Add 'compiler/rustc_codegen_gcc/' from commit 'afae271d5d'

git-subtree-dir: compiler/rustc_codegen_gcc
git-subtree-mainline: ae90dcf020
git-subtree-split: afae271d5d

compiler/rustc_codegen_gcc/src/callee.rs

@@ -0,0 +1,99 @@
+use gccjit::{FunctionType, RValue};
+use rustc_codegen_ssa::traits::BaseTypeMethods;
+use rustc_middle::ty::{Instance, TypeFoldable};
+use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
+use rustc_target::abi::call::FnAbi;
+
+use crate::abi::FnAbiGccExt;
+use crate::context::CodegenCx;
+
+/// Codegens a reference to a fn/method item, monomorphizing and
+/// inlining as it goes.
+///
+/// # Parameters
+///
+/// - `cx`: the crate context
+/// - `instance`: the instance to be instantiated
+pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>) -> RValue<'gcc> {
+    let tcx = cx.tcx();
+
+    //debug!("get_fn(instance={:?})", instance);
+
+    assert!(!instance.substs.needs_infer());
+    assert!(!instance.substs.has_escaping_bound_vars());
+    assert!(!instance.substs.has_param_types_or_consts());
+
+    if let Some(&func) = cx.instances.borrow().get(&instance) {
+        return func;
+    }
+
+    let sym = tcx.symbol_name(instance).name;
+    //debug!("get_fn({:?}: {:?}) => {}", instance, instance.monomorphic_ty(cx.tcx()), sym);
+
+    let fn_abi = FnAbi::of_instance(cx, instance, &[]);
+
+    // TODO
+    let func =
+        if let Some(func) = cx.get_declared_value(&sym) {
+            // Create a fn pointer with the new signature.
+            let ptrty = fn_abi.ptr_to_gcc_type(cx);
+
+            // This is subtle and surprising, but sometimes we have to bitcast
+            // the resulting fn pointer.  The reason has to do with external
+            // functions.  If you have two crates that both bind the same C
+            // library, they may not use precisely the same types: for
+            // example, they will probably each declare their own structs,
+            // which are distinct types from LLVM's point of view (nominal
+            // types).
+            //
+            // Now, if those two crates are linked into an application, and
+            // they contain inlined code, you can wind up with a situation
+            // where both of those functions wind up being loaded into this
+            // application simultaneously. In that case, the same function
+            // (from LLVM's point of view) requires two types. But of course
+            // LLVM won't allow one function to have two types.
+            //
+            // What we currently do, therefore, is declare the function with
+            // one of the two types (whichever happens to come first) and then
+            // bitcast as needed when the function is referenced to make sure
+            // it has the type we expect.
+            //
+            // This can occur on either a crate-local or crate-external
+            // reference. It also occurs when testing libcore and in some
+            // other weird situations. Annoying.
+            if cx.val_ty(func) != ptrty {
+                //debug!("get_fn: casting {:?} to {:?}", func, ptrty);
+                // TODO
+                //cx.const_ptrcast(func, ptrty)
+                func
+            }
+            else {
+                //debug!("get_fn: not casting pointer!");
+                func
+            }
+        }
+        else {
+            cx.linkage.set(FunctionType::Extern);
+            let func = cx.declare_fn(&sym, &fn_abi);
+            //cx.linkage.set(FunctionType::Internal);
+            //debug!("get_fn: not casting pointer!");
+
+            // TODO
+            //attributes::from_fn_attrs(cx, func, instance);
+
+            //let instance_def_id = instance.def_id();
+
+            // TODO
+            /*if cx.use_dll_storage_attrs && tcx.is_dllimport_foreign_item(instance_def_id) {
+              unsafe {
+              llvm::LLVMSetDLLStorageClass(func, llvm::DLLStorageClass::DllImport);
+              }
+              }*/
+
+            func
+        };
+
+    cx.instances.borrow_mut().insert(instance, func);
+
+    func
+}