Rollup merge of #119094 - celinval:smir-layout, r=compiler-errors

Add function ABI and type layout to StableMIR

This change introduces a new module to StableMIR named `abi` with information from `rustc_target::abi` and `rustc_abi`, that allow users to retrieve more low level information required to perform bit-precise analysis.

The layout of a type can be retrieved via `Ty::layout`, and the instance ABI can be retrieved via `Instance::fn_abi()`.

To properly handle errors while retrieve layout information, we had to implement a few layout related traits.

r? ```@compiler-errors```

3 files changed, 146 insertions, 4 deletions

diff --git a/tests/ui-fulldeps/stable-mir/check_abi.rs b/tests/ui-fulldeps/stable-mir/check_abi.rs
new file mode 100644
index 00000000000..30b42bc3bfa
--- /dev/null
+++ b/tests/ui-fulldeps/stable-mir/check_abi.rs
@@ -0,0 +1,143 @@
+// run-pass
+//! Test information regarding type layout.
+
+// ignore-stage1
+// ignore-cross-compile
+// ignore-remote
+// ignore-windows-gnu mingw has troubles with linking https://github.com/rust-lang/rust/pull/116837
+
+#![feature(rustc_private)]
+#![feature(assert_matches)]
+#![feature(control_flow_enum)]
+#![feature(ascii_char, ascii_char_variants)]
+
+extern crate rustc_hir;
+extern crate rustc_middle;
+#[macro_use]
+extern crate rustc_smir;
+extern crate rustc_driver;
+extern crate rustc_interface;
+extern crate stable_mir;
+
+use rustc_middle::ty::TyCtxt;
+use rustc_smir::rustc_internal;
+use stable_mir::abi::{ArgAbi, CallConvention, FieldsShape, PassMode, VariantsShape};
+use stable_mir::mir::mono::Instance;
+use stable_mir::{CrateDef, CrateItem, CrateItems, ItemKind};
+use std::assert_matches::assert_matches;
+use std::convert::TryFrom;
+use std::io::Write;
+use std::ops::ControlFlow;
+
+const CRATE_NAME: &str = "input";
+
+/// This function uses the Stable MIR APIs to get information about the test crate.
+fn test_stable_mir(_tcx: TyCtxt<'_>) -> ControlFlow<()> {
+    // Find items in the local crate.
+    let items = stable_mir::all_local_items();
+
+    // Test fn_abi
+    let target_fn = *get_item(&items, (ItemKind::Fn, "fn_abi")).unwrap();
+    let instance = Instance::try_from(target_fn).unwrap();
+    let fn_abi = instance.fn_abi().unwrap();
+    assert_eq!(fn_abi.conv, CallConvention::Rust);
+    assert_eq!(fn_abi.args.len(), 2);
+
+    check_ignore(&fn_abi.args[0]);
+    check_primitive(&fn_abi.args[1]);
+    check_result(fn_abi.ret);
+
+    // Test variadic function.
+    let variadic_fn = *get_item(&items, (ItemKind::Fn, "variadic_fn")).unwrap();
+    check_variadic(variadic_fn);
+
+    ControlFlow::Continue(())
+}
+
+/// Check the variadic function ABI:
+/// ```no_run
+/// pub unsafe extern "C" fn variadic_fn(n: usize, mut args: ...) -> usize {
+///     0
+/// }
+/// ```
+fn check_variadic(variadic_fn: CrateItem) {
+    let instance = Instance::try_from(variadic_fn).unwrap();
+    let abi = instance.fn_abi().unwrap();
+    assert!(abi.c_variadic);
+    assert_eq!(abi.args.len(), 1);
+}
+
+/// Check the argument to be ignored: `ignore: [u8; 0]`.
+fn check_ignore(abi: &ArgAbi) {
+    assert!(abi.ty.kind().is_array());
+    assert_eq!(abi.mode, PassMode::Ignore);
+    let layout = abi.layout.shape();
+    assert!(layout.is_sized());
+    assert!(layout.is_1zst());
+}
+
+/// Check the primitive argument: `primitive: char`.
+fn check_primitive(abi: &ArgAbi) {
+    assert!(abi.ty.kind().is_char());
+    assert_matches!(abi.mode, PassMode::Direct(_));
+    let layout = abi.layout.shape();
+    assert!(layout.is_sized());
+    assert!(!layout.is_1zst());
+    assert_matches!(layout.fields, FieldsShape::Primitive);
+}
+
+/// Check the return value: `Result<usize, &str>`.
+fn check_result(abi: ArgAbi) {
+    assert!(abi.ty.kind().is_enum());
+    assert_matches!(abi.mode, PassMode::Indirect { .. });
+    let layout = abi.layout.shape();
+    assert!(layout.is_sized());
+    assert_matches!(layout.fields, FieldsShape::Arbitrary { .. });
+    assert_matches!(layout.variants, VariantsShape::Multiple { .. })
+}
+
+fn get_item<'a>(
+    items: &'a CrateItems,
+    item: (ItemKind, &str),
+) -> Option<&'a stable_mir::CrateItem> {
+    items.iter().find(|crate_item| (item.0 == crate_item.kind()) && crate_item.name() == item.1)
+}
+
+/// This test will generate and analyze a dummy crate using the stable mir.
+/// For that, it will first write the dummy crate into a file.
+/// Then it will create a `StableMir` using custom arguments and then
+/// it will run the compiler.
+fn main() {
+    let path = "alloc_input.rs";
+    generate_input(&path).unwrap();
+    let args = vec![
+        "rustc".to_string(),
+        "--crate-type=lib".to_string(),
+        "--crate-name".to_string(),
+        CRATE_NAME.to_string(),
+        path.to_string(),
+    ];
+    run!(args, tcx, test_stable_mir(tcx)).unwrap();
+}
+
+fn generate_input(path: &str) -> std::io::Result<()> {
+    let mut file = std::fs::File::create(path)?;
+    write!(
+        file,
+        r#"
+        #![feature(c_variadic)]
+        #![allow(unused_variables)]
+
+        pub fn fn_abi(ignore: [u8; 0], primitive: char) -> Result<usize, &'static str> {{
+            // We only care about the signature.
+            todo!()
+        }}
+
+
+        pub unsafe extern "C" fn variadic_fn(n: usize, mut args: ...) -> usize {{
+            0
+        }}
+        "#
+    )?;
+    Ok(())
+}
diff --git a/tests/ui-fulldeps/stable-mir/check_allocation.rs b/tests/ui-fulldeps/stable-mir/check_allocation.rs
index 8554630e9c9..7ce3597206b 100644
--- a/tests/ui-fulldeps/stable-mir/check_allocation.rs
+++ b/tests/ui-fulldeps/stable-mir/check_allocation.rs
@@ -209,7 +209,6 @@ fn check_len(item: CrateItem) {
     assert_eq!(alloc.read_uint(), Ok(2));
 }
 
-// Use internal API to find a function in a crate.
 fn get_item<'a>(
     items: &'a CrateItems,
     item: (ItemKind, &str),
diff --git a/tests/ui-fulldeps/stable-mir/check_defs.rs b/tests/ui-fulldeps/stable-mir/check_defs.rs
index ad667511332..e9a2599d873 100644
--- a/tests/ui-fulldeps/stable-mir/check_defs.rs
+++ b/tests/ui-fulldeps/stable-mir/check_defs.rs
@@ -69,9 +69,9 @@ fn extract_elem_ty(ty: Ty) -> Ty {
 
 /// Check signature and type of `Vec::<u8>::new` and its generic version.
 fn test_vec_new(instance: mir::mono::Instance) {
-    let sig = instance.ty().kind().fn_sig().unwrap().skip_binder();
-    assert_matches!(sig.inputs(), &[]);
-    let elem_ty = extract_elem_ty(sig.output());
+    let sig = instance.fn_abi().unwrap();
+    assert_eq!(&sig.args, &[]);
+    let elem_ty = extract_elem_ty(sig.ret.ty);
     assert_matches!(elem_ty.kind(), TyKind::RigidTy(RigidTy::Uint(UintTy::U8)));
 
     // Get the signature for Vec::<T>::new.