Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 832 insertions, 0 deletions

diff --git a/third_party/wasm2c/src/decompiler.cc b/third_party/wasm2c/src/decompiler.cc
new file mode 100644
index 0000000000..25fd75a1bb
--- /dev/null
+++ b/third_party/wasm2c/src/decompiler.cc
@@ -0,0 +1,832 @@
+/*
+ * Copyright 2019 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "src/decompiler.h"
+
+#include "src/decompiler-ast.h"
+#include "src/decompiler-ls.h"
+#include "src/decompiler-naming.h"
+
+#include "src/stream.h"
+
+#define WABT_TRACING 0
+#include "src/tracing.h"
+
+#include <inttypes.h>
+
+namespace wabt {
+
+struct Decompiler {
+  Decompiler(const Module& module, const DecompileOptions& options)
+      : mc(module), options(options) {}
+
+  // Sorted such that "greater precedence" is also the bigger enum val.
+  enum Precedence {
+    // Low precedence.
+    None,      // precedence doesn't matter, since never nested.
+    Assign,    // =
+    OtherBin,  // min
+    Bit,       // & |
+    Equal,     // == != < > >= <=
+    Shift,     // << >>
+    Add,       // + -
+    Multiply,  // * / %
+    If,        // if{}
+    Indexing,  // []
+    Atomic,    // (), a, 1, a()
+    // High precedence.
+  };
+
+  // Anything besides these will get parentheses if used with equal precedence,
+  // for clarity.
+  bool Associative(Precedence p) {
+    return p == Precedence::Add || p == Precedence::Multiply;
+  }
+
+  struct Value {
+    std::vector<std::string> v;
+    // Lazily add bracketing only if the parent requires it.
+    // This is the precedence level of this value, for example, if this
+    // precedence is Add, and the parent is Multiply, bracketing is needed,
+    // but not if it is the reverse.
+    Precedence precedence;
+
+    Value(std::vector<std::string>&& v, Precedence p)
+      : v(v), precedence(p) {}
+
+    size_t width() {
+      size_t w = 0;
+      for (auto &s : v) {
+        w = std::max(w, s.size());
+      }
+      return w;
+    }
+
+    // This value should really never be copied, only moved.
+    Value(Value&& rhs) = default;
+    Value(const Value& rhs) = delete;
+    Value& operator=(Value&& rhs) = default;
+    Value& operator=(const Value& rhs) = delete;
+  };
+
+  std::string to_string(double d) {
+    auto s = std::to_string(d);
+    // Remove redundant trailing '0's that to_string produces.
+    while (s.size() > 2 && s.back() == '0' && s[s.size() - 2] != '.')
+      s.pop_back();
+    return s;
+  }
+
+  std::string Indent(size_t amount) {
+    return std::string(amount, ' ');
+  }
+
+  std::string OpcodeToToken(Opcode opcode) {
+    std::string s = opcode.GetDecomp();
+    std::replace(s.begin(), s.end(), '.', '_');
+    return s;
+  }
+
+  void IndentValue(Value &val, size_t amount, string_view first_indent) {
+    auto indent = Indent(amount);
+    for (auto& stat : val.v) {
+      auto is = (&stat != &val.v[0] || first_indent.empty())
+                    ? string_view(indent)
+                    : first_indent;
+      stat.insert(0, is.data(), is.size());
+    }
+  }
+
+  Value WrapChild(Value &child, string_view prefix, string_view postfix,
+                  Precedence precedence) {
+    auto width = prefix.size() + postfix.size() + child.width();
+    auto &v = child.v;
+    if (width < target_exp_width ||
+        (prefix.size() <= indent_amount && postfix.size() <= indent_amount)) {
+      if (v.size() == 1) {
+        // Fits in a single line.
+        v[0].insert(0, prefix.data(), prefix.size());
+        v[0].append(postfix.data(), postfix.size());
+      } else {
+        // Multiline, but with prefix on same line.
