Rollup merge of #112168 - scottmcm:lower-div-rem-unchecked-to-mir, r=oli-obk

Lower `unchecked_div`/`_rem` to MIR's `BinOp::Div`/`Rem`

As described in <https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/enum.BinOp.html#variant.Div>, the ordinary `BinOp`s for these are already UB for division by zero ([or overflow](https://llvm.org/docs/LangRef.html#sdiv-instruction), [demo](https://rust.godbolt.org/z/71e7P7Exh)), as MIR building is responsible for inserting code to panic for those cases regardless of whether the overflow checks are enabled.

So we can lower these in the same arm that lowers `wrapping_add` to MIR `BinOp::Add` and such, as all these cases turn into ordinary `Rvalue::BinaryOp`s.

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -475,9 +475,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::unchecked_add
         | sym::unchecked_sub
         | sym::unchecked_mul
-        | sym::unchecked_div
         | sym::exact_div
-        | sym::unchecked_rem
         | sym::unchecked_shl
         | sym::unchecked_shr => {
             intrinsic_args!(fx, args => (x, y); intrinsic);
@@ -487,8 +485,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                 sym::unchecked_add => BinOp::Add,
                 sym::unchecked_sub => BinOp::Sub,
                 sym::unchecked_mul => BinOp::Mul,
-                sym::unchecked_div | sym::exact_div => BinOp::Div,
+                sym::exact_div => BinOp::Div,
-                sym::unchecked_rem => BinOp::Rem,
                 sym::unchecked_shl => BinOp::Shl,
                 sym::unchecked_shr => BinOp::Shr,
                 _ => unreachable!(),

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -211,8 +211,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 args[1].val.unaligned_volatile_store(bx, dst);
                 return;
             }
-            | sym::unchecked_div
-            | sym::unchecked_rem
             | sym::unchecked_shl
             | sym::unchecked_shr
             | sym::unchecked_add
@@ -229,20 +227,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 bx.exactudiv(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        sym::unchecked_div => {
-                            if signed {
-                                bx.sdiv(args[0].immediate(), args[1].immediate())
-                            } else {
-                                bx.udiv(args[0].immediate(), args[1].immediate())
-                            }
-                        }
-                        sym::unchecked_rem => {
-                            if signed {
-                                bx.srem(args[0].immediate(), args[1].immediate())
-                            } else {
-                                bx.urem(args[0].immediate(), args[1].immediate())
-                            }
-                        }
                         sym::unchecked_shl => bx.shl(args[0].immediate(), args[1].immediate()),
                         sym::unchecked_shr => {
                             if signed {

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -238,9 +238,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             | sym::unchecked_shr
             | sym::unchecked_add
             | sym::unchecked_sub
-            | sym::unchecked_mul
+            | sym::unchecked_mul => {
-            | sym::unchecked_div
-            | sym::unchecked_rem => {
                 let l = self.read_immediate(&args[0])?;
                 let r = self.read_immediate(&args[1])?;
                 let bin_op = match intrinsic_name {
@@ -249,8 +247,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     sym::unchecked_add => BinOp::Add,
                     sym::unchecked_sub => BinOp::Sub,
                     sym::unchecked_mul => BinOp::Mul,
-                    sym::unchecked_div => BinOp::Div,
-                    sym::unchecked_rem => BinOp::Rem,
                     _ => bug!(),
                 };
                 let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, &l, &r)?;

compiler/rustc_middle/src/mir/syntax.rs

@@ -1273,13 +1273,18 @@ pub enum BinOp {
     Mul,
     /// The `/` operator (division)
     ///
-    /// Division by zero is UB, because the compiler should have inserted checks
+    /// For integer types, division by zero is UB, as is `MIN / -1` for signed.
-    /// prior to this.
+    /// The compiler should have inserted checks prior to this.
+    ///
+    /// Floating-point division by zero is safe, and does not need guards.
     Div,
     /// The `%` operator (modulus)
     ///
-    /// Using zero as the modulus (second operand) is UB, because the compiler
+    /// For integer types, using zero as the modulus (second operand) is UB,
-    /// should have inserted checks prior to this.
+    /// as is `MIN % -1` for signed.
+    /// The compiler should have inserted checks prior to this.
+    ///
+    /// Floating-point remainder by zero is safe, and does not need guards.
     Rem,
     /// The `^` operator (bitwise xor)
     BitXor,

