Merge pull request #936 from alexcrichton/import-gc

Import the `wasm-gc-api` crate into this repository

crates/cli-support/Cargo.toml

@@ -19,4 +19,4 @@ serde_json = "1.0"
 tempfile = "3.0"
 wasm-bindgen-shared = { path = "../shared", version = '=0.2.24' }
 wasm-bindgen-wasm-interpreter = { path = "../wasm-interpreter", version = '=0.2.24' }
-wasm-gc-api = "0.1.9"
+wasm-bindgen-gc = { path = '../gc', version = '=0.2.24' }

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

@@ -3,10 +3,9 @@ use std::fmt::Write;
 use std::mem;
 
 use failure::{Error, ResultExt};
-use parity_wasm;
 use parity_wasm::elements::*;
 use shared;
-use wasm_gc;
+use wasm_bindgen_gc;
 
 use super::Bindgen;
 use descriptor::{Descriptor, VectorKind};
@@ -403,7 +402,7 @@ impl<'a> Context<'a> {
         self.create_memory_export();
         self.unexport_unused_internal_exports();
         closures::rewrite(self)?;
-        self.gc()?;
+        self.gc();
 
         // Note that it's important `throw` comes last *after* we gc. The
         // `__wbindgen_malloc` function may call this but we only want to
@@ -482,7 +481,7 @@ impl<'a> Context<'a> {
         };
 
         self.export_table();
-        self.gc()?;
+        self.gc();
 
         while js.contains("\n\n\n") {
             js = js.replace("\n\n\n", "\n\n");
@@ -1661,18 +1660,12 @@ impl<'a> Context<'a> {
         );
     }
 
-    fn gc(&mut self) -> Result<(), Error> {
+    fn gc(&mut self) {
         self.parse_wasm_names();
-        let module = mem::replace(self.module, Module::default());
-        let result = wasm_gc::Config::new()
+        wasm_bindgen_gc::Config::new()
             .demangle(self.config.demangle)
             .keep_debug(self.config.keep_debug || self.config.debug)
-            .run(module, |m| parity_wasm::serialize(m).unwrap())?;
-        *self.module = match result.into_module() {
-            Ok(m) => m,
-            Err(result) => deserialize_buffer(&result.into_bytes()?)?,
-        };
-        Ok(())
+            .run(&mut self.module);
     }
 
     fn parse_wasm_names(&mut self) {

crates/cli-support/src/lib.rs

@@ -3,7 +3,7 @@
 extern crate parity_wasm;
 extern crate serde_json;
 extern crate wasm_bindgen_shared as shared;
-extern crate wasm_gc;
+extern crate wasm_bindgen_gc;
 #[macro_use]
 extern crate failure;
 extern crate wasm_bindgen_wasm_interpreter as wasm_interpreter;

crates/gc/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "wasm-bindgen-gc"
+version = "0.2.24"
+authors = ["The wasm-bindgen Developers"]
+license = "MIT/Apache-2.0"
+repository = "https://github.com/rustwasm/wasm-bindgen/tree/master/crates/gc"
+homepage = "https://rustwasm.github.io/wasm-bindgen/"
+documentation = "https://docs.rs/wasm-bindgen-gc"
+description = """
+Support for removing unused items from a wasm executable
+"""
+
+[dependencies]
+parity-wasm = "0.32"
+log = "0.4"
+rustc-demangle = "0.1.9"

crates/gc/src/bitvec.rs

@@ -0,0 +1,66 @@
+use std::mem;
+
+type T = usize;
+
+const BITS: usize = mem::size_of::<T>() * 8;
+
+pub struct BitSet {
+    bits: Vec<T>,
+}
+
+impl BitSet {
+    pub fn new() -> BitSet {
+        BitSet { bits: Vec::new() }
+    }
+
+    pub fn insert(&mut self, i: u32) -> bool {
+        let i = i as usize;
+        let idx = i / BITS;
+        let bit = 1 << (i % BITS);
+        if self.bits.len() <= idx {
+            self.bits.resize(idx + 1, 0);
+        }
+        let slot = &mut self.bits[idx];
+        if *slot & bit != 0 {
+            false
+        } else {
+            *slot |= bit;
+            true
+        }
+    }
+
+    pub fn contains(&self, i: &u32) -> bool {
+        let i = *i as usize;
+        let idx = i / BITS;
+        let bit = 1 << (i % BITS);
+        self.bits.get(idx)
+            .map(|x| *x & bit != 0)
+            .unwrap_or(false)
+    }
+}
+
+impl Default for BitSet {
+    fn default() -> BitSet {
+        BitSet::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::BitSet;
+
+    #[test]
+    fn simple() {
+        let mut x = BitSet::new();
+        assert!(!x.contains(&1));
+        assert!(!x.contains(&0));
+        assert!(!x.contains(&3));
+        assert!(x.insert(3));
+        assert!(x.contains(&3));
+        assert!(!x.insert(3));
+        assert!(x.contains(&3));
+        assert!(!x.contains(&1));
+        assert!(x.insert(2));
+        assert!(x.contains(&2));
+    }
+}