+        IndentValue(child, prefix.size(), prefix);
+        v.back().append(postfix.data(), postfix.size());
+      }
+    } else {
+      // Multiline with prefix on its own line.
+      IndentValue(child, indent_amount, {});
+      v.insert(v.begin(), std::string(prefix));
+      v.back().append(postfix.data(), postfix.size());
+    }
+    child.precedence = precedence;
+    return std::move(child);
+  }
+
+  void BracketIfNeeded(Value &val, Precedence parent_precedence) {
+    if (parent_precedence < val.precedence ||
+        (parent_precedence == val.precedence &&
+         Associative(parent_precedence))) return;
+    val = WrapChild(val, "(", ")", Precedence::Atomic);
+  }
+
+  Value WrapBinary(std::vector<Value>& args, string_view infix,
+                   bool indent_right, Precedence precedence) {
+    assert(args.size() == 2);
+    auto& left = args[0];
+    auto& right = args[1];
+    BracketIfNeeded(left, precedence);
+    BracketIfNeeded(right, precedence);
+    auto width = infix.size() + left.width() + right.width() + 2;
+    if (width < target_exp_width && left.v.size() == 1 && right.v.size() == 1) {
+      return Value{{cat(left.v[0], " ", infix, " ", right.v[0])}, precedence};
+    } else {
+      Value bin { {}, precedence };
+      std::move(left.v.begin(), left.v.end(), std::back_inserter(bin.v));
+      bin.v.back().append(" ", 1);
+      bin.v.back().append(infix.data(), infix.size());
+      if (indent_right) IndentValue(right, indent_amount, {});
+      std::move(right.v.begin(), right.v.end(), std::back_inserter(bin.v));
+      return bin;
+    }
+  }
+
+  Value WrapNAry(std::vector<Value>& args, string_view prefix,
+                 string_view postfix, Precedence precedence) {
+    size_t total_width = 0;
+    size_t max_width = 0;
+    bool multiline = false;
+    for (auto& child : args) {
+      auto w = child.width();
+      max_width = std::max(max_width, w);
+      total_width += w;
+      multiline = multiline || child.v.size() > 1;
+    }
+    if (!multiline &&
+        (total_width + prefix.size() + postfix.size() < target_exp_width ||
+         args.empty())) {
+      // Single line.
+      auto s = std::string(prefix);
+      for (auto& child : args) {
+        if (&child != &args[0])
+          s += ", ";
+        s += child.v[0];
+      }
+      s += postfix;
+      return Value{{std::move(s)}, precedence};
+    } else {
+      // Multi-line.
+      Value ml { {}, precedence };
+      auto ident_with_name = max_width + prefix.size() < target_exp_width;
+      size_t i = 0;
+      for (auto& child : args) {
+        IndentValue(child, ident_with_name ? prefix.size() : indent_amount,
+                    !i && ident_with_name ? prefix : string_view {});
+        if (i < args.size() - 1) child.v.back() += ",";
+        std::move(child.v.begin(), child.v.end(),
+                  std::back_inserter(ml.v));
+        i++;
+      }
+      if (!ident_with_name) ml.v.insert(ml.v.begin(), std::string(prefix));
+      ml.v.back() += postfix;
+      return ml;
+    }
+  }
+
+  string_view VarName(string_view name) {
+    assert(!name.empty());
+    return name[0] == '$' ? name.substr(1) : name;
+  }
+
+  template<ExprType T> Value Get(const VarExpr<T>& ve) {
+    return Value{{std::string(VarName(ve.var.name()))}, Precedence::Atomic};
+  }
+
+  template<ExprType T> Value Set(Value& child, const VarExpr<T>& ve) {
+    return WrapChild(child, VarName(ve.var.name()) + " = ", "", Precedence::Assign);
+  }
+
+  std::string TempVarName(Index n) {
+    // FIXME: this needs much better variable naming. Problem is, the code
+    // in generate-names.cc has allready run, its dictionaries deleted, so it
+    // is not easy to integrate with it.