compiler/rustc_mir_transform/src/lower_intrinsics.rs

@@ -82,30 +82,35 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                         drop(args);
                         terminator.kind = TerminatorKind::Goto { target };
                     }
-                    sym::wrapping_add | sym::wrapping_sub | sym::wrapping_mul => {
+                    sym::wrapping_add
-                        if let Some(target) = *target {
+                    | sym::wrapping_sub
-                            let lhs;
+                    | sym::wrapping_mul
-                            let rhs;
+                    | sym::unchecked_div
-                            {
+                    | sym::unchecked_rem => {
-                                let mut args = args.drain(..);
+                        let target = target.unwrap();
-                                lhs = args.next().unwrap();
+                        let lhs;
-                                rhs = args.next().unwrap();
+                        let rhs;
-                            }
+                        {
-                            let bin_op = match intrinsic_name {
+                            let mut args = args.drain(..);
-                                sym::wrapping_add => BinOp::Add,
+                            lhs = args.next().unwrap();
-                                sym::wrapping_sub => BinOp::Sub,
+                            rhs = args.next().unwrap();
-                                sym::wrapping_mul => BinOp::Mul,
-                                _ => bug!("unexpected intrinsic"),
-                            };
-                            block.statements.push(Statement {
-                                source_info: terminator.source_info,
-                                kind: StatementKind::Assign(Box::new((
-                                    *destination,
-                                    Rvalue::BinaryOp(bin_op, Box::new((lhs, rhs))),
-                                ))),
-                            });
-                            terminator.kind = TerminatorKind::Goto { target };
                         }
+                        let bin_op = match intrinsic_name {
+                            sym::wrapping_add => BinOp::Add,
+                            sym::wrapping_sub => BinOp::Sub,
+                            sym::wrapping_mul => BinOp::Mul,
+                            sym::unchecked_div => BinOp::Div,
+                            sym::unchecked_rem => BinOp::Rem,
+                            _ => bug!("unexpected intrinsic"),
+                        };
+                        block.statements.push(Statement {
+                            source_info: terminator.source_info,
+                            kind: StatementKind::Assign(Box::new((
+                                *destination,
+                                Rvalue::BinaryOp(bin_op, Box::new((lhs, rhs))),
+                            ))),
+                        });
+                        terminator.kind = TerminatorKind::Goto { target };
                     }
                     sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
                         if let Some(target) = *target {

tests/mir-opt/lower_intrinsics.align_of.LowerIntrinsics.diff

@@ -7,7 +7,7 @@
       bb0: {
 -         _0 = std::intrinsics::min_align_of::<T>() -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:42
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:21:5: 21:40
+-                                          // + span: $DIR/lower_intrinsics.rs:27:5: 27:40
 -                                          // + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::min_align_of::<T>}, val: Value(<ZST>) }
 +         _0 = AlignOf(T);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:42
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:42

tests/mir-opt/lower_intrinsics.assume.LowerIntrinsics.diff

@@ -11,7 +11,7 @@
           StorageLive(_1);                 // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
 -         _1 = std::intrinsics::assume(const true) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:106:9: 106:32
+-                                          // + span: $DIR/lower_intrinsics.rs:112:9: 112:32
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(bool) {std::intrinsics::assume}, val: Value(<ZST>) }
 +         assume(const true);              // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
 +         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38

