Auto merge of #98123 - JohnTitor:rollup-rfg1a4s, r=JohnTitor

Rollup of 7 pull requests

Successful merges:

 - #97822 (Filter out intrinsics if we have other import candidates to suggest)
 - #98026 (Move some tests to more reasonable directories)
 - #98067 (compiler: remove unused deps)
 - #98078 (Use unchecked mul to compute slice sizes)
 - #98083 (Rename rustc_serialize::opaque::Encoder as MemEncoder.)
 - #98087 (Suggest adding a `#[macro_export]` to a private macro)
 - #98113 (Fix misspelling of "constraint" as "contraint")

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 29 insertions, 0 deletions

diff --git a/src/test/codegen/issue-96497-slice-size-nowrap.rs b/src/test/codegen/issue-96497-slice-size-nowrap.rs
new file mode 100644
index 00000000000..a5dbef93460
--- /dev/null
+++ b/src/test/codegen/issue-96497-slice-size-nowrap.rs
@@ -0,0 +1,29 @@
+// This test case checks that LLVM is aware that computing the size of a slice cannot wrap.
+// The possibility of wrapping results in an additional branch when dropping boxed slices
+// in some situations, see https://github.com/rust-lang/rust/issues/96497#issuecomment-1112865218
+
+// compile-flags: -O
+// min-llvm-version: 14.0
+
+#![crate_type="lib"]
+
+// CHECK-LABEL: @simple_size_of_nowrap
+#[no_mangle]
+pub fn simple_size_of_nowrap(x: &[u32]) -> usize {
+    // Make sure the shift used to compute the size has a nowrap flag.
+
+    // CHECK: [[A:%.*]] = shl nsw {{.*}}, 2
+    // CHECK-NEXT: ret {{.*}} [[A]]
+    core::mem::size_of_val(x)
+}
+
+// CHECK-LABEL: @drop_write
+#[no_mangle]
+pub fn drop_write(mut x: Box<[u32]>) {
+    // Check that this write is optimized out.
+    // This depends on the size calculation not wrapping,
+    // since otherwise LLVM can't tell that the memory is always deallocated if the slice len > 0.
+
+    // CHECK-NOT: store i32 42
+    x[1] = 42;
+}