Rollup merge of rust-lang#102675 - ouz-a:mir-technical-debt, r=oli-obk

Remove `mir::CastKind::Misc` As discussed in rust-lang#97649 `mir::CastKind::Misc` is not clear, this PR addresses that by creating a new enum variant for every valid cast. r? ``@oli-obk``
matthiaskrgr · Oct 8, 2022 · 4d883e7 · 4d883e7
2 parents bffc2ce + d59c7ff
commit 4d883e7
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Showing 25 changed files with 190 additions and 57 deletions.
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2209,25 +2209,104 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             }
                         }
                     }
-
-                    CastKind::Misc => {
+                    CastKind::IntToInt => {
                         let ty_from = op.ty(body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
-                        // Misc casts are either between floats and ints, or one ptr type to another.
                         match (cast_ty_from, cast_ty_to) {
-                            (
-                                Some(CastTy::Int(_) | CastTy::Float),
-                                Some(CastTy::Int(_) | CastTy::Float),
-                            )
-                            | (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Ptr(_))) => (),
+                            (Some(CastTy::Int(_)), Some(CastTy::Int(_))) => (),
                             _ => {
                                 span_mirbug!(
                                     self,
                                     rvalue,
-                                    "Invalid Misc cast {:?} -> {:?}",
+                                    "Invalid IntToInt cast {:?} -> {:?}",
                                     ty_from,
-                                    ty,
+                                    ty
+                                )
+                            }
+                        }
+                    }
+                    CastKind::IntToFloat => {
+                        let ty_from = op.ty(body, tcx);
+                        let cast_ty_from = CastTy::from_ty(ty_from);
+                        let cast_ty_to = CastTy::from_ty(*ty);
+                        match (cast_ty_from, cast_ty_to) {
+                            (Some(CastTy::Int(_)), Some(CastTy::Float)) => (),
+                            _ => {
+                                span_mirbug!(
+                                    self,
+                                    rvalue,
+                                    "Invalid IntToFloat cast {:?} -> {:?}",
+                                    ty_from,
+                                    ty
+                                )
+                            }
+                        }
+                    }
+                    CastKind::FloatToInt => {
+                        let ty_from = op.ty(body, tcx);
+                        let cast_ty_from = CastTy::from_ty(ty_from);
+                        let cast_ty_to = CastTy::from_ty(*ty);
+                        match (cast_ty_from, cast_ty_to) {
+                            (Some(CastTy::Float), Some(CastTy::Int(_))) => (),
+                            _ => {
+                                span_mirbug!(
+                                    self,
+                                    rvalue,
+                                    "Invalid FloatToInt cast {:?} -> {:?}",
+                                    ty_from,
+                                    ty
+                                )
+                            }
+                        }
+                    }
+                    CastKind::FloatToFloat => {
+                        let ty_from = op.ty(body, tcx);
+                        let cast_ty_from = CastTy::from_ty(ty_from);
+                        let cast_ty_to = CastTy::from_ty(*ty);
+                        match (cast_ty_from, cast_ty_to) {
+                            (Some(CastTy::Float), Some(CastTy::Float)) => (),
+                            _ => {
+                                span_mirbug!(
+                                    self,
+                                    rvalue,
+                                    "Invalid FloatToFloat cast {:?} -> {:?}",
+                                    ty_from,
+                                    ty
+                                )
+                            }
+                        }
+                    }
+                    CastKind::FnPtrToPtr => {
+                        let ty_from = op.ty(body, tcx);
+                        let cast_ty_from = CastTy::from_ty(ty_from);
+                        let cast_ty_to = CastTy::from_ty(*ty);
+                        match (cast_ty_from, cast_ty_to) {
+                            (Some(CastTy::FnPtr), Some(CastTy::Ptr(_))) => (),
+                            _ => {
+                                span_mirbug!(
+                                    self,
+                                    rvalue,
+                                    "Invalid FnPtrToPtr cast {:?} -> {:?}",
+                                    ty_from,
+                                    ty
+                                )
+                            }
+                        }
+                    }
+                    CastKind::PtrToPtr => {
+                        let ty_from = op.ty(body, tcx);
+                        let cast_ty_from = CastTy::from_ty(ty_from);
+                        let cast_ty_to = CastTy::from_ty(*ty);
+                        match (cast_ty_from, cast_ty_to) {
+                            (Some(CastTy::Ptr(_)), Some(CastTy::Ptr(_))) => (),
+                            _ => {
+                                span_mirbug!(
+                                    self,
+                                    rvalue,
+                                    "Invalid PtrToPtr cast {:?} -> {:?}",
+                                    ty_from,
+                                    ty
                                 )
                             }
                         }

diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -633,7 +633,12 @@ fn codegen_stmt<'tcx>(
                     lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
                 }
                 Rvalue::Cast(
-                    CastKind::Misc
+                    CastKind::IntToInt
+                    | CastKind::FloatToFloat
+                    | CastKind::FloatToInt
+                    | CastKind::IntToFloat
+                    | CastKind::FnPtrToPtr
+                    | CastKind::PtrToPtr
                     | CastKind::PointerExposeAddress
                     | CastKind::PointerFromExposedAddress,
                     ref operand,

diff --git a/compiler/rustc_codegen_cranelift/src/constant.rs b/compiler/rustc_codegen_cranelift/src/constant.rs
@@ -490,7 +490,16 @@ pub(crate) fn mir_operand_get_const_val<'tcx>(
                     match &stmt.kind {
                         StatementKind::Assign(local_and_rvalue) if &local_and_rvalue.0 == place => {
                             match &local_and_rvalue.1 {
-                                Rvalue::Cast(CastKind::Misc, operand, ty) => {
+                                Rvalue::Cast(
+                                    CastKind::IntToInt
+                                    | CastKind::FloatToFloat
+                                    | CastKind::FloatToInt
+                                    | CastKind::IntToFloat
+                                    | CastKind::FnPtrToPtr
+                                    | CastKind::PtrToPtr,
+                                    operand,
+                                    ty,
+                                ) => {
                                     if computed_const_val.is_some() {
                                         return None; // local assigned twice
                                     }

diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -250,7 +250,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         OperandValue::Pair(lldata, llextra)
                     }
                     mir::CastKind::Pointer(PointerCast::MutToConstPointer)
-                    | mir::CastKind::Misc
+                    | mir::CastKind::PtrToPtr
                         if bx.cx().is_backend_scalar_pair(operand.layout) =>
                     {
                         if let OperandValue::Pair(data_ptr, meta) = operand.val {
@@ -290,7 +290,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     mir::CastKind::Pointer(
                         PointerCast::MutToConstPointer | PointerCast::ArrayToPointer,
                     )
-                    | mir::CastKind::Misc
+                    | mir::CastKind::IntToInt
+                    | mir::CastKind::FloatToInt
+                    | mir::CastKind::FloatToFloat
+                    | mir::CastKind::IntToFloat
+                    | mir::CastKind::PtrToPtr
+                    | mir::CastKind::FnPtrToPtr
+
                     // Since int2ptr can have arbitrary integer types as input (so we have to do
                     // sign extension and all that), it is currently best handled in the same code
                     // path as the other integer-to-X casts.

diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -42,8 +42,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let res = self.pointer_from_exposed_address_cast(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;
             }
-
-            Misc => {
+            // FIXME: We shouldn't use `misc_cast` for these but handle them separately.
+            IntToInt | FloatToInt | FloatToFloat | IntToFloat | FnPtrToPtr | PtrToPtr => {
                 let src = self.read_immediate(src)?;
                 let res = self.misc_cast(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;

diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -553,7 +553,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 unimplemented!()
             }
 
-            Rvalue::Cast(CastKind::Misc, _, _) => {}
+            Rvalue::Cast(_, _, _) => {}
 
             Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => {}
             Rvalue::ShallowInitBox(_, _) => {}

diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -557,7 +557,14 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             }
             Rvalue::Cast(kind, operand, target_type) => {
                 match kind {
-                    CastKind::Misc => {
+                    CastKind::DynStar => {
+                        // FIXME(dyn-star): make sure nothing needs to be done here.
+                    }
+                    // Nothing to check here
+                    CastKind::PointerFromExposedAddress
+                    | CastKind::PointerExposeAddress
+                    | CastKind::Pointer(_) => {}
+                    _ => {
                         let op_ty = operand.ty(self.body, self.tcx);
                         if op_ty.is_enum() {
                             self.fail(
@@ -568,13 +575,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             );
                         }
                     }
-                    CastKind::DynStar => {
-                        // FIXME(dyn-star): make sure nothing needs to be done here.
-                    }
-                    // Nothing to check here
-                    CastKind::PointerFromExposedAddress
-                    | CastKind::PointerExposeAddress
-                    | CastKind::Pointer(_) => {}
                 }
             }
             Rvalue::Repeat(_, _)

diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
@@ -1834,7 +1834,14 @@ impl<'tcx> Rvalue<'tcx> {
             | Rvalue::AddressOf(_, _)
             | Rvalue::Len(_)
             | Rvalue::Cast(
-                CastKind::Misc | CastKind::Pointer(_) | CastKind::PointerFromExposedAddress,
+                CastKind::IntToInt
+                | CastKind::FloatToInt
+                | CastKind::FloatToFloat
+                | CastKind::IntToFloat
+                | CastKind::FnPtrToPtr
+                | CastKind::PtrToPtr
+                | CastKind::Pointer(_)
+                | CastKind::PointerFromExposedAddress,
                 _,
                 _,
             )

diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
@@ -1149,8 +1149,12 @@ pub enum CastKind {
     Pointer(PointerCast),
     /// Cast into a dyn* object.
     DynStar,
-    /// Remaining unclassified casts.
-    Misc,
+    IntToInt,
+    FloatToInt,
+    FloatToFloat,
+    IntToFloat,
+    PtrToPtr,
+    FnPtrToPtr,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]

diff --git a/compiler/rustc_middle/src/ty/cast.rs b/compiler/rustc_middle/src/ty/cast.rs
@@ -2,6 +2,7 @@
 // typeck and codegen.
 
 use crate::ty::{self, Ty};
+use rustc_middle::mir;
 
 use rustc_macros::HashStable;
 
@@ -75,3 +76,28 @@ impl<'tcx> CastTy<'tcx> {
         }
     }
 }
+
+/// Returns `mir::CastKind` from the given parameters.
+pub fn mir_cast_kind<'tcx>(from_ty: Ty<'tcx>, cast_ty: Ty<'tcx>) -> mir::CastKind {
+    let from = CastTy::from_ty(from_ty);
+    let cast = CastTy::from_ty(cast_ty);
+    let cast_kind = match (from, cast) {
+        (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Int(_))) => {
+            mir::CastKind::PointerExposeAddress
+        }
+        (Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => mir::CastKind::PointerFromExposedAddress,
+        (_, Some(CastTy::DynStar)) => mir::CastKind::DynStar,
+        (Some(CastTy::Int(_)), Some(CastTy::Int(_))) => mir::CastKind::IntToInt,
+        (Some(CastTy::FnPtr), Some(CastTy::Ptr(_))) => mir::CastKind::FnPtrToPtr,
+
+        (Some(CastTy::Float), Some(CastTy::Int(_))) => mir::CastKind::FloatToInt,
+        (Some(CastTy::Int(_)), Some(CastTy::Float)) => mir::CastKind::IntToFloat,
+        (Some(CastTy::Float), Some(CastTy::Float)) => mir::CastKind::FloatToFloat,
+        (Some(CastTy::Ptr(_)), Some(CastTy::Ptr(_))) => mir::CastKind::PtrToPtr,
+
+        (_, _) => {
+            bug!("Attempting to cast non-castable types {:?} and {:?}", from_ty, cast_ty)
+        }
+    };
+    cast_kind
+}
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -12,7 +12,7 @@ use rustc_middle::mir::AssertKind;
 use rustc_middle::mir::Place;
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
-use rustc_middle::ty::cast::CastTy;
+use rustc_middle::ty::cast::{mir_cast_kind, CastTy};
 use rustc_middle::ty::{self, Ty, UpvarSubsts};
 use rustc_span::Span;
 
@@ -217,16 +217,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let from_ty = CastTy::from_ty(ty);
                 let cast_ty = CastTy::from_ty(expr.ty);
                 debug!("ExprKind::Cast from_ty={from_ty:?}, cast_ty={:?}/{cast_ty:?}", expr.ty,);
-                let cast_kind = match (from_ty, cast_ty) {
-                    (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Int(_))) => {
-                        CastKind::PointerExposeAddress
-                    }
-                    (Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => {
-                        CastKind::PointerFromExposedAddress
-                    }
-                    (_, Some(CastTy::DynStar)) => CastKind::DynStar,
-                    (_, _) => CastKind::Misc,
-                };
+                let cast_kind = mir_cast_kind(ty, expr.ty);
                 block.and(Rvalue::Cast(cast_kind, source, expr.ty))
             }
             ExprKind::Pointer { cast, source } => {

diff --git a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
@@ -823,9 +823,10 @@ where
             // tmp = &raw mut P;
             // cur = tmp as *mut T;
             // end = Offset(cur, len);
+            let mir_cast_kind = ty::cast::mir_cast_kind(iter_ty, tmp_ty);
             vec![
                 self.assign(tmp, Rvalue::AddressOf(Mutability::Mut, self.place)),
-                self.assign(cur, Rvalue::Cast(CastKind::Misc, Operand::Move(tmp), iter_ty)),
+                self.assign(cur, Rvalue::Cast(mir_cast_kind, Operand::Move(tmp), iter_ty)),
                 self.assign(
                     length_or_end,
                     Rvalue::BinaryOp(

diff --git a/src/test/mir-opt/const_prop/cast.main.ConstProp.diff b/src/test/mir-opt/const_prop/cast.main.ConstProp.diff
@@ -14,10 +14,10 @@
 
       bb0: {
           StorageLive(_1);                 // scope 0 at $DIR/cast.rs:+1:9: +1:10
--         _1 = const 42_u8 as u32 (Misc);  // scope 0 at $DIR/cast.rs:+1:13: +1:24
+-         _1 = const 42_u8 as u32 (IntToInt); // scope 0 at $DIR/cast.rs:+1:13: +1:24
 +         _1 = const 42_u32;               // scope 0 at $DIR/cast.rs:+1:13: +1:24
           StorageLive(_2);                 // scope 1 at $DIR/cast.rs:+3:9: +3:10
--         _2 = const 42_u32 as u8 (Misc);  // scope 1 at $DIR/cast.rs:+3:13: +3:24
+-         _2 = const 42_u32 as u8 (IntToInt); // scope 1 at $DIR/cast.rs:+3:13: +3:24
 +         _2 = const 42_u8;                // scope 1 at $DIR/cast.rs:+3:13: +3:24
           _0 = const ();                   // scope 0 at $DIR/cast.rs:+0:11: +4:2
           StorageDead(_2);                 // scope 1 at $DIR/cast.rs:+4:1: +4:2

diff --git a/src/test/mir-opt/const_prop/indirect.main.ConstProp.diff b/src/test/mir-opt/const_prop/indirect.main.ConstProp.diff
@@ -13,7 +13,7 @@
       bb0: {
           StorageLive(_1);                 // scope 0 at $DIR/indirect.rs:+1:9: +1:10
           StorageLive(_2);                 // scope 0 at $DIR/indirect.rs:+1:13: +1:25
--         _2 = const 2_u32 as u8 (Misc);   // scope 0 at $DIR/indirect.rs:+1:13: +1:25
+-         _2 = const 2_u32 as u8 (IntToInt); // scope 0 at $DIR/indirect.rs:+1:13: +1:25
 -         _3 = CheckedAdd(_2, const 1_u8); // scope 0 at $DIR/indirect.rs:+1:13: +1:29
 -         assert(!move (_3.1: bool), "attempt to compute `{} + {}`, which would overflow", move _2, const 1_u8) -> bb1; // scope 0 at $DIR/indirect.rs:+1:13: +1:29
 +         _2 = const 2_u8;                 // scope 0 at $DIR/indirect.rs:+1:13: +1:25