tests/mir-opt/lower_intrinsics.discriminant.LowerIntrinsics.diff

@@ -31,7 +31,7 @@
           _3 = &(*_4);                     // scope 0 at $DIR/lower_intrinsics.rs:+1:42: +1:44
 -         _2 = discriminant_value::<T>(move _3) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:45
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:82:5: 82:41
+-                                          // + span: $DIR/lower_intrinsics.rs:88:5: 88:41
 -                                          // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a T) -> <T as DiscriminantKind>::Discriminant {discriminant_value::<T>}, val: Value(<ZST>) }
 +         _2 = discriminant((*_3));        // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:45
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:45
@@ -46,13 +46,13 @@
           StorageLive(_7);                 // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
           _19 = const _;                   // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
                                            // mir::Constant
-                                           // + span: $DIR/lower_intrinsics.rs:83:42: 83:44
+                                           // + span: $DIR/lower_intrinsics.rs:89:42: 89:44
                                            // + literal: Const { ty: &i32, val: Unevaluated(discriminant, [T], Some(promoted[2])) }
           _7 = &(*_19);                    // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
           _6 = &(*_7);                     // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
 -         _5 = discriminant_value::<i32>(move _6) -> [return: bb2, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+2:5: +2:45
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:83:5: 83:41
+-                                          // + span: $DIR/lower_intrinsics.rs:89:5: 89:41
 -                                          // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a i32) -> <i32 as DiscriminantKind>::Discriminant {discriminant_value::<i32>}, val: Value(<ZST>) }
 +         _5 = discriminant((*_6));        // scope 0 at $DIR/lower_intrinsics.rs:+2:5: +2:45
 +         goto -> bb2;                     // scope 0 at $DIR/lower_intrinsics.rs:+2:5: +2:45
@@ -67,13 +67,13 @@
           StorageLive(_11);                // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
           _18 = const _;                   // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
                                            // mir::Constant
-                                           // + span: $DIR/lower_intrinsics.rs:84:42: 84:45
+                                           // + span: $DIR/lower_intrinsics.rs:90:42: 90:45
                                            // + literal: Const { ty: &(), val: Unevaluated(discriminant, [T], Some(promoted[1])) }
           _11 = &(*_18);                   // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
           _10 = &(*_11);                   // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
 -         _9 = discriminant_value::<()>(move _10) -> [return: bb3, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+3:5: +3:46
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:84:5: 84:41
+-                                          // + span: $DIR/lower_intrinsics.rs:90:5: 90:41
 -                                          // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a ()) -> <() as DiscriminantKind>::Discriminant {discriminant_value::<()>}, val: Value(<ZST>) }
 +         _9 = discriminant((*_10));       // scope 0 at $DIR/lower_intrinsics.rs:+3:5: +3:46
 +         goto -> bb3;                     // scope 0 at $DIR/lower_intrinsics.rs:+3:5: +3:46
@@ -88,13 +88,13 @@
           StorageLive(_15);                // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
           _17 = const _;                   // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
                                            // mir::Constant
-                                           // + span: $DIR/lower_intrinsics.rs:85:42: 85:47
+                                           // + span: $DIR/lower_intrinsics.rs:91:42: 91:47
                                            // + literal: Const { ty: &E, val: Unevaluated(discriminant, [T], Some(promoted[0])) }
           _15 = &(*_17);                   // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
           _14 = &(*_15);                   // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
 -         _13 = discriminant_value::<E>(move _14) -> [return: bb4, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+4:5: +4:48
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:85:5: 85:41
+-                                          // + span: $DIR/lower_intrinsics.rs:91:5: 91:41
 -                                          // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a E) -> <E as DiscriminantKind>::Discriminant {discriminant_value::<E>}, val: Value(<ZST>) }
 +         _13 = discriminant((*_14));      // scope 0 at $DIR/lower_intrinsics.rs:+4:5: +4:48
 +         goto -> bb4;                     // scope 0 at $DIR/lower_intrinsics.rs:+4:5: +4:48

tests/mir-opt/lower_intrinsics.f_copy_nonoverlapping.LowerIntrinsics.diff

@@ -49,7 +49,7 @@
           StorageDead(_9);                 // scope 3 at $DIR/lower_intrinsics.rs:+4:90: +4:91
 -         _3 = copy_nonoverlapping::<i32>(move _4, move _8, const 0_usize) -> [return: bb1, unwind unreachable]; // scope 3 at $DIR/lower_intrinsics.rs:+4:9: +4:95
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:99:9: 99:28
+-                                          // + span: $DIR/lower_intrinsics.rs:105:9: 105:28
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const i32, *mut i32, usize) {copy_nonoverlapping::<i32>}, val: Value(<ZST>) }
 +         copy_nonoverlapping(dst = move _8, src = move _4, count = const 0_usize); // scope 3 at $DIR/lower_intrinsics.rs:+4:9: +4:95
 +         goto -> bb1;                     // scope 3 at $DIR/lower_intrinsics.rs:+4:9: +4:95

tests/mir-opt/lower_intrinsics.forget.LowerIntrinsics.diff

@@ -11,7 +11,7 @@
           _2 = move _1;                    // scope 0 at $DIR/lower_intrinsics.rs:+1:30: +1:31
 -         _0 = std::intrinsics::forget::<T>(move _2) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:32
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:26:5: 26:29
+-                                          // + span: $DIR/lower_intrinsics.rs:32:5: 32:29
 -                                          // + literal: Const { ty: extern "rust-intrinsic" fn(T) {std::intrinsics::forget::<T>}, val: Value(<ZST>) }
 +         _0 = const ();                   // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:32
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:32

