8 files changed, 134 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,
diff --git a/src/test/ui/simd/issue-85915-simd-ptrs.rs b/src/test/ui/simd/issue-85915-simd-ptrs.rs
new file mode 100644
index 00000000000..6fe415545f8
--- /dev/null
+++ b/src/test/ui/simd/issue-85915-simd-ptrs.rs
@@ -0,0 +1,67 @@
+// run-pass
+// ignore-emscripten
+
+// Short form of the generic gather/scatter tests,
+// verifying simd([*const T; N]) and simd([*mut T; N]) pass typeck and work.
+#![feature(repr_simd, platform_intrinsics)]
+#![allow(non_camel_case_types)]
+
+#[repr(simd)]
+#[derive(Copy, Clone, PartialEq, Debug)]
+struct cptrx4<T>([*const T; 4]);
+
+#[repr(simd)]
+#[derive(Copy, Clone, PartialEq, Debug)]
+struct mptrx4<T>([*mut T; 4]);
+
+#[repr(simd)]
+#[derive(Copy, Clone, PartialEq, Debug)]
+struct f32x4([f32; 4]);
+
+#[repr(simd)]
+#[derive(Copy, Clone, PartialEq, Debug)]
+struct i32x4([i32; 4]);
+
+extern "platform-intrinsic" {
+    fn simd_gather<T, U, V>(x: T, y: U, z: V) -> T;
+    fn simd_scatter<T, U, V>(x: T, y: U, z: V) -> ();
+}
+
+fn main() {
+    let mut x = [0_f32, 1., 2., 3., 4., 5., 6., 7.];
+
+    let default = f32x4([-3_f32, -3., -3., -3.]);
+    let s_strided = f32x4([0_f32, 2., -3., 6.]);
+    let mask = i32x4([-1_i32, -1, 0, -1]);
+
+    // reading from *const
+    unsafe {
+        let pointer = &x as *const f32;
+        let pointers =  cptrx4([
+            pointer.offset(0) as *const f32,
+            pointer.offset(2),
+            pointer.offset(4),
+            pointer.offset(6)
+        ]);
+
+        let r_strided = simd_gather(default, pointers, mask);
+
+        assert_eq!(r_strided, s_strided);
+    }
+
+    // writing to *mut
+    unsafe {
+        let pointer = &mut x as *mut f32;
+        let pointers = mptrx4([
+            pointer.offset(0) as *mut f32,
+            pointer.offset(2),
+            pointer.offset(4),
+            pointer.offset(6)
+        ]);
+
+        let values = f32x4([42_f32, 43_f32, 44_f32, 45_f32]);
+        simd_scatter(values, pointers, mask);
+
+        assert_eq!(x, [42., 1., 43., 3., 4., 5., 45., 7.]);
+    }
+}
diff --git a/src/test/ui/simd/simd-type-generic-monomorphisation-extern-nonnull-ptr.rs b/src/test/ui/simd/simd-type-generic-monomorphisation-extern-nonnull-ptr.rs
new file mode 100644
index 00000000000..ae321c974b9
--- /dev/null
+++ b/src/test/ui/simd/simd-type-generic-monomorphisation-extern-nonnull-ptr.rs
@@ -0,0 +1,23 @@
+// run-pass
+// ignore-emscripten
+
+#![feature(extern_types)]
+#![feature(repr_simd)]
+
+use std::ptr::NonNull;
+
+extern {
+    type Extern;
+}
+
+#[repr(simd)]
+struct S<T>(T);
+
+#[inline(never)]
+fn identity<T>(v: T) -> T {
+    v
+}
+
+fn main() {
+    let _v: S<[Option<NonNull<Extern>>; 4]> = identity(S([None; 4]));
+}
diff --git a/src/test/ui/simd/simd-type-generic-monomorphisation-wide-ptr.rs b/src/test/ui/simd/simd-type-generic-monomorphisation-wide-ptr.rs
new file mode 100644
index 00000000000..3e02b08ce5d
--- /dev/null
+++ b/src/test/ui/simd/simd-type-generic-monomorphisation-wide-ptr.rs
@@ -0,0 +1,12 @@
+// build-fail
+
+#![feature(repr_simd)]
+
+// error-pattern:monomorphising SIMD type `S<[*mut [u8]; 4]>` with a non-primitive-scalar (integer/float/pointer) element type `*mut [u8]`
+
+#[repr(simd)]
+struct S<T>(T);
+
+fn main() {
+    let _v: Option<S<[*mut [u8]; 4]>> = None;
+}
diff --git a/src/test/ui/simd/simd-type-generic-monomorphisation-wide-ptr.stderr b/src/test/ui/simd/simd-type-generic-monomorphisation-wide-ptr.stderr
new file mode 100644
index 00000000000..3888e7a0f38
--- /dev/null
+++ b/src/test/ui/simd/simd-type-generic-monomorphisation-wide-ptr.stderr
@@ -0,0 +1,4 @@
+error: monomorphising SIMD type `S<[*mut [u8]; 4]>` with a non-primitive-scalar (integer/float/pointer) element type `*mut [u8]`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/simd/simd-type-wide-ptr.rs b/src/test/ui/simd/simd-type-wide-ptr.rs
new file mode 100644
index 00000000000..88f62a07ea0
--- /dev/null
+++ b/src/test/ui/simd/simd-type-wide-ptr.rs
@@ -0,0 +1,12 @@
+// build-fail
+
+#![feature(repr_simd)]
+
+// error-pattern:monomorphising SIMD type `S` with a non-primitive-scalar (integer/float/pointer) element type `*mut [u8]`
+
+#[repr(simd)]
+struct S([*mut [u8]; 4]);
+
+fn main() {
+    let _v: Option<S> = None;
+}
diff --git a/src/test/ui/simd/simd-type-wide-ptr.stderr b/src/test/ui/simd/simd-type-wide-ptr.stderr
new file mode 100644
index 00000000000..51d3c005072
--- /dev/null
+++ b/src/test/ui/simd/simd-type-wide-ptr.stderr
@@ -0,0 +1,4 @@
+error: monomorphising SIMD type `S` with a non-primitive-scalar (integer/float/pointer) element type `*mut [u8]`
+
+error: aborting due to previous error
+