Auto merge of #94638 - erikdesjardins:noextranull, r=nagisa

cleanup: remove unused ability to have LLVM null-terminate const strings

(and the copied function in rustc_codegen_gcc)

Noticed this while writing https://github.com/rust-lang/rust/pull/94450#issuecomment-1059687348.

r? `@nagisa`

compiler/rustc_codegen_gcc/src/common.rs

@@ -26,18 +26,6 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         bytes_in_context(self, bytes)
     }
 
-    fn const_cstr(&self, symbol: Symbol, _null_terminated: bool) -> LValue<'gcc> {
-        // TODO(antoyo): handle null_terminated.
-        if let Some(&value) = self.const_cstr_cache.borrow().get(&symbol) {
-            return value;
-        }
-
-        let global = self.global_string(symbol.as_str());
-
-        self.const_cstr_cache.borrow_mut().insert(symbol, global);
-        global
-    }
-
     fn global_string(&self, string: &str) -> LValue<'gcc> {
         // TODO(antoyo): handle non-null-terminated strings.
         let string = self.context.new_string_literal(&*string);
@@ -171,8 +159,12 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
     }
 
     fn const_str(&self, s: Symbol) -> (RValue<'gcc>, RValue<'gcc>) {
-        let len = s.as_str().len();
+        let s_str = s.as_str();
-        let cs = self.const_ptrcast(self.const_cstr(s, false).get_address(None),
+        let str_global = *self.const_str_cache.borrow_mut().entry(s).or_insert_with(|| {
+            self.global_string(s_str)
+        });
+        let len = s_str.len();
+        let cs = self.const_ptrcast(str_global.get_address(None),
             self.type_ptr_to(self.layout_of(self.tcx.types.str_).gcc_type(self, true)),
         );
         (cs, self.const_usize(len as u64))

compiler/rustc_codegen_gcc/src/context.rs

@@ -85,7 +85,7 @@ pub struct CodegenCx<'gcc, 'tcx> {
     pub const_globals: RefCell<FxHashMap<RValue<'gcc>, RValue<'gcc>>>,
 
     /// Cache of constant strings,
-    pub const_cstr_cache: RefCell<FxHashMap<Symbol, LValue<'gcc>>>,
+    pub const_str_cache: RefCell<FxHashMap<Symbol, LValue<'gcc>>>,
 
     /// Cache of globals.
     pub globals: RefCell<FxHashMap<String, RValue<'gcc>>>,
@@ -195,7 +195,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
             function_instances: Default::default(),
             vtables: Default::default(),
             const_globals: Default::default(),
-            const_cstr_cache: Default::default(),
+            const_str_cache: Default::default(),
             globals: Default::default(),
             scalar_types: Default::default(),
             types: Default::default(),

compiler/rustc_codegen_llvm/src/common.rs

@@ -106,32 +106,6 @@ impl<'ll> CodegenCx<'ll, '_> {
         bytes_in_context(self.llcx, bytes)
     }
 
-    fn const_cstr(&self, s: Symbol, null_terminated: bool) -> &'ll Value {
-        unsafe {
-            if let Some(&llval) = self.const_cstr_cache.borrow().get(&s) {
-                return llval;
-            }
-
-            let s_str = s.as_str();
-            let sc = llvm::LLVMConstStringInContext(
-                self.llcx,
-                s_str.as_ptr() as *const c_char,
-                s_str.len() as c_uint,
-                !null_terminated as Bool,
-            );
-            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::LLVMSetInitializer(g, sc);
-            llvm::LLVMSetGlobalConstant(g, True);
-            llvm::LLVMRustSetLinkage(g, llvm::Linkage::InternalLinkage);
-
-            self.const_cstr_cache.borrow_mut().insert(s, g);
-            g
-        }
-    }
-
     pub fn const_get_elt(&self, v: &'ll Value, idx: u64) -> &'ll Value {
         unsafe {
             assert_eq!(idx as c_uint as u64, idx);
@@ -204,9 +178,23 @@ impl<'ll, 'tcx> ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 
     fn const_str(&self, s: Symbol) -> (&'ll Value, &'ll Value) {
-        let len = s.as_str().len();
+        let s_str = s.as_str();
+        let str_global = *self.const_str_cache.borrow_mut().entry(s).or_insert_with(|| {
+            let sc = self.const_bytes(s_str.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);
+            });
+            unsafe {
+                llvm::LLVMSetInitializer(g, sc);
+                llvm::LLVMSetGlobalConstant(g, True);
+                llvm::LLVMRustSetLinkage(g, llvm::Linkage::InternalLinkage);
+            }
+            g
+        });
+        let len = s_str.len();
         let cs = consts::ptrcast(
-            self.const_cstr(s, false),
+            str_global,
             self.type_ptr_to(self.layout_of(self.tcx.types.str_).llvm_type(self)),
         );
         (cs, self.const_usize(len as u64))

compiler/rustc_codegen_llvm/src/context.rs

@@ -55,7 +55,7 @@ pub struct CodegenCx<'ll, 'tcx> {
     pub vtables:
         RefCell<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), &'ll Value>>,
     /// Cache of constant strings,
-    pub const_cstr_cache: RefCell<FxHashMap<Symbol, &'ll Value>>,
+    pub const_str_cache: RefCell<FxHashMap<Symbol, &'ll Value>>,
 
     /// Reverse-direction for const ptrs cast from globals.
     ///
@@ -415,7 +415,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             codegen_unit,
             instances: Default::default(),
             vtables: Default::default(),
-            const_cstr_cache: Default::default(),
+            const_str_cache: Default::default(),
             const_unsized: Default::default(),
             const_globals: Default::default(),
             statics_to_rauw: RefCell::new(Vec::new()),