tests/mir-opt/lower_intrinsics.non_const.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           StorageLive(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:+2:9: +2:18
           _1 = std::intrinsics::size_of::<T>; // scope 0 at $DIR/lower_intrinsics.rs:+2:21: +2:51
                                            // mir::Constant
-                                           // + span: $DIR/lower_intrinsics.rs:37:21: 37:51
+                                           // + span: $DIR/lower_intrinsics.rs:43:21: 43:51
                                            // + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}, val: Value(<ZST>) }
           StorageLive(_2);                 // scope 1 at $DIR/lower_intrinsics.rs:+3:5: +3:14
           _2 = _1;                         // scope 1 at $DIR/lower_intrinsics.rs:+3:5: +3:14

tests/mir-opt/lower_intrinsics.option_payload.LowerIntrinsics.diff

@@ -24,7 +24,7 @@
           _4 = &raw const (*_1);           // scope 1 at $DIR/lower_intrinsics.rs:+2:55: +2:56
 -         _3 = option_payload_ptr::<usize>(move _4) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+2:18: +2:57
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:137:18: 137:54
+-                                          // + span: $DIR/lower_intrinsics.rs:143:18: 143:54
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const Option<usize>) -> *const usize {option_payload_ptr::<usize>}, val: Value(<ZST>) }
 +         _3 = &raw const (((*_4) as Some).0: usize); // scope 1 at $DIR/lower_intrinsics.rs:+2:18: +2:57
 +         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:+2:18: +2:57
@@ -37,7 +37,7 @@
           _6 = &raw const (*_2);           // scope 2 at $DIR/lower_intrinsics.rs:+3:55: +3:56
 -         _5 = option_payload_ptr::<String>(move _6) -> [return: bb2, unwind unreachable]; // scope 2 at $DIR/lower_intrinsics.rs:+3:18: +3:57
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:138:18: 138:54
+-                                          // + span: $DIR/lower_intrinsics.rs:144:18: 144:54
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const Option<String>) -> *const String {option_payload_ptr::<String>}, val: Value(<ZST>) }
 +         _5 = &raw const (((*_6) as Some).0: std::string::String); // scope 2 at $DIR/lower_intrinsics.rs:+3:18: +3:57
 +         goto -> bb2;                     // scope 2 at $DIR/lower_intrinsics.rs:+3:18: +3:57

tests/mir-opt/lower_intrinsics.ptr_offset.LowerIntrinsics.diff

@@ -15,7 +15,7 @@
           _4 = _2;                         // scope 0 at $DIR/lower_intrinsics.rs:+1:33: +1:34
 -         _0 = offset::<*const i32, isize>(move _3, move _4) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:35
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:144:5: 144:29
+-                                          // + span: $DIR/lower_intrinsics.rs:150:5: 150:29
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const i32, isize) -> *const i32 {offset::<*const i32, isize>}, val: Value(<ZST>) }
 +         _0 = Offset(move _3, move _4);   // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:35
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:35

tests/mir-opt/lower_intrinsics.read_via_copy_primitive.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           _2 = &raw const (*_1);           // scope 1 at $DIR/lower_intrinsics.rs:+1:46: +1:47
 -         _0 = read_via_copy::<i32>(move _2) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:48
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:119:14: 119:45
+-                                          // + span: $DIR/lower_intrinsics.rs:125:14: 125:45
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const i32) -> i32 {read_via_copy::<i32>}, val: Value(<ZST>) }
 +         _0 = (*_2);                      // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:48
 +         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:48

tests/mir-opt/lower_intrinsics.read_via_copy_uninhabited.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           _2 = &raw const (*_1);           // scope 1 at $DIR/lower_intrinsics.rs:+1:46: +1:47
 -         _0 = read_via_copy::<Never>(move _2) -> unwind unreachable; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:48
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:124:14: 124:45
+-                                          // + span: $DIR/lower_intrinsics.rs:130:14: 130:45
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const Never) -> Never {read_via_copy::<Never>}, val: Value(<ZST>) }
 +         unreachable;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:48
       }

tests/mir-opt/lower_intrinsics.rs

@@ -11,6 +11,12 @@ pub fn wrapping(a: i32, b: i32) {
     let _z = core::intrinsics::wrapping_mul(a, b);
 }
 
