Rollup merge of rust-lang#144667 - scottmcm:alignment-is-usize, r=tgross35

Zalathar · web-flow · commit 85ded3556f07 · 2025-08-03T13:53:12.000+10:00
`AlignmentEnum` should just be `repr(usize)` now

These used to use specific sizes because they were compiled on all widths.  But now that the types themselves are `#[cfg]`'d, we can save some conversions by having it always be `repr(usize)`.
diff --git a/library/core/src/ptr/alignment.rs b/library/core/src/ptr/alignment.rs
@@ -1,3 +1,5 @@
+#![allow(clippy::enum_clike_unportable_variant)]
+
 use crate::num::NonZero;
 use crate::ub_checks::assert_unsafe_precondition;
 use crate::{cmp, fmt, hash, mem, num};
@@ -241,7 +243,7 @@ impl const Default for Alignment {
 
 #[cfg(target_pointer_width = "16")]
 #[derive(Copy, Clone, PartialEq, Eq)]
-#[repr(u16)]
+#[repr(usize)]
 enum AlignmentEnum {
     _Align1Shl0 = 1 << 0,
     _Align1Shl1 = 1 << 1,
@@ -263,7 +265,7 @@ enum AlignmentEnum {
 
 #[cfg(target_pointer_width = "32")]
 #[derive(Copy, Clone, PartialEq, Eq)]
-#[repr(u32)]
+#[repr(usize)]
 enum AlignmentEnum {
     _Align1Shl0 = 1 << 0,
     _Align1Shl1 = 1 << 1,
@@ -301,7 +303,7 @@ enum AlignmentEnum {
 
 #[cfg(target_pointer_width = "64")]
 #[derive(Copy, Clone, PartialEq, Eq)]
-#[repr(u64)]
+#[repr(usize)]
 enum AlignmentEnum {
     _Align1Shl0 = 1 << 0,
     _Align1Shl1 = 1 << 1,
diff --git a/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.32bit.panic-abort.mir b/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.32bit.panic-abort.mir
@@ -8,7 +8,7 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
             let _2: std::ptr::NonNull<[T]>;
             let mut _3: *mut [T];
             let mut _4: *const [T];
-            let _12: ();
+            let _11: ();
             scope 3 {
                 let _8: std::ptr::alignment::AlignmentEnum;
                 scope 4 {
@@ -31,12 +31,11 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
                         scope 20 (inlined NonNull::<u8>::as_ptr) {
                         }
                         scope 21 (inlined std::alloc::dealloc) {
-                            let mut _11: usize;
+                            let mut _10: usize;
                             scope 22 (inlined Layout::size) {
                             }
                             scope 23 (inlined Layout::align) {
                                 scope 24 (inlined std::ptr::Alignment::as_usize) {
-                                    let mut _10: u32;
                                 }
                             }
                         }
@@ -87,16 +86,13 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
     bb2: {
         StorageLive(_9);
         _9 = copy _3 as *mut u8 (PtrToPtr);
-        StorageLive(_11);
         StorageLive(_10);
         _10 = discriminant(_8);
-        _11 = move _10 as usize (IntToInt);
-        StorageDead(_10);
-        _12 = alloc::alloc::__rust_dealloc(move _9, move _5, move _11) -> [return: bb3, unwind unreachable];
+        _11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
     }
 
