Initial conversion to const generics (#1018)

Author: Amanieu

crates/assert-instr-macro/src/lib.rs

@@ -62,6 +62,7 @@ pub fn assert_instr(
     );
     let mut inputs = Vec::new();
     let mut input_vals = Vec::new();
+    let mut const_vals = Vec::new();
     let ret = &func.sig.output;
     for arg in func.sig.inputs.iter() {
         let capture = match *arg {
@@ -82,6 +83,20 @@ pub fn assert_instr(
             input_vals.push(quote! { #ident });
         }
     }
+    for arg in func.sig.generics.params.iter() {
+        let c = match *arg {
+            syn::GenericParam::Const(ref c) => c,
+            ref v => panic!(
+                "only const generics are allowed: `{:?}`",
+                v.clone().into_token_stream()
+            ),
+        };
+        if let Some(&(_, ref tokens)) = invoc.args.iter().find(|a| c.ident == a.0) {
+            const_vals.push(quote! { #tokens });
+        } else {
+            panic!("const generics must have a value for tests");
+        }
+    }
 
     let attrs = func
         .attrs
@@ -133,7 +148,7 @@ pub fn assert_instr(
                 std::mem::transmute(#shim_name_str.as_bytes().as_ptr()),
                 std::sync::atomic::Ordering::Relaxed,
             );
-            #name(#(#input_vals),*)
+            #name::<#(#const_vals),*>(#(#input_vals),*)
         }
     };
 

crates/core_arch/src/lib.rs

@@ -53,7 +53,8 @@
     clippy::shadow_reuse,
     clippy::cognitive_complexity,
     clippy::similar_names,
-    clippy::many_single_char_names
+    clippy::many_single_char_names,
+    non_upper_case_globals
 )]
 #![cfg_attr(test, allow(unused_imports))]
 #![no_std]

crates/core_arch/src/x86/avx512f.rs

@@ -22694,7 +22694,7 @@ pub unsafe fn _mm_mask_shuffle_ps(
 ) -> __m128 {
     macro_rules! call {
         ($imm8:expr) => {
-            _mm_shuffle_ps(a, b, $imm8)
+            _mm_shuffle_ps::<$imm8>(a, b)
         };
     }
     let r = constify_imm8_sae!(imm8, call);
@@ -22711,7 +22711,7 @@ pub unsafe fn _mm_mask_shuffle_ps(
 pub unsafe fn _mm_maskz_shuffle_ps(k: __mmask8, a: __m128, b: __m128, imm8: i32) -> __m128 {
     macro_rules! call {
         ($imm8:expr) => {
-            _mm_shuffle_ps(a, b, $imm8)
+            _mm_shuffle_ps::<$imm8>(a, b)
         };
     }
     let r = constify_imm8_sae!(imm8, call);

