Revert "Remove #[alloc_error_handler] from the compiler and library"

This reverts commit abc0660.

example/alloc_example.rs

@@ -1,4 +1,4 @@
-#![feature(start, core_intrinsics)]
+#![feature(start, core_intrinsics, alloc_error_handler)]
 #![no_std]
 
 extern crate alloc;
@@ -22,6 +22,11 @@ fn panic_handler(_: &core::panic::PanicInfo) -> ! {
     core::intrinsics::abort();
 }
 
+#[alloc_error_handler]
+fn alloc_error_handler(_: alloc::alloc::Layout) -> ! {
+    core::intrinsics::abort();
+}
+
 #[start]
 fn main(_argc: isize, _argv: *const *const u8) -> isize {
     let world: Box<&str> = Box::new("Hello World!\0");

src/allocator.rs

@@ -6,6 +6,7 @@ use crate::prelude::*;
 use rustc_ast::expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};
 use rustc_codegen_ssa::base::allocator_kind_for_codegen;
 use rustc_session::config::OomStrategy;
+use rustc_span::symbol::sym;
 
 /// Returns whether an allocator shim was created
 pub(crate) fn codegen(
@@ -14,14 +15,21 @@ pub(crate) fn codegen(
     unwind_context: &mut UnwindContext,
 ) -> bool {
     let Some(kind) = allocator_kind_for_codegen(tcx) else { return false };
-    codegen_inner(module, unwind_context, kind, tcx.sess.opts.unstable_opts.oom);
+    codegen_inner(
+        module,
+        unwind_context,
+        kind,
+        tcx.alloc_error_handler_kind(()).unwrap(),
+        tcx.sess.opts.unstable_opts.oom,
+    );
     true
 }
 
 fn codegen_inner(
     module: &mut impl Module,
     unwind_context: &mut UnwindContext,
     kind: AllocatorKind,
+    alloc_error_handler_kind: AllocatorKind,
     oom_strategy: OomStrategy,
 ) {
     let usize_ty = module.target_config().pointer_type();
@@ -63,6 +71,19 @@ fn codegen_inner(
         );
     }
 
+    let sig = Signature {
+        call_conv: module.target_config().default_call_conv,
+        params: vec![AbiParam::new(usize_ty), AbiParam::new(usize_ty)],
+        returns: vec![],
+    };
+    crate::common::create_wrapper_function(
+        module,
+        unwind_context,
+        sig,
+        "__rust_alloc_error_handler",
+        &alloc_error_handler_kind.fn_name(sym::oom),
+    );
+
     let data_id = module.declare_data(OomStrategy::SYMBOL, Linkage::Export, false, false).unwrap();
     let mut data_ctx = DataContext::new();
     data_ctx.set_align(1);