Rollup merge of #98441 - calebzulawski:simd_as, r=oli-obk

Implement simd_as for pointers

Expands `simd_as` (and `simd_cast`) to handle pointer-to-pointer, pointer-to-integer, and integer-to-pointer conversions.

cc ``@programmerjake`` ``@thomcc``

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -1705,6 +1705,97 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
     bitwise_red!(simd_reduce_all: vector_reduce_and, true);
     bitwise_red!(simd_reduce_any: vector_reduce_or, true);
 
+    if name == sym::simd_cast_ptr {
+        require_simd!(ret_ty, "return");
+        let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
+        require!(
+            in_len == out_len,
+            "expected return type with length {} (same as input type `{}`), \
+                  found `{}` with length {}",
+            in_len,
+            in_ty,
+            ret_ty,
+            out_len
+        );
+
+        match in_elem.kind() {
+            ty::RawPtr(p) => {
+                let (metadata, check_sized) = p.ty.ptr_metadata_ty(bx.tcx, |ty| {
+                    bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
+                });
+                assert!(!check_sized); // we are in codegen, so we shouldn't see these types
+                require!(metadata.is_unit(), "cannot cast fat pointer `{}`", in_elem)
+            }
+            _ => return_error!("expected pointer, got `{}`", in_elem),
+        }
+        match out_elem.kind() {
+            ty::RawPtr(p) => {
+                let (metadata, check_sized) = p.ty.ptr_metadata_ty(bx.tcx, |ty| {
+                    bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
+                });
+                assert!(!check_sized); // we are in codegen, so we shouldn't see these types
+                require!(metadata.is_unit(), "cannot cast to fat pointer `{}`", out_elem)
+            }
+            _ => return_error!("expected pointer, got `{}`", out_elem),
+        }
+
+        if in_elem == out_elem {
+            return Ok(args[0].immediate());
+        } else {
+            return Ok(bx.pointercast(args[0].immediate(), llret_ty));
+        }
+    }
+
+    if name == sym::simd_expose_addr {
+        require_simd!(ret_ty, "return");
+        let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
+        require!(
+            in_len == out_len,
+            "expected return type with length {} (same as input type `{}`), \
+                  found `{}` with length {}",
+            in_len,
+            in_ty,
+            ret_ty,
+            out_len
+        );
+
+        match in_elem.kind() {
+            ty::RawPtr(_) => {}
+            _ => return_error!("expected pointer, got `{}`", in_elem),
+        }
+        match out_elem.kind() {
+            ty::Uint(ty::UintTy::Usize) => {}
+            _ => return_error!("expected `usize`, got `{}`", out_elem),
+        }
+
+        return Ok(bx.ptrtoint(args[0].immediate(), llret_ty));
+    }
+
+    if name == sym::simd_from_exposed_addr {
+        require_simd!(ret_ty, "return");
+        let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
+        require!(
+            in_len == out_len,
+            "expected return type with length {} (same as input type `{}`), \
+                  found `{}` with length {}",
+            in_len,
+            in_ty,
+            ret_ty,
+            out_len
+        );
+
+        match in_elem.kind() {
+            ty::Uint(ty::UintTy::Usize) => {}
+            _ => return_error!("expected `usize`, got `{}`", in_elem),
+        }
+        match out_elem.kind() {
+            ty::RawPtr(_) => {}
+            _ => return_error!("expected pointer, got `{}`", out_elem),
+        }
+
+        return Ok(bx.inttoptr(args[0].immediate(), llret_ty));
+    }
+
     if name == sym::simd_cast || name == sym::simd_as {
         require_simd!(ret_ty, "return");
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());