Revert non-power-of-two vector restriction

src/test/ui/simd/issue-17170.rs

@@ -1,8 +1,8 @@
+// run-pass
 #![feature(repr_simd)]
 
 #[repr(simd)]
 struct T(f64, f64, f64);
-//~^ ERROR SIMD vector length must be a power of two
 
 static X: T = T(0.0, 0.0, 0.0);
 

src/test/ui/simd/issue-17170.stderr

@@ -1,11 +0,0 @@
-error[E0075]: SIMD vector length must be a power of two
-  --> $DIR/issue-17170.rs:4:1
-   |
-LL | struct T(f64, f64, f64);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: monomorphising SIMD type `T` of non-power-of-two length
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0075`.

src/test/ui/simd/issue-39720.rs

@@ -1,3 +1,4 @@
+// run-pass
 // ignore-emscripten FIXME(#45351)
 
 #![feature(repr_simd, platform_intrinsics)]
@@ -5,12 +6,10 @@
 #[repr(simd)]
 #[derive(Copy, Clone, Debug)]
 pub struct Char3(pub i8, pub i8, pub i8);
-//~^ ERROR SIMD vector length must be a power of two
 
 #[repr(simd)]
 #[derive(Copy, Clone, Debug)]
 pub struct Short3(pub i16, pub i16, pub i16);
-//~^ ERROR SIMD vector length must be a power of two
 
 extern "platform-intrinsic" {
     fn simd_cast<T, U>(x: T) -> U;

src/test/ui/simd/issue-39720.stderr

@@ -1,15 +0,0 @@
-error[E0075]: SIMD vector length must be a power of two
-  --> $DIR/issue-39720.rs:7:1
-   |
-LL | pub struct Char3(pub i8, pub i8, pub i8);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error[E0075]: SIMD vector length must be a power of two
-  --> $DIR/issue-39720.rs:12:1
-   |
-LL | pub struct Short3(pub i16, pub i16, pub i16);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0075`.

src/test/ui/simd/simd-type.stderr

@@ -10,12 +10,6 @@ error[E0075]: SIMD vector cannot be empty
 LL | struct empty2([f32; 0]);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0075]: SIMD vector length must be a power of two
-  --> $DIR/simd-type.rs:13:1
-   |
-LL | struct pow2([f32; 7]);
-   | ^^^^^^^^^^^^^^^^^^^^^^
-
 error[E0076]: SIMD vector should be homogeneous
   --> $DIR/simd-type.rs:16:1
    |