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      1 // Copyright 2015 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef V8_WASM_WASM_MODULE_BUILDER_H_
      6 #define V8_WASM_WASM_MODULE_BUILDER_H_
      7 
      8 #include "src/signature.h"
      9 #include "src/zone/zone-containers.h"
     10 
     11 #include "src/wasm/leb-helper.h"
     12 #include "src/wasm/wasm-macro-gen.h"
     13 #include "src/wasm/wasm-module.h"
     14 #include "src/wasm/wasm-opcodes.h"
     15 #include "src/wasm/wasm-result.h"
     16 
     17 namespace v8 {
     18 namespace internal {
     19 namespace wasm {
     20 
     21 class ZoneBuffer : public ZoneObject {
     22  public:
     23   static const uint32_t kInitialSize = 4096;
     24   explicit ZoneBuffer(Zