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Rollup merge of #137741 - cuviper:const_str-raw_entry, r=Mark-Simulacrum

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Stop using `hash_raw_entry` in `CodegenCx::const_str`

That unstable feature (#56167) completed fcp-close, so the compiler needs to be
migrated away to allow its removal. In this case, `cg_llvm` and `cg_gcc`
were using raw entries to optimize their `const_str_cache` lookup and
insertion. We can change that to separate `get` and (on miss) `insert`
calls, so we still have the fast path avoiding string allocation when
the cache hits.
This commit is contained in:
Matthias Krüger 2025-03-03 10:41:00 +01:00 • committed by GitHub
commit fd4bf82264
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4 changed files with 25 additions and 31 deletions
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40
compiler/rustc_codegen_llvm/src/common.rs
View file

@ -209,28 +209,24 @@ impl<'ll, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
fn const_str(&self, s: &str) -> (&'ll Value, &'ll Value) {
let str_global = *self
.const_str_cache
.borrow_mut()
.raw_entry_mut()
.from_key(s)
.or_insert_with(|| {
let sc = self.const_bytes(s.as_bytes());
let sym = self.generate_local_symbol_name("str");
let g = self.define_global(&sym, self.val_ty(sc)).unwrap_or_else(|| {
bug!("symbol `{}` is already defined", sym);
});
llvm::set_initializer(g, sc);
unsafe {
llvm::LLVMSetGlobalConstant(g, True);
llvm::LLVMSetUnnamedAddress(g, llvm::UnnamedAddr::Global);
}
llvm::set_linkage(g, llvm::Linkage::InternalLinkage);
// Cast to default address space if globals are in a different addrspace
let g = self.const_pointercast(g, self.type_ptr());
(s.to_owned(), g)
})
.1;
let mut const_str_cache = self.const_str_cache.borrow_mut();
let str_global = const_str_cache.get(s).copied().unwrap_or_else(|| {
let sc = self.const_bytes(s.as_bytes());
let sym = self.generate_local_symbol_name("str");
let g = self.define_global(&sym, self.val_ty(sc)).unwrap_or_else(|| {
bug!("symbol `{}` is already defined", sym);
});
llvm::set_initializer(g, sc);
unsafe {
llvm::LLVMSetGlobalConstant(g, True);
llvm::LLVMSetUnnamedAddress(g, llvm::UnnamedAddr::Global);
}
llvm::set_linkage(g, llvm::Linkage::InternalLinkage);
// Cast to default address space if globals are in a different addrspace
let g = self.const_pointercast(g, self.type_ptr());
const_str_cache.insert(s.to_owned(), g);
g
});
let len = s.len();
(str_global, self.const_usize(len as u64))
}

1
compiler/rustc_codegen_llvm/src/lib.rs
View file

@ -12,7 +12,6 @@
#![feature(exact_size_is_empty)]
#![feature(extern_types)]
#![feature(file_buffered)]
#![feature(hash_raw_entry)]
#![feature(if_let_guard)]
#![feature(impl_trait_in_assoc_type)]
#![feature(iter_intersperse)]