Revert non-power-of-two vector restriction

compiler/rustc_middle/src/ty/layout.rs

@@ -732,11 +732,6 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                 // Can't be caught in typeck if the array length is generic.
                 if e_len == 0 {
                     tcx.sess.fatal(&format!("monomorphising SIMD type `{}` of zero length", ty));
-                } else if !e_len.is_power_of_two() {
-                    tcx.sess.fatal(&format!(
-                        "monomorphising SIMD type `{}` of non-power-of-two length",
-                        ty
-                    ));
                 } else if e_len > MAX_SIMD_LANES {
                     tcx.sess.fatal(&format!(
                         "monomorphising SIMD type `{}` of length greater than {}",

compiler/rustc_typeck/src/check/check.rs

@@ -1161,15 +1161,6 @@ pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
                 if len == 0 {
                     struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
                     return;
-                } else if !len.is_power_of_two() {
-                    struct_span_err!(
-                        tcx.sess,
-                        sp,
-                        E0075,
-                        "SIMD vector length must be a power of two"
-                    )
-                    .emit();
-                    return;
                 } else if len > MAX_SIMD_LANES {
                     struct_span_err!(
                         tcx.sess,

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-39720.rs

@@ -1,16 +1,15 @@
+// run-pass
 // ignore-emscripten FIXME(#45351)
 
 #![feature(repr_simd, platform_intrinsics)]
 
 #[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/simd-type-generic-monomorphisation-power-of-two.rs

@@ -1,9 +1,7 @@
-// build-fail
+// run-pass
 
 #![feature(repr_simd, platform_intrinsics)]
 
-// error-pattern:monomorphising SIMD type `Simd<3_usize>` of non-power-of-two length
-
 #[repr(simd)]
 struct Simd<const N: usize>([f32; N]);
 

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

@@ -10,7 +10,7 @@ struct empty; //~ ERROR SIMD vector cannot be empty
 struct empty2([f32; 0]); //~ ERROR SIMD vector cannot be empty
 
 #[repr(simd)]
-struct pow2([f32; 7]); //~ ERROR SIMD vector length must be a power of two
+struct pow2([f32; 7]);
 
 #[repr(simd)]
 struct i64f64(i64, f64); //~ ERROR SIMD vector should be homogeneous

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
    |
@@ -40,7 +34,7 @@ error[E0075]: SIMD vector cannot have more than 32768 elements
 LL | struct TooBig([f32; 65536]);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 7 previous errors
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0075, E0076, E0077.
 For more information about an error, try `rustc --explain E0075`.