+// EMIT_MIR lower_intrinsics.unchecked.LowerIntrinsics.diff
+pub unsafe fn unchecked(a: i32, b: i32) {
+    let _x = core::intrinsics::unchecked_div(a, b);
+    let _y = core::intrinsics::unchecked_rem(a, b);
+}
+
 // EMIT_MIR lower_intrinsics.size_of.LowerIntrinsics.diff
 pub fn size_of<T>() -> usize {
     core::intrinsics::size_of::<T>()

tests/mir-opt/lower_intrinsics.size_of.LowerIntrinsics.diff

@@ -7,7 +7,7 @@
       bb0: {
 -         _0 = std::intrinsics::size_of::<T>() -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:37
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:16:5: 16:35
+-                                          // + span: $DIR/lower_intrinsics.rs:22:5: 22:35
 -                                          // + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}, val: Value(<ZST>) }
 +         _0 = SizeOf(T);                  // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:37
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:37

tests/mir-opt/lower_intrinsics.transmute_inhabited.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           _2 = _1;                         // scope 1 at $DIR/lower_intrinsics.rs:+1:34: +1:35
 -         _0 = transmute::<std::cmp::Ordering, i8>(move _2) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:36
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:43:14: 43:33
+-                                          // + span: $DIR/lower_intrinsics.rs:49:14: 49:33
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(std::cmp::Ordering) -> i8 {transmute::<std::cmp::Ordering, i8>}, val: Value(<ZST>) }
 +         _0 = move _2 as i8 (Transmute);  // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:36
 +         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:36

tests/mir-opt/lower_intrinsics.transmute_ref_dst.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           _2 = _1;                         // scope 1 at $DIR/lower_intrinsics.rs:+1:34: +1:35
 -         _0 = transmute::<&T, *const T>(move _2) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:36
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:53:14: 53:33
+-                                          // + span: $DIR/lower_intrinsics.rs:59:14: 59:33
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(&T) -> *const T {transmute::<&T, *const T>}, val: Value(<ZST>) }
 +         _0 = move _2 as *const T (Transmute); // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:36
 +         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:36

tests/mir-opt/lower_intrinsics.transmute_to_box_uninhabited.LowerIntrinsics.diff

@@ -12,7 +12,7 @@
           StorageLive(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:9: +1:10
 -         _1 = transmute::<usize, Box<Never>>(const 1_usize) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:25: +1:52
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:70:25: 70:44
+-                                          // + span: $DIR/lower_intrinsics.rs:76:25: 76:44
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(usize) -> Box<Never> {transmute::<usize, Box<Never>>}, val: Value(<ZST>) }
 +         _1 = const 1_usize as std::boxed::Box<Never> (Transmute); // scope 0 at $DIR/lower_intrinsics.rs:+1:25: +1:52
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:25: +1:52

tests/mir-opt/lower_intrinsics.transmute_to_mut_uninhabited.LowerIntrinsics.diff

@@ -12,7 +12,7 @@
           StorageLive(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:9: +1:10
 -         _1 = transmute::<usize, &mut Never>(const 1_usize) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:25: +1:52
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:64:25: 64:44
+-                                          // + span: $DIR/lower_intrinsics.rs:70:25: 70:44
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(usize) -> &mut Never {transmute::<usize, &mut Never>}, val: Value(<ZST>) }
 +         _1 = const 1_usize as &mut Never (Transmute); // scope 0 at $DIR/lower_intrinsics.rs:+1:25: +1:52
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:25: +1:52

tests/mir-opt/lower_intrinsics.transmute_to_ref_uninhabited.LowerIntrinsics.diff

@@ -12,7 +12,7 @@
           StorageLive(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:9: +1:10
 -         _1 = transmute::<usize, &Never>(const 1_usize) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:21: +1:48
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:58:21: 58:40
+-                                          // + span: $DIR/lower_intrinsics.rs:64:21: 64:40
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(usize) -> &Never {transmute::<usize, &Never>}, val: Value(<ZST>) }
 +         _1 = const 1_usize as &Never (Transmute); // scope 0 at $DIR/lower_intrinsics.rs:+1:21: +1:48
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:21: +1:48

tests/mir-opt/lower_intrinsics.transmute_uninhabited.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           _2 = _1;                         // scope 1 at $DIR/lower_intrinsics.rs:+1:47: +1:48
 -         _0 = transmute::<(), Never>(move _2) -> unwind unreachable; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:49
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:48:14: 48:46
+-                                          // + span: $DIR/lower_intrinsics.rs:54:14: 54:46
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(()) -> Never {transmute::<(), Never>}, val: Value(<ZST>) }
 +         _0 = move _2 as Never (Transmute); // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:49
 +         unreachable;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:49

