Implement the wide-arithmetic proposal

This commit implements the [wide-arithmetic] proposal in Wasmtime. This is a pretty easy proposal to implement due to Cranelift already having support for all the various instructions. The features implemented here are: * Cranelift support for the four new instructions. * A new `Config::wasm_wide_arithmetic` option. * A new `-Wwide-arithmetic` CLI flag. * A new `wasmtime_config_wasm_wide_arithmetic_set` C API function. * Support for fuzzing this proposal * Generation is implemented in `wasm-smith` . * While it's off-by-default in `wasm-smith` it's enabled-by-default here. * Differential execution is only possible against Wasmtime right now. * Single-instruction module support was added for these new instructions. * Tests for some simple cases plus randomly-generated tests. * Example disassemblies for new instructions on Cranelift architectures. [wide-arithmetic]: https://github.com/WebAssembly/wide-arithmetic
alexcrichton · Oct 8, 2024 · 51e8a10 · 51e8a10
1 parent d51a921
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Showing 18 changed files with 884 additions and 20 deletions.
diff --git a/crates/c-api/include/wasmtime/config.h b/crates/c-api/include/wasmtime/config.h
@@ -240,6 +240,14 @@ WASMTIME_CONFIG_PROP(void, wasm_multi_memory, bool)
  */
 WASMTIME_CONFIG_PROP(void, wasm_memory64, bool)
 
+/**
+ * \brief Configures whether the WebAssembly wide-arithmetic proposal is
+ * enabled.
+ *
+ * This setting is `false` by default.
+ */
+WASMTIME_CONFIG_PROP(void, wasm_wide_arithmetic, bool)
+
 #ifdef WASMTIME_FEATURE_COMPILER
 
 /**

diff --git a/crates/c-api/src/config.rs b/crates/c-api/src/config.rs
@@ -460,3 +460,8 @@ pub unsafe extern "C" fn wasmtime_config_host_memory_creator_set(
 pub extern "C" fn wasmtime_config_memory_init_cow_set(c: &mut wasm_config_t, enable: bool) {
     c.config.memory_init_cow(enable);
 }
+
+#[no_mangle]
+pub extern "C" fn wasmtime_config_wasm_wide_arithmetic_set(c: &mut wasm_config_t, enable: bool) {
+    c.config.wasm_wide_arithmetic(enable);
+}
diff --git a/crates/cli-flags/src/lib.rs b/crates/cli-flags/src/lib.rs
@@ -281,6 +281,8 @@ wasmtime_option_group! {
         pub gc: Option<bool>,
         /// Configure support for the custom-page-sizes proposal.
         pub custom_page_sizes: Option<bool>,
+        /// Configure support for the wide-arithmetic proposal.
+        pub wide_arithmetic: Option<bool>,
     }
 
     enum Wasm {
@@ -724,6 +726,9 @@ impl CommonOptions {
         if let Some(enable) = self.wasm.custom_page_sizes.or(all) {
             config.wasm_custom_page_sizes(enable);
         }
+        if let Some(enable) = self.wasm.wide_arithmetic.or(all) {
+            config.wasm_wide_arithmetic(enable);
+        }
 
         macro_rules! handle_conditionally_compiled {
             ($(($feature:tt, $field:tt, $method:tt))*) => ($(

diff --git a/crates/cranelift/src/translate/code_translator.rs b/crates/cranelift/src/translate/code_translator.rs
@@ -2793,13 +2793,37 @@ pub fn translate_operator<FE: FuncEnvironment + ?Sized>(
             ));
         }
 
