rustc_mir: run the lower_intrinsics pass on MIR shims.

Author: eddyb

compiler/rustc_mir_transform/src/shim.rs

@@ -21,7 +21,8 @@ use tracing::{debug, instrument};
 
 use crate::{
     abort_unwinding_calls, add_call_guards, add_moves_for_packed_drops, deref_separator,
-    instsimplify, mentioned_items, pass_manager as pm, remove_noop_landing_pads, simplify,
+    instsimplify, lower_intrinsics, mentioned_items, pass_manager as pm, remove_noop_landing_pads,
+    simplify,
 };
 
 mod async_destructor_ctor;
@@ -153,6 +154,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceKind<'tcx>) -> Body<
             &add_moves_for_packed_drops::AddMovesForPackedDrops,
             &deref_separator::Derefer,
             &remove_noop_landing_pads::RemoveNoopLandingPads,
+            &lower_intrinsics::LowerIntrinsics,
             &simplify::SimplifyCfg::MakeShim,
             &instsimplify::InstSimplify::BeforeInline,
             &abort_unwinding_calls::AbortUnwindingCalls,

tests/mir-opt/lower_intrinsics.core.intrinsics-#1-discriminant_value.LowerIntrinsics.diff

@@ -0,0 +1,23 @@
+- // MIR for `discriminant_value` before LowerIntrinsics
++ // MIR for `discriminant_value` after LowerIntrinsics
+
+  fn discriminant_value(_1: &T) -> <T as DiscriminantKind>::Discriminant {
+      let mut _0: <T as std::marker::DiscriminantKind>::Discriminant; // return place in scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+
+      bb0: {
+-         _0 = discriminant_value::<T>(move _1) -> bb1; // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // mir::Constant
+-                                          // + span: $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // + literal: Const { ty: for<'r> extern "rust-intrinsic" fn(&'r T) -> <T as std::marker::DiscriminantKind>::Discriminant {std::intrinsics::discriminant_value::<T>}, val: Value(Scalar(<ZST>)) }
++         _0 = discriminant((*_1));        // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
++         goto -> bb1;                     // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb1: {
+          return;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb2 (cleanup): {
+          resume;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+  }

tests/mir-opt/lower_intrinsics.core.intrinsics-#1-forget.LowerIntrinsics.diff

@@ -0,0 +1,23 @@
+- // MIR for `std::intrinsics::forget` before LowerIntrinsics
++ // MIR for `std::intrinsics::forget` after LowerIntrinsics
+
+  fn std::intrinsics::forget(_1: T) -> () {
+      let mut _0: ();                      // return place in scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+
+      bb0: {
+-         _0 = std::intrinsics::forget::<T>(move _1) -> bb1; // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // mir::Constant
+-                                          // + span: $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // + literal: Const { ty: extern "rust-intrinsic" fn(T) {std::intrinsics::forget::<T>}, val: Value(Scalar(<ZST>)) }
++         _0 = const ();                   // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
++         goto -> bb1;                     // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb1: {
+          return;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb2 (cleanup): {
+          resume;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+  }

tests/mir-opt/lower_intrinsics.core.intrinsics-#1-size_of.LowerIntrinsics.diff

@@ -0,0 +1,23 @@
+- // MIR for `std::intrinsics::size_of` before LowerIntrinsics
++ // MIR for `std::intrinsics::size_of` after LowerIntrinsics
+
+  fn std::intrinsics::size_of() -> usize {
+      let mut _0: usize;                   // return place in scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+
+      bb0: {
+-         _0 = std::intrinsics::size_of::<T>() -> bb1; // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // mir::Constant
+-                                          // + span: $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}, val: Value(Scalar(<ZST>)) }
++         _0 = SizeOf(T);                  // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
++         goto -> bb1;                     // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb1: {
+          return;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb2 (cleanup): {
+          resume;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+  }

tests/mir-opt/lower_intrinsics.core.intrinsics-#1-unreachable.LowerIntrinsics.diff

@@ -0,0 +1,22 @@
+- // MIR for `std::intrinsics::unreachable` before LowerIntrinsics
++ // MIR for `std::intrinsics::unreachable` after LowerIntrinsics
+
+  fn std::intrinsics::unreachable() -> ! {
+      let mut _0: !;                       // return place in scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+
+      bb0: {
+-         _0 = std::intrinsics::unreachable() -> bb1; // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // mir::Constant
+-                                          // + span: $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn() -> ! {std::intrinsics::unreachable}, val: Value(Scalar(<ZST>)) }
++         unreachable;                     // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb1: {
+          return;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb2 (cleanup): {
+          resume;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+  }

tests/mir-opt/lower_intrinsics.core.intrinsics-#1-wrapping_add.LowerIntrinsics.diff

@@ -0,0 +1,23 @@
+- // MIR for `wrapping_add` before LowerIntrinsics
++ // MIR for `wrapping_add` after LowerIntrinsics
+
+  fn wrapping_add(_1: T, _2: T) -> T {
+      let mut _0: T;                       // return place in scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+
+      bb0: {
+-         _0 = wrapping_add::<T>(move _1, move _2) -> bb1; // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // mir::Constant
+-                                          // + span: $SRC_DIR/core/src/intrinsics.rs:LL:COL
+-                                          // + literal: Const { ty: extern "rust-intrinsic" fn(T, T) -> T {std::intrinsics::wrapping_add::<T>}, val: Value(Scalar(<ZST>)) }
++         _0 = Add(move _1, move _2);      // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
++         goto -> bb1;                     // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb1: {
+          return;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+
+      bb2 (cleanup): {
+          resume;                          // scope 0 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
+      }
+  }

tests/mir-opt/lower_intrinsics.rs

@@ -267,3 +267,15 @@ pub fn get_metadata(a: *const i32, b: *const [u8], c: *const dyn std::fmt::Debug
     let _usize = ptr_metadata(b);
     let _vtable = ptr_metadata(c);
 }
+
+// Check that the MIR shims used for reifying intrinsics to `fn` pointers,
+// also go through the lowering pass.
+pub fn reify_intrinsics() -> impl Copy {
+    (
+        core::intrinsics::wrapping_add::<u32> as unsafe fn(_, _) -> _,
+        core::intrinsics::size_of::<u8> as unsafe fn() -> _,
+        core::intrinsics::unreachable as unsafe fn() -> !,
+        core::intrinsics::forget::<E> as unsafe fn(_),
+        core::intrinsics::discriminant_value::<E> as unsafe fn(_) -> _,
+    )
+}