diff --git a/src/test/mir-opt/enum_cast.bar.mir_map.0.mir b/src/test/mir-opt/enum_cast.bar.mir_map.0.mir
@@ -7,7 +7,7 @@ fn bar(_1: Bar) -> usize {
 
     bb0: {
         _2 = discriminant(_1);           // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
-        _0 = move _2 as usize (Misc);    // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
+        _0 = move _2 as usize (IntToInt); // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
         return;                          // scope 0 at $DIR/enum_cast.rs:+2:2: +2:2
     }
 }
diff --git a/src/test/mir-opt/enum_cast.boo.mir_map.0.mir b/src/test/mir-opt/enum_cast.boo.mir_map.0.mir
@@ -7,7 +7,7 @@ fn boo(_1: Boo) -> usize {
 
     bb0: {
         _2 = discriminant(_1);           // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
-        _0 = move _2 as usize (Misc);    // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
+        _0 = move _2 as usize (IntToInt); // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
         return;                          // scope 0 at $DIR/enum_cast.rs:+2:2: +2:2
     }
 }
diff --git a/src/test/mir-opt/enum_cast.droppy.mir_map.0.mir b/src/test/mir-opt/enum_cast.droppy.mir_map.0.mir
@@ -26,7 +26,7 @@ fn droppy() -> () {
         FakeRead(ForLet(None), _2);      // scope 0 at $DIR/enum_cast.rs:+2:13: +2:14
         StorageLive(_3);                 // scope 3 at $DIR/enum_cast.rs:+5:13: +5:14
         _4 = discriminant(_2);           // scope 3 at $DIR/enum_cast.rs:+5:17: +5:27
-        _3 = move _4 as usize (Misc);    // scope 3 at $DIR/enum_cast.rs:+5:17: +5:27
+        _3 = move _4 as usize (IntToInt); // scope 3 at $DIR/enum_cast.rs:+5:17: +5:27
         FakeRead(ForLet(None), _3);      // scope 3 at $DIR/enum_cast.rs:+5:13: +5:14
         _1 = const ();                   // scope 0 at $DIR/enum_cast.rs:+1:5: +6:6
         StorageDead(_3);                 // scope 1 at $DIR/enum_cast.rs:+6:5: +6:6

diff --git a/src/test/mir-opt/enum_cast.foo.mir_map.0.mir b/src/test/mir-opt/enum_cast.foo.mir_map.0.mir
@@ -7,7 +7,7 @@ fn foo(_1: Foo) -> usize {
 
     bb0: {
         _2 = discriminant(_1);           // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
-        _0 = move _2 as usize (Misc);    // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
+        _0 = move _2 as usize (IntToInt); // scope 0 at $DIR/enum_cast.rs:+1:5: +1:17
         return;                          // scope 0 at $DIR/enum_cast.rs:+2:2: +2:2
     }
 }
diff --git a/src/test/mir-opt/funky_arms.float_to_exponential_common.ConstProp.diff b/src/test/mir-opt/funky_arms.float_to_exponential_common.ConstProp.diff
@@ -91,7 +91,7 @@
           StorageLive(_15);                // scope 3 at $DIR/funky_arms.rs:+15:59: +15:75
           StorageLive(_16);                // scope 3 at $DIR/funky_arms.rs:+15:59: +15:68
           _16 = _10;                       // scope 3 at $DIR/funky_arms.rs:+15:59: +15:68
-          _15 = move _16 as u32 (Misc);    // scope 3 at $DIR/funky_arms.rs:+15:59: +15:75
+          _15 = move _16 as u32 (IntToInt); // scope 3 at $DIR/funky_arms.rs:+15:59: +15:75
           StorageDead(_16);                // scope 3 at $DIR/funky_arms.rs:+15:74: +15:75
           _14 = Add(move _15, const 1_u32); // scope 3 at $DIR/funky_arms.rs:+15:59: +15:79
           StorageDead(_15);                // scope 3 at $DIR/funky_arms.rs:+15:78: +15:79