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use rustc_data_structures::stable_hasher::{Hash64, HashStable, StableHasher};
use rustc_hir::def_id::CrateNum;
use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
use rustc_middle::ty::print::{PrettyPrinter, Print, Printer};
use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeVisitableExt};
use rustc_middle::ty::{GenericArg, GenericArgKind};
use rustc_middle::util::common::record_time;
use std::fmt::{self, Write};
use std::mem::{self, discriminant};
pub(super) fn mangle<'tcx>(
tcx: TyCtxt<'tcx>,
instance: Instance<'tcx>,
instantiating_crate: Option<CrateNum>,
) -> String {
let def_id = instance.def_id();
// We want to compute the "type" of this item. Unfortunately, some
// kinds of items (e.g., closures) don't have an entry in the
// item-type array. So walk back up the find the closest parent
// that DOES have an entry.
let mut ty_def_id = def_id;
let instance_ty;
loop {
let key = tcx.def_key(ty_def_id);
match key.disambiguated_data.data {
DefPathData::TypeNs(_) | DefPathData::ValueNs(_) => {
instance_ty = tcx.type_of(ty_def_id).instantiate_identity();
debug!(?instance_ty);
break;
}
_ => {
// if we're making a symbol for something, there ought
// to be a value or type-def or something in there
// *somewhere*
ty_def_id.index = key.parent.unwrap_or_else(|| {
bug!(
"finding type for {:?}, encountered def-id {:?} with no \
parent",
def_id,
ty_def_id
);
});
}
}
}
// Erase regions because they may not be deterministic when hashed
// and should not matter anyhow.
let instance_ty = tcx.erase_regions(instance_ty);
let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate);
let mut printer = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false };
printer
.print_def_path(
def_id,
if let ty::InstanceDef::DropGlue(_, _) = instance.def {
// Add the name of the dropped type to the symbol name
&*instance.args
} else {
&[]
},
)
.unwrap();
if let ty::InstanceDef::ThreadLocalShim(..) = instance.def {
let _ = printer.write_str("{{tls-shim}}");
}
if let ty::InstanceDef::VTableShim(..) = instance.def {
let _ = printer.write_str("{{vtable-shim}}");
}
if let ty::InstanceDef::ReifyShim(..) = instance.def {
let _ = printer.write_str("{{reify-shim}}");
}
printer.path.finish(hash)
}
fn get_symbol_hash<'tcx>(
tcx: TyCtxt<'tcx>,
// instance this name will be for
instance: Instance<'tcx>,
// type of the item, without any generic
// parameters substituted; this is
// included in the hash as a kind of
// safeguard.
item_type: Ty<'tcx>,
instantiating_crate: Option<CrateNum>,
) -> Hash64 {
let def_id = instance.def_id();
let args = instance.args;
debug!("get_symbol_hash(def_id={:?}, parameters={:?})", def_id, args);
tcx.with_stable_hashing_context(|mut hcx| {
let mut hasher = StableHasher::new();
record_time(&tcx.sess.perf_stats.symbol_hash_time, || {
// the main symbol name is not necessarily unique; hash in the
// compiler's internal def-path, guaranteeing each symbol has a
// truly unique path
tcx.def_path_hash(def_id).hash_stable(&mut hcx, &mut hasher);
// Include the main item-type. Note that, in this case, the
// assertions about `has_param` may not hold, but this item-type
// ought to be the same for every reference anyway.
assert!(!item_type.has_erasable_regions());
hcx.while_hashing_spans(false, |hcx| {
item_type.hash_stable(hcx, &mut hasher);
// If this is a function, we hash the signature as well.
// This is not *strictly* needed, but it may help in some
// situations, see the `run-make/a-b-a-linker-guard` test.
if let ty::FnDef(..) = item_type.kind() {
item_type.fn_sig(tcx).hash_stable(hcx, &mut hasher);
}
// also include any type parameters (for generic items)
args.hash_stable(hcx, &mut hasher);
if let Some(instantiating_crate) = instantiating_crate {
tcx.def_path_hash(instantiating_crate.as_def_id())
.stable_crate_id()
.hash_stable(hcx, &mut hasher);
}
// We want to avoid accidental collision between different types of instances.
// Especially, `VTableShim`s and `ReifyShim`s may overlap with their original
// instances without this.
discriminant(&instance.def).hash_stable(hcx, &mut hasher);
});
});
// 64 bits should be enough to avoid collisions.
hasher.finish::<Hash64>()
})
}
// Follow C++ namespace-mangling style, see
// https://en.wikipedia.org/wiki/Name_mangling for more info.