crates/core_arch/src/x86/sse.rs

@@ -1007,52 +1007,20 @@ pub const fn _MM_SHUFFLE(z: u32, y: u32, x: u32, w: u32) -> i32 {
 #[inline]
 #[target_feature(enable = "sse")]
 #[cfg_attr(test, assert_instr(shufps, mask = 3))]
-#[rustc_args_required_const(2)]
-#[stable(feature = "simd_x86", since = "1.27.0")]
-pub unsafe fn _mm_shuffle_ps(a: __m128, b: __m128, mask: i32) -> __m128 {
-    let mask = (mask & 0xFF) as u8;
-
-    macro_rules! shuffle_done {
-        ($x01:expr, $x23:expr, $x45:expr, $x67:expr) => {
-            simd_shuffle4(a, b, [$x01, $x23, $x45, $x67])
-        };
-    }
-    macro_rules! shuffle_x67 {
-        ($x01:expr, $x23:expr, $x45:expr) => {
-            match (mask >> 6) & 0b11 {
-                0b00 => shuffle_done!($x01, $x23, $x45, 4),
-                0b01 => shuffle_done!($x01, $x23, $x45, 5),
-                0b10 => shuffle_done!($x01, $x23, $x45, 6),
-                _ => shuffle_done!($x01, $x23, $x45, 7),
-            }
-        };
-    }
-    macro_rules! shuffle_x45 {
-        ($x01:expr, $x23:expr) => {
-            match (mask >> 4) & 0b11 {
-                0b00 => shuffle_x67!($x01, $x23, 4),
-                0b01 => shuffle_x67!($x01, $x23, 5),
-                0b10 => shuffle_x67!($x01, $x23, 6),
-                _ => shuffle_x67!($x01, $x23, 7),
-            }
-        };
-    }
-    macro_rules! shuffle_x23 {
-        ($x01:expr) => {
-            match (mask >> 2) & 0b11 {
-                0b00 => shuffle_x45!($x01, 0),
-                0b01 => shuffle_x45!($x01, 1),
-                0b10 => shuffle_x45!($x01, 2),
-                _ => shuffle_x45!($x01, 3),
-            }
-        };
-    }
-    match mask & 0b11 {
-        0b00 => shuffle_x23!(0),
-        0b01 => shuffle_x23!(1),
-        0b10 => shuffle_x23!(2),
-        _ => shuffle_x23!(3),
-    }
+#[rustc_legacy_const_generics(2)]
+#[stable(feature = "simd_x86", since = "1.27.0")]
+pub unsafe fn _mm_shuffle_ps<const mask: i32>(a: __m128, b: __m128) -> __m128 {
+    assert!(mask >= 0 && mask <= 255);
+    simd_shuffle4(
+        a,
+        b,
+        [
+            mask as u32 & 0b11,
+            (mask as u32 >> 2) & 0b11,
+            ((mask as u32 >> 4) & 0b11) + 4,
+            ((mask as u32 >> 6) & 0b11) + 4,
+        ],
+    )
 }
 
 /// Unpacks and interleave single-precision (32-bit) floating-point elements
@@ -1725,6 +1693,14 @@ pub const _MM_HINT_T2: i32 = 1;
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub const _MM_HINT_NTA: i32 = 0;
 
+/// See [`_mm_prefetch`](fn._mm_prefetch.html).
+#[stable(feature = "simd_x86", since = "1.27.0")]
+pub const _MM_HINT_ET0: i32 = 7;
+
+/// See [`_mm_prefetch`](fn._mm_prefetch.html).
+#[stable(feature = "simd_x86", since = "1.27.0")]
+pub const _MM_HINT_ET1: i32 = 6;
+
 /// Fetch the cache line that contains address `p` using the given `strategy`.
 ///
 /// The `strategy` must be one of:
@@ -1742,6 +1718,10 @@ pub const _MM_HINT_NTA: i32 = 0;
 ///   but outside of the cache hierarchy. This is used to reduce access latency
 ///   without polluting the cache.
 ///
+/// * [`_MM_HINT_ET0`](constant._MM_HINT_ET0.html) and
+///   [`_MM_HINT_ET1`](constant._MM_HINT_ET1.html) are similar to `_MM_HINT_T0`
+///   and `_MM_HINT_T1` but indicate an anticipation to write to the address.
+///
 /// The actual implementation depends on the particular CPU. This instruction
 /// is considered a hint, so the CPU is also free to simply ignore the request.
 ///
@@ -1769,24 +1749,12 @@ pub const _MM_HINT_NTA: i32 = 0;
 #[cfg_attr(test, assert_instr(prefetcht1, strategy = _MM_HINT_T1))]
 #[cfg_attr(test, assert_instr(prefetcht2, strategy = _MM_HINT_T2))]
 #[cfg_attr(test, assert_instr(prefetchnta, strategy = _MM_HINT_NTA))]
-#[rustc_args_required_const(1)]
-#[stable(feature = "simd_x86", since = "1.27.0")]
-pub unsafe fn _mm_prefetch(p: *const i8, strategy: i32) {
-    // The `strategy` must be a compile-time constant, so we use a short form
-    // of `constify_imm8!` for now.
-    // We use the `llvm.prefetch` instrinsic with `rw` = 0 (read), and
-    // `cache type` = 1 (data cache). `locality` is based on our `strategy`.
-    macro_rules! pref {
-        ($imm8:expr) => {
-            match $imm8 {
-                0 => prefetch(p, 0, 0, 1),
-                1 => prefetch(p, 0, 1, 1),
-                2 => prefetch(p, 0, 2, 1),
-                _ => prefetch(p, 0, 3, 1),
-            }
-        };
-    }
-    pref!(strategy)
+#[rustc_legacy_const_generics(1)]
+#[stable(feature = "simd_x86", since = "1.27.0")]
+pub unsafe fn _mm_prefetch<const strategy: i32>(p: *const i8) {
+    // We use the `llvm.prefetch` instrinsic with `cache type` = 1 (data cache).
+    // `locality` and `rw` are based on our `strategy`.
+    prefetch(p, (strategy >> 2) & 1, strategy & 3, 1);
 }
 
