wasmparser: merge VisitSimdOperator back into VisitOperator

The `simd` feature remains in place, but now does not affect the API in
this way. Rather parts of implementation pertaining to SIMD in
wasmparser get disabled, reducing the compilation time and artifact
size impact slightly, though less than in the original approach.

The results on my machine are roughly:

* origin/main simd: 4.26s producing 30M .rlib
* origin/main !simd: 3.49s producing 23M .rlib
* this simd: 4.19s producing a 26M .rlib
* this !simd: 3.96s producing a 25M .rlib

I'm not quite sure why the rlib size decreased so significantly when the
SIMD feature is enabled (I guess less inlining is occurring?) and there
is indeed a .5s hit on the compilation time to this PR.

Are those half a second worth a clunkier API? I'm not convinced :)

Author: nagisa

crates/wasmparser/benches/benchmark.rs

@@ -4,7 +4,6 @@ use once_cell::unsync::Lazy;
 use std::fs;
 use std::path::Path;
 use std::path::PathBuf;
-use wasmparser::VisitSimdOperator;
 use wasmparser::{DataKind, ElementKind, Parser, Payload, Validator, VisitOperator, WasmFeatures};
 
 /// A benchmark input.
@@ -375,15 +374,5 @@ macro_rules! define_visit_operator {
 #[allow(unused_variables)]
 impl<'a> VisitOperator<'a> for NopVisit {
     type Output = ();
-
-    fn simd_visitor(&mut self) -> Option<&mut dyn VisitSimdOperator<'a, Output = Self::Output>> {
-        Some(self)
-    }
-
-    wasmparser::for_each_visit_operator!(define_visit_operator);
-}
-
-#[allow(unused_variables)]
-impl<'a> VisitSimdOperator<'a> for NopVisit {
-    wasmparser::for_each_visit_simd_operator!(define_visit_operator);
+    wasmparser::for_each_operator!(define_visit_operator);
 }

crates/wasmparser/src/lib.rs

@@ -827,21 +827,14 @@ macro_rules! define_for_each_non_simd_operator {
                 $m! { $($t)* }
             }
         }
-
-        // When simd is disabled then this macro is additionally the
-        // `for_each_operator!` macro implementation
-        #[cfg(not(feature = "simd"))]
-        #[doc(hidden)]
-        pub use _for_each_visit_operator_impl as _for_each_operator_impl;
     };
 }
 _for_each_operator_group!(define_for_each_non_simd_operator);
 
 /// When the simd feature is enabled then `_for_each_operator_impl` is defined
 /// to be the same as the above `define_for_each_non_simd_operator` macro except
 /// with all proposals thrown in.
-#[cfg(feature = "simd")]
-macro_rules! define_for_each_operator_impl_with_simd {
+macro_rules! define_for_each_operator_impl {
     (
         $(
             @$proposal:ident {
@@ -864,14 +857,12 @@ macro_rules! define_for_each_operator_impl_with_simd {
         }
     };
 }
-#[cfg(feature = "simd")]
-_for_each_operator_group!(define_for_each_operator_impl_with_simd);
+_for_each_operator_group!(define_for_each_operator_impl);
 
 /// Helper macro to define the `_for_each_simd_operator_impl` macro.
 ///
 /// This is basically the same as `define_for_each_non_simd_operator` above
 /// except that it's filtering on different proposals.
-#[cfg(feature = "simd")]
 macro_rules! define_for_each_simd_operator {
     // Switch to "tt muncher" mode
     (@ $($t:tt)*) => {define_for_each_simd_operator!(filter [] @ $($t)*);};
@@ -924,7 +915,7 @@ macro_rules! define_for_each_simd_operator {
         }
     };
 }
-#[cfg(feature = "simd")]
+
 _for_each_operator_group!(define_for_each_simd_operator);
 
 /// Used to implement routines for the [`Operator`] enum.
@@ -1085,10 +1076,10 @@ pub use _for_each_operator_impl as for_each_operator;
 /// - `@stack_switching`: [Wasm `stack-switching` proposal]
 /// - `@wide_arithmetic`: [Wasm `wide-arithmetic` proposal]
 ///
-/// Note that this macro does not iterate over the SIMD-related proposals. Those
-/// are provided in [`VisitSimdOperator`] and [`for_each_visit_simd_operator`].
-/// This macro only handles non-SIMD related operators and so users wanting to
-/// handle the SIMD-class of operators need to use that trait/macro as well.
+/// Note that this macro does not iterate over the SIMD-related proposals. To include SIMD
+/// instructions use [`for_each_visit_simd_operator`] or [`for_each_operator`] instead. This macro
+/// only handles non-SIMD related operators and so users wanting to handle the SIMD-class of
+/// operators need to use that trait/macro as well.
 ///
 /// [Wasm `exception-handling` proposal]:
 /// https://github.com/WebAssembly/exception-handling
@@ -1218,7 +1209,7 @@ pub use _for_each_operator_impl as for_each_operator;
 #[doc(inline)]
 pub use _for_each_visit_operator_impl as for_each_visit_operator;
 
-/// Used to implement the [`VisitSimdOperator`] trait.
+/// Used to implement the methods for simd extension of `VisitOperator` trait.
 ///
 /// The list of specializable Wasm proposals is as follows:
 ///
@@ -1234,22 +1225,12 @@ pub use _for_each_visit_operator_impl as for_each_visit_operator;
 /// [Wasm `relaxed-simd` proposal]:
 /// https://github.com/WebAssembly/relaxed-simd
 ///
-/// [`VisitSimdOperator`]: crate::VisitSimdOperator
-///
 /// ```
 /// # macro_rules! define_visit_operator {
 /// #     ($( @$proposal:ident $op:ident $({ $($arg:ident: $argty:ty),* })? => $visit:ident ($($ann:tt)*))*) => {
 /// #         $( fn $visit(&mut self $($(,$arg: $argty)*)?) {} )*
 /// #     }
 /// # }
-/// pub struct VisitAndDoNothing;
-///
-/// impl<'a> wasmparser::VisitOperator<'a> for VisitAndDoNothing {
-///     type Output = ();
-///
-///     // implement all the visit methods ..
-///     # wasmparser::for_each_visit_operator!(define_visit_operator);
-/// }
 ///
 /// macro_rules! define_visit_simd_operator {
 ///     // The outer layer of repetition represents how all operators are
@@ -1267,12 +1248,16 @@ pub use _for_each_visit_operator_impl as for_each_visit_operator;
 ///         )*
 ///     }
 /// }
+/// pub struct VisitAndDoNothing;
+///
+/// impl<'a> wasmparser::VisitOperator<'a> for VisitAndDoNothing {
+///     type Output = ();
 ///
-/// impl<'a> wasmparser::VisitSimdOperator<'a> for VisitAndDoNothing {
+///     // implement all the visit methods ..
+///     wasmparser::for_each_visit_operator!(define_visit_operator);
 ///     wasmparser::for_each_visit_simd_operator!(define_visit_simd_operator);
 /// }
 /// ```
-#[cfg(feature = "simd")]
 #[doc(inline)]
 pub use _for_each_visit_simd_operator_impl as for_each_visit_simd_operator;