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

This reverts commit abc0660118cc95f47445fd33502a11dd448f5968.

Author: matthiaskrgr

example/alloc_example.rs

@@ -1,4 +1,4 @@
-#![feature(start, core_intrinsics, lang_items)]
+#![feature(start, core_intrinsics, alloc_error_handler, lang_items)]
 #![no_std]
 
 extern crate alloc;
@@ -21,6 +21,11 @@ fn panic_handler(_: &core::panic::PanicInfo) -> ! {
     core::intrinsics::abort();
 }
 
+#[alloc_error_handler]
+fn alloc_error_handler(_: alloc::alloc::Layout) -> ! {
+    core::intrinsics::abort();
+}
+
 #[lang = "eh_personality"]
 fn eh_personality() -> ! {
     loop {}

src/allocator.rs

@@ -5,10 +5,11 @@ use rustc_ast::expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::OomStrategy;
+use rustc_span::symbol::sym;
 
 use crate::GccContext;
 
-pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut GccContext, _module_name: &str, kind: AllocatorKind) {
+pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut GccContext, _module_name: &str, kind: AllocatorKind, alloc_error_handler_kind: AllocatorKind) {
     let context = &mods.context;
     let usize =
         match tcx.sess.target.pointer_width {
@@ -86,6 +87,37 @@ pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut GccContext, _module_nam
         // as described in https://github.com/rust-lang/rust/commit/77a96ed5646f7c3ee8897693decc4626fe380643
     }
 
+    let types = [usize, usize];
+    let name = "__rust_alloc_error_handler".to_string();
+    let args: Vec<_> = types.iter().enumerate()
+        .map(|(index, typ)| context.new_parameter(None, *typ, &format!("param{}", index)))
+        .collect();
+    let func = context.new_function(None, FunctionType::Exported, void, &args, name, false);
+
+    if tcx.sess.target.default_hidden_visibility {
+        #[cfg(feature="master")]
+        func.add_attribute(FnAttribute::Visibility(gccjit::Visibility::Hidden));
+    }
+
+    let callee = alloc_error_handler_kind.fn_name(sym::oom);
+    let args: Vec<_> = types.iter().enumerate()
+        .map(|(index, typ)| context.new_parameter(None, *typ, &format!("param{}", index)))
+        .collect();
+    let callee = context.new_function(None, FunctionType::Extern, void, &args, callee, false);
+    #[cfg(feature="master")]
+    callee.add_attribute(FnAttribute::Visibility(gccjit::Visibility::Hidden));
+
+    let block = func.new_block("entry");
+
+    let args = args
+        .iter()
+        .enumerate()
+        .map(|(i, _)| func.get_param(i as i32).to_rvalue())
+        .collect::<Vec<_>>();
+    let _ret = context.new_call(None, callee, &args);
+    //llvm::LLVMSetTailCall(ret, True);
+    block.end_with_void_return(None);
+
     let name = OomStrategy::SYMBOL.to_string();
     let global = context.new_global(None, GlobalKind::Exported, i8, name);
     let value = tcx.sess.opts.unstable_opts.oom.should_panic();

src/lib.rs

@@ -163,11 +163,11 @@ impl CodegenBackend for GccCodegenBackend {
 }
 
 impl ExtraBackendMethods for GccCodegenBackend {
-    fn codegen_allocator<'tcx>(&self, tcx: TyCtxt<'tcx>, module_name: &str, kind: AllocatorKind) -> Self::Module {
+    fn codegen_allocator<'tcx>(&self, tcx: TyCtxt<'tcx>, module_name: &str, kind: AllocatorKind, alloc_error_handler_kind: AllocatorKind) -> Self::Module {
         let mut mods = GccContext {
             context: Context::default(),
         };
-        unsafe { allocator::codegen(tcx, &mut mods, module_name, kind); }
+        unsafe { allocator::codegen(tcx, &mut mods, module_name, kind, alloc_error_handler_kind); }
         mods
     }