 /// Returns vector of type __m128 with undefined elements.
@@ -2976,7 +2944,7 @@ mod tests {
     unsafe fn test_mm_shuffle_ps() {
         let a = _mm_setr_ps(1.0, 2.0, 3.0, 4.0);
         let b = _mm_setr_ps(5.0, 6.0, 7.0, 8.0);
-        let r = _mm_shuffle_ps(a, b, 0b00_01_01_11);
+        let r = _mm_shuffle_ps::<0b00_01_01_11>(a, b);
         assert_eq_m128(r, _mm_setr_ps(4.0, 2.0, 6.0, 5.0));
     }
 

crates/stdarch-verify/src/lib.rs

@@ -81,13 +81,21 @@ fn functions(input: TokenStream, dirs: &[&str]) -> TokenStream {
             let name = &f.sig.ident;
             // println!("{}", name);
             let mut arguments = Vec::new();
+            let mut const_arguments = Vec::new();
             for input in f.sig.inputs.iter() {
                 let ty = match *input {
                     syn::FnArg::Typed(ref c) => &c.ty,
                     _ => panic!("invalid argument on {}", name),
                 };
                 arguments.push(to_type(ty));
             }
+            for generic in f.sig.generics.params.iter() {
+                let ty = match *generic {
+                    syn::GenericParam::Const(ref c) => &c.ty,
+                    _ => panic!("invalid generic argument on {}", name),
+                };
+                const_arguments.push(to_type(ty));
+            }
             let ret = match f.sig.output {
                 syn::ReturnType::Default => quote! { None },
                 syn::ReturnType::Type(_, ref t) => {
@@ -101,7 +109,23 @@ fn functions(input: TokenStream, dirs: &[&str]) -> TokenStream {
             } else {
                 quote! { None }
             };
-            let required_const = find_required_const(&f.attrs);
+
+            let required_const = find_required_const("rustc_args_required_const", &f.attrs);
+            let mut legacy_const_generics =
+                find_required_const("rustc_legacy_const_generics", &f.attrs);
+            if !required_const.is_empty() && !legacy_const_generics.is_empty() {
+                panic!(
+                    "Can't have both #[rustc_args_required_const] and \
+                     #[rustc_legacy_const_generics]"
+                );
+            }
+            legacy_const_generics.sort();
+            for (idx, ty) in legacy_const_generics
+                .into_iter()
+                .zip(const_arguments.into_iter())
+            {
+                arguments.insert(idx, ty);
+            }
 
             // strip leading underscore from fn name when building a test
             // _mm_foo -> mm_foo such that the test name is test_mm_foo.
@@ -390,11 +414,11 @@ fn find_target_feature(attrs: &[syn::Attribute]) -> Option<syn::Lit> {
         })
 }
 
-fn find_required_const(attrs: &[syn::Attribute]) -> Vec<usize> {
+fn find_required_const(name: &str, attrs: &[syn::Attribute]) -> Vec<usize> {
     attrs
         .iter()
         .flat_map(|a| {
-            if a.path.segments[0].ident == "rustc_args_required_const" {
+            if a.path.segments[0].ident == name {
                 syn::parse::<RustcArgsRequiredConst>(a.tokens.clone().into())
                     .unwrap()
                     .args