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``

8 files changed, 200 insertions, 14 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)
+}
diff --git a/tests/mir-opt/building/custom/operators.g.runtime.after.mir b/tests/mir-opt/building/custom/operators.g.runtime.after.mir
new file mode 100644
index 00000000000..a0ad7d0f93f
--- /dev/null
+++ b/tests/mir-opt/building/custom/operators.g.runtime.after.mir
@@ -0,0 +1,13 @@
+// MIR for `g` after runtime
+
+fn g(_1: *const i32, _2: *const [i32]) -> () {
+    let mut _0: ();
+    let mut _3: ();
+    let mut _4: usize;
+
+    bb0: {
+        _3 = PtrMetadata(_1);
+        _4 = PtrMetadata(_2);
+        return;
+    }
+}
diff --git a/tests/mir-opt/building/custom/operators.rs b/tests/mir-opt/building/custom/operators.rs
index eb97bcc73b7..ff0e8dcbb41 100644
--- a/tests/mir-opt/building/custom/operators.rs
+++ b/tests/mir-opt/building/custom/operators.rs
@@ -30,3 +30,13 @@ pub fn f(a: i32, b: bool) -> i32 {
         Return()
     })
 }
+
+// EMIT_MIR operators.g.runtime.after.mir
+#[custom_mir(dialect = "runtime")]
+pub fn g(p: *const i32, q: *const [i32]) {
+    mir!({
+        let a = PtrMetadata(p);
+        let b = PtrMetadata(q);
+        Return()
+    })
+}
diff --git a/tests/mir-opt/lower_intrinsics.get_metadata.LowerIntrinsics.panic-abort.diff b/tests/mir-opt/lower_intrinsics.get_metadata.LowerIntrinsics.panic-abort.diff
new file mode 100644
index 00000000000..d256058c05e
--- /dev/null
+++ b/tests/mir-opt/lower_intrinsics.get_metadata.LowerIntrinsics.panic-abort.diff
@@ -0,0 +1,63 @@
+- // MIR for `get_metadata` before LowerIntrinsics
++ // MIR for `get_metadata` after LowerIntrinsics
+  
+  fn get_metadata(_1: *const i32, _2: *const [u8], _3: *const dyn Debug) -> () {
+      debug a => _1;
+      debug b => _2;
+      debug c => _3;
+      let mut _0: ();
+      let _4: ();
+      let mut _5: *const i32;
+      let mut _7: *const [u8];
+      let mut _9: *const dyn std::fmt::Debug;
+      scope 1 {
+          debug _unit => _4;
+          let _6: usize;
+          scope 2 {
+              debug _usize => _6;
+              let _8: std::ptr::DynMetadata<dyn std::fmt::Debug>;
+              scope 3 {
+                  debug _vtable => _8;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_4);
+          StorageLive(_5);
+          _5 = _1;
+-         _4 = ptr_metadata::<i32, ()>(move _5) -> [return: bb1, unwind unreachable];
++         _4 = PtrMetadata(move _5);
++         goto -> bb1;
+      }
+  
+      bb1: {
+          StorageDead(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+          _7 = _2;
+-         _6 = ptr_metadata::<[u8], usize>(move _7) -> [return: bb2, unwind unreachable];
++         _6 = PtrMetadata(move _7);
++         goto -> bb2;
+      }
+  
+      bb2: {
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+          _9 = _3;
+-         _8 = ptr_metadata::<dyn Debug, DynMetadata<dyn Debug>>(move _9) -> [return: bb3, unwind unreachable];
++         _8 = PtrMetadata(move _9);
++         goto -> bb3;
+      }
+  
+      bb3: {
+          StorageDead(_9);
+          _0 = const ();
+          StorageDead(_8);
+          StorageDead(_6);
+          StorageDead(_4);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/lower_intrinsics.get_metadata.LowerIntrinsics.panic-unwind.diff b/tests/mir-opt/lower_intrinsics.get_metadata.LowerIntrinsics.panic-unwind.diff
new file mode 100644
index 00000000000..d256058c05e
--- /dev/null
+++ b/tests/mir-opt/lower_intrinsics.get_metadata.LowerIntrinsics.panic-unwind.diff
@@ -0,0 +1,63 @@
+- // MIR for `get_metadata` before LowerIntrinsics
++ // MIR for `get_metadata` after LowerIntrinsics
+  
+  fn get_metadata(_1: *const i32, _2: *const [u8], _3: *const dyn Debug) -> () {
+      debug a => _1;
+      debug b => _2;
+      debug c => _3;
+      let mut _0: ();
+      let _4: ();
+      let mut _5: *const i32;
+      let mut _7: *const [u8];
+      let mut _9: *const dyn std::fmt::Debug;
+      scope 1 {
+          debug _unit => _4;
+          let _6: usize;
+          scope 2 {
+              debug _usize => _6;
+              let _8: std::ptr::DynMetadata<dyn std::fmt::Debug>;
+              scope 3 {
+                  debug _vtable => _8;
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_4);
+          StorageLive(_5);
+          _5 = _1;
+-         _4 = ptr_metadata::<i32, ()>(move _5) -> [return: bb1, unwind unreachable];
