Auto merge of #146823 - HKalbasi:noalias-inline, r=<try>

[Experiment] Do not emit noalias for inline functions

Author: rust-bors[bot]

compiler/rustc_ty_utils/src/abi.rs

@@ -3,6 +3,7 @@ use std::iter;
 use rustc_abi::Primitive::Pointer;
 use rustc_abi::{BackendRepr, ExternAbi, PointerKind, Scalar, Size};
 use rustc_hir as hir;
+use rustc_hir::attrs::InlineAttr;
 use rustc_hir::lang_items::LangItem;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
@@ -275,6 +276,7 @@ fn arg_attrs_for_rust_scalar<'tcx>(
     offset: Size,
     is_return: bool,
     drop_target_pointee: Option<Ty<'tcx>>,
+    is_inline: bool,
 ) -> ArgAttributes {
     let mut attrs = ArgAttributes::new();
 
@@ -348,9 +350,10 @@ fn arg_attrs_for_rust_scalar<'tcx>(
                 PointerKind::MutableRef { unpin } => unpin && noalias_mut_ref,
                 PointerKind::Box { unpin, global } => unpin && global && noalias_for_box,
             };
+
             // We can never add `noalias` in return position; that LLVM attribute has some very surprising semantics
             // (see <https://github.com/rust-lang/unsafe-code-guidelines/issues/385#issuecomment-1368055745>).
-            if no_alias && !is_return {
+            if no_alias && !is_inline && !is_return {
                 attrs.set(ArgAttribute::NoAlias);
             }
 
@@ -509,6 +512,11 @@ fn fn_abi_new_uncached<'tcx>(
         extra_args
     };
 
+    let is_inline = determined_fn_def_id.is_some_and(|def_id| {
+        let inline_attrs = tcx.codegen_fn_attrs(def_id).inline;
+        inline_attrs == InlineAttr::Hint || inline_attrs == InlineAttr::Always
+    });
+
     let is_drop_in_place = determined_fn_def_id.is_some_and(|def_id| {
         tcx.is_lang_item(def_id, LangItem::DropInPlace)
             || tcx.is_lang_item(def_id, LangItem::AsyncDropInPlace)
@@ -535,7 +543,15 @@ fn fn_abi_new_uncached<'tcx>(
         };
 
         let mut arg = ArgAbi::new(cx, layout, |layout, scalar, offset| {
-            arg_attrs_for_rust_scalar(*cx, scalar, *layout, offset, is_return, drop_target_pointee)
+            arg_attrs_for_rust_scalar(
+                *cx,
+                scalar,
+                *layout,
+                offset,
+                is_return,
+                drop_target_pointee,
+                is_inline,
+            )
         });
 
         if arg.layout.is_zst() {