+    return "t" + std::to_string(n);
+  }
+
+  std::string LocalDecl(const std::string& name, Type t) {
+    auto struc = lst.GenTypeDecl(name);
+    return cat(VarName(name), ":",
+               struc.empty() ? GetDecompTypeName(t) : struc);
+  }
+
+  bool ConstIntVal(const Expr* e, uint64_t &dest) {
+    dest = 0;
+    if (!e || e->type() != ExprType::Const) return false;
+    auto& c = cast<ConstExpr>(e)->const_;
+    if (c.type() != Type::I32 && c.type() != Type::I64) return false;
+    dest = c.type() == Type::I32 ? c.u32() : c.u64();
+    return true;
+  }
+
+  void LoadStore(Value &val, const Node& addr_exp, uint64_t offset,
+                  Opcode opc, Address align, Type op_type) {
+    bool append_type = true;
+    auto access = lst.GenAccess(offset, addr_exp);
+    if (!access.empty()) {
+      if (access == "*") {
+        // The variable was declared as a typed pointer, so this access
+        // doesn't need a type.
+        append_type = false;
+      } else {
+        // We can do this load/store as a struct access.
+        BracketIfNeeded(val, Precedence::Indexing);
+        val.v.back() += "." + access;
+        return;
+      }
+    }
+    // Detect absolute addressing, which we try to turn into references to the
+    // data section when possible.
+    uint64_t abs_base;
+    if (ConstIntVal(addr_exp.e, abs_base)) {
+      // We don't care what part of the absolute address was stored where,
+      // 1[0] and 0[1] are the same.
+      abs_base += offset;
+      // FIXME: make this less expensive with a binary search or whatever.
+      for (auto dat : mc.module.data_segments) {
+        uint64_t dat_base;
+        if (dat->offset.size() == 1 &&
+            ConstIntVal(&dat->offset.front(), dat_base) &&
+            abs_base >= dat_base &&
+            abs_base < dat_base + dat->data.size()) {
+          // We are inside the range of this data segment!
+          // Turn expression into data_name[index]
+          val = Value { { dat->name }, Precedence::Atomic };
+          // The new offset is from the start of the data segment, instead of
+          // whatever it was.. this may be a different value from both the
+          // original const and offset!
+          offset = abs_base - dat_base;
+        }
+      }
+    }
+    // Do the load/store as a generalized indexing operation.
+    // The offset is divisible by the alignment in 99.99% of
+    // cases, but the spec doesn't guarantee it, so we must
+    // have a backup syntax.
+    auto index = offset % align == 0
+                ? std::to_string(offset / align)
+                : cat(std::to_string(offset), "@", std::to_string(align));
+    // Detect the very common case of (base + (index << 2))[0]:int etc.
+    // so we can instead do base[index]:int
+    // TODO: (index << 2) on the left of + occurs also.
+    // TODO: sadly this does not address cases where the shift amount > align.
+    // (which happens for arrays of structs or arrays of long (with align=4)).
+    // TODO: also very common is (v = base + (index << 2))[0]:int
+    if (addr_exp.etype == ExprType::Binary) {
+      auto& pe = *cast<BinaryExpr>(addr_exp.e);
+      auto& shift_exp = addr_exp.children[1];
+      if (pe.opcode == Opcode::I32Add &&
+          shift_exp.etype == ExprType::Binary) {
+        auto& se = *cast<BinaryExpr>(shift_exp.e);
+        auto& const_exp = shift_exp.children[1];
+        if (se.opcode == Opcode::I32Shl &&
+            const_exp.etype == ExprType::Const) {
+          auto& ce = *cast<ConstExpr>(const_exp.e);
+          if (ce.const_.type() == Type::I32 &&
+              (1ULL << ce.const_.u32()) == align) {
+            // Pfew, case detected :( Lets re-write this in Haskell.