tests/mir-opt/lower_intrinsics.unchecked.LowerIntrinsics.diff

@@ -0,0 +1,60 @@
+- // MIR for `unchecked` before LowerIntrinsics
++ // MIR for `unchecked` after LowerIntrinsics
+  
+  fn unchecked(_1: i32, _2: i32) -> () {
+      debug a => _1;                       // in scope 0 at $DIR/lower_intrinsics.rs:+0:25: +0:26
+      debug b => _2;                       // in scope 0 at $DIR/lower_intrinsics.rs:+0:33: +0:34
+      let mut _0: ();                      // return place in scope 0 at $DIR/lower_intrinsics.rs:+0:41: +0:41
+      let _3: i32;                         // in scope 0 at $DIR/lower_intrinsics.rs:+1:9: +1:11
+      let mut _4: i32;                     // in scope 0 at $DIR/lower_intrinsics.rs:+1:46: +1:47
+      let mut _5: i32;                     // in scope 0 at $DIR/lower_intrinsics.rs:+1:49: +1:50
+      let mut _7: i32;                     // in scope 0 at $DIR/lower_intrinsics.rs:+2:46: +2:47
+      let mut _8: i32;                     // in scope 0 at $DIR/lower_intrinsics.rs:+2:49: +2:50
+      scope 1 {
+          debug _x => _3;                  // in scope 1 at $DIR/lower_intrinsics.rs:+1:9: +1:11
+          let _6: i32;                     // in scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:11
+          scope 2 {
+              debug _y => _6;              // in scope 2 at $DIR/lower_intrinsics.rs:+2:9: +2:11
+          }
+      }
+  
+      bb0: {
+          StorageLive(_3);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:9: +1:11
+          StorageLive(_4);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:46: +1:47
+          _4 = _1;                         // scope 0 at $DIR/lower_intrinsics.rs:+1:46: +1:47
+          StorageLive(_5);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:49: +1:50
+          _5 = _2;                         // scope 0 at $DIR/lower_intrinsics.rs:+1:49: +1:50
+-         _3 = unchecked_div::<i32>(move _4, move _5) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:14: +1:51
+-                                          // mir::Constant
+-                                          // + span: $DIR/lower_intrinsics.rs:16:14: 16:45
+-                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(i32, i32) -> i32 {unchecked_div::<i32>}, val: Value(<ZST>) }
++         _3 = Div(move _4, move _5);      // scope 0 at $DIR/lower_intrinsics.rs:+1:14: +1:51
++         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:14: +1:51
+      }
+  
+      bb1: {
+          StorageDead(_5);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:50: +1:51
+          StorageDead(_4);                 // scope 0 at $DIR/lower_intrinsics.rs:+1:50: +1:51
+          StorageLive(_6);                 // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:11
+          StorageLive(_7);                 // scope 1 at $DIR/lower_intrinsics.rs:+2:46: +2:47
+          _7 = _1;                         // scope 1 at $DIR/lower_intrinsics.rs:+2:46: +2:47
+          StorageLive(_8);                 // scope 1 at $DIR/lower_intrinsics.rs:+2:49: +2:50
+          _8 = _2;                         // scope 1 at $DIR/lower_intrinsics.rs:+2:49: +2:50
+-         _6 = unchecked_rem::<i32>(move _7, move _8) -> [return: bb2, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+2:14: +2:51
+-                                          // mir::Constant
+-                                          // + span: $DIR/lower_intrinsics.rs:17:14: 17:45
+-                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(i32, i32) -> i32 {unchecked_rem::<i32>}, val: Value(<ZST>) }
++         _6 = Rem(move _7, move _8);      // scope 1 at $DIR/lower_intrinsics.rs:+2:14: +2:51
++         goto -> bb2;                     // scope 1 at $DIR/lower_intrinsics.rs:+2:14: +2:51
+      }
+  
+      bb2: {
+          StorageDead(_8);                 // scope 1 at $DIR/lower_intrinsics.rs:+2:50: +2:51
+          StorageDead(_7);                 // scope 1 at $DIR/lower_intrinsics.rs:+2:50: +2:51
+          _0 = const ();                   // scope 0 at $DIR/lower_intrinsics.rs:+0:41: +3:2
+          StorageDead(_6);                 // scope 1 at $DIR/lower_intrinsics.rs:+3:1: +3:2
+          StorageDead(_3);                 // scope 0 at $DIR/lower_intrinsics.rs:+3:1: +3:2
+          return;                          // scope 0 at $DIR/lower_intrinsics.rs:+3:2: +3:2
+      }
+  }
+  