//
// It turns out that on macOS you can actually have arbitrary symbols in
// function names (at least when given to LLVM), but this is not possible
// when using unix's linker. Perhaps one day when we just use a linker from LLVM
// we won't need to do this name mangling. The problem with name mangling is
// that it seriously limits the available characters. For example we can't
// have things like &T in symbol names when one would theoretically
// want them for things like impls of traits on that type.
//
// To be able to work on all platforms and get *some* reasonable output, we
// use C++ name-mangling.
#[derive(Debug)]
struct SymbolPath {
result: String,
temp_buf: String,
}
impl SymbolPath {
fn new() -> Self {
let mut result =
SymbolPath { result: String::with_capacity(64), temp_buf: String::with_capacity(16) };
result.result.push_str("_ZN"); // _Z == Begin name-sequence, N == nested
result
}
fn finalize_pending_component(&mut self) {
if !self.temp_buf.is_empty() {
let _ = write!(self.result, "{}{}", self.temp_buf.len(), self.temp_buf);
self.temp_buf.clear();
}
}
fn finish(mut self, hash: Hash64) -> String {
self.finalize_pending_component();
// E = end name-sequence
let _ = write!(self.result, "17h{hash:016x}E");
self.result
}
}
struct SymbolPrinter<'tcx> {
tcx: TyCtxt<'tcx>,
path: SymbolPath,
// When `true`, `finalize_pending_component` isn't used.
// This is needed when recursing into `path_qualified`,
// or `path_generic_args`, as any nested paths are
// logically within one component.
keep_within_component: bool,
}
// HACK(eddyb) this relies on using the `fmt` interface to get
// `PrettyPrinter` aka pretty printing of e.g. types in paths,
// symbol names should have their own printing machinery.
impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> {
type Error = fmt::Error;
type Path = Self;
type Region = Self;
type Type = Self;
type DynExistential = Self;
type Const = Self;
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
Ok(self)
}
fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
match *ty.kind() {
// Print all nominal types as paths (unlike `pretty_print_type`).
ty::FnDef(def_id, args)
| ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. })
| ty::Closure(def_id, args)
| ty::Generator(def_id, args, _) => self.print_def_path(def_id, args),
// The `pretty_print_type` formatting of array size depends on
// -Zverbose flag, so we cannot reuse it here.
ty::Array(ty, size) => {
self.write_str("[")?;
self = self.print_type(ty)?;
self.write_str("; ")?;
if let Some(size) = size.try_to_target_usize(self.tcx()) {
write!(self, "{size}")?
} else if let ty::ConstKind::Param(param) = size.kind() {
self = param.print(self)?
} else {
self.write_str("_")?
}
self.write_str("]")?;
Ok(self)
}
ty::Alias(ty::Inherent, _) => panic!("unexpected inherent projection"),
_ => self.pretty_print_type(ty),
}
}
fn print_dyn_existential(
mut self,
predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Result<Self::DynExistential, Self::Error> {
let mut first = true;
for p in predicates {
if !first {
write!(self, "+")?;
}
first = false;
self = p.print(self)?;
}
Ok(self)
}
fn print_const(self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
// only print integers
match (ct.kind(), ct.ty().kind()) {
(ty::ConstKind::Value(ty::ValTree::Leaf(scalar)), ty::Int(_) | ty::Uint(_)) => {
// The `pretty_print_const` formatting depends on -Zverbose
// flag, so we cannot reuse it here.
let signed = matches!(ct.ty().kind(), ty::Int(_));
write!(
self,
"{:#?}",
ty::ConstInt::new(scalar, signed, ct.ty().is_ptr_sized_integral())
)?;
}
_ => self.write_str("_")?,
}
Ok(self)
}
fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
self.write_str(self.tcx.crate_name(cnum).as_str())?;
Ok(self)
}
fn path_qualified(
self,
self_ty: Ty<'tcx>,
trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
// Similar to `pretty_path_qualified`, but for the other
// types that are printed as paths (see `print_type` above).
match self_ty.kind() {
ty::FnDef(..) | ty::Alias(..) | ty::Closure(..) | ty::Generator(..)
