unsafe {
let file_name = path_to_c_string(file_name);
llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
}
}
// WARNING: the features after applying `to_llvm_features` must be known
// to LLVM or the feature detection code will walk past the end of the feature
// array, leading to crashes.
//
// To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
// where the * matches the architecture's name
// Beware to not use the llvm github project for this, but check the git submodule
// found in src/llvm-project
// Though note that Rust can also be build with an external precompiled version of LLVM
// which might lead to failures if the oldest tested / supported LLVM version
// doesn't yet support the relevant intrinsics
pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]> {
let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
match (arch, s) {
("x86", "sse4.2") => {
if get_version() >= (14, 0, 0) {
smallvec!["sse4.2", "crc32"]
} else {
smallvec!["sse4.2"]
}
}
("x86", "pclmulqdq") => smallvec!["pclmul"],
("x86", "rdrand") => smallvec!["rdrnd"],
("x86", "bmi1") => smallvec!["bmi"],
("x86", "cmpxchg16b") => smallvec!["cx16"],
("x86", "avx512vaes") => smallvec!["vaes"],
("x86", "avx512gfni") => smallvec!["gfni"],
("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"],
("aarch64", "rcpc2") => smallvec!["rcpc-immo"],
("aarch64", "dpb") => smallvec!["ccpp"],
("aarch64", "dpb2") => smallvec!["ccdp"],
("aarch64", "frintts") => smallvec!["fptoint"],
("aarch64", "fcma") => smallvec!["complxnum"],
("aarch64", "pmuv3") => smallvec!["perfmon"],
("aarch64", "paca") => smallvec!["pauth"],
("aarch64", "pacg") => smallvec!["pauth"],
// Rust ties fp and neon together. In LLVM neon implicitly enables fp,
// but we manually enable neon when a feature only implicitly enables fp
("aarch64", "f32mm") => smallvec!["f32mm", "neon"],
("aarch64", "f64mm") => smallvec!["f64mm", "neon"],
("aarch64", "fhm") => smallvec!["fp16fml", "neon"],
("aarch64", "fp16") => smallvec!["fullfp16", "neon"],
("aarch64", "jsconv") => smallvec!["jsconv", "neon"],
("aarch64", "sve") => smallvec!["sve", "neon"],
("aarch64", "sve2") => smallvec!["sve2", "neon"],
("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"],
("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"],
("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"],
("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"],
(_, s) => smallvec![s],
}
}
// Given a map from target_features to whether they are enabled or disabled,
// ensure only valid combinations are allowed.
pub fn check_tied_features(
sess: &Session,
features: &FxHashMap<&str, bool>,
) -> Option<&'static [&'static str]> {
if !features.is_empty() {
for tied in tied_target_features(sess) {
// Tied features must be set to the same value, or not set at all
let mut tied_iter = tied.iter();
let enabled = features.get(tied_iter.next().unwrap());
if tied_iter.any(|f| enabled != features.get(f)) {
return Some(tied);
}
}
}
return None;
}
// Used to generate cfg variables and apply features
// Must express features in the way Rust understands them
pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
let target_machine = create_informational_target_machine(sess);
let mut features: Vec<Symbol> = supported_target_features(sess)
.iter()
.filter_map(|&(feature, gate)| {
if sess.is_nightly_build() || allow_unstable || gate.is_none() {
Some(feature)
} else {
None
}
})
.filter(|feature| {
// check that all features in a given smallvec are enabled
for llvm_feature in to_llvm_features(sess, feature) {
let cstr = SmallCStr::new(llvm_feature);
if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
return false;
}
}
true
})
.map(|feature| Symbol::intern(feature))
.collect();
// LLVM 14 changed the ABI for i128 arguments to __float/__fix builtins on Win64
// (see https://reviews.llvm.org/D110413). This unstable target feature is intended for use
// by compiler-builtins, to export the builtins with the expected, LLVM-version-dependent ABI.
