Auto merge of #121516 - RalfJung:platform-intrinsics-begone, r=oli-obk

remove platform-intrinsics ABI; make SIMD intrinsics be regular intrinsics

`@Amanieu` `@workingjubilee` I don't think there is any reason these need to be "special"? The [original RFC](https://rust-lang.github.io/rfcs/1199-simd-infrastructure.html) indicated eventually making them stable, but I think that is no longer the plan, so seems to me like we can clean this up a bit.

Blocked on rust-lang/stdarch#1538, rust-lang/rust#121542.

Author: bors

tests/fail/intrinsics/simd-div-by-zero.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    pub(crate) fn simd_div<T>(x: T, y: T) -> T;
-}
+use std::intrinsics::simd::simd_div;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-div-overflow.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    pub(crate) fn simd_div<T>(x: T, y: T) -> T;
-}
+use std::intrinsics::simd::simd_div;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-reduce-invalid-bool.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    pub(crate) fn simd_reduce_any<T>(x: T) -> bool;
-}
+use std::intrinsics::simd::simd_reduce_any;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-rem-by-zero.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    pub(crate) fn simd_rem<T>(x: T, y: T) -> T;
-}
+use std::intrinsics::simd::simd_rem;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-select-bitmask-invalid.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    fn simd_select_bitmask<M, T>(m: M, yes: T, no: T) -> T;
-}
+use std::intrinsics::simd::simd_select_bitmask;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-select-invalid-bool.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    fn simd_select<M, T>(m: M, yes: T, no: T) -> T;
-}
+use std::intrinsics::simd::simd_select;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-shl-too-far.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    pub(crate) fn simd_shl<T>(x: T, y: T) -> T;
-}
+use std::intrinsics::simd::simd_shl;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/fail/intrinsics/simd-shr-too-far.rs

@@ -1,8 +1,6 @@
-#![feature(platform_intrinsics, repr_simd)]
+#![feature(core_intrinsics, repr_simd)]
 
-extern "platform-intrinsic" {
-    pub(crate) fn simd_shr<T>(x: T, y: T) -> T;
-}
+use std::intrinsics::simd::simd_shr;
 
 #[repr(simd)]
 #[allow(non_camel_case_types)]

tests/pass/float_nan.rs

@@ -1,4 +1,4 @@
-#![feature(float_gamma, portable_simd, core_intrinsics, platform_intrinsics)]
+#![feature(float_gamma, portable_simd, core_intrinsics)]
 use std::collections::HashSet;
 use std::fmt;
 use std::hash::Hash;
@@ -525,12 +525,6 @@ fn test_simd() {
     use std::intrinsics::simd::*;
     use std::simd::*;
 
-    extern "platform-intrinsic" {
-        fn simd_fsqrt<T>(x: T) -> T;
-        fn simd_ceil<T>(x: T) -> T;
-        fn simd_fma<T>(x: T, y: T, z: T) -> T;
-    }
-
     let nan = F32::nan(Neg, Quiet, 0).as_f32();
     check_all_outcomes(
         HashSet::from_iter([F32::nan(Pos, Quiet, 0), F32::nan(Neg, Quiet, 0)]),

tests/pass/portable-simd-ptrs.rs

@@ -1,6 +1,6 @@
 // Separate test without strict provenance
 //@compile-flags: -Zmiri-permissive-provenance
-#![feature(portable_simd, platform_intrinsics)]
+#![feature(portable_simd)]
 use std::ptr;
 use std::simd::prelude::*;