Don't special case constant operands when lowering intrinsics

compiler/rustc_mir/src/transform/lower_intrinsics.rs

@@ -11,15 +11,11 @@ pub struct LowerIntrinsics;
 
 impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        for block in body.basic_blocks_mut() {
+        let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
+        for block in basic_blocks {
             let terminator = block.terminator.as_mut().unwrap();
-            if let TerminatorKind::Call {
-                func: Operand::Constant(box Constant { literal: ty::Const { ty: func_ty, .. }, .. }),
-                args,
-                destination,
-                ..
-            } = &mut terminator.kind
-            {
+            if let TerminatorKind::Call { func, args, destination, .. } = &mut terminator.kind {
+                let func_ty = func.ty(local_decls, tcx);
                 let (intrinsic_name, substs) = match resolve_rust_intrinsic(tcx, func_ty) {
                     None => continue,
                     Some(it) => it,

src/test/mir-opt/lower_intrinsics.non_const.LowerIntrinsics.diff

@@ -0,0 +1,31 @@
+- // MIR for `non_const` before LowerIntrinsics
++ // MIR for `non_const` after LowerIntrinsics
+
+  fn non_const() -> usize {
+      let mut _0: usize;                   // return place in scope 0 at $DIR/lower_intrinsics.rs:55:26: 55:31
+      let _1: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}; // in scope 0 at $DIR/lower_intrinsics.rs:57:9: 57:18
+      let mut _2: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}; // in scope 0 at $DIR/lower_intrinsics.rs:58:5: 58:14
+      scope 1 {
+          debug size_of_t => _1;           // in scope 1 at $DIR/lower_intrinsics.rs:57:9: 57:18
+      }
+
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:57:9: 57:18
+          _1 = std::intrinsics::size_of::<T>; // scope 0 at $DIR/lower_intrinsics.rs:57:21: 57:51
+                                           // mir::Constant
+                                           // + span: $DIR/lower_intrinsics.rs:57:21: 57:51
+                                           // + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}, val: Value(Scalar(<ZST>)) }
+          StorageLive(_2);                 // scope 1 at $DIR/lower_intrinsics.rs:58:5: 58:14
+          _2 = _1;                         // scope 1 at $DIR/lower_intrinsics.rs:58:5: 58:14
+-         _0 = move _2() -> bb1;           // scope 1 at $DIR/lower_intrinsics.rs:58:5: 58:16
++         _0 = SizeOf(T);                  // scope 1 at $DIR/lower_intrinsics.rs:58:5: 58:16
++         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:58:5: 58:16
+      }
+
+      bb1: {
+          StorageDead(_2);                 // scope 1 at $DIR/lower_intrinsics.rs:58:15: 58:16
+          StorageDead(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:59:1: 59:2
+          return;                          // scope 0 at $DIR/lower_intrinsics.rs:59:2: 59:2
+      }
+  }
+

src/test/mir-opt/lower_intrinsics.rs

@@ -50,3 +50,10 @@ pub fn f_zst<T>(t: T) {
 
 #[inline(never)]
 pub fn f_non_zst<T>(t: T) {}
+
+// EMIT_MIR lower_intrinsics.non_const.LowerIntrinsics.diff
+pub fn non_const<T>() -> usize {
+    // Check that lowering works with non-const operand as a func.
+    let size_of_t = core::intrinsics::size_of::<T>;
+    size_of_t()
+}