+            // TODO: we're decompiling these twice.
+            // The thing to the left of << is going to be part of the index.
+            auto ival = DecompileExpr(shift_exp.children[0], &shift_exp);
+            if (ival.v.size() == 1) {  // Don't bother if huge.
+              if (offset == 0) {
+                index = ival.v[0];
+              } else {
+                BracketIfNeeded(ival, Precedence::Add);
+                index = cat(ival.v[0], " + ", index);
+              }
+              // We're going to use the thing to the left of + as the new
+              // base address:
+              val = DecompileExpr(addr_exp.children[0], &addr_exp);
+            }
+          }
+        }
+      }
+    }
+    BracketIfNeeded(val, Precedence::Indexing);
+    val.v.back() += cat("[", index, "]");
+    if (append_type) {
+      val.v.back() +=
+        cat(":", GetDecompTypeName(GetMemoryType(op_type, opc)),
+            lst.GenAlign(align, opc));
+    }
+    val.precedence = Precedence::Indexing;
+  }
+
+  Value DecompileExpr(const Node& n, const Node* parent) {
+    std::vector<Value> args;
+    for (auto& c : n.children) {
+      args.push_back(DecompileExpr(c, &n));
+    }
+    // First deal with the specialized node types.
+    switch (n.ntype) {
+      case NodeType::FlushToVars: {
+        std::string decls = "let ";
+        for (Index i = 0; i < n.u.var_count; i++) {
+          if (i) decls += ", ";
+          decls += TempVarName(n.u.var_start + i);
+        }
+        decls += " = ";
+        return WrapNAry(args, decls, "", Precedence::Assign);
+      }
+      case NodeType::FlushedVar: {
+        return Value { { TempVarName(n.u.var_start) }, Precedence::Atomic };
+      }
+      case NodeType::Statements: {
+        Value stats { {}, Precedence::None };
+        for (size_t i = 0; i < n.children.size(); i++) {
+          auto& s = args[i].v.back();
+          if (s.back() != '}' && s.back() != ':') s += ';';
+          std::move(args[i].v.begin(), args[i].v.end(),
+                    std::back_inserter(stats.v));
+        }
+        return stats;
+      }
+      case NodeType::EndReturn: {
+        return WrapNAry(args, "return ", "", Precedence::None);
+      }
+      case NodeType::Decl: {
+        cur_ast->vars_defined[n.u.var->name()].defined = true;
+        return Value{
+            {"var " + LocalDecl(std::string(n.u.var->name()),
+                                cur_func->GetLocalType(*n.u.var))},
+            Precedence::None};
+      }
+      case NodeType::DeclInit: {
+        if (cur_ast->vars_defined[n.u.var->name()].defined) {
+          // This has already been pre-declared, output as assign.
+          return WrapChild(args[0], cat(VarName(n.u.var->name()), " = "), "",
+                           Precedence::None);
+        } else {
+          return WrapChild(
+              args[0],
+              cat("var ",
+                  LocalDecl(std::string(n.u.var->name()),
+                            cur_func->GetLocalType(*n.u.var)),
+                  " = "),
+              "", Precedence::None);
+        }
+      }
+      case NodeType::Expr:
+        // We're going to fall thru to the second switch to deal with ExprType.
+        break;
+      case NodeType::Uninitialized:
+        assert(false);
+        break;
+    }
+    // Existing ExprTypes.
+    switch (n.etype) {
+      case ExprType::Const: {
+        auto& c = cast<ConstExpr>(n.e)->const_;
+        switch (c.type()) {
+          case Type::I32:
+            return Value{{std::to_string(static_cast<int32_t>(c.u32()))},
+                         Precedence::Atomic};
+          case Type::I64:
+            return Value{{std::to_string(static_cast<int64_t>(c.u64())) + "L"},
+                         Precedence::Atomic};
+          case Type::F32: {
+            float f = Bitcast<float>(c.f32_bits());
+            return Value{{to_string(f) + "f"}, Precedence::Atomic};
+          }
+          case Type::F64: {
+            double d = Bitcast<double>(c.f64_bits());
+            return Value{{to_string(d)}, Precedence::Atomic};
+          }
+          case Type::V128:
+            return Value{{"V128"}, Precedence::Atomic};  // FIXME
+          default:
+            WABT_UNREACHABLE;
+        }
+      }
+      case ExprType::LocalGet: {
+        return Get(*cast<LocalGetExpr>(n.e));
+      }
+      case ExprType::GlobalGet: {
+        return Get(*cast<GlobalGetExpr>(n.e));
+      }
+      case ExprType::LocalSet: {
+        return Set(args[0], *cast<LocalSetExpr>(n.e));
+      }
+      case ExprType::GlobalSet: {
+        return Set(args[0], *cast<GlobalSetExpr>(n.e));
+      }
+      case ExprType::LocalTee: {
+        auto& te = *cast<LocalTeeExpr>(n.e);
+        return args.empty() ? Get(te) : Set(args[0], te);
+      }
+      case ExprType::Binary: {
+        auto& be = *cast<BinaryExpr>(n.e);
+        auto opcs = OpcodeToToken(be.opcode);
+        // TODO: Is this selection better done on Opcode values directly?
+        // What if new values get added and OtherBin doesn't make sense?
+        auto prec = Precedence::OtherBin;
+        if (opcs == "*" || opcs == "/" || opcs == "%") {
+          prec = Precedence::Multiply;
+        } else if (opcs == "+" || opcs == "-") {
+          prec = Precedence::Add;
+        } else if (opcs == "&" || opcs == "|" || opcs == "^") {
+          prec = Precedence::Bit;
+        } else if (opcs == "<<" || opcs == ">>") {
+          prec = Precedence::Shift;
+        }
+        return WrapBinary(args, opcs, false, prec);
+      }
+      case ExprType::Compare: {
+        auto& ce = *cast<CompareExpr>(n.e);
+        return WrapBinary(args, OpcodeToToken(ce.opcode), false,
+                          Precedence::Equal);
+      }
+      case ExprType::Unary: {
+        auto& ue = *cast<UnaryExpr>(n.e);
+        //BracketIfNeeded(stack.back());
+        // TODO: also version without () depending on precedence.
+        return WrapChild(args[0], OpcodeToToken(ue.opcode) + "(", ")",
+                         Precedence::Atomic);
+      }
+      case ExprType::Load: {
+        auto& le = *cast<LoadExpr>(n.e);
+        LoadStore(args[0], n.children[0], le.offset, le.opcode, le.align,
+                  le.opcode.GetResultType());
+        return std::move(args[0]);
+      }
+      case ExprType::Store: {
+        auto& se = *cast<StoreExpr>(n.e);
+        LoadStore(args[0], n.children[0], se.offset, se.opcode, se.align,
+                  se.opcode.GetParamType2());
+        return WrapBinary(args, "=", true, Precedence::Assign);
+      }
+      case ExprType::If: {
+        auto ife = cast<IfExpr>(n.e);
+        Value *elsep = nullptr;
+        if (!ife->false_.empty()) {
+          elsep = &args[2];
+        }
+        auto& thenp = args[1];
+        auto& ifs = args[0];
+        bool multiline = ifs.v.size() > 1 || thenp.v.size() > 1;
+        size_t width = ifs.width() + thenp.width();
+        if (elsep) {
+          width += elsep->width();
+          multiline = multiline || elsep->v.size() > 1;
+        }
+        multiline = multiline || width > target_exp_width;
+        if (multiline) {
+          auto if_start = string_view("if (");
+          IndentValue(ifs, if_start.size(), if_start);
+          ifs.v.back() += ") {";
+          IndentValue(thenp, indent_amount, {});
+          std::move(thenp.v.begin(), thenp.v.end(), std::back_inserter(ifs.v));
+          if (elsep) {
+            ifs.v.push_back("} else {");
+            IndentValue(*elsep, indent_amount, {});
+            std::move(elsep->v.begin(), elsep->v.end(), std::back_inserter(ifs.v));
+          }
+          ifs.v.push_back("}");
+          ifs.precedence = Precedence::If;
+          return std::move(ifs);
+        } else {
+          auto s = cat("if (", ifs.v[0], ") { ", thenp.v[0], " }");
+          if (elsep)
+            s += cat(" else { ", elsep->v[0], " }");
+          return Value{{std::move(s)}, Precedence::If};
+        }
+      }
+      case ExprType::Block: {
+        auto& val = args[0];
+        val.v.push_back(
+              cat("label ", VarName(cast<BlockExpr>(n.e)->block.label), ":"));
+        // If this block is part of a larger statement scope, it doesn't
+        // need its own indenting, but if its part of an exp we wrap it in {}.
