Auto merge of #143833 - scottmcm:final-mcp-838, r=compiler-errors

Ban projecting into SIMD types [MCP838]

Closes rust-lang/compiler-team#838

The actual compiler change here is tiny; there's just a bazillion tests to update.

~~Since I'm sure I've missed some, for now~~
~~r ghost~~

try-job: test-various
try-job: x86_64-gnu-nopt

Author: bors

example/float-minmax-pass.rs

@@ -11,6 +11,12 @@
 #[derive(Copy, Clone, PartialEq, Debug)]
 struct f32x4(pub [f32; 4]);
 
+impl f32x4 {
+    fn into_array(self) -> [f32; 4] {
+        unsafe { std::mem::transmute(self) }
+    }
+}
+
 use std::intrinsics::simd::*;
 
 fn main() {
@@ -29,22 +35,22 @@ fn main() {
     unsafe {
         let min0 = simd_fmin(x, y);
         let min1 = simd_fmin(y, x);
-        assert_eq!(min0, min1);
+        assert_eq!(min0.into_array(), min1.into_array());
         let e = f32x4([1.0, 1.0, 3.0, 3.0]);
-        assert_eq!(min0, e);
+        assert_eq!(min0.into_array(), e.into_array());
         let minn = simd_fmin(x, n);
-        assert_eq!(minn, x);
+        assert_eq!(minn.into_array(), x.into_array());
         let minn = simd_fmin(y, n);
-        assert_eq!(minn, y);
+        assert_eq!(minn.into_array(), y.into_array());
 
         let max0 = simd_fmax(x, y);
         let max1 = simd_fmax(y, x);
-        assert_eq!(max0, max1);
+        assert_eq!(max0.into_array(), max1.into_array());
         let e = f32x4([2.0, 2.0, 4.0, 4.0]);
-        assert_eq!(max0, e);
+        assert_eq!(max0.into_array(), e.into_array());
         let maxn = simd_fmax(x, n);
-        assert_eq!(maxn, x);
+        assert_eq!(maxn.into_array(), x.into_array());
         let maxn = simd_fmax(y, n);
-        assert_eq!(maxn, y);
+        assert_eq!(maxn.into_array(), y.into_array());
     }
 }

example/mini_core_hello_world.rs

@@ -348,7 +348,8 @@ fn main() {
     struct V([f64; 2]);
 
     let f = V([0.0, 1.0]);
-    let _a = f.0[0];
+    let fp = (&raw const f) as *const [f64; 2];
+    let _a = (unsafe { &*fp })[0];
 
     stack_val_align();
 }