     bb3: {
-        StorageDead(_11);
+        StorageDead(_10);
         StorageDead(_9);
         goto -> bb4;
     }
diff --git a/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.32bit.panic-unwind.mir b/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.32bit.panic-unwind.mir
@@ -8,7 +8,7 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
             let _2: std::ptr::NonNull<[T]>;
             let mut _3: *mut [T];
             let mut _4: *const [T];
-            let _12: ();
+            let _11: ();
             scope 3 {
                 let _8: std::ptr::alignment::AlignmentEnum;
                 scope 4 {
@@ -31,12 +31,11 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
                         scope 20 (inlined NonNull::<u8>::as_ptr) {
                         }
                         scope 21 (inlined std::alloc::dealloc) {
-                            let mut _11: usize;
+                            let mut _10: usize;
                             scope 22 (inlined Layout::size) {
                             }
                             scope 23 (inlined Layout::align) {
                                 scope 24 (inlined std::ptr::Alignment::as_usize) {
-                                    let mut _10: u32;
                                 }
                             }
                         }
@@ -87,16 +86,13 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
     bb2: {
         StorageLive(_9);
         _9 = copy _3 as *mut u8 (PtrToPtr);
-        StorageLive(_11);
         StorageLive(_10);
         _10 = discriminant(_8);
-        _11 = move _10 as usize (IntToInt);
-        StorageDead(_10);
-        _12 = alloc::alloc::__rust_dealloc(move _9, move _5, move _11) -> [return: bb3, unwind unreachable];
+        _11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
     }
 
     bb3: {
-        StorageDead(_11);
+        StorageDead(_10);
         StorageDead(_9);
         goto -> bb4;
     }
diff --git a/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.64bit.panic-abort.mir b/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.64bit.panic-abort.mir
@@ -8,7 +8,7 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
             let _2: std::ptr::NonNull<[T]>;
             let mut _3: *mut [T];
             let mut _4: *const [T];
-            let _12: ();
+            let _11: ();
             scope 3 {
                 let _8: std::ptr::alignment::AlignmentEnum;
                 scope 4 {
@@ -31,12 +31,11 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
                         scope 20 (inlined NonNull::<u8>::as_ptr) {
                         }
                         scope 21 (inlined std::alloc::dealloc) {
-                            let mut _11: usize;
+                            let mut _10: usize;
                             scope 22 (inlined Layout::size) {
                             }
                             scope 23 (inlined Layout::align) {
                                 scope 24 (inlined std::ptr::Alignment::as_usize) {
-                                    let mut _10: u64;
                                 }
                             }
                         }
@@ -87,16 +86,13 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
     bb2: {
         StorageLive(_9);
         _9 = copy _3 as *mut u8 (PtrToPtr);
-        StorageLive(_11);
         StorageLive(_10);
         _10 = discriminant(_8);
-        _11 = move _10 as usize (IntToInt);
-        StorageDead(_10);
-        _12 = alloc::alloc::__rust_dealloc(move _9, move _5, move _11) -> [return: bb3, unwind unreachable];
+        _11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
     }
 
     bb3: {
-        StorageDead(_11);
+        StorageDead(_10);
         StorageDead(_9);
         goto -> bb4;
     }
diff --git a/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.64bit.panic-unwind.mir b/tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.64bit.panic-unwind.mir
@@ -8,7 +8,7 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
             let _2: std::ptr::NonNull<[T]>;
             let mut _3: *mut [T];
             let mut _4: *const [T];
-            let _12: ();
+            let _11: ();
             scope 3 {
                 let _8: std::ptr::alignment::AlignmentEnum;
                 scope 4 {
@@ -31,12 +31,11 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
                         scope 20 (inlined NonNull::<u8>::as_ptr) {
                         }
                         scope 21 (inlined std::alloc::dealloc) {
-                            let mut _11: usize;
+                            let mut _10: usize;
                             scope 22 (inlined Layout::size) {
                             }
                             scope 23 (inlined Layout::align) {
                                 scope 24 (inlined std::ptr::Alignment::as_usize) {
-                                    let mut _10: u64;
                                 }
                             }
                         }
@@ -87,16 +86,13 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
     bb2: {
         StorageLive(_9);
         _9 = copy _3 as *mut u8 (PtrToPtr);
-        StorageLive(_11);
         StorageLive(_10);
         _10 = discriminant(_8);
-        _11 = move _10 as usize (IntToInt);
-        StorageDead(_10);
-        _12 = alloc::alloc::__rust_dealloc(move _9, move _5, move _11) -> [return: bb3, unwind unreachable];
+        _11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
     }
 