+        if (parent && parent->ntype != NodeType::Statements
+                   && parent->etype != ExprType::Block
+                   && parent->etype != ExprType::Loop
+                   && (parent->etype != ExprType::If ||
+                       &parent->children[0] == &n)) {
+          IndentValue(val, indent_amount, {});
+          val.v.insert(val.v.begin(), "{");
+          val.v.push_back("}");
+        }
+        val.precedence = Precedence::Atomic;
+        return std::move(val);
+      }
+      case ExprType::Loop: {
+        auto& val = args[0];
+        auto& block = cast<LoopExpr>(n.e)->block;
+        IndentValue(val, indent_amount, {});
+        val.v.insert(val.v.begin(), cat("loop ", VarName(block.label), " {"));
+        val.v.push_back("}");
+        val.precedence = Precedence::Atomic;
+        return std::move(val);
+      }
+      case ExprType::Br: {
+        auto be = cast<BrExpr>(n.e);
+        return Value{{(n.u.lt == LabelType::Loop ? "continue " : "goto ") +
+                      VarName(be->var.name())},
+                     Precedence::None};
+      }
+      case ExprType::BrIf: {
+        auto bie = cast<BrIfExpr>(n.e);
+        auto jmp = n.u.lt == LabelType::Loop ? "continue" : "goto";
+        return WrapChild(args[0], "if (", cat(") ", jmp, " ",
+                                              VarName(bie->var.name())),
+                         Precedence::None);
+      }
+      case ExprType::Return: {
+        return WrapNAry(args, "return ", "", Precedence::None);
+      }
+      case ExprType::Rethrow: {
+        return WrapNAry(args, "rethrow ", "", Precedence::None);
+      }
+      case ExprType::Drop: {
+        // Silent dropping of return values is very common, so currently
+        // don't output this.
+        return std::move(args[0]);
+      }
+      case ExprType::Nop: {
+        return Value{{"nop"}, Precedence::None};
+      }
+      case ExprType::Unreachable: {
+        return Value{{"unreachable"}, Precedence::None};
+      }
+      case ExprType::RefNull: {
+        return Value{{"null"}, Precedence::Atomic};
+      }
+      case ExprType::BrTable: {
+        auto bte = cast<BrTableExpr>(n.e);
+        std::string ts = "br_table[";
+        for (auto &v : bte->targets) {
+          ts += VarName(v.name());
+          ts += ", ";
+        }
+        ts += "..";
+        ts += VarName(bte->default_target.name());
+        ts += "](";
+        return WrapChild(args[0], ts, ")", Precedence::Atomic);
+      }
+      default: {
+        // Everything that looks like a function call.
