Auto merge of #88575 - eddyb:fn-abi-queries, r=nagisa

Querify `FnAbi::of_{fn_ptr,instance}` as `fn_abi_of_{fn_ptr,instance}`.

*Note: opening this PR as draft because it's based on #88499*

This more or less replicates the `LayoutOf::layout_of` setup from #88499, to replace `FnAbi::of_{fn_ptr,instance}` with `FnAbiOf::fn_abi_of_{fn_ptr,instance}`, and also route them through queries (which `layout_of` has used for a while).

The two changes at the use sites (other than the names) are:
* return type is now wrapped in `&'tcx`
  * the value *is* interned, which may affect performance
* the `extra_args` list is now an interned `&'tcx ty::List<Ty<'tcx>>`
  * should be cheap (it's empty for anything other than C variadics)

Theoretically, a `FnAbiOfHelpers` implementer could choose to keep the `Result<...>` instead of eagerly erroring, but the only existing users of these APIs are codegen backends, so they don't (want to) take advantage of this.
At least miri could make use of this, since it prefers propagating errors (it "just" doesn't use `FnAbi` yet - cc `@RalfJung).`

The way this is done is probably less efficient than what is possible, because the queries handle the correctness-oriented API (i.e. the split into `fn` pointers vs instances), whereas a lower-level query could end up with more reuse between different instances with identical signatures.

r? `@nagisa` cc `@oli-obk` `@bjorn3`

3 files changed, 27 insertions, 22 deletions

diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 0861aab2e31..4be050fb88c 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -14,7 +14,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_index::vec::Idx;
 use rustc_middle::mir::AssertKind;
 use rustc_middle::mir::{self, SwitchTargets};
-use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt, LayoutOf};
+use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
 use rustc_span::source_map::Span;
@@ -124,7 +124,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
         &self,
         fx: &mut FunctionCx<'a, 'tcx, Bx>,
         bx: &mut Bx,
-        fn_abi: FnAbi<'tcx, Ty<'tcx>>,
+        fn_abi: &'tcx FnAbi<'tcx, Ty<'tcx>>,
         fn_ptr: Bx::Value,
         llargs: &[Bx::Value],
         destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
@@ -337,7 +337,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
                     substs: drop_fn.substs,
                 };
-                let fn_abi = FnAbi::of_instance(&bx, virtual_drop, &[]);
+                let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
                 let vtable = args[1];
                 args = &args[..1];
                 (
@@ -346,7 +346,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     fn_abi,
                 )
             }
-            _ => (bx.get_fn_addr(drop_fn), FnAbi::of_instance(&bx, drop_fn, &[])),
+            _ => (bx.get_fn_addr(drop_fn), bx.fn_abi_of_instance(drop_fn, ty::List::empty())),
         };
         helper.do_call(
             self,
@@ -433,7 +433,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // Obtain the panic entry point.
         let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
         let instance = ty::Instance::mono(bx.tcx(), def_id);
-        let fn_abi = FnAbi::of_instance(&bx, instance, &[]);
+        let fn_abi = bx.fn_abi_of_instance(instance, ty::List::empty());
         let llfn = bx.get_fn_addr(instance);
 
         // Codegen the actual panic invoke/call.
@@ -494,7 +494,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let def_id =
                     common::langcall(bx.tcx(), Some(source_info.span), "", LangItem::Panic);
                 let instance = ty::Instance::mono(bx.tcx(), def_id);
-                let fn_abi = FnAbi::of_instance(bx, instance, &[]);
+                let fn_abi = bx.fn_abi_of_instance(instance, ty::List::empty());
                 let llfn = bx.get_fn_addr(instance);
 
                 // Codegen the actual panic invoke/call.
@@ -570,17 +570,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         };
 
         let extra_args = &args[sig.inputs().skip_binder().len()..];
-        let extra_args = extra_args
-            .iter()
-            .map(|op_arg| {
-                let op_ty = op_arg.ty(self.mir, bx.tcx());
-                self.monomorphize(op_ty)
-            })
-            .collect::<Vec<_>>();
+        let extra_args = bx.tcx().mk_type_list(extra_args.iter().map(|op_arg| {
+            let op_ty = op_arg.ty(self.mir, bx.tcx());
+            self.monomorphize(op_ty)
+        }));
 
         let fn_abi = match instance {
-            Some(instance) => FnAbi::of_instance(&bx, instance, &extra_args),
-            None => FnAbi::of_fn_ptr(&bx, sig, &extra_args),
+            Some(instance) => bx.fn_abi_of_instance(instance, extra_args),
+            None => bx.fn_abi_of_fn_ptr(sig, extra_args),
         };
 
         if intrinsic == Some(sym::transmute) {
diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs
index 581860ee8b5..8e3982c72d7 100644
--- a/compiler/rustc_codegen_ssa/src/mir/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs
@@ -2,7 +2,7 @@ use crate::traits::*;
 use rustc_errors::ErrorReported;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::ErrorHandled;
-use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt, TyAndLayout};
+use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, TyAndLayout};
 use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
 use rustc_target::abi::call::{FnAbi, PassMode};
 
@@ -29,7 +29,7 @@ pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
 
     cx: &'a Bx::CodegenCx,
 
-    fn_abi: FnAbi<'tcx, Ty<'tcx>>,
+    fn_abi: &'tcx FnAbi<'tcx, Ty<'tcx>>,
 
     /// When unwinding is initiated, we have to store this personality
     /// value somewhere so that we can load it and re-use it in the
@@ -139,7 +139,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
     let mir = cx.tcx().instance_mir(instance.def);
 
-    let fn_abi = FnAbi::of_instance(cx, instance, &[]);
+    let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
     debug!("fn_abi: {:?}", fn_abi);
 
     let debug_context = cx.create_function_debug_context(instance, &fn_abi, llfn, &mir);
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index dbb7e1ee8b1..82b79fd0b2a 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -8,14 +8,15 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorReported;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
 use rustc_middle::middle::cstore::{EncodedMetadata, MetadataLoaderDyn};
-use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, LayoutOf, TyAndLayout};
 use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_session::{
     config::{self, OutputFilenames, PrintRequest},
     Session,
 };
 use rustc_span::symbol::Symbol;
+use rustc_target::abi::call::FnAbi;
 use rustc_target::spec::Target;
 
 pub use rustc_data_structures::sync::MetadataRef;
@@ -38,12 +39,19 @@ pub trait BackendTypes {
 }
 
 pub trait Backend<'tcx>:
-    Sized + BackendTypes + HasTyCtxt<'tcx> + LayoutOf<'tcx, LayoutOfResult = TyAndLayout<'tcx>>
+    Sized
+    + BackendTypes
+    + HasTyCtxt<'tcx>
+    + LayoutOf<'tcx, LayoutOfResult = TyAndLayout<'tcx>>
+    + FnAbiOf<'tcx, FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>>
 {
 }
 
 impl<'tcx, T> Backend<'tcx> for T where
-    Self: BackendTypes + HasTyCtxt<'tcx> + LayoutOf<'tcx, LayoutOfResult = TyAndLayout<'tcx>>
+    Self: BackendTypes
+        + HasTyCtxt<'tcx>
+        + LayoutOf<'tcx, LayoutOfResult = TyAndLayout<'tcx>>
+        + FnAbiOf<'tcx, FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>>
 {
 }