Store pointer to data directly in Rc and Arc

Author: EFanZh

library/alloc/src/rc.rs

@@ -0,0 +1,78 @@
+//@ compile-flags: -O -Z merge-functions=disabled
+
+#![crate_type = "lib"]
+
+use std::rc::Rc;
+use std::sync::Arc;
+
+// CHECK-LABEL: @deref_rc_sized(
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn deref_rc_sized(rc: &Rc<u32>) -> &u32 {
+    &rc
+}
+
+// CHECK-LABEL: @deref_rc_unsized(
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn deref_rc_unsized(rc: &Rc<str>) -> &str {
+    &rc
+}
+
+// CHECK-LABEL: @deref_arc_sized(
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn deref_arc_sized(arc: &Arc<u32>) -> &u32 {
+    &arc
+}
+
+// CHECK-LABEL: @deref_arc_unsized(
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn deref_arc_unsized(arc: &Arc<str>) -> &str {
+    &arc
+}
+
+// CHECK-LABEL: @rc_slice_to_ref_slice_sized(
+// CHECK-NOT: getelementptr
+// CHECK: tail call void @llvm.memcpy
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn rc_slice_to_ref_slice_sized(s: &[Rc<u32>]) -> Box<[&u32]> {
+    s.iter().map(|x| &**x).collect()
+}
+
+// CHECK-LABEL: @rc_slice_to_ref_slice_unsized(
+// CHECK-NOT: getelementptr
+// CHECK: tail call void @llvm.memcpy
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn rc_slice_to_ref_slice_unsized(s: &[Rc<str>]) -> Box<[&str]> {
+    s.iter().map(|x| &**x).collect()
+}
+
+// CHECK-LABEL: @arc_slice_to_ref_slice_sized(
+// CHECK-NOT: getelementptr
+// CHECK: tail call void @llvm.memcpy
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn arc_slice_to_ref_slice_sized(s: &[Arc<u32>]) -> Box<[&u32]> {
+    s.iter().map(|x| &**x).collect()
+}
+
+// CHECK-LABEL: @arc_slice_to_ref_slice_unsized(
+// CHECK-NOT: getelementptr
+// CHECK: tail call void @llvm.memcpy
+// CHECK-NOT: getelementptr
+// CHECK: ret
+#[no_mangle]
+pub fn arc_slice_to_ref_slice_unsized(s: &[Arc<str>]) -> Box<[&str]> {
+    s.iter().map(|x| &**x).collect()
+}

library/alloc/src/sync.rs

@@ -126,7 +126,7 @@ mod prelude {
         value: T,
     }
     pub struct Rc<T: ?Sized, A = Global> {
-        ptr: NonNull<RcInner<T>>,
+        ptr: NonNull<T>,
         phantom: PhantomData<RcInner<T>>,
         alloc: A,
     }
@@ -140,7 +140,7 @@ mod prelude {
         data: T,
     }
     pub struct Arc<T: ?Sized, A = Global> {
-        ptr: NonNull<ArcInner<T>>,
+        ptr: NonNull<T>,
         phantom: PhantomData<ArcInner<T>>,
         alloc: A,
     }