crates/gc/src/lib.rs

@@ -0,0 +1,787 @@
+//! NO GUARANTEES ARE MADE ABOUT THE BACKWARDS COMPATIBILITY OF THIS LIBRARY
+//!
+//! Internal library of `wasm-gc` to remove unreferenced items from a wasm
+//! executable.
+
+extern crate parity_wasm;
+#[macro_use]
+extern crate log;
+extern crate rustc_demangle;
+
+use std::mem;
+use std::collections::HashSet;
+
+use parity_wasm::elements::*;
+
+use bitvec::BitSet;
+
+mod bitvec;
+
+pub struct Config {
+    demangle: bool,
+    keep_debug: bool,
+}
+
+impl Config {
+    /// Creates a blank slate of configuration, ready to gc wasm files.
+    pub fn new() -> Config {
+        Config {
+            demangle: true,
+            keep_debug: false,
+        }
+    }
+
+    /// Configures whether or not this will demangle symbols as part of the gc
+    /// pass.
+    pub fn demangle(&mut self, demangle: bool) -> &mut Self {
+        self.demangle = demangle;
+        self
+    }
+
+    /// Configures whether or not debug sections will be preserved.
+    pub fn keep_debug(&mut self, keep_debug: bool) -> &mut Self {
+        self.keep_debug = keep_debug;
+        self
+    }
+
+    pub fn run(&mut self, module: &mut Module) {
+        run(self, module);
+    }
+}
+
+fn run(config: &mut Config, module: &mut Module) {
+    let analysis = {
+        let mut cx = LiveContext::new(&module);
+        cx.blacklist.insert("rust_eh_personality");
+
+        if let Some(section) = module.export_section() {
+            for (i, entry) in section.entries().iter().enumerate() {
+                cx.add_export_entry(entry, i as u32);
+            }
+        }
+        if let Some(section) = module.import_section() {
+            for (i, entry) in section.entries().iter().enumerate() {
+                debug!("import {:?}", entry);
+                if let External::Memory(_) = *entry.external() {
+                    cx.add_import_entry(entry, i as u32);
+                }
+            }
+        }
+        if let Some(section) = module.data_section() {
+            for entry in section.entries() {
+                cx.add_data_segment(entry);
+            }
+        }
+        if let Some(tables) = module.table_section() {
+            for i in 0..tables.entries().len() as u32 {
+                cx.add_table(i);
+            }
+        }
+        if let Some(elements) = module.elements_section() {
+            for seg in elements.entries() {
+                cx.add_element_segment(seg);
+            }
+        }
+        if let Some(i) = module.start_section() {
+            cx.add_function(i);
+        }
+        cx.analysis
+    };
+
+    let cx = RemapContext::new(&module, &analysis, config);
+    for i in (0..module.sections().len()).rev() {
+        let retain = match module.sections_mut()[i] {
+            Section::Unparsed { .. } => {
+                info!("unparsed section");
+                continue
+            }
+            Section::Custom(ref s) => {
+                if !cx.config.keep_debug && s.name().starts_with(".debug_") {
+                    false
+                } else {
+                    info!("skipping custom section: {}", s.name());
+                    continue
+                }
+            }
+            Section::Reloc(..) => {
+                info!("skipping reloc section");
+                continue
+            }
+            Section::Type(ref mut s) => cx.remap_type_section(s),
+            Section::Import(ref mut s) => cx.remap_import_section(s),
+            Section::Function(ref mut s) => cx.remap_function_section(s),
+            Section::Table(ref mut s) => cx.remap_table_section(s),
+            Section::Memory(ref mut s) => cx.remap_memory_section(s),
+            Section::Global(ref mut s) => cx.remap_global_section(s),
+            Section::Export(ref mut s) => cx.remap_export_section(s),
+            Section::Start(ref mut i) => { cx.remap_function_idx(i); true }
+            Section::Element(ref mut s) => cx.remap_element_section(s),
+            Section::Code(ref mut s) => cx.remap_code_section(s),
+            Section::Data(ref mut s) => cx.remap_data_section(s),
+            Section::Name(ref mut s) => { cx.remap_name_section(s); true }
+        };
+        if !retain {
+            debug!("remove empty section");
+            module.sections_mut().remove(i);
+        }
+    }
+}
+
+#[derive(Default)]
+struct Analysis {
