Rollup merge of #124251 - scottmcm:unop-ptr-metadata, r=oli-obk

Add an intrinsic for `ptr::metadata`

The follow-up to #123840, so we can remove `PtrComponents` and `PtrRepr` from libcore entirely (well, after a bootstrap update).

As discussed in <https://rust-lang.zulipchat.com/#narrow/stream/189540-t-compiler.2Fwg-mir-opt/topic/.60ptr_metadata.60.20in.20MIR/near/435637808>, this introduces `UnOp::PtrMetadata` taking a raw pointer and returning the associated metadata value.

By no longer going through a `union`, this should also help future PRs better optimize pointer operations.

r? ``@oli-obk``

1 files changed, 36 insertions, 0 deletions

diff --git a/tests/codegen/intrinsics/ptr_metadata.rs b/tests/codegen/intrinsics/ptr_metadata.rs
new file mode 100644
index 00000000000..f4bf5a1f5f1
--- /dev/null
+++ b/tests/codegen/intrinsics/ptr_metadata.rs
@@ -0,0 +1,36 @@
+//@ compile-flags: -O -C no-prepopulate-passes -Z inline-mir
+//@ only-64bit (so I don't need to worry about usize)
+
+#![crate_type = "lib"]
+#![feature(core_intrinsics)]
+
+use std::intrinsics::ptr_metadata;
+
+// CHECK-LABEL: @thin_metadata(
+#[no_mangle]
+pub fn thin_metadata(p: *const ()) {
+    // CHECK: start
+    // CHECK-NEXT: ret void
+    ptr_metadata(p)
+}
+
+// CHECK-LABEL: @slice_metadata(
+#[no_mangle]
+pub fn slice_metadata(p: *const [u8]) -> usize {
+    // CHECK: start
+    // CHECK-NEXT: ret i64 %p.1
+    ptr_metadata(p)
+}
+
+// CHECK-LABEL: @dyn_byte_offset(
+#[no_mangle]
+pub unsafe fn dyn_byte_offset(
+    p: *const dyn std::fmt::Debug,
+    n: usize,
+) -> *const dyn std::fmt::Debug {
+    // CHECK: %[[Q:.+]] = getelementptr inbounds i8, ptr %p.0, i64 %n
+    // CHECK: %[[TEMP1:.+]] = insertvalue { ptr, ptr } poison, ptr %[[Q]], 0
+    // CHECK: %[[TEMP2:.+]] = insertvalue { ptr, ptr } %[[TEMP1]], ptr %p.1, 1
+    // CHECK: ret { ptr, ptr } %[[TEMP2]]
+    p.byte_add(n)
+}