++         _4 = PtrMetadata(move _5);
++         goto -> bb1;
+      }
+  
+      bb1: {
+          StorageDead(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+          _7 = _2;
+-         _6 = ptr_metadata::<[u8], usize>(move _7) -> [return: bb2, unwind unreachable];
++         _6 = PtrMetadata(move _7);
++         goto -> bb2;
+      }
+  
+      bb2: {
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+          _9 = _3;
+-         _8 = ptr_metadata::<dyn Debug, DynMetadata<dyn Debug>>(move _9) -> [return: bb3, unwind unreachable];
++         _8 = PtrMetadata(move _9);
++         goto -> bb3;
+      }
+  
+      bb3: {
+          StorageDead(_9);
+          _0 = const ();
+          StorageDead(_8);
+          StorageDead(_6);
+          StorageDead(_4);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/lower_intrinsics.rs b/tests/mir-opt/lower_intrinsics.rs
index 180bfd0a924..2569f4f4de5 100644
--- a/tests/mir-opt/lower_intrinsics.rs
+++ b/tests/mir-opt/lower_intrinsics.rs
@@ -258,3 +258,12 @@ pub fn make_pointers(a: *const u8, b: *mut (), n: usize) {
     let _slice_const: *const [u16] = aggregate_raw_ptr(a, n);
     let _slice_mut: *mut [u64] = aggregate_raw_ptr(b, n);
 }
+
+// EMIT_MIR lower_intrinsics.get_metadata.LowerIntrinsics.diff
+pub fn get_metadata(a: *const i32, b: *const [u8], c: *const dyn std::fmt::Debug) {
+    use std::intrinsics::ptr_metadata;
+
+    let _unit = ptr_metadata(a);
+    let _usize = ptr_metadata(b);
+    let _vtable = ptr_metadata(c);
+}
diff --git a/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-abort.mir b/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-abort.mir
index db0c84bd560..ea4ed271305 100644
--- a/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-abort.mir
+++ b/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-abort.mir
@@ -13,9 +13,8 @@ fn demo_byte_add_fat(_1: *const [u32], _2: usize) -> *const [u32] {
         }
         scope 4 (inlined std::ptr::const_ptr::<impl *const u8>::with_metadata_of::<[u32]>) {
             let mut _5: *const ();
-            let mut _7: usize;
+            let mut _6: usize;
             scope 5 (inlined std::ptr::metadata::<[u32]>) {
-                let mut _6: std::ptr::metadata::PtrRepr<[u32]>;
             }
             scope 6 (inlined std::ptr::from_raw_parts::<[u32]>) {
             }
@@ -30,13 +29,10 @@ fn demo_byte_add_fat(_1: *const [u32], _2: usize) -> *const [u32] {
         StorageDead(_3);
         StorageLive(_5);
         _5 = _4 as *const () (PtrToPtr);
-        StorageLive(_7);
         StorageLive(_6);
-        _6 = std::ptr::metadata::PtrRepr::<[u32]> { const_ptr: _1 };
-        _7 = ((_6.2: std::ptr::metadata::PtrComponents<[u32]>).1: usize);
+        _6 = PtrMetadata(_1);
+        _0 = *const [u32] from (_5, _6);
         StorageDead(_6);
-        _0 = *const [u32] from (_5, _7);
-        StorageDead(_7);
         StorageDead(_5);
         StorageDead(_4);
         return;
diff --git a/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-unwind.mir
index db0c84bd560..ea4ed271305 100644
--- a/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-unwind.mir
+++ b/tests/mir-opt/pre-codegen/ptr_offset.demo_byte_add_fat.PreCodegen.after.panic-unwind.mir
@@ -13,9 +13,8 @@ fn demo_byte_add_fat(_1: *const [u32], _2: usize) -> *const [u32] {
         }
         scope 4 (inlined std::ptr::const_ptr::<impl *const u8>::with_metadata_of::<[u32]>) {
             let mut _5: *const ();
-            let mut _7: usize;
+            let mut _6: usize;
             scope 5 (inlined std::ptr::metadata::<[u32]>) {
-                let mut _6: std::ptr::metadata::PtrRepr<[u32]>;
             }
             scope 6 (inlined std::ptr::from_raw_parts::<[u32]>) {
             }
@@ -30,13 +29,10 @@ fn demo_byte_add_fat(_1: *const [u32], _2: usize) -> *const [u32] {
         StorageDead(_3);
         StorageLive(_5);
         _5 = _4 as *const () (PtrToPtr);
-        StorageLive(_7);
         StorageLive(_6);
-        _6 = std::ptr::metadata::PtrRepr::<[u32]> { const_ptr: _1 };
-        _7 = ((_6.2: std::ptr::metadata::PtrComponents<[u32]>).1: usize);
+        _6 = PtrMetadata(_1);
+        _0 = *const [u32] from (_5, _6);
         StorageDead(_6);
-        _0 = *const [u32] from (_5, _7);
-        StorageDead(_7);
         StorageDead(_5);
         StorageDead(_4);
         return;