// The target feature can be dropped once we no longer support older LLVM versions.
if sess.is_nightly_build() && get_version() >= (14, 0, 0) {
features.push(Symbol::intern("llvm14-builtins-abi"));
}
features
}
pub fn print_version() {
let (major, minor, patch) = get_version();
println!("LLVM version: {}.{}.{}", major, minor, patch);
}
pub fn get_version() -> (u32, u32, u32) {
// Can be called without initializing LLVM
unsafe {
(llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
}
}
pub fn print_passes() {
// Can be called without initializing LLVM
unsafe {
llvm::LLVMRustPrintPasses();
}
}
fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
let mut ret = Vec::with_capacity(len);
for i in 0..len {
unsafe {
let mut feature = ptr::null();
let mut desc = ptr::null();
llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
if feature.is_null() || desc.is_null() {
bug!("LLVM returned a `null` target feature string");
}
let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
bug!("LLVM returned a non-utf8 feature string: {}", e);
});
let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
bug!("LLVM returned a non-utf8 feature string: {}", e);
});
ret.push((feature, desc));
}
}
ret
}
fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
let mut target_features = llvm_target_features(tm);
let mut rustc_target_features = supported_target_features(sess)
.iter()
.filter_map(|(feature, _gate)| {
for llvm_feature in to_llvm_features(sess, *feature) {
// LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok().map(
|index| {
let (_f, desc) = target_features.remove(index);
(*feature, desc)
},
) {
Some(v) => return Some(v),
None => {}
}
}
None
})
.collect::<Vec<_>>();
rustc_target_features.extend_from_slice(&[(
"crt-static",
"Enables C Run-time Libraries to be statically linked",
)]);
let max_feature_len = target_features
.iter()
.chain(rustc_target_features.iter())
.map(|(feature, _desc)| feature.len())
.max()
.unwrap_or(0);
println!("Features supported by rustc for this target:");
for (feature, desc) in &rustc_target_features {
println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
}
println!("\nCode-generation features supported by LLVM for this target:");
for (feature, desc) in &target_features {
println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
}
if target_features.is_empty() {
println!(" Target features listing is not supported by this LLVM version.");
}
println!("\nUse +feature to enable a feature, or -feature to disable it.");
println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
println!("Code-generation features cannot be used in cfg or #[target_feature],");
println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
}
pub(crate) fn print(req: PrintRequest, sess: &Session) {
require_inited();
let tm = create_informational_target_machine(sess);
match req {
PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
PrintRequest::TargetFeatures => print_target_features(sess, tm),
_ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
}
}
fn handle_native(name: &str) -> &str {
if name != "native" {
return name;
}
unsafe {
let mut len = 0;
let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
}
}
pub fn target_cpu(sess: &Session) -> &str {
match sess.opts.cg.target_cpu {
Some(ref name) => handle_native(name),
None => handle_native(sess.target.cpu.as_ref()),
}
}
/// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
/// `--target` and similar).
pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<String> {
// Features that come earlier are overridden by conflicting features later in the string.
// Typically we'll want more explicit settings to override the implicit ones, so:
//
// * Features from -Ctarget-cpu=*; are overridden by [^1]
// * Features implied by --target; are overridden by
// * Features from -Ctarget-feature; are overridden by
// * function specific features.
//
// [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
// through LLVM TargetMachine implementation.
//
// FIXME(nagisa): it isn't clear what's the best interaction between features implied by
// `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
// override anything that's implicit, so e.g. when there's no `--target` flag, features implied
// the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
// `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
// flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
// should be taken in cases like these.
let mut features = vec![];
// -Ctarget-cpu=native
match sess.opts.cg.target_cpu {
Some(ref s) if s == "native" => {
let features_string = unsafe {
let ptr = llvm::LLVMGetHostCPUFeatures();
let features_string = if !ptr.is_null() {
CStr::from_ptr(ptr)
.to_str()
.unwrap_or_else(|e| {
bug!("LLVM returned a non-utf8 features string: {}", e);
})
.to_owned()
} else {
bug!("could not allocate host CPU features, LLVM returned a `null` string");
};
llvm::LLVMDisposeMessage(ptr);
features_string
};
features.extend(features_string.split(',').map(String::from));
}
Some(_) | None => {}
};
// Features implied by an implicit or explicit `--target`.
features.extend(
sess.target
.features
.split(',')
.filter(|v| !v.is_empty() && backend_feature_name(v).is_some())
// Drop +atomics-32 feature introduced in LLVM 15.
