Rollup merge of rust-lang#151465 - RalfJung:fn-call-vars, r=mati865

codegen: clarify some variable names around function calls

I looked at rust-lang#145932 to try to understand how it works, and quickly got lost in the variable names -- what refers to the caller, what to the callee? So here's my attempt at making those more clear. Hopefully the new names are correct.^^

Cc @JamieCunliffe

Author: JonathanBrouwer

compiler/rustc_codegen_llvm/src/builder.rs

@@ -1397,12 +1397,12 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn call(
         &mut self,
         llty: &'ll Type,
-        fn_call_attrs: Option<&CodegenFnAttrs>,
+        caller_attrs: Option<&CodegenFnAttrs>,
         fn_abi: Option<&FnAbi<'tcx, Ty<'tcx>>>,
         llfn: &'ll Value,
         args: &[&'ll Value],
         funclet: Option<&Funclet<'ll>>,
-        instance: Option<Instance<'tcx>>,
+        callee_instance: Option<Instance<'tcx>>,
     ) -> &'ll Value {
         debug!("call {:?} with args ({:?})", llfn, args);
 
@@ -1414,10 +1414,10 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         }
 
         // Emit CFI pointer type membership test
-        self.cfi_type_test(fn_call_attrs, fn_abi, instance, llfn);
+        self.cfi_type_test(caller_attrs, fn_abi, callee_instance, llfn);
 
         // Emit KCFI operand bundle
-        let kcfi_bundle = self.kcfi_operand_bundle(fn_call_attrs, fn_abi, instance, llfn);
+        let kcfi_bundle = self.kcfi_operand_bundle(caller_attrs, fn_abi, callee_instance, llfn);
         if let Some(kcfi_bundle) = kcfi_bundle.as_ref().map(|b| b.as_ref()) {
             bundles.push(kcfi_bundle);
         }
@@ -1435,17 +1435,17 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             )
         };
 
-        if let Some(instance) = instance {
+        if let Some(callee_instance) = callee_instance {
             // Attributes on the function definition being called
-            let fn_defn_attrs = self.cx.tcx.codegen_fn_attrs(instance.def_id());
-            if let Some(fn_call_attrs) = fn_call_attrs
+            let callee_attrs = self.cx.tcx.codegen_fn_attrs(callee_instance.def_id());
+            if let Some(caller_attrs) = caller_attrs
                 // If there is an inline attribute and a target feature that matches
                 // we will add the attribute to the callsite otherwise we'll omit
                 // this and not add the attribute to prevent soundness issues.
-                && let Some(inlining_rule) = attributes::inline_attr(&self.cx, self.cx.tcx, instance)
+                && let Some(inlining_rule) = attributes::inline_attr(&self.cx, self.cx.tcx, callee_instance)
                 && self.cx.tcx.is_target_feature_call_safe(
-                    &fn_defn_attrs.target_features,
-                    &fn_call_attrs.target_features.iter().cloned().chain(
+                    &callee_attrs.target_features,
+                    &caller_attrs.target_features.iter().cloned().chain(
                         self.cx.tcx.sess.target_features.iter().map(|feat| TargetFeature {
                             name: *feat,
                             kind: TargetFeatureKind::Implied,
@@ -1470,14 +1470,15 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn tail_call(
         &mut self,
         llty: Self::Type,
-        fn_attrs: Option<&CodegenFnAttrs>,
+        caller_attrs: Option<&CodegenFnAttrs>,
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         llfn: Self::Value,
         args: &[Self::Value],
         funclet: Option<&Self::Funclet>,
-        instance: Option<Instance<'tcx>>,
+        callee_instance: Option<Instance<'tcx>>,
     ) {
-        let call = self.call(llty, fn_attrs, Some(fn_abi), llfn, args, funclet, instance);
+        let call =
+            self.call(llty, caller_attrs, Some(fn_abi), llfn, args, funclet, callee_instance);
         llvm::LLVMSetTailCallKind(call, llvm::TailCallKind::MustTail);
 
         match &fn_abi.ret.mode {

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -199,12 +199,12 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
         // do an invoke, otherwise do a call.
         let fn_ty = bx.fn_decl_backend_type(fn_abi);
 
