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cg_llvm: fewer_names in uncached_llvm_type

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This commit changes `uncached_llvm_type` so that a named struct type
(with an empty name) is always created when the `fewer_names` option
is enabled. By skipping the generation of names, we can improve perf.
Giving `LLVMStructCreateNamed` an empty name works because LLVM will
perform random renames to avoid collisions.

Signed-off-by: David Wood <david@davidtw.co>
This commit is contained in:
David Wood 2020-08-28 16:24:52 +01:00
parent 6c44bcc4ff
commit fa01ce802f
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GPG Key ID: 2592E76C87381FD9
1 changed files with 14 additions and 10 deletions
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24
compiler/rustc_codegen_llvm/src/type_of.rs
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@ -51,30 +51,34 @@ fn uncached_llvm_type<'a, 'tcx>(
}
let name = match layout.ty.kind {
ty::Closure(..) |
ty::Generator(..) |
ty::Adt(..) |
// FIXME(eddyb) producing readable type names for trait objects can result
// in problematically distinct types due to HRTB and subtyping (see #47638).
// ty::Dynamic(..) |
ty::Foreign(..) |
ty::Str => {
ty::Adt(..) | ty::Closure(..) | ty::Foreign(..) | ty::Generator(..) | ty::Str
if !cx.sess().fewer_names() =>
{
let mut name = layout.ty.to_string();
if let (&ty::Adt(def, _), &Variants::Single { index })
= (&layout.ty.kind, &layout.variants)
if let (&ty::Adt(def, _), &Variants::Single { index }) =
(&layout.ty.kind, &layout.variants)
{
if def.is_enum() && !def.variants.is_empty() {
write!(&mut name, "::{}", def.variants[index].ident).unwrap();
}
}
if let (&ty::Generator(_, _, _), &Variants::Single { index })
= (&layout.ty.kind, &layout.variants)
if let (&ty::Generator(_, _, _), &Variants::Single { index }) =
(&layout.ty.kind, &layout.variants)
{
write!(&mut name, "::{}", ty::GeneratorSubsts::variant_name(index)).unwrap();
}
Some(name)
}
_ => None
ty::Adt(..) => {
// If `Some` is returned then a named struct is created in LLVM. Name collisions are
// avoided by LLVM (with increasing suffixes). If rustc doesn't generate names then that
// can improve perf.
Some(String::new())
}
_ => None,
};
match layout.fields {