From 5f742ca4c473af3e529e1d5700e11dea281bfc78 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Tue, 26 Mar 2019 18:12:24 +0000
Subject: [PATCH] Simplify ABI for Option<char>

Flatten None to a special u32 value instead of using an intermediate pointer.
---
 crates/cli-support/src/js/js2rust.rs | 16 ++++-----------
 crates/cli-support/src/js/rust2js.rs | 14 +++-----------
 src/convert/impls.rs                 | 29 ++++++----------------------
 3 files changed, 13 insertions(+), 46 deletions(-)

diff --git a/crates/cli-support/src/js/js2rust.rs b/crates/cli-support/src/js/js2rust.rs
index 1b25307a..07831b44 100644
--- a/crates/cli-support/src/js/js2rust.rs
+++ b/crates/cli-support/src/js/js2rust.rs
@@ -343,9 +343,8 @@ impl<'a, 'b> Js2Rust<'a, 'b> {
                     self.cx.expose_is_like_none();
                     self.js_arguments
                         .push((name.clone(), "string | undefined".to_string()));
-                    self.rust_arguments.push(format!("!isLikeNone({0})", name));
                     self.rust_arguments
-                        .push(format!("isLikeNone({0}) ? 0 : {0}.codePointAt(0)", name));
+                        .push(format!("isLikeNone({0}) ? 0xFFFFFF : {0}.codePointAt(0)", name));
                     return Ok(self);
                 }
                 Descriptor::Enum { hole } => {
@@ -632,17 +631,10 @@ impl<'a, 'b> Js2Rust<'a, 'b> {
                 }
                 Descriptor::Char => {
                     self.ret_ty = "string | undefined".to_string();
-                    self.cx.expose_global_argument_ptr()?;
-                    self.cx.expose_uint32_memory();
-                    self.prelude("const retptr = globalArgumentPtr();");
-                    self.rust_arguments.insert(0, "retptr".to_string());
                     self.ret_expr = "
-                        RET;
-                        const present = getUint32Memory()[retptr / 4];
-                        const value = getUint32Memory()[retptr / 4 + 1];
-                        return present === 0 ? undefined : String.fromCodePoint(value);
-                    "
-                    .to_string();
+                        const ret = RET;
+                        return ret === 0xFFFFFF ? undefined : String.fromCodePoint(ret);
+                    ".to_string();
                     return Ok(self);
                 }
                 Descriptor::Enum { hole } => {
diff --git a/crates/cli-support/src/js/rust2js.rs b/crates/cli-support/src/js/rust2js.rs
index de4640a1..366fd84b 100644
--- a/crates/cli-support/src/js/rust2js.rs
+++ b/crates/cli-support/src/js/rust2js.rs
@@ -215,12 +215,8 @@ impl<'a, 'b> Rust2Js<'a, 'b> {
                     return Ok(());
                 }
                 Descriptor::Char => {
-                    let value = self.shim_argument();
-                    self.js_arguments.push(format!(
-                        "{present} === 0 ? undefined : String.fromCodePoint({value})",
-                        value = value,
-                        present = abi,
-                    ));
+                    self.js_arguments
+                        .push(format!("{0} === 0xFFFFFF ? undefined : String.fromCodePoint({0})", abi));
                     return Ok(());
                 }
                 Descriptor::RustStruct(ref class) => {
@@ -468,13 +464,9 @@ impl<'a, 'b> Rust2Js<'a, 'b> {
                     return Ok(());
                 }
                 Descriptor::Char => {
-                    self.cx.expose_is_like_none();
-                    self.cx.expose_uint32_memory();
-                    self.shim_arguments.insert(0, "ret".to_string());
                     self.ret_expr = "
                         const val = JS;
-                        getUint32Memory()[ret / 4] = !isLikeNone(val);
-                        getUint32Memory()[ret / 4 + 1] = isLikeNone(val) ? 0 : val.codePointAt(0);
+                        return isLikeNone(val) ? 0xFFFFFF : val.codePointAt(0);
                     "
                     .to_string();
                     return Ok(());
diff --git a/src/convert/impls.rs b/src/convert/impls.rs
index ec66a9aa..c779ef13 100644
--- a/src/convert/impls.rs
+++ b/src/convert/impls.rs
@@ -258,34 +258,17 @@ impl FromWasmAbi for char {
     }
 }
 
-impl IntoWasmAbi for Option<char> {
-    type Abi = WasmOptionalU32;
-
+impl OptionIntoWasmAbi for char {
     #[inline]
-    fn into_abi(self, _extra: &mut Stack) -> WasmOptionalU32 {
-        match self {
-            None => WasmOptionalU32 {
-                present: 0,
-                value: 0,
-            },
-            Some(me) => WasmOptionalU32 {
-                present: 1,
-                value: me as u32,
-            },
-        }
+    fn none() -> u32 {
+        0xFFFFFFu32
     }
 }
 
-impl FromWasmAbi for Option<char> {
-    type Abi = WasmOptionalU32;
-
+impl OptionFromWasmAbi for char {
     #[inline]
-    unsafe fn from_abi(js: WasmOptionalU32, _extra: &mut Stack) -> Self {
-        if js.present == 0 {
-            None
-        } else {
-            Some(char::from_u32_unchecked(js.value))
-        }
+    fn is_none(js: &u32) -> bool {
+        *js == 0xFFFFFFu32
     }
 }