Support for stack switching proposal

Cargo.toml

@@ -431,6 +431,7 @@ default = [
   "gc",
   "gc-drc",
   "gc-null",
+  "stack-switching",
   "winch",
   "pulley",
 
@@ -489,6 +490,7 @@ gc = ["wasmtime-cli-flags/gc", "wasmtime/gc"]
 gc-drc = ["gc", "wasmtime/gc-drc", "wasmtime-cli-flags/gc-drc"]
 gc-null = ["gc", "wasmtime/gc-null", "wasmtime-cli-flags/gc-null"]
 pulley = ["wasmtime-cli-flags/pulley"]
+stack-switching = ["wasmtime/stack-switching", "wasmtime-cli-flags/stack-switching"]
 
 # CLI subcommands for the `wasmtime` executable. See `wasmtime $cmd --help`
 # for more information on each subcommand.

cranelift/codegen/src/ir/function.rs

@@ -255,6 +255,13 @@ impl FunctionStencil {
         self.get_dyn_scale(dyn_ty)
     }
 
+    /// Find the data for the given stack slot
+    pub fn get_stack_slot_data(&self, stack_slot: StackSlot) -> &StackSlotData {
+        self.sized_stack_slots
+            .get(stack_slot)
+            .expect("undeclared stack slot: {stack_slot}")
+    }
+
     /// Get a concrete `Type` from a user defined `DynamicType`.
     pub fn get_concrete_dynamic_ty(&self, ty: DynamicType) -> Option<Type> {
         self.dfg

cranelift/codegen/src/isa/x64/abi.rs

@@ -104,6 +104,7 @@ impl ABIMachineSpec for X64ABIMachineSpec {
         mut args: ArgsAccumulator,
     ) -> CodegenResult<(u32, Option<usize>)> {
         let is_fastcall = call_conv == CallConv::WindowsFastcall;
+        let is_tail = call_conv == CallConv::Tail;
 
         let mut next_gpr = 0;
         let mut next_vreg = 0;
@@ -182,6 +183,11 @@ impl ABIMachineSpec for X64ABIMachineSpec {
             //   This is consistent with LLVM's behavior, and is needed for
             //   some uses of Cranelift (e.g., the rustc backend).
             //
+            // - Otherwise, if the calling convention is Tail, we behave as in
+            //   the previous case, even if `enable_llvm_abi_extensions` is not
+            //   set in the flags: This is a custom calling convention defined
+            //   by Cranelift, LLVM doesn't know about it.
+            //
             // - Otherwise, both SysV and Fastcall specify behavior (use of
             //   vector register, a register pair, or passing by reference
             //   depending on the case), but for simplicity, we will just panic if
@@ -195,6 +201,7 @@ impl ABIMachineSpec for X64ABIMachineSpec {
             if param.value_type.bits() > 64
                 && !(param.value_type.is_vector() || param.value_type.is_float())
                 && !flags.enable_llvm_abi_extensions()
+                && !is_tail
             {
                 panic!(
                     "i128 args/return values not supported unless LLVM ABI extensions are enabled"

crates/c-api/include/wasmtime/config.h

@@ -250,6 +250,22 @@ WASMTIME_CONFIG_PROP(void, wasm_wide_arithmetic, bool)
 
 #ifdef WASMTIME_FEATURE_COMPILER
 
+/**
+ * \brief Configures whether the WebAssembly function references
+ * proposal is enabled.
+ *
+ * This setting is `false` by default.
+ */
+WASMTIME_CONFIG_PROP(void, wasm_function_references, bool)
+
+/**
+ * \brief Configures whether the WebAssembly stack switching
+ * proposal is enabled.
+ *
+ * This setting is `false` by default.
+ */
+WASMTIME_CONFIG_PROP(void, wasm_stack_switching, bool)
+
 /**
  * \brief Configures how JIT code will be compiled.
  *

crates/c-api/include/wasmtime/linker.h

@@ -66,6 +66,16 @@ WASM_API_EXTERN void wasmtime_linker_delete(wasmtime_linker_t *linker);
 WASM_API_EXTERN void wasmtime_linker_allow_shadowing(wasmtime_linker_t *linker,
                                                      bool allow_shadowing);
 
+/**
+ * \brief Configures whether the given Linker will allow unknown exports from
+ * command modules.
+ *
+ * By default this setting is `false`.
+ */
+WASM_API_EXTERN void
+wasmtime_linker_allow_unknown_exports(wasmtime_linker_t *linker,
+                                      bool allow_unknown_exports);
+
 /**
  * \brief Defines a new item in this linker.
  *

crates/c-api/src/config.rs

@@ -137,6 +137,10 @@ pub extern "C" fn wasmtime_config_wasm_memory64_set(c: &mut wasm_config_t, enabl
 }
 
 #[unsafe(no_mangle)]
+pub extern "C" fn wasmtime_config_wasm_stack_switching_set(c: &mut wasm_config_t, enable: bool) {
+    c.config.wasm_stack_switching(enable);
+}
+
 #[cfg(any(feature = "cranelift", feature = "winch"))]
 pub extern "C" fn wasmtime_config_strategy_set(
     c: &mut wasm_config_t,

crates/cli-flags/Cargo.toml

@@ -39,3 +39,4 @@ gc-null = ["gc", "wasmtime/gc-null"]
 threads = ["wasmtime/threads"]
 memory-protection-keys = ["wasmtime/memory-protection-keys"]
 pulley = ["wasmtime/pulley"]
+stack-switching = ["wasmtime/stack-switching"]

crates/cli-flags/src/lib.rs

@@ -331,6 +331,8 @@ wasmtime_option_group! {
         pub trap_on_grow_failure: Option<bool>,
         /// Maximum execution time of wasm code before timing out (1, 2s, 100ms, etc)
         pub timeout: Option<Duration>,
+        /// Size of stacks created with cont.new instructions
+        pub stack_switching_stack_size: Option<usize>,
         /// Configures support for all WebAssembly proposals implemented.
         pub all_proposals: Option<bool>,
         /// Configure support for the bulk memory proposal.
@@ -366,6 +368,8 @@ wasmtime_option_group! {
         pub component_model_async: Option<bool>,
         /// Configure support for the function-references proposal.
         pub function_references: Option<bool>,
+        /// Configure support for the stack-switching proposal.
+        pub stack_switching: Option<bool>,
         /// Configure support for the GC proposal.
         pub gc: Option<bool>,
         /// Configure support for the custom-page-sizes proposal.
@@ -803,6 +807,12 @@ impl CommonOptions {
             config.native_unwind_info(enable);
         }
 
+        match_feature! {
+            ["stack-switching" : self.wasm.stack_switching_stack_size]
+            size => config.stack_switching_stack_size(size),
+            _ => err,
+        }
+
         match_feature! {
             ["pooling-allocator" : self.opts.pooling_allocator.or(pooling_allocator_default)]
             enable => {
@@ -964,6 +974,9 @@ impl CommonOptions {
         if let Some(enable) = self.wasm.memory64.or(all) {
             config.wasm_memory64(enable);
         }
+        if let Some(enable) = self.wasm.stack_switching {
+            config.wasm_stack_switching(enable);
+        }
         if let Some(enable) = self.wasm.custom_page_sizes.or(all) {
             config.wasm_custom_page_sizes(enable);
         }
@@ -994,6 +1007,7 @@ impl CommonOptions {
             ("gc", gc, wasm_gc)
             ("gc", reference_types, wasm_reference_types)
             ("gc", function_references, wasm_function_references)
+            ("stack-switching", stack_switching, wasm_stack_switching)
         }
         Ok(())
     }