Codegen 128bit atomic loads and stores for compiler builtins as trap

128bit atomics are unstable and only enabled on AArch64 and x86_64 macOS.
Cranelift doesn't support 128bit atomics yet.

Author: bjorn3

build_sysroot/Cargo.lock

@@ -14,7 +14,6 @@ compiler_builtins = { version = "0.1.39", default-features = false, features = [
 rustc-std-workspace-core = { path = "./sysroot_src/library/rustc-std-workspace-core" }
 rustc-std-workspace-alloc = { path = "./sysroot_src/library/rustc-std-workspace-alloc" }
 rustc-std-workspace-std = { path = "./sysroot_src/library/rustc-std-workspace-std" }
-compiler_builtins = { path = "./compiler-builtins" }
 
 [profile.dev]
 lto = "off"
@@ -23,3 +22,14 @@ lto = "off"
 debug = true
 incremental = true
 lto = "off"
+
+# Mandatory for correctly compiling compiler-builtins
+[profile.dev.package.compiler_builtins]
+debug-assertions = false
+overflow-checks = false
+codegen-units = 10000
+
+[profile.release.package.compiler_builtins]
+debug-assertions = false
+overflow-checks = false
+codegen-units = 10000

build_sysroot/Cargo.toml

@@ -81,14 +81,6 @@ fn prepare_sysroot() {
     init_git_repo(&sysroot_src);
 
     apply_patches("sysroot", &sysroot_src);
-
-    clone_repo_shallow_github(
-        "build_sysroot/compiler-builtins",
-        "rust-lang",
-        "compiler-builtins",
-        "0.1.70",
-    );
-    apply_patches("compiler-builtins", Path::new("build_sysroot/compiler-builtins"));
 }
 
 #[allow(dead_code)]

build_system/prepare.rs

@@ -12,18 +12,6 @@ git checkout -- .
 git checkout "$(rustc -V | cut -d' ' -f3 | tr -d '(')"
 
 git apply - <<EOF
-diff --git a/Cargo.toml b/Cargo.toml
-index 5bd1147cad5..10d68a2ff14 100644
---- a/Cargo.toml
-+++ b/Cargo.toml
-@@ -111,5 +111,7 @@ rustc-std-workspace-std = { path = 'library/rustc-std-workspace-std' }
- rustc-std-workspace-alloc = { path = 'library/rustc-std-workspace-alloc' }
- rustc-std-workspace-std = { path = 'library/rustc-std-workspace-std' }
-
-+compiler_builtins = { path = "../build_sysroot/compiler-builtins" }
-+
- [patch."https://github.com/rust-lang/rust-clippy"]
- clippy_lints = { path = "src/tools/clippy/clippy_lints" }
 diff --git a/library/alloc/Cargo.toml b/library/alloc/Cargo.toml
 index d95b5b7f17f..00b6f0e3635 100644
 --- a/library/alloc/Cargo.toml

patches/0001-compiler-builtins-Disable-128bit-atomic-operations.patch

@@ -749,6 +749,18 @@ fn codegen_regular_intrinsic_call<'tcx>(
         _ if intrinsic.as_str().starts_with("atomic_load"), (v ptr) {
             let ty = substs.type_at(0);
             match ty.kind() {
+                ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
+                    // FIXME implement 128bit atomics
+                    if fx.tcx.is_compiler_builtins(LOCAL_CRATE) {
+                        // special case for compiler-builtins to avoid having to patch it
+                        crate::trap::trap_unimplemented(fx, "128bit atomics not yet supported");
+                        let ret_block = fx.get_block(destination.unwrap().1);
+                        fx.bcx.ins().jump(ret_block, &[]);
+                        return;
+                    } else {
+                        fx.tcx.sess.span_fatal(span, "128bit atomics not yet supported");
+                    }
+                }
                 ty::Uint(_) | ty::Int(_) | ty::RawPtr(..) => {}
                 _ => {
                     report_atomic_type_validation_error(fx, intrinsic, span, ty);
@@ -765,6 +777,18 @@ fn codegen_regular_intrinsic_call<'tcx>(
         _ if intrinsic.as_str().starts_with("atomic_store"), (v ptr, c val) {
             let ty = substs.type_at(0);
             match ty.kind() {
+                ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
+                    // FIXME implement 128bit atomics
+                    if fx.tcx.is_compiler_builtins(LOCAL_CRATE) {
+                        // special case for compiler-builtins to avoid having to patch it
+                        crate::trap::trap_unimplemented(fx, "128bit atomics not yet supported");
+                        let ret_block = fx.get_block(destination.unwrap().1);
+                        fx.bcx.ins().jump(ret_block, &[]);
+                        return;
+                    } else {
+                        fx.tcx.sess.span_fatal(span, "128bit atomics not yet supported");
+                    }
+                }
                 ty::Uint(_) | ty::Int(_) | ty::RawPtr(..) => {}
                 _ => {
                     report_atomic_type_validation_error(fx, intrinsic, span, ty);
@@ -1115,10 +1139,6 @@ fn codegen_regular_intrinsic_call<'tcx>(
         };
     }
 
-    if let Some((_, dest)) = destination {
-        let ret_block = fx.get_block(dest);
-        fx.bcx.ins().jump(ret_block, &[]);
-    } else {
-        fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
-    }
+    let ret_block = fx.get_block(destination.unwrap().1);
+    fx.bcx.ins().jump(ret_block, &[]);
 }