     bb3: {
-        StorageDead(_11);
+        StorageDead(_10);
         StorageDead(_9);
         goto -> bb4;
     }
diff --git a/tests/mir-opt/pre-codegen/drop_boxed_slice.rs b/tests/mir-opt/pre-codegen/drop_boxed_slice.rs
@@ -13,7 +13,6 @@ pub unsafe fn generic_in_place<T: Copy>(ptr: *mut Box<[T]>) {
     // CHECK: [[B:_.+]] = copy [[ALIGN]] as std::ptr::Alignment (Transmute);
     // CHECK: [[C:_.+]] = move ([[B]].0: std::ptr::alignment::AlignmentEnum);
     // CHECK: [[D:_.+]] = discriminant([[C]]);
-    // CHECK: [[E:_.+]] = move [[D]] as usize (IntToInt);
-    // CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[E]]) ->
+    // CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[D]]) ->
     std::ptr::drop_in_place(ptr)
 }

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {`
`8`	`8`	`let _2: std::ptr::NonNull<[T]>;`
`9`	`9`	`let mut _3: *mut [T];`
`10`	`10`	`let mut _4: *const [T];`
`11`		`- let _12: ();`
	`11`	`+ let _11: ();`
`12`	`12`	`scope 3 {`
`13`	`13`	`let _8: std::ptr::alignment::AlignmentEnum;`
`14`	`14`	`scope 4 {`
`@@ -31,12 +31,11 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {`
`31`	`31`	`scope 20 (inlined NonNull::<u8>::as_ptr) {`
`32`	`32`	`}`
`33`	`33`	`scope 21 (inlined std::alloc::dealloc) {`
`34`		`- let mut _11: usize;`
	`34`	`+ let mut _10: usize;`
`35`	`35`	`scope 22 (inlined Layout::size) {`
`36`	`36`	`}`
`37`	`37`	`scope 23 (inlined Layout::align) {`
`38`	`38`	`scope 24 (inlined std::ptr::Alignment::as_usize) {`
`39`		`- let mut _10: u32;`
`40`	`39`	`}`
`41`	`40`	`}`
`42`	`41`	`}`
`@@ -87,16 +86,13 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {`
`87`	`86`	`bb2: {`
`88`	`87`	`StorageLive(_9);`
`89`	`88`	`_9 = copy _3 as *mut u8 (PtrToPtr);`
`90`		`- StorageLive(_11);`
`91`	`89`	`StorageLive(_10);`
`92`	`90`	`_10 = discriminant(_8);`
`93`		`- _11 = move _10 as usize (IntToInt);`
`94`		`- StorageDead(_10);`
`95`		`- _12 = alloc::alloc::__rust_dealloc(move _9, move _5, move _11) -> [return: bb3, unwind unreachable];`
	`91`	`+ _11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];`
`96`	`92`	`}`
`97`	`93`
`98`	`94`	`bb3: {`
`99`		`- StorageDead(_11);`
	`95`	`+ StorageDead(_10);`
`100`	`96`	`StorageDead(_9);`
`101`	`97`	`goto -> bb4;`
`102`	`98`	`}`
Original file line number	Diff line number	Diff line change
`@@ -13,7 +13,6 @@ pub unsafe fn generic_in_place<T: Copy>(ptr: *mut Box<[T]>) {`
`13`	`13`	`// CHECK: [[B:_.+]] = copy [[ALIGN]] as std::ptr::Alignment (Transmute);`
`14`	`14`	`// CHECK: [[C:_.+]] = move ([[B]].0: std::ptr::alignment::AlignmentEnum);`
`15`	`15`	`// CHECK: [[D:_.+]] = discriminant([[C]]);`
`16`		`- // CHECK: [[E:_.+]] = move [[D]] as usize (IntToInt);`
`17`		`- // CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[E]]) ->`
	`16`	`+ // CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[D]]) ->`
`18`	`17`	`std::ptr::drop_in_place(ptr)`
`19`	`18`	`}`