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

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

That unstable feature (rust-lang#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.

Author: matthiaskrgr

Diff for: compiler/rustc_codegen_gcc/src/common.rs

@@ -146,13 +146,12 @@ impl<'gcc, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
     }
 
     fn const_str(&self, s: &str) -> (RValue<'gcc>, RValue<'gcc>) {
-        let str_global = *self
-            .const_str_cache
-            .borrow_mut()
-            .raw_entry_mut()
-            .from_key(s)
-            .or_insert_with(|| (s.to_owned(), self.global_string(s)))
-            .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 g = self.global_string(s);
+            const_str_cache.insert(s.to_owned(), g);
+            g
+        });
         let len = s.len();
         let cs = self.const_ptrcast(
             str_global.get_address(None),

Diff for: compiler/rustc_codegen_gcc/src/lib.rs

@@ -16,7 +16,7 @@
 #![allow(internal_features)]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
-#![feature(rustc_private, decl_macro, never_type, trusted_len, hash_raw_entry, let_chains)]
+#![feature(rustc_private, decl_macro, never_type, trusted_len, let_chains)]
 #![allow(broken_intra_doc_links)]
 #![recursion_limit = "256"]
 #![warn(rust_2018_idioms)]

Diff for: compiler/rustc_codegen_llvm/src/common.rs

@@ -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))
     }

Diff for: compiler/rustc_codegen_llvm/src/lib.rs

@@ -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)]