Auto merge of #111634 - marc0246:arc-new-uninit-bloat, r=thomcc

Fix duplicate `arcinner_layout_for_value_layout` calls when using the uninit `Arc` constructors

What this fixes is the duplicate calls to `arcinner_layout_for_value_layout` seen here: https://godbolt.org/z/jr5Gxozhj

The issue was discovered alongside #111603 but is otherwise unrelated to the duplicate `alloca`s, which remain unsolved. Everything I tried to solve said main issue has failed.

As for the duplicate layout calculations, I also tried slapping `#[inline]` and `#[inline(always)]` on everything in sight but the only thing that worked in the end is to dedup the calls by hand.

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/codegen/issues/issue-111603.rs b/tests/codegen/issues/issue-111603.rs
new file mode 100644
index 00000000000..90b3c314d2f
--- /dev/null
+++ b/tests/codegen/issues/issue-111603.rs
@@ -0,0 +1,28 @@
+// compile-flags: -O
+
+#![crate_type = "lib"]
+#![feature(get_mut_unchecked, new_uninit)]
+
+use std::sync::Arc;
+
+// CHECK-LABEL: @new_uninit
+#[no_mangle]
+pub fn new_uninit(x: u64) -> Arc<[u64; 1000]> {
+    // CHECK: call alloc::sync::arcinner_layout_for_value_layout
+    // CHECK-NOT: call alloc::sync::arcinner_layout_for_value_layout
+    let mut arc = Arc::new_uninit();
+    unsafe { Arc::get_mut_unchecked(&mut arc) }.write([x; 1000]);
+    unsafe { arc.assume_init() }
+}
+
+// CHECK-LABEL: @new_uninit_slice
+#[no_mangle]
+pub fn new_uninit_slice(x: u64) -> Arc<[u64]> {
+    // CHECK: call alloc::sync::arcinner_layout_for_value_layout
+    // CHECK-NOT: call alloc::sync::arcinner_layout_for_value_layout
+    let mut arc = Arc::new_uninit_slice(1000);
+    for elem in unsafe { Arc::get_mut_unchecked(&mut arc) } {
+        elem.write(x);
+    }
+    unsafe { arc.assume_init() }
+}