-        Operator::I64Add128
-        | Operator::I64Sub128
-        | Operator::I64MulWideS
-        | Operator::I64MulWideU => {
-            return Err(wasm_unsupported!(
-                "wide-arithmetic operators are not yet implemented"
-            ));
+        Operator::I64MulWideS => {
+            let (arg1, arg2) = state.pop2();
+            let arg1 = builder.ins().sextend(I128, arg1);
+            let arg2 = builder.ins().sextend(I128, arg2);
+            let result = builder.ins().imul(arg1, arg2);
+            let (lo, hi) = builder.ins().isplit(result);
+            state.push2(lo, hi);
+        }
+        Operator::I64MulWideU => {
+            let (arg1, arg2) = state.pop2();
+            let arg1 = builder.ins().uextend(I128, arg1);
+            let arg2 = builder.ins().uextend(I128, arg2);
+            let result = builder.ins().imul(arg1, arg2);
+            let (lo, hi) = builder.ins().isplit(result);
+            state.push2(lo, hi);
+        }
+        Operator::I64Add128 => {
+            let (arg1, arg2, arg3, arg4) = state.pop4();
+            let arg1 = builder.ins().iconcat(arg1, arg2);
+            let arg2 = builder.ins().iconcat(arg3, arg4);
+            let result = builder.ins().iadd(arg1, arg2);
+            let (res1, res2) = builder.ins().isplit(result);
+            state.push2(res1, res2);
+        }
+        Operator::I64Sub128 => {
+            let (arg1, arg2, arg3, arg4) = state.pop4();
+            let arg1 = builder.ins().iconcat(arg1, arg2);
+            let arg2 = builder.ins().iconcat(arg3, arg4);
+            let result = builder.ins().isub(arg1, arg2);
+            let (res1, res2) = builder.ins().isplit(result);
+            state.push2(res1, res2);
         }
     };
     Ok(())

diff --git a/crates/cranelift/src/translate/state.rs b/crates/cranelift/src/translate/state.rs
@@ -295,6 +295,12 @@ impl FuncTranslationState {
         self.stack.push(val);
     }
 
+    /// Push two values.
+    pub(crate) fn push2(&mut self, val1: Value, val2: Value) {
+        self.stack.push(val1);
+        self.stack.push(val2);
+    }
+
     /// Push multiple values.
     pub(crate) fn pushn(&mut self, vals: &[Value]) {
         self.stack.extend_from_slice(vals);

diff --git a/crates/fuzzing/src/generators/config.rs b/crates/fuzzing/src/generators/config.rs
@@ -170,6 +170,7 @@ impl Config {
             .wasm_threads(self.module_config.config.threads_enabled)
             .wasm_function_references(self.module_config.config.gc_enabled)
             .wasm_gc(self.module_config.config.gc_enabled)
+            .wasm_wide_arithmetic(self.module_config.config.wide_arithmetic_enabled)
             .native_unwind_info(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info)
             .cranelift_nan_canonicalization(self.wasmtime.canonicalize_nans)
             .cranelift_opt_level(self.wasmtime.opt_level.to_wasmtime())
@@ -474,6 +475,10 @@ impl WasmtimeConfig {
         // Not fully implemented in Wasmtime and fuzzing.
         config.gc_enabled = false;
 
+        // Off-by-default in wasm-smith but implemented in wasmtime, so give the
+        // fuzzers a chance to run it.
+        config.wide_arithmetic_enabled = u.arbitrary()?;
+
         // Winch doesn't support the same set of wasm proposal as Cranelift at
         // this time, so if winch is selected be sure to disable wasm proposals
         // in `Config` to ensure that Winch can compile the module that
@@ -485,6 +490,7 @@ impl WasmtimeConfig {
             config.threads_enabled = false;
             config.tail_call_enabled = false;
             config.reference_types_enabled = false;
+            config.wide_arithmetic_enabled = false;
 
             // Winch requires host trap handlers to be enabled at this time.
             self.signals_based_traps = true;

diff --git a/crates/fuzzing/src/generators/single_inst_module.rs b/crates/fuzzing/src/generators/single_inst_module.rs
@@ -163,36 +163,38 @@ impl<'a> SingleInstModule<'a> {
 // instructions compactly and allow for easier changes to the Rust code (e.g.,
 // `SingleInstModule`).
 
-macro_rules! valtype {
-    (i32) => {
+macro_rules! valtypes {
+    (@list ($($ty:tt),*)) => {&[$(valtypes!(@one $ty)),*]};
+    (@list $ty:tt) => {&[valtypes!(@one $ty)]};
+    (@one i32) => {
         ValType::I32
     };
-    (i64) => {
+    (@one i64) => {
         ValType::I64
     };
-    (f32) => {
+    (@one f32) => {
         ValType::F32
     };
-    (f64) => {
+    (@one f64) => {
         ValType::F64
     };
-    (v128) => {
+    (@one v128) => {
         ValType::V128
     };
 }
 