-        let fn_attrs = if bx.tcx().def_kind(fx.instance.def_id()).has_codegen_attrs() {
+        let caller_attrs = if bx.tcx().def_kind(fx.instance.def_id()).has_codegen_attrs() {
             Some(bx.tcx().codegen_instance_attrs(fx.instance.def))
         } else {
             None
         };
-        let fn_attrs = fn_attrs.as_deref();
+        let caller_attrs = caller_attrs.as_deref();
 
         if !fn_abi.can_unwind {
             unwind = mir::UnwindAction::Unreachable;
@@ -233,7 +233,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
         };
 
         if kind == CallKind::Tail {
-            bx.tail_call(fn_ty, fn_attrs, fn_abi, fn_ptr, llargs, self.funclet(fx), instance);
+            bx.tail_call(fn_ty, caller_attrs, fn_abi, fn_ptr, llargs, self.funclet(fx), instance);
             return MergingSucc::False;
         }
 
@@ -245,7 +245,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
             };
             let invokeret = bx.invoke(
                 fn_ty,
-                fn_attrs,
+                caller_attrs,
                 Some(fn_abi),
                 fn_ptr,
                 llargs,
@@ -268,8 +268,15 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
             }
             MergingSucc::False
         } else {
-            let llret =
-                bx.call(fn_ty, fn_attrs, Some(fn_abi), fn_ptr, llargs, self.funclet(fx), instance);
+            let llret = bx.call(
+                fn_ty,
+                caller_attrs,
+                Some(fn_abi),
+                fn_ptr,
+                llargs,
+                self.funclet(fx),
+                instance,
+            );
             if fx.mir[self.bb].is_cleanup {
                 bx.apply_attrs_to_cleanup_callsite(llret);
             }

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -600,10 +600,13 @@ pub trait BuilderMethods<'a, 'tcx>:
     ///
     /// ## Arguments
     ///
-    /// The `fn_attrs`, `fn_abi`, and `instance` arguments are Options because they are advisory.
-    /// They relate to optional codegen enhancements like LLVM CFI, and do not affect ABI per se.
-    /// Any ABI-related transformations should be handled by different, earlier stages of codegen.
-    /// For instance, in the caller of `BuilderMethods::call`.
+    /// `caller_attrs` are the attributes of the surrounding caller; they have nothing to do with
+    /// the callee.
+    ///
+    /// The `caller_attrs`, `fn_abi`, and `callee_instance` arguments are Options because they are
+    /// advisory. They relate to optional codegen enhancements like LLVM CFI, and do not affect ABI
+    /// per se. Any ABI-related transformations should be handled by different, earlier stages of
+    /// codegen. For instance, in the caller of `BuilderMethods::call`.
     ///
     /// This means that a codegen backend which disregards `fn_attrs`, `fn_abi`, and `instance`
     /// should still do correct codegen, and code should not be miscompiled if they are omitted.
@@ -620,23 +623,23 @@ pub trait BuilderMethods<'a, 'tcx>:
     fn call(
         &mut self,
         llty: Self::Type,
-        fn_attrs: Option<&CodegenFnAttrs>,
+        caller_attrs: Option<&CodegenFnAttrs>,
         fn_abi: Option<&FnAbi<'tcx, Ty<'tcx>>>,
         fn_val: Self::Value,
         args: &[Self::Value],
         funclet: Option<&Self::Funclet>,
-        instance: Option<Instance<'tcx>>,
+        callee_instance: Option<Instance<'tcx>>,
     ) -> Self::Value;
 
     fn tail_call(
         &mut self,
         llty: Self::Type,
-        fn_attrs: Option<&CodegenFnAttrs>,
+        caller_attrs: Option<&CodegenFnAttrs>,
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         llfn: Self::Value,
         args: &[Self::Value],
         funclet: Option<&Self::Funclet>,
-        instance: Option<Instance<'tcx>>,
+        callee_instance: Option<Instance<'tcx>>,
     );
 
     fn zext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;