Auto merge of #85919 - workingjubilee:simd-ptrs-are-valid, r=petrochenkov

Allow raw pointers in SIMD types

Closes #85915 by loosening the strictness in typechecking and adding a test to guarantee it passes.

This still might be too strict, as references currently do pass monomorphization, but my understanding is that they are not guaranteed to be "scalar" in the same way.

2 files changed, 12 insertions, 8 deletions

diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 012d9bd82c8..c1f71fbbfa4 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -1891,11 +1891,6 @@ impl<'tcx> TyS<'tcx> {
     }
 
     #[inline]
-    pub fn is_machine(&self) -> bool {
-        matches!(self.kind(), Int(..) | Uint(..) | Float(..))
-    }
-
-    #[inline]
     pub fn has_concrete_skeleton(&self) -> bool {
         !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
     }
diff --git a/compiler/rustc_typeck/src/check/check.rs b/compiler/rustc_typeck/src/check/check.rs
index 92d7ea26003..166410731d2 100644
--- a/compiler/rustc_typeck/src/check/check.rs
+++ b/compiler/rustc_typeck/src/check/check.rs
@@ -1214,10 +1214,19 @@ pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
                 }
             }
 
+            // Check that we use types valid for use in the lanes of a SIMD "vector register"
+            // These are scalar types which directly match a "machine" type
+            // Yes: Integers, floats, "thin" pointers
+            // No: char, "fat" pointers, compound types
             match e.kind() {
-                ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
-                _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
-                ty::Array(ty, _c) if ty.is_machine() => { /* struct([f32; 4]) */ }
+                ty::Param(_) => (), // pass struct<T>(T, T, T, T) through, let monomorphization catch errors
+                ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) => (), // struct(u8, u8, u8, u8) is ok
+                ty::Array(t, _clen)
+                    if matches!(
+                        t.kind(),
+                        ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_)
+                    ) =>
+                { /* struct([f32; 4]) is ok */ }
                 _ => {
                     struct_span_err!(
                         tcx.sess,