tests/mir-opt/lower_intrinsics.unreachable.LowerIntrinsics.diff

@@ -13,7 +13,7 @@
           StorageLive(_2);                 // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:45
 -         _2 = std::intrinsics::unreachable() -> unwind unreachable; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:45
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:31:14: 31:43
+-                                          // + span: $DIR/lower_intrinsics.rs:37:14: 37:43
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn() -> ! {std::intrinsics::unreachable}, val: Value(<ZST>) }
 +         unreachable;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:45
       }

tests/mir-opt/lower_intrinsics.with_overflow.LowerIntrinsics.diff

@@ -32,7 +32,7 @@
           _5 = _2;                         // scope 0 at $DIR/lower_intrinsics.rs:+1:53: +1:54
 -         _3 = add_with_overflow::<i32>(move _4, move _5) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:14: +1:55
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:112:14: 112:49
+-                                          // + span: $DIR/lower_intrinsics.rs:118:14: 118:49
 -                                          // + literal: Const { ty: extern "rust-intrinsic" fn(i32, i32) -> (i32, bool) {add_with_overflow::<i32>}, val: Value(<ZST>) }
 +         _3 = CheckedAdd(move _4, move _5); // scope 0 at $DIR/lower_intrinsics.rs:+1:14: +1:55
 +         goto -> bb1;                     // scope 0 at $DIR/lower_intrinsics.rs:+1:14: +1:55
@@ -48,7 +48,7 @@
           _8 = _2;                         // scope 1 at $DIR/lower_intrinsics.rs:+2:53: +2:54
 -         _6 = sub_with_overflow::<i32>(move _7, move _8) -> [return: bb2, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+2:14: +2:55
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:113:14: 113:49
+-                                          // + span: $DIR/lower_intrinsics.rs:119:14: 119:49
 -                                          // + literal: Const { ty: extern "rust-intrinsic" fn(i32, i32) -> (i32, bool) {sub_with_overflow::<i32>}, val: Value(<ZST>) }
 +         _6 = CheckedSub(move _7, move _8); // scope 1 at $DIR/lower_intrinsics.rs:+2:14: +2:55
 +         goto -> bb2;                     // scope 1 at $DIR/lower_intrinsics.rs:+2:14: +2:55
@@ -64,7 +64,7 @@
           _11 = _2;                        // scope 2 at $DIR/lower_intrinsics.rs:+3:53: +3:54
 -         _9 = mul_with_overflow::<i32>(move _10, move _11) -> [return: bb3, unwind unreachable]; // scope 2 at $DIR/lower_intrinsics.rs:+3:14: +3:55
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:114:14: 114:49
+-                                          // + span: $DIR/lower_intrinsics.rs:120:14: 120:49
 -                                          // + literal: Const { ty: extern "rust-intrinsic" fn(i32, i32) -> (i32, bool) {mul_with_overflow::<i32>}, val: Value(<ZST>) }
 +         _9 = CheckedMul(move _10, move _11); // scope 2 at $DIR/lower_intrinsics.rs:+3:14: +3:55
 +         goto -> bb3;                     // scope 2 at $DIR/lower_intrinsics.rs:+3:14: +3:55

tests/mir-opt/lower_intrinsics.write_via_move_string.LowerIntrinsics.diff

@@ -17,7 +17,7 @@
           _4 = move _2;                    // scope 1 at $DIR/lower_intrinsics.rs:+1:50: +1:51
 -         _0 = write_via_move::<String>(move _3, move _4) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:52
 -                                          // mir::Constant
--                                          // + span: $DIR/lower_intrinsics.rs:129:14: 129:46
+-                                          // + span: $DIR/lower_intrinsics.rs:135:14: 135:46
 -                                          // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*mut String, String) {write_via_move::<String>}, val: Value(<ZST>) }
 +         (*_3) = move _4;                 // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:52
 +         goto -> bb1;                     // scope 1 at $DIR/lower_intrinsics.rs:+1:14: +1:52