if trait_ref.is_none() =>
{
self.print_type(self_ty)
}
_ => self.pretty_path_qualified(self_ty, trait_ref),
}
}
fn path_append_impl(
self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
_disambiguated_data: &DisambiguatedDefPathData,
self_ty: Ty<'tcx>,
trait_ref: Option<ty::TraitRef<'tcx>>,
) -> Result<Self::Path, Self::Error> {
self.pretty_path_append_impl(
|mut cx| {
cx = print_prefix(cx)?;
if cx.keep_within_component {
// HACK(eddyb) print the path similarly to how `FmtPrinter` prints it.
cx.write_str("::")?;
} else {
cx.path.finalize_pending_component();
}
Ok(cx)
},
self_ty,
trait_ref,
)
}
fn path_append(
mut self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
disambiguated_data: &DisambiguatedDefPathData,
) -> Result<Self::Path, Self::Error> {
self = print_prefix(self)?;
// Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
return Ok(self);
}
if self.keep_within_component {
// HACK(eddyb) print the path similarly to how `FmtPrinter` prints it.
self.write_str("::")?;
} else {
self.path.finalize_pending_component();
}
write!(self, "{}", disambiguated_data.data)?;
Ok(self)
}
fn path_generic_args(
mut self,
print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
args: &[GenericArg<'tcx>],
) -> Result<Self::Path, Self::Error> {
self = print_prefix(self)?;
let args =
args.iter().cloned().filter(|arg| !matches!(arg.unpack(), GenericArgKind::Lifetime(_)));
if args.clone().next().is_some() {
self.generic_delimiters(|cx| cx.comma_sep(args))
} else {
Ok(self)
}
}
}
impl<'tcx> PrettyPrinter<'tcx> for &mut SymbolPrinter<'tcx> {
fn should_print_region(&self, _region: ty::Region<'_>) -> bool {
false
}
fn comma_sep<T>(mut self, mut elems: impl Iterator<Item = T>) -> Result<Self, Self::Error>
where
T: Print<'tcx, Self, Output = Self, Error = Self::Error>,
{
if let Some(first) = elems.next() {
self = first.print(self)?;
for elem in elems {
self.write_str(",")?;
self = elem.print(self)?;
}
}
Ok(self)
}
fn generic_delimiters(
mut self,
f: impl FnOnce(Self) -> Result<Self, Self::Error>,
) -> Result<Self, Self::Error> {
write!(self, "<")?;
let kept_within_component = mem::replace(&mut self.keep_within_component, true);
self = f(self)?;
self.keep_within_component = kept_within_component;
write!(self, ">")?;
Ok(self)
}
}
impl fmt::Write for SymbolPrinter<'_> {
fn write_str(&mut self, s: &str) -> fmt::Result {
// Name sanitation. LLVM will happily accept identifiers with weird names, but
// gas doesn't!
// gas accepts the following characters in symbols: a-z, A-Z, 0-9, ., _, $
// NVPTX assembly has more strict naming rules than gas, so additionally, dots
// are replaced with '$' there.
for c in s.chars() {
if self.path.temp_buf.is_empty() {
match c {
'a'..='z' | 'A'..='Z' | '_' => {}
_ => {
// Underscore-qualify anything that didn't start as an ident.
self.path.temp_buf.push('_');
}
}
}
match c {
// Escape these with $ sequences
'@' => self.path.temp_buf.push_str("$SP$"),
'*' => self.path.temp_buf.push_str("$BP$"),
'&' => self.path.temp_buf.push_str("$RF$"),
'<' => self.path.temp_buf.push_str("$LT$"),
'>' => self.path.temp_buf.push_str("$GT$"),
'(' => self.path.temp_buf.push_str("$LP$"),
')' => self.path.temp_buf.push_str("$RP$"),
',' => self.path.temp_buf.push_str("$C$"),
'-' | ':' | '.' if self.tcx.has_strict_asm_symbol_naming() => {
// NVPTX doesn't support these characters in symbol names.
self.path.temp_buf.push('$')
}
// '.' doesn't occur in types and functions, so reuse it
// for ':' and '-'
'-' | ':' => self.path.temp_buf.push('.'),
// Avoid crashing LLVM in certain (LTO-related) situations, see #60925.
'm' if self.path.temp_buf.ends_with(".llv") => self.path.temp_buf.push_str("$u6d$"),
// These are legal symbols
'a'..='z' | 'A'..='Z' | '0'..='9' | '_' | '.' | '$' => self.path.temp_buf.push(c),
_ => {
self.path.temp_buf.push('$');
for c in c.escape_unicode().skip(1) {
match c {
'{' => {}
'}' => self.path.temp_buf.push('$'),
c => self.path.temp_buf.push(c),
}
}
}
}
}
Ok(())
}
}