From b8794448b01c8e3d2f54fc893dd990c2f398f5e0 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Fri, 16 Oct 2020 08:22:13 -0700
Subject: [PATCH] Avoid allocations in trampoline shims

There's no need to name each export since each synthetic instance we're
creating only has one export, so let's use the empty string which
doesn't require any allocations.
---
 crates/wasmtime/src/trampoline/func.rs   |  4 ++--
 crates/wasmtime/src/trampoline/global.rs |  4 ++--
 crates/wasmtime/src/trampoline/memory.rs |  2 +-
 crates/wasmtime/src/trampoline/mod.rs    | 10 +++++-----
 crates/wasmtime/src/trampoline/table.rs  |  2 +-
 5 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/crates/wasmtime/src/trampoline/func.rs b/crates/wasmtime/src/trampoline/func.rs
index 29bf5af087..27545e66e5 100644
--- a/crates/wasmtime/src/trampoline/func.rs
+++ b/crates/wasmtime/src/trampoline/func.rs
@@ -230,7 +230,7 @@ pub fn create_handle_with_function(
     let func_id = module.functions.push(sig_id);
     module
         .exports
-        .insert("trampoline".to_string(), EntityIndex::Function(func_id));
+        .insert(String::new(), EntityIndex::Function(func_id));
     let trampoline = make_trampoline(isa.as_ref(), &mut code_memory, &mut fn_builder_ctx, &sig);
     finished_functions.push(trampoline);
 
@@ -289,7 +289,7 @@ pub unsafe fn create_handle_with_raw_function(
     let func_id = module.functions.push(sig_id);
     module
         .exports
-        .insert("trampoline".to_string(), EntityIndex::Function(func_id));
+        .insert(String::new(), EntityIndex::Function(func_id));
     finished_functions.push(func);
     let sig_id = store.register_signature(ft.to_wasm_func_type(), sig);
     trampolines.insert(sig_id, trampoline);
diff --git a/crates/wasmtime/src/trampoline/global.rs b/crates/wasmtime/src/trampoline/global.rs
index b0f060cc4d..3524e94bc3 100644
--- a/crates/wasmtime/src/trampoline/global.rs
+++ b/crates/wasmtime/src/trampoline/global.rs
@@ -61,7 +61,7 @@ pub fn create_global(store: &Store, gt: &GlobalType, val: Val) -> Result<StoreIn
     let global_id = module.globals.push(global);
     module
         .exports
-        .insert("global".to_string(), EntityIndex::Global(global_id));
+        .insert(String::new(), EntityIndex::Global(global_id));
     let handle = create_handle(
         module,
         store,
@@ -72,7 +72,7 @@ pub fn create_global(store: &Store, gt: &GlobalType, val: Val) -> Result<StoreIn
     )?;
 
     if let Some(x) = externref_init {
-        match handle.lookup("global").unwrap() {
+        match handle.lookup("").unwrap() {
             wasmtime_runtime::Export::Global(g) => unsafe {
                 *(*g.definition).as_externref_mut() = Some(x.inner);
             },
diff --git a/crates/wasmtime/src/trampoline/memory.rs b/crates/wasmtime/src/trampoline/memory.rs
index f8ed9a2565..09c814713e 100644
--- a/crates/wasmtime/src/trampoline/memory.rs
+++ b/crates/wasmtime/src/trampoline/memory.rs
@@ -27,7 +27,7 @@ pub fn create_handle_with_memory(
     let memory_id = module.memory_plans.push(memory_plan);
     module
         .exports
-        .insert("memory".to_string(), EntityIndex::Memory(memory_id));
+        .insert(String::new(), EntityIndex::Memory(memory_id));
 
     create_handle(
         module,
diff --git a/crates/wasmtime/src/trampoline/mod.rs b/crates/wasmtime/src/trampoline/mod.rs
index a3a6aac71a..e8c836b2ec 100644
--- a/crates/wasmtime/src/trampoline/mod.rs
+++ b/crates/wasmtime/src/trampoline/mod.rs
@@ -55,7 +55,7 @@ pub fn generate_func_export(
     VMTrampoline,
 )> {
     let (instance, trampoline) = create_handle_with_function(ft, func, store)?;
-    match instance.lookup("trampoline").expect("trampoline export") {
+    match instance.lookup("").expect("trampoline export") {
         wasmtime_runtime::Export::Function(f) => Ok((instance, f, trampoline)),
         _ => unreachable!(),
     }
@@ -72,7 +72,7 @@ pub unsafe fn generate_raw_func_export(
     state: Box<dyn Any>,
 ) -> Result<(StoreInstanceHandle, wasmtime_runtime::ExportFunction)> {
     let instance = func::create_handle_with_raw_function(ft, func, trampoline, store, state)?;
-    match instance.lookup("trampoline").expect("trampoline export") {
+    match instance.lookup("").expect("trampoline export") {
         wasmtime_runtime::Export::Function(f) => Ok((instance, f)),
         _ => unreachable!(),
     }
@@ -84,7 +84,7 @@ pub fn generate_global_export(
     val: Val,
 ) -> Result<(StoreInstanceHandle, wasmtime_runtime::ExportGlobal)> {
     let instance = create_global(store, gt, val)?;
-    match instance.lookup("global").expect("global export") {
+    match instance.lookup("").expect("global export") {
         wasmtime_runtime::Export::Global(g) => Ok((instance, g)),
         _ => unreachable!(),
     }
@@ -95,7 +95,7 @@ pub fn generate_memory_export(
     m: &MemoryType,
 ) -> Result<(StoreInstanceHandle, wasmtime_runtime::ExportMemory)> {
     let instance = create_handle_with_memory(store, m)?;
-    match instance.lookup("memory").expect("memory export") {
+    match instance.lookup("").expect("memory export") {
         wasmtime_runtime::Export::Memory(m) => Ok((instance, m)),
         _ => unreachable!(),
     }
@@ -106,7 +106,7 @@ pub fn generate_table_export(
     t: &TableType,
 ) -> Result<(StoreInstanceHandle, wasmtime_runtime::ExportTable)> {
     let instance = create_handle_with_table(store, t)?;
-    match instance.lookup("table").expect("table export") {
+    match instance.lookup("").expect("table export") {
         wasmtime_runtime::Export::Table(t) => Ok((instance, t)),
         _ => unreachable!(),
     }
diff --git a/crates/wasmtime/src/trampoline/table.rs b/crates/wasmtime/src/trampoline/table.rs
index 002a495586..f0819eb882 100644
--- a/crates/wasmtime/src/trampoline/table.rs
+++ b/crates/wasmtime/src/trampoline/table.rs
@@ -25,7 +25,7 @@ pub fn create_handle_with_table(store: &Store, table: &TableType) -> Result<Stor
     let table_id = module.table_plans.push(table_plan);
     module
         .exports
-        .insert("table".to_string(), EntityIndex::Table(table_id));
+        .insert(String::new(), EntityIndex::Table(table_id));
 
     create_handle(
         module,