Move computation of allocator shim contents to cg_ssa

In the future this should make it easier to use weak symbols for the
allocator shim on platforms that properly support weak symbols. And it
would allow reusing the allocator shim code for handling default
implementations of the upcoming externally implementable items feature
on platforms that don't properly support weak symbols.

Author: bjorn3

src/allocator.rs

@@ -3,10 +3,9 @@
 
 use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
 use rustc_ast::expand::allocator::{
-    ALLOC_ERROR_HANDLER, ALLOCATOR_METHODS, AllocatorKind, AllocatorTy, NO_ALLOC_SHIM_IS_UNSTABLE,
-    default_fn_name, global_fn_name,
+    AllocatorMethod, AllocatorTy, NO_ALLOC_SHIM_IS_UNSTABLE, default_fn_name, global_fn_name,
 };
-use rustc_codegen_ssa::base::allocator_kind_for_codegen;
+use rustc_codegen_ssa::base::{allocator_kind_for_codegen, allocator_shim_contents};
 use rustc_session::config::OomStrategy;
 use rustc_symbol_mangling::mangle_internal_symbol;
 
@@ -15,74 +14,54 @@ use crate::prelude::*;
 /// Returns whether an allocator shim was created
 pub(crate) fn codegen(tcx: TyCtxt<'_>, module: &mut dyn Module) -> bool {
     let Some(kind) = allocator_kind_for_codegen(tcx) else { return false };
-    codegen_inner(
-        tcx,
-        module,
-        kind,
-        tcx.alloc_error_handler_kind(()).unwrap(),
-        tcx.sess.opts.unstable_opts.oom,
-    );
+    let methods = allocator_shim_contents(tcx, kind);
+    codegen_inner(tcx, module, &methods, tcx.sess.opts.unstable_opts.oom);
     true
 }
 
 fn codegen_inner(
     tcx: TyCtxt<'_>,
     module: &mut dyn Module,
-    kind: AllocatorKind,
-    alloc_error_handler_kind: AllocatorKind,
+    methods: &[AllocatorMethod],
     oom_strategy: OomStrategy,
 ) {
     let usize_ty = module.target_config().pointer_type();
 
-    if kind == AllocatorKind::Default {
-        for method in ALLOCATOR_METHODS {
-            let mut arg_tys = Vec::with_capacity(method.inputs.len());
-            for input in method.inputs.iter() {
-                match input.ty {
-                    AllocatorTy::Layout => {
-                        arg_tys.push(usize_ty); // size
-                        arg_tys.push(usize_ty); // align
-                    }
-                    AllocatorTy::Ptr => arg_tys.push(usize_ty),
-                    AllocatorTy::Usize => arg_tys.push(usize_ty),
-
-                    AllocatorTy::ResultPtr | AllocatorTy::Unit => panic!("invalid allocator arg"),
+    for method in methods {
+        let mut arg_tys = Vec::with_capacity(method.inputs.len());
+        for input in method.inputs.iter() {
+            match input.ty {
+                AllocatorTy::Layout => {
+                    arg_tys.push(usize_ty); // size
+                    arg_tys.push(usize_ty); // align
                 }
-            }
-            let output = match method.output {
-                AllocatorTy::ResultPtr => Some(usize_ty),
-                AllocatorTy::Unit => None,
+                AllocatorTy::Ptr => arg_tys.push(usize_ty),
+                AllocatorTy::Usize => arg_tys.push(usize_ty),
 
-                AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
-                    panic!("invalid allocator output")
+                AllocatorTy::Never | AllocatorTy::ResultPtr | AllocatorTy::Unit => {
+                    panic!("invalid allocator arg")
                 }
-            };
-
-            let sig = Signature {
-                call_conv: module.target_config().default_call_conv,
-                params: arg_tys.iter().cloned().map(AbiParam::new).collect(),
-                returns: output.into_iter().map(AbiParam::new).collect(),
-            };
-            crate::common::create_wrapper_function(
-                module,
-                sig,
-                &mangle_internal_symbol(tcx, &global_fn_name(method.name)),
-                &mangle_internal_symbol(tcx, &default_fn_name(method.name)),
-            );
+            }
         }
-    }
+        let output = match method.output {
+            AllocatorTy::ResultPtr => Some(usize_ty),
+            AllocatorTy::Never | AllocatorTy::Unit => None,
+
+            AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
+                panic!("invalid allocator output")
+            }
+        };
 
-    if alloc_error_handler_kind == AllocatorKind::Default {
         let sig = Signature {
             call_conv: module.target_config().default_call_conv,
-            params: vec![AbiParam::new(usize_ty), AbiParam::new(usize_ty)],
-            returns: vec![],
+            params: arg_tys.iter().cloned().map(AbiParam::new).collect(),
+            returns: output.into_iter().map(AbiParam::new).collect(),
         };
         crate::common::create_wrapper_function(
             module,
             sig,
-            &mangle_internal_symbol(tcx, &global_fn_name(ALLOC_ERROR_HANDLER)),
-            &mangle_internal_symbol(tcx, &default_fn_name(ALLOC_ERROR_HANDLER)),
+            &mangle_internal_symbol(tcx, &global_fn_name(method.name)),
+            &mangle_internal_symbol(tcx, &default_fn_name(method.name)),
         );
     }