.filter(|v| *v != "+atomics-32" || get_version() >= (15, 0, 0))
.map(String::from),
);
// -Ctarget-features
let supported_features = supported_target_features(sess);
let mut featsmap = FxHashMap::default();
let feats = sess
.opts
.cg
.target_feature
.split(',')
.filter_map(|s| {
let enable_disable = match s.chars().next() {
None => return None,
Some(c @ '+' | c @ '-') => c,
Some(_) => {
if diagnostics {
let mut diag = sess.struct_warn(&format!(
"unknown feature specified for `-Ctarget-feature`: `{}`",
s
));
diag.note("features must begin with a `+` to enable or `-` to disable it");
diag.emit();
}
return None;
}
};
let feature = backend_feature_name(s)?;
// Warn against use of LLVM specific feature names on the CLI.
if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) {
let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
let llvm_features = to_llvm_features(sess, rust_feature);
if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) {
Some(rust_feature)
} else {
None
}
});
let mut diag = sess.struct_warn(&format!(
"unknown feature specified for `-Ctarget-feature`: `{}`",
feature
));
diag.note("it is still passed through to the codegen backend");
if let Some(rust_feature) = rust_feature {
diag.help(&format!("you might have meant: `{}`", rust_feature));
} else {
diag.note("consider filing a feature request");
}
diag.emit();
}
if diagnostics {
// FIXME(nagisa): figure out how to not allocate a full hashset here.
featsmap.insert(feature, enable_disable == '+');
}
// rustc-specific features do not get passed down to LLVM…
if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
return None;
}
// ... otherwise though we run through `to_llvm_features` when
// passing requests down to LLVM. This means that all in-language
// features also work on the command line instead of having two
// different names when the LLVM name and the Rust name differ.
Some(
to_llvm_features(sess, feature)
.into_iter()
.map(move |f| format!("{}{}", enable_disable, f)),
)
})
.flatten();
features.extend(feats);
if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
sess.err(&format!(
"target features {} must all be enabled or disabled together",
f.join(", ")
));
}
features
}
/// Returns a feature name for the given `+feature` or `-feature` string.
///
/// Only allows features that are backend specific (i.e. not [`RUSTC_SPECIFIC_FEATURES`].)
fn backend_feature_name(s: &str) -> Option<&str> {
// features must start with a `+` or `-`.
let feature = s.strip_prefix(&['+', '-'][..]).unwrap_or_else(|| {
bug!("target feature `{}` must begin with a `+` or `-`", s);
});
// Rustc-specific feature requests like `+crt-static` or `-crt-static`
// are not passed down to LLVM.
if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
return None;
}
Some(feature)
}
pub fn tune_cpu(sess: &Session) -> Option<&str> {
let name = sess.opts.unstable_opts.tune_cpu.as_ref()?;
Some(handle_native(name))
}
pub(crate) fn should_use_new_llvm_pass_manager(user_opt: &Option<bool>, target_arch: &str) -> bool {
// The new pass manager is enabled by default for LLVM >= 13.
// This matches Clang, which also enables it since Clang 13.
// Since LLVM 15, the legacy pass manager is no longer supported.
if llvm_util::get_version() >= (15, 0, 0) {
return true;
}
// There are some perf issues with the new pass manager when targeting
// s390x with LLVM 13, so enable the new pass manager only with LLVM 14.
// See https://github.com/rust-lang/rust/issues/89609.
let min_version = if target_arch == "s390x" { 14 } else { 13 };
user_opt.unwrap_or_else(|| llvm_util::get_version() >= (min_version, 0, 0))
}