 macro_rules! inst {
-    ($inst:ident, ($($arguments_ty:tt),*) -> $result_ty:tt) => {
-        inst! { $inst, ($($arguments_ty),*) -> $result_ty, |_| true }
+    ($inst:ident, $arguments:tt -> $results:tt) => {
+        inst! { $inst, $arguments -> $results, |_| true }
     };
-    ($inst:ident, ($($arguments_ty:tt),*) -> $result_ty:tt, $feature:expr) => {
-        inst! { $inst, ($($arguments_ty),*) -> $result_ty, $feature, None }
+    ($inst:ident, $arguments:tt -> $results:tt, $feature:expr) => {
+        inst! { $inst, $arguments -> $results, $feature, None }
     };
-    ($inst:ident, ($($arguments_ty:tt),*) -> $result_ty:tt, $feature:expr, $nan:expr) => {
+    ($inst:ident, $arguments:tt -> $results:tt, $feature:expr, $nan:expr) => {
         SingleInstModule {
             instruction: Instruction::$inst,
-            parameters: &[$(valtype!($arguments_ty)),*],
-            results: &[valtype!($result_ty)],
+            parameters: valtypes!(@list $arguments),
+            results: valtypes!(@list $results),
             feature: $feature,
             canonicalize_nan: $nan,
         }
@@ -568,6 +570,11 @@ static INSTRUCTIONS: &[SingleInstModule] = &[
     inst!(F64x2ConvertLowI32x4U, (v128) -> v128, |c| c.config.simd_enabled),
     inst!(F32x4DemoteF64x2Zero, (v128) -> v128, |c| c.config.simd_enabled),
     inst!(F64x2PromoteLowF32x4, (v128) -> v128, |c| c.config.simd_enabled),
+    // wide arithmetic
+    inst!(I64Add128, (i64, i64, i64, i64) -> (i64, i64), |c| c.config.wide_arithmetic_enabled && c.config.multi_value_enabled),
+    inst!(I64Sub128, (i64, i64, i64, i64) -> (i64, i64), |c| c.config.wide_arithmetic_enabled && c.config.multi_value_enabled),
+    inst!(I64MulWideS, (i64, i64) -> (i64, i64), |c| c.config.wide_arithmetic_enabled && c.config.multi_value_enabled),
+    inst!(I64MulWideU, (i64, i64) -> (i64, i64), |c| c.config.wide_arithmetic_enabled && c.config.multi_value_enabled),
 ];
 
 #[cfg(test)]

diff --git a/crates/fuzzing/src/oracles/diff_spec.rs b/crates/fuzzing/src/oracles/diff_spec.rs
@@ -25,6 +25,7 @@ impl SpecInterpreter {
         config.reference_types_enabled = false;
         config.tail_call_enabled = false;
         config.relaxed_simd_enabled = false;
+        config.wide_arithmetic_enabled = false;
 
         Self
     }

diff --git a/crates/fuzzing/src/oracles/diff_v8.rs b/crates/fuzzing/src/oracles/diff_v8.rs
@@ -32,6 +32,7 @@ impl V8Engine {
         config.min_memories = config.min_memories.min(1);
         config.max_memories = config.max_memories.min(1);
         config.memory64_enabled = false;
+        config.wide_arithmetic_enabled = false;
 
         Self {
             isolate: Rc::new(RefCell::new(v8::Isolate::new(Default::default()))),

diff --git a/crates/fuzzing/src/oracles/diff_wasmi.rs b/crates/fuzzing/src/oracles/diff_wasmi.rs
@@ -20,6 +20,7 @@ impl WasmiEngine {
         config.threads_enabled = false;
         config.exceptions_enabled = false;
         config.gc_enabled = false;
+        config.wide_arithmetic_enabled = false;
         config.max_memories = config.max_memories.min(1);
         config.min_memories = config.min_memories.min(1);
 

diff --git a/crates/wasmtime/src/config.rs b/crates/wasmtime/src/config.rs
@@ -818,6 +818,17 @@ impl Config {
         self
     }
 
+    /// Configures whether the [WebAssembly wide-arithmetic][proposal] will be
+    /// enabled for compilation.
+    ///
+    /// This feature is `false` by default.
+    ///
+    /// [proposal]: https://github.com/WebAssembly/wide-arithmetic
+    pub fn wasm_wide_arithmetic(&mut self, enable: bool) -> &mut Self {
+        self.wasm_feature(WasmFeatures::WIDE_ARITHMETIC, enable);
+        self
+    }
+
     /// Configures whether the [WebAssembly Garbage Collection
     /// proposal][proposal] will be enabled for compilation.
     ///

diff --git a/docs/stability-tiers.md b/docs/stability-tiers.md
@@ -73,13 +73,15 @@ For explanations of what each tier means see below.
 | Target               | Support for `#![no_std]`   | Support beyond CI checks    |
 | WebAssembly Proposal | [`memory64`]               | Unstable wasm proposal      |
 | WebAssembly Proposal | [`function-references`]    | Unstable wasm proposal      |
+| WebAssembly Proposal | [`wide-arithmetic`]        | Unstable wasm proposal      |
 
 [`memory64`]: https://github.com/WebAssembly/memory64/blob/master/proposals/memory64/Overview.md
 [`multi-memory`]: https://github.com/WebAssembly/multi-memory/blob/master/proposals/multi-memory/Overview.md
 [`threads`]: https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md
 [`component-model`]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md
 [`relaxed-simd`]: https://github.com/WebAssembly/relaxed-simd/blob/main/proposals/relaxed-simd/Overview.md
 [`function-references`]: https://github.com/WebAssembly/function-references/blob/main/proposals/function-references/Overview.md
+[`wide-arithmetic`]: https://github.com/WebAssembly/wide-arithmetic/blob/main/proposals/wide-arithmetic/Overview.md
 
 #### Tier 3
 

diff --git a/tests/disas/aarch64-wide-arithmetic.wat b/tests/disas/aarch64-wide-arithmetic.wat
@@ -0,0 +1,91 @@
+;;! target = "aarch64"
+;;! test = "compile"
+;;! flags = "-Wwide-arithmetic"
+
+(module
+  (func $add128 (param i64 i64 i64 i64) (result i64 i64)
+    local.get 0
+    local.get 1
+    local.get 2
+    local.get 3
+    i64.add128)
+
+  (func $sub128 (param i64 i64 i64 i64) (result i64 i64)
+    local.get 0
+    local.get 1
+    local.get 2
+    local.get 3
+    i64.sub128)
+
+  (func $signed (param i64 i64) (result i64 i64)
+    local.get 0
+    local.get 1
+    i64.mul_wide_s)
+
+  (func $unsigned (param i64 i64) (result i64 i64)
+    local.get 0
+    local.get 1
+    i64.mul_wide_u)
+
+  (func $signed_only_high (param i64 i64) (result i64)
+    local.get 0
+    local.get 1
+    i64.mul_wide_s
+    local.set 0
+    drop
+    local.get 0)
+
+  (func $unsigned_only_high (param i64 i64) (result i64)
+    local.get 0
+    local.get 1
+    i64.mul_wide_u
+    local.set 0
+    drop
+    local.get 0)
+)
+
+;; wasm[0]::function[0]::add128:
+;;       stp     x29, x30, [sp, #-0x10]!
+;;       mov     x29, sp
+;;       adds    x2, x4, x6
+;;       adc     x3, x5, x7
+;;       ldp     x29, x30, [sp], #0x10
+;;       ret
+;;
+;; wasm[0]::function[1]::sub128:
+;;       stp     x29, x30, [sp, #-0x10]!
+;;       mov     x29, sp
+;;       subs    x2, x4, x6
+;;       sbc     x3, x5, x7
+;;       ldp     x29, x30, [sp], #0x10
+;;       ret
+;;
+;; wasm[0]::function[2]::signed:
+;;       stp     x29, x30, [sp, #-0x10]!
+;;       mov     x29, sp
+;;       mul     x2, x4, x5
+;;       smulh   x3, x4, x5
+;;       ldp     x29, x30, [sp], #0x10
+;;       ret
+;;
+;; wasm[0]::function[3]::unsigned:
+;;       stp     x29, x30, [sp, #-0x10]!
+;;       mov     x29, sp
+;;       mul     x2, x4, x5
+;;       umulh   x3, x4, x5
+;;       ldp     x29, x30, [sp], #0x10
+;;       ret
+;;
+;; wasm[0]::function[4]::signed_only_high:
+;;       stp     x29, x30, [sp, #-0x10]!
+;;       mov     x29, sp
+;;       smulh   x2, x4, x5
+;;       ldp     x29, x30, [sp], #0x10
+;;       ret
+;;
+;; wasm[0]::function[5]::unsigned_only_high:
+;;       stp     x29, x30, [sp, #-0x10]!
+;;       mov     x29, sp
+;;       umulh   x2, x4, x5
+;;       ldp     x29, x30, [sp], #0x10
+;;       ret