+        std::string name;
+        auto precedence = Precedence::Atomic;
+        switch (n.etype) {
+          case ExprType::Call:
+            name = cast<CallExpr>(n.e)->var.name();
+            break;
+          case ExprType::ReturnCall:
+            name = "return_call " + cast<ReturnCallExpr>(n.e)->var.name();
+            precedence = Precedence::None;
+            break;
+          case ExprType::Convert:
+            name = std::string(OpcodeToToken(cast<ConvertExpr>(n.e)->opcode));
+            break;
+          case ExprType::Ternary:
+            name = std::string(OpcodeToToken(cast<TernaryExpr>(n.e)->opcode));
+            break;
+          case ExprType::Select:
+            // This one looks like it could be translated to "?:" style ternary,
+            // but the arguments are NOT lazy, and side effects definitely do
+            // occur in the branches. So it has no clear equivalent in C-syntax.
+            // To emphasize that all args are being evaluated in order, we
+            // leave it as a function call.
+            name = "select_if";
+            break;
+          case ExprType::MemoryGrow:
+            name = "memory_grow";
+            break;
+          case ExprType::MemorySize:
+            name = "memory_size";
+            break;
+          case ExprType::MemoryCopy:
+            name = "memory_copy";
+            break;
+          case ExprType::MemoryFill:
+            name = "memory_fill";
+            break;
+          case ExprType::RefIsNull:
+            name = "is_null";
+            break;
+          case ExprType::CallIndirect:
+            name = "call_indirect";
+            break;
+          case ExprType::ReturnCallIndirect:
+            name = "return_call call_indirect";
+            break;
+          default:
+            name = GetExprTypeName(n.etype);
+            break;
+        }
+        return WrapNAry(args, name + "(", ")", precedence);
+      }
+    }
+  }
+
+  bool CheckImportExport(std::string& s,
+                         ExternalKind kind,
+                         Index index,
+                         string_view name) {
+    // Figure out if this thing is imported, exported, or neither.
+    auto is_import = mc.module.IsImport(kind, Var(index));
+    // TODO: is this the best way to check for export?
+    // FIXME: this doesn't work for functions that get renamed in some way,
+    // as the export has the original name..
+    auto xport = mc.module.GetExport(name);
+    auto is_export = xport && xport->kind == kind;
+    if (is_export)
+      s += "export ";
+    if (is_import)
+      s += "import ";
+    return is_import;
+  }
+
+  std::string InitExp(const ExprList &el) {
+    assert(!el.empty());
+    AST ast(mc, nullptr);
+    ast.Construct(el, 1, 0, false);
+    auto val = DecompileExpr(ast.exp_stack[0], nullptr);
+    assert(ast.exp_stack.size() == 1 && val.v.size() == 1);
+    return std::move(val.v[0]);
+  }
+
+  // FIXME: Merge with WatWriter::WriteQuotedData somehow.
+  std::string BinaryToString(const std::vector<uint8_t> &in) {
+    std::string s = "\"";
+    size_t line_start = 0;
+    static const char s_hexdigits[] = "0123456789abcdef";
+    for (auto c : in) {
+      if (c >= ' ' && c <= '~') {
+        s += c;
+      } else {
+        s += '\\';
+        s += s_hexdigits[c >> 4];
+        s += s_hexdigits[c & 0xf];
+      }
+      if (s.size() - line_start > target_exp_width) {
+        if (line_start == 0) {
+          s = "  " + s;
+        }
+        s += "\"\n  ";
+        line_start = s.size();
+        s += "\"";
+      }
+    }
+    s += '\"';
+    return s;
+  }
+
+  std::string Decompile() {
+    std::string s;
+    // Memories.
+    Index memory_index = 0;
+    for (auto m : mc.module.memories) {
+      auto is_import =
+          CheckImportExport(s, ExternalKind::Memory, memory_index, m->name);
+      s += cat("memory ", m->name);
+      if (!is_import) {
+        s += cat("(initial: ", std::to_string(m->page_limits.initial),
+                 ", max: ", std::to_string(m->page_limits.max), ")");
+      }
+      s += ";\n";
+      memory_index++;
+    }
+    if (!mc.module.memories.empty())
+      s += "\n";
+
+    // Globals.
