Wasm: Use Vec instead of MutSet for called preloads

compiler/gen_wasm/src/backend.rs

@@ -2,7 +2,7 @@ use bumpalo::{self, collections::Vec};
 
 use code_builder::Align;
 use roc_builtins::bitcode::{self, IntWidth};
-use roc_collections::all::{MutMap, MutSet};
+use roc_collections::all::MutMap;
 use roc_module::ident::Ident;
 use roc_module::low_level::{LowLevel, LowLevelWrapperType};
 use roc_module::symbol::{Interns, Symbol};
@@ -42,7 +42,7 @@ pub struct WasmBackend<'a> {
     layout_ids: LayoutIds<'a>,
     next_constant_addr: u32,
     fn_index_offset: u32,
-    called_preload_fns: MutSet<u32>,
+    called_preload_fns: Vec<'a, u32>,
     proc_symbols: Vec<'a, (Symbol, u32)>,
     helper_proc_gen: CodeGenHelp<'a>,
 
@@ -87,7 +87,7 @@ impl<'a> WasmBackend<'a> {
             layout_ids,
             next_constant_addr: CONST_SEGMENT_BASE_ADDR,
             fn_index_offset,
-            called_preload_fns: MutSet::default(),
+            called_preload_fns: Vec::with_capacity_in(2, env.arena),
             proc_symbols,
             helper_proc_gen,
 
@@ -122,7 +122,7 @@ impl<'a> WasmBackend<'a> {
         self.module.linking.symbol_table.push(linker_symbol);
     }
 
-    pub fn finalize(self) -> (WasmModule<'a>, MutSet<u32>) {
+    pub fn finalize(self) -> (WasmModule<'a>, Vec<'a, u32>) {
         (self.module, self.called_preload_fns)
     }
 
@@ -1474,7 +1474,7 @@ impl<'a> WasmBackend<'a> {
         let num_wasm_args = param_types.len();
         let has_return_val = ret_type.is_some();
         let fn_index = self.module.names.functions[name.as_bytes()];
-        self.called_preload_fns.insert(fn_index);
+        self.called_preload_fns.push(fn_index);
         let linker_symbol_index = u32::MAX;
 
         self.code_builder

compiler/gen_wasm/src/lib.rs

@@ -57,7 +57,7 @@ pub fn build_module_without_test_wrapper<'a>(
     interns: &'a mut Interns,
     preload_bytes: &[u8],
     procedures: MutMap<(Symbol, ProcLayout<'a>), Proc<'a>>,
-) -> (WasmModule<'a>, MutSet<u32>, u32) {
+) -> (WasmModule<'a>, Vec<'a, u32>, u32) {
     let mut layout_ids = LayoutIds::default();
     let mut procs = Vec::with_capacity_in(procedures.len(), env.arena);
     let mut proc_symbols = Vec::with_capacity_in(procedures.len() * 2, env.arena);

compiler/gen_wasm/src/wasm_module/dead_code.rs

@@ -16,10 +16,10 @@ Or, more specifically, "dead function replacement"
       and checking which function index they refer to. Store this in a `PreloadsCallGraph`
 - While compiling Roc code:
     - Run the backend as usual, adding more data into various sections of the Wasm module
-    - Whenever a call to a builtin or platform function is made, record its index in a Set.
+    - Whenever a call to a builtin or platform function is made, record its index.
       These are the "live" preloaded functions that we are not allowed to eliminate.
 - Call graph analysis:
-    - Starting with the set of live preloaded functions, trace their call graphs using the info we
+    - Starting with the live preloaded functions, trace their call graphs using the info we
       collected earlier in `PreloadsCallGraph`. Mark all function indices in the call graph as "live".
 - Dead function replacement:
     - We actually don't want to just *delete* dead functions, because that would change the indices