+    codes: BitSet,
+    tables: BitSet,
+    memories: BitSet,
+    globals: BitSet,
+    types: BitSet,
+    imports: BitSet,
+    exports: BitSet,
+    functions: BitSet,
+    all_globals: BitSet,
+}
+
+enum Memories<'a> {
+    Exported(&'a MemorySection),
+    Imported(&'a MemoryType),
+}
+
+impl<'a> Memories<'a> {
+    fn has_entry(&self, idx: usize) -> bool {
+        match *self {
+            Memories::Exported(memory_section) => idx < memory_section.entries().len(),
+            Memories::Imported(_) => idx == 0,
+        }
+    }
+}
+
+struct LiveContext<'a> {
+    blacklist: HashSet<&'static str>,
+    function_section: Option<&'a FunctionSection>,
+    type_section: Option<&'a TypeSection>,
+    code_section: Option<&'a CodeSection>,
+    table_section: Option<&'a TableSection>,
+    memories: Option<Memories<'a>>,
+    global_section: Option<&'a GlobalSection>,
+    import_section: Option<&'a ImportSection>,
+    imported_functions: u32,
+    imported_globals: u32,
+    analysis: Analysis,
+}
+
+impl<'a> LiveContext<'a> {
+    fn new(module: &'a Module) -> LiveContext<'a> {
+        let memories = module.memory_section().map(Memories::Exported).or_else(|| {
+            if let Some(import_section) = module.import_section() {
+                for entry in import_section.entries() {
+                    if let External::Memory(ref memory_type) = *entry.external() {
+                        return Some(Memories::Imported(memory_type));
+                    }
+                }
+            }
+
+            None
+        });
+
+        LiveContext {
+            blacklist: HashSet::new(),
+            function_section: module.function_section(),
+            type_section: module.type_section(),
+            code_section: module.code_section(),
+            table_section: module.table_section(),
+            memories: memories,
+            global_section: module.global_section(),
+            import_section: module.import_section(),
+            imported_functions: module.import_section()
+                .map(|s| s.functions())
+                .unwrap_or(0) as u32,
+            imported_globals: module.import_section()
+                .map(|s| s.globals())
+                .unwrap_or(0) as u32,
+            analysis: Analysis::default(),
+        }
+    }
+
+    fn add_function(&mut self, idx: u32) {
+        if !self.analysis.functions.insert(idx) {
+            return
+        }
+
+        if idx < self.imported_functions {
+            let imports = self.import_section.unwrap();
+            debug!("adding import: {}", idx);
+            let (i, import) = imports.entries()
+                .iter()
+                .enumerate()
+                .filter(|&(_, i)| {
+                    match *i.external() {
+                        External::Function(_) => true,
+                        _ => false,
+                    }
+                })
+                .skip(idx as usize)
+                .next()
+                .expect("expected an imported function with this index");
+            let i = i as u32;
+            self.analysis.imports.insert(i);
+            return self.add_import_entry(import, i);
+        }
+        let idx = idx - self.imported_functions;
+
+        if !self.analysis.codes.insert(idx) {
+            return
+        }
+
+        debug!("adding function: {}", idx);
+        let functions = self.function_section.expect("no functions section");
+        self.add_type(functions.entries()[idx as usize].type_ref());
+        let codes = self.code_section.expect("no codes section");
+        self.add_func_body(&codes.bodies()[idx as usize]);
+    }
+
+    fn add_table(&mut self, mut idx: u32) {
+        if let Some(imports) = self.import_section {
+            let imported_tables = imports.entries()
+                .iter()
+                .filter(|i| {
+                    match *i.external() {
+                        External::Table(_) => true,
+                        _ => false,
+                    }
+                })
+                .count();
+            let imported_tables = imported_tables as u32;
+            if idx < imported_tables {
+                debug!("adding table import: {}", idx);
+                let (i, import) = imports.entries()
+                    .iter()
+                    .enumerate()
+                    .filter(|&(_, i)| {
+                        match *i.external() {
+                            External::Table(_) => true,
+                            _ => false,
+                        }
+                    })
+                    .skip(idx as usize)
+                    .next()
+                    .expect("expected an imported table with this index");
+                let i = i as u32;
+                self.analysis.imports.insert(i);
+                return self.add_import_entry(import, i);
+            }
+            idx -= imported_tables;
+        }
+        if !self.analysis.tables.insert(idx) {
+            return
+        }
+        let tables = self.table_section.expect("no table section");
+        let table = &tables.entries()[idx as usize];
+        drop(table);
+    }
+
+    fn add_memory(&mut self, idx: u32) {
+        if !self.analysis.memories.insert(idx) {
+            return
+        }
+        let memories = self.memories.as_ref().expect("no memory section or imported memory");
+        assert!(memories.has_entry(idx as usize));
+    }
+
+    fn add_global(&mut self, idx: u32) {
+        if !self.analysis.all_globals.insert(idx) {
+            return
+        }
+
+        if idx < self.imported_globals {
+            let imports = self.import_section.unwrap();
+            debug!("adding global import: {}", idx);
+            let (i, import) = imports.entries()
+                .iter()
+                .enumerate()
+                .filter(|&(_, i)| {
+                    match *i.external() {
+                        External::Global(_) => true,
+                        _ => false,
+                    }
+                })
+                .skip(idx as usize)
+                .next()
+                .expect("expected an imported global with this index");
+            let i = i as u32;
+            self.analysis.imports.insert(i);
+            return self.add_import_entry(import, i);
+        }
+        let idx = idx - self.imported_globals;
+
+        if !self.analysis.globals.insert(idx) {
+            return
+        }
+        let globals = self.global_section.expect("no global section");
+        let global = &globals.entries()[idx as usize];
+        self.add_global_type(global.global_type());
+        self.add_init_expr(global.init_expr());
+    }
+
+    fn add_global_type(&mut self, t: &GlobalType) {
+        self.add_value_type(&t.content_type());
+    }
+
+    fn add_init_expr(&mut self, t: &InitExpr) {
+        for opcode in t.code() {
+            self.add_opcode(opcode);
+        }
+    }
+
+    fn add_type(&mut self, idx: u32) {
+        if !self.analysis.types.insert(idx) {
+            return
+        }
+        let types = self.type_section.expect("no types section");
+        match types.types()[idx as usize] {
+            Type::Function(ref f) => {
+                for param in f.params() {
+                    self.add_value_type(param);
+                }
+                if let Some(ref ret) = f.return_type() {
+                    self.add_value_type(ret);
+                }
+            }
+        }
+    }
+
+    fn add_value_type(&mut self, value: &ValueType) {
+        match *value {
+            ValueType::I32 => {}
+            ValueType::I64 => {}
+            ValueType::F32 => {}
+            ValueType::F64 => {}
+        }
+    }
+
+    fn add_func_body(&mut self, body: &FuncBody) {
+        for local in body.locals() {
+            self.add_value_type(&local.value_type());
+        }
+        self.add_opcodes(body.code());
+    }
+
+    fn add_opcodes(&mut self, code: &Instructions) {
+        for opcode in code.elements() {
+            self.add_opcode(opcode);
+        }
+    }
+
+    fn add_opcode(&mut self, code: &Instruction) {
+        match *code {
+            Instruction::Block(ref b) |
+            Instruction::Loop(ref b) |
+            Instruction::If(ref b) => self.add_block_type(b),
+            Instruction::Call(f) => self.add_function(f),
+            Instruction::CallIndirect(t, _) => self.add_type(t),
+            Instruction::GetGlobal(i) |
+            Instruction::SetGlobal(i) => self.add_global(i),
+            _ => {}
+        }
+    }
+
+    fn add_block_type(&mut self, bt: &BlockType) {
+        match *bt {
+            BlockType::Value(ref v) => self.add_value_type(v),
+            BlockType::NoResult => {}
+        }
+    }
+
+    fn add_export_entry(&mut self, entry: &ExportEntry, idx: u32) {
+        if self.blacklist.contains(entry.field()) {
+            return
+        }
+        self.analysis.exports.insert(idx);
+        match *entry.internal() {
+            Internal::Function(i) => self.add_function(i),
+            Internal::Table(i) => self.add_table(i),
+            Internal::Memory(i) => self.add_memory(i),
+            Internal::Global(i) => self.add_global(i),
+        }
+    }
+
+    fn add_import_entry(&mut self, entry: &ImportEntry, idx: u32) {
+        match *entry.external() {
+            External::Function(i) => self.add_type(i),
+            External::Table(_) => {},
+            External::Memory(_) => {
+                self.add_memory(0);
+                self.analysis.imports.insert(idx);
+            },
+            External::Global(_) => {},
+        }
+    }
+
+    fn add_data_segment(&mut self, data: &DataSegment) {
+        self.add_memory(data.index());
+        self.add_init_expr(data.offset());
+    }
+
+    fn add_element_segment(&mut self, seg: &ElementSegment) {
+        for member in seg.members() {
+            self.add_function(*member);
+        }
+        self.add_table(seg.index());
+        self.add_init_expr(seg.offset());
+    }
+}
+
+struct RemapContext<'a> {
+    analysis: &'a Analysis,
+    config: &'a Config,
+    functions: Vec<u32>,
+    globals: Vec<u32>,
+    types: Vec<u32>,
+    tables: Vec<u32>,
+    memories: Vec<u32>,
+}
+
+impl<'a> RemapContext<'a> {
+    fn new(m: &Module, analysis: &'a Analysis, config: &'a Config) -> RemapContext<'a> {
+        let mut nfunctions = 0;
+        let mut functions = Vec::new();
+        let mut nglobals = 0;
+        let mut globals = Vec::new();
+        let mut types = Vec::new();
+        let mut ntables = 0;
+        let mut tables = Vec::new();
+        let mut nmemories = 0;
+        let mut memories = Vec::new();
+
+        if let Some(s) = m.type_section() {
+            let mut removed = 0;
+            for i in 0..(s.types().len() as u32) {
+                if analysis.types.contains(&i) {
+                    types.push(i - removed);
+                } else {
+                    debug!("gc type {}", i);
+                    types.push(u32::max_value());
+                    removed += 1;
+                }
+            }
+        }
+        if let Some(s) = m.import_section() {
+            for (i, import) in s.entries().iter().enumerate() {
+                let (dst, ndst) = match *import.external() {
+                    External::Function(_) => (&mut functions, &mut nfunctions),
+                    External::Table(_) => (&mut tables, &mut ntables),
+                    External::Memory(_) => (&mut memories, &mut nmemories),
+                    External::Global(_) => (&mut globals, &mut nglobals),
+                };
+                if analysis.imports.contains(&(i as u32)) {
+                    dst.push(*ndst);
+                    *ndst += 1;
+                } else {
+                    debug!("gc import {}", i);
+                    dst.push(u32::max_value());
+                }
+            }
+        }
+        if let Some(s) = m.function_section() {
+            for i in 0..(s.entries().len() as u32) {
+                if analysis.codes.contains(&i) {
+                    functions.push(nfunctions);
+                    nfunctions += 1;
+                } else {
+                    debug!("gc function {}", i);
+                    functions.push(u32::max_value());
+                }
+            }
+        }
+        if let Some(s) = m.global_section() {
+            for i in 0..(s.entries().len() as u32) {
+                if analysis.globals.contains(&i) {
+                    globals.push(nglobals);
+                    nglobals += 1;
+                } else {
+                    debug!("gc global {}", i);
+                    globals.push(u32::max_value());
+                }
+            }
+        }
+        if let Some(s) = m.table_section() {
+            for i in 0..(s.entries().len() as u32) {
+                if analysis.tables.contains(&i) {
+                    tables.push(ntables);
+                    ntables += 1;
+                } else {
+                    debug!("gc table {}", i);
+                    tables.push(u32::max_value());
+                }
+            }
+        }
+        if let Some(s) = m.memory_section() {
+            for i in 0..(s.entries().len() as u32) {
+                if analysis.memories.contains(&i) {
+                    memories.push(nmemories);
+                    nmemories += 1;
+                } else {
+                    debug!("gc memory {}", i);
+                    memories.push(u32::max_value());
+                }
+            }
+        }
+
+        RemapContext {
+            analysis,
+            functions,
+            globals,
+            memories,
+            tables,
+            types,
+            config,
+        }
+    }
+
+    fn retain<T>(&self, set: &BitSet, list: &mut Vec<T>, name: &str) {
+        for i in (0..list.len()).rev().map(|x| x as u32) {
+            if !set.contains(&i) {
+                debug!("removing {} {}", name, i);
+                list.remove(i as usize);
+            }
+        }
+    }
+
+    fn remap_type_section(&self, s: &mut TypeSection) -> bool {
+        self.retain(&self.analysis.types, s.types_mut(), "type");
+        for t in s.types_mut() {
+            self.remap_type(t);
+        }
+        s.types().len() > 0
+    }
+
+    fn remap_type(&self, t: &mut Type) {
+        match *t {
+            Type::Function(ref mut t) => self.remap_function_type(t),
+        }
+    }
+
+    fn remap_function_type(&self, t: &mut FunctionType) {
+        for param in t.params_mut() {
+            self.remap_value_type(param);
+        }
+        if let Some(m) = t.return_type_mut().as_mut() {
+            self.remap_value_type(m);
+        }
+    }
+
+    fn remap_value_type(&self, t: &mut ValueType) {
+        drop(t);
+    }
+
+    fn remap_import_section(&self, s: &mut ImportSection) -> bool {
+        self.retain(&self.analysis.imports, s.entries_mut(), "import");
+        for i in s.entries_mut() {
+            self.remap_import_entry(i);
+        }
+        s.entries().len() > 0
+    }
+
+    fn remap_import_entry(&self, s: &mut ImportEntry) {
+        debug!("remap import entry {:?}", s);
+        match *s.external_mut() {
+            External::Function(ref mut f) => self.remap_type_idx(f),
+            External::Table(_) => {}
+            External::Memory(_) => {}
+            External::Global(_) => {}
+        }
+    }
+
+    fn remap_function_section(&self, s: &mut FunctionSection) -> bool {
+        self.retain(&self.analysis.codes, s.entries_mut(), "function");
+        for f in s.entries_mut() {
+            self.remap_func(f);
+        }
+        s.entries().len() > 0
+    }
+
+    fn remap_func(&self, f: &mut Func) {
+        self.remap_type_idx(f.type_ref_mut());
+    }
+
+    fn remap_table_section(&self, s: &mut TableSection) -> bool {
+        self.retain(&self.analysis.tables, s.entries_mut(), "table");
+        for t in s.entries_mut() {
+            drop(t); // TODO
+        }
+        s.entries().len() > 0
+    }
+
+    fn remap_memory_section(&self, s: &mut MemorySection) -> bool {
+        self.retain(&self.analysis.memories, s.entries_mut(), "memory");
+        for m in s.entries_mut() {
+            drop(m); // TODO
+        }
+        s.entries().len() > 0
+    }
+
+    fn remap_global_section(&self, s: &mut GlobalSection) -> bool {
+        self.retain(&self.analysis.globals, s.entries_mut(), "global");
+        for g in s.entries_mut() {
+            self.remap_global_entry(g);
+        }
+        s.entries().len() > 0
+    }
+
+    fn remap_global_entry(&self, s: &mut GlobalEntry) {
+        self.remap_global_type(s.global_type_mut());
+        self.remap_init_expr(s.init_expr_mut());
+    }
+
+    fn remap_global_type(&self, s: &mut GlobalType) {
+        drop(s);
+    }
+
+    fn remap_init_expr(&self, s: &mut InitExpr) {
+        for code in s.code_mut() {
+            self.remap_instruction(code);
+        }
+    }
+
+    fn remap_export_section(&self, s: &mut ExportSection) -> bool {
+        self.retain(&self.analysis.exports, s.entries_mut(), "export");
+        for s in s.entries_mut() {
+            self.remap_export_entry(s);
+        }
+        s.entries().len() > 0
+    }
+
+    fn remap_export_entry(&self, s: &mut ExportEntry) {
+        match *s.internal_mut() {
+            Internal::Function(ref mut i) => self.remap_function_idx(i),
+            Internal::Table(ref mut i) => self.remap_table_idx(i),
+            Internal::Memory(ref mut i) => self.remap_memory_idx(i),
+            Internal::Global(ref mut i) => self.remap_global_idx(i),
+        }
+    }
+
+    fn remap_element_section(&self, s: &mut ElementSection) -> bool {
+        for s in s.entries_mut() {
+            self.remap_element_segment(s);
+        }
+        true
+    }
+
+    fn remap_element_segment(&self, s: &mut ElementSegment) {
+        let mut i = s.index();
+        self.remap_table_idx(&mut i);
+        assert_eq!(s.index(), i);
+        for m in s.members_mut() {
+            self.remap_function_idx(m);
+        }
+        self.remap_init_expr(s.offset_mut());
+    }
+
+    fn remap_code_section(&self, s: &mut CodeSection) -> bool {
+        self.retain(&self.analysis.codes, s.bodies_mut(), "code");
+        for s in s.bodies_mut() {
+            self.remap_func_body(s);
+        }
+        s.bodies().len() > 0
+    }
+
+    fn remap_func_body(&self, b: &mut FuncBody) {
+        self.remap_code(b.code_mut());
+    }
+
+    fn remap_code(&self, c: &mut Instructions) {
+        for i in c.elements_mut() {
+            self.remap_instruction(i);
+        }
+    }
+
+    fn remap_instruction(&self, i: &mut Instruction) {
+        match *i {
+            Instruction::Block(ref mut b) |
+            Instruction::Loop(ref mut b) |
+            Instruction::If(ref mut b) => self.remap_block_type(b),
+            Instruction::Call(ref mut f) => self.remap_function_idx(f),
+            Instruction::CallIndirect(ref mut t, _) => self.remap_type_idx(t),
+            Instruction::GetGlobal(ref mut i) |
+            Instruction::SetGlobal(ref mut i) => self.remap_global_idx(i),
+            _ => {}
+        }
+    }
+
+    fn remap_block_type(&self, bt: &mut BlockType) {
+        match *bt {
+            BlockType::Value(ref mut v) => self.remap_value_type(v),
+            BlockType::NoResult => {}
+        }
+    }
+
+    fn remap_data_section(&self, s: &mut DataSection) -> bool {
+        for data in s.entries_mut() {
+            self.remap_data_segment(data);
+        }
+        true
+    }
+
+    fn remap_data_segment(&self, segment: &mut DataSegment) {
+        let mut i = segment.index();
+        self.remap_memory_idx(&mut i);
+        assert_eq!(segment.index(), i);
+        self.remap_init_expr(segment.offset_mut());
+    }
+
+    fn remap_type_idx(&self, i: &mut u32) {
+        *i = self.types[*i as usize];
+        assert!(*i != u32::max_value());
+    }
+
+    fn remap_function_idx(&self, i: &mut u32) {
+        *i = self.functions[*i as usize];
+        assert!(*i != u32::max_value());
+    }
+
+    fn remap_global_idx(&self, i: &mut u32) {
+        trace!("global {} => {}", *i, self.globals[*i as usize]);
+        *i = self.globals[*i as usize];
+        assert!(*i != u32::max_value());
+    }
+
+    fn remap_table_idx(&self, i: &mut u32) {
+        *i = self.tables[*i as usize];
+        assert!(*i != u32::max_value());
+    }
+
+    fn remap_memory_idx(&self, i: &mut u32) {
+        *i = self.memories[*i as usize];
+        assert!(*i != u32::max_value());
+    }
+
+    fn remap_name_section(&self, s: &mut NameSection) {
+        match *s {
+            NameSection::Module(_) => {}
+            NameSection::Function(ref mut f) => {
+                let map = f.names_mut();
+                let new = IndexMap::with_capacity(map.len());
+                for (idx, name) in mem::replace(map, new) {
+                    let new_idx = self.functions[idx as usize];
+                    let name = if self.config.demangle {
+                        rustc_demangle::demangle(&name).to_string()
+                    } else {
+                        name
+                    };
+                    if new_idx != u32::max_value() {
+                        map.insert(new_idx, name);
+                    }
+                }
+            }
+            NameSection::Local(ref mut l) => {
+                let map = l.local_names_mut();
+                let new = IndexMap::with_capacity(map.len());
+                for (idx, value) in mem::replace(map, new) {
+                    let new_idx = self.functions[idx as usize];
+                    if new_idx != u32::max_value() {
+                        map.insert(new_idx, value);
+                    }
+                }
+            }
+            NameSection::Unparsed { .. } => {}
+        }
+    }
+}