+    Index global_index = 0;
+    for (auto g : mc.module.globals) {
+      auto is_import =
+          CheckImportExport(s, ExternalKind::Global, global_index, g->name);
+      s += cat("global ", g->name, ":", GetDecompTypeName(g->type));
+      if (!is_import) {
+        s += cat(" = ", InitExp(g->init_expr));
+      }
+      s += ";\n";
+      global_index++;
+    }
+    if (!mc.module.globals.empty())
+      s += "\n";
+
+    // Tables.
+    Index table_index = 0;
+    for (auto tab : mc.module.tables) {
+      auto is_import =
+          CheckImportExport(s, ExternalKind::Table, table_index, tab->name);
+      s += cat("table ", tab->name, ":", GetDecompTypeName(tab->elem_type));
+      if (!is_import) {
+        s += cat("(min: ", std::to_string(tab->elem_limits.initial),
+                 ", max: ", std::to_string(tab->elem_limits.max), ")");
+      }
+      s += ";\n";
+      table_index++;
+    }
+    if (!mc.module.tables.empty())
+      s += "\n";
+
+    // Data.
+    for (auto dat : mc.module.data_segments) {
+      s += cat("data ", dat->name, "(offset: ", InitExp(dat->offset), ") =");
+      auto ds = BinaryToString(dat->data);
+      if (ds.size() > target_exp_width / 2) {
+        s += "\n";
+      } else {
+        s += " ";
+      }
+      s += ds;
+      s += ";\n";
+    }
+    if (!mc.module.data_segments.empty())
+      s += "\n";
+
+    // Code.
+    Index func_index = 0;
+    for (auto f : mc.module.funcs) {
+      cur_func = f;
+      auto is_import =
+          CheckImportExport(s, ExternalKind::Func, func_index, f->name);
+      AST ast(mc, f);
+      cur_ast = &ast;
+      if (!is_import) {
+        ast.Construct(f->exprs, f->GetNumResults(), 0, true);
+        lst.Track(ast.exp_stack[0]);
+        lst.CheckLayouts();
+      }
+      s += cat("function ", f->name, "(");
+      for (Index i = 0; i < f->GetNumParams(); i++) {
+        if (i)
+          s += ", ";
+        auto t = f->GetParamType(i);
+        auto name = "$" + IndexToAlphaName(i);
+        s += LocalDecl(name, t);
+      }
+      s += ")";
+      if (f->GetNumResults()) {
+        if (f->GetNumResults() == 1) {
+          s += cat(":", GetDecompTypeName(f->GetResultType(0)));
+        } else {
+          s += ":(";
+          for (Index i = 0; i < f->GetNumResults(); i++) {
+            if (i)
+              s += ", ";
+            s += GetDecompTypeName(f->GetResultType(i));
+          }
+          s += ")";
+        }
+      }
+      if (is_import) {
+        s += ";";
+      } else {
+        s += " {\n";
+        auto val = DecompileExpr(ast.exp_stack[0], nullptr);
+        IndentValue(val, indent_amount, {});
+        for (auto& stat : val.v) {
+          s += stat;
+          s += "\n";
+        }
+        s += "}";
+      }
+      s += "\n\n";
+      mc.EndFunc();
+      lst.Clear();
+      func_index++;
+      cur_ast = nullptr;
+      cur_func = nullptr;
+    }
+    return s;
+  }
+
+  ModuleContext mc;
+  const DecompileOptions& options;
+  size_t indent_amount = 2;
+  size_t target_exp_width = 70;
+  const Func* cur_func = nullptr;
+  AST* cur_ast = nullptr;
+  LoadStoreTracking lst;
+};
+
+std::string Decompile(const Module& module, const DecompileOptions& options) {
+  Decompiler decompiler(module, options);
+  return decompiler.Decompile();
+}
+
+}  // namespace wabt