Rework DeferCallCore to DeferFree

Co-Authored-By: Liam Murphy <43807659+Liamolucko@users.noreply.github.com>

Author: daxpedda

crates/cli-support/src/js/binding.rs

@@ -548,15 +548,17 @@ fn instruction(js: &mut JsBuilder, instr: &Instruction, log_error: &mut bool) ->
         | Instruction::CallExport(_)
         | Instruction::CallAdapter(_)
         | Instruction::CallTableElement(_)
-        | Instruction::DeferCallCore(_) => {
+        | Instruction::DeferFree { .. } => {
             let invoc = Invocation::from(instr, js.cx.module)?;
             let (mut params, results) = invoc.params_results(js.cx);
 
             let mut args = Vec::new();
             let tmp = js.tmp();
             if invoc.defer() {
-                // substract alignment
-                params -= 1;
+                if let Instruction::DeferFree { .. } = instr {
+                    // substract alignment
+                    params -= 1;
+                }
                 // If the call is deferred, the arguments to the function still need to be
                 // accessible in the `finally` block, so we declare variables to hold the args
                 // outside of the try-finally block and then set those to the args.
@@ -566,8 +568,10 @@ fn instruction(js: &mut JsBuilder, instr: &Instruction, log_error: &mut bool) ->
                     writeln!(js.prelude, "{name} = {arg};").unwrap();
                     args.push(name);
                 }
-                // add alignment
-                args.push(String::from("4"));
+                if let Instruction::DeferFree { align, .. } = instr {
+                    // add alignment
+                    args.push(align.to_string());
+                }
             } else {
                 // Otherwise, pop off the number of parameters for the function we're calling.
                 for _ in 0..params {
@@ -1194,8 +1198,8 @@ impl Invocation {
                 defer: false,
             },
 
-            DeferCallCore(f) => Invocation::Core {
-                id: *f,
+            DeferFree { free, .. } => Invocation::Core {
+                id: *free,
                 defer: true,
             },
 

crates/cli-support/src/wit/outgoing.rs

@@ -105,7 +105,7 @@ impl InstructionBuilder<'_, '_> {
                 // ... then defer a call to `free` to happen later
                 let free = self.cx.free()?;
                 self.instructions.push(InstructionData {
-                    instr: Instruction::DeferCallCore(free),
+                    instr: Instruction::DeferFree { free, align: 4 },
                     stack_change: StackChange::Modified {
                         popped: 2,
                         pushed: 2,
@@ -389,7 +389,7 @@ impl InstructionBuilder<'_, '_> {
                 // special case it.
                 assert!(!self.instructions[len..]
                     .iter()
-                    .any(|idata| matches!(idata.instr, Instruction::DeferCallCore(_))));
+                    .any(|idata| matches!(idata.instr, Instruction::DeferFree { .. })));
 
                 // Finally, we add the two inputs to UnwrapResult, and everything checks out
                 //
@@ -429,7 +429,7 @@ impl InstructionBuilder<'_, '_> {
                 // implementation.
                 let free = self.cx.free()?;
                 self.instructions.push(InstructionData {
-                    instr: Instruction::DeferCallCore(free),
+                    instr: Instruction::DeferFree { free, align: 4 },
                     stack_change: StackChange::Modified {
                         popped: 2,
                         pushed: 2,

crates/cli-support/src/wit/standard.rs

@@ -95,7 +95,10 @@ pub enum Instruction {
     CallCore(walrus::FunctionId),
     /// Schedules a function to be called after the whole lift/lower cycle is
     /// finished, e.g. to deallocate a string or something.
-    DeferCallCore(walrus::FunctionId),
+    DeferFree {
+        free: walrus::FunctionId,
+        align: usize,
+    },
     /// A call to one of our own defined adapters, similar to the standard
     /// call-adapter instruction
     CallAdapter(AdapterId),
@@ -423,7 +426,7 @@ impl walrus::CustomSection for NonstandardWitSection {
             };
             for instr in instrs {
                 match instr.instr {
-                    DeferCallCore(f) | CallCore(f) => {
+                    DeferFree { free: f, .. } | CallCore(f) => {
                         roots.push_func(f);
                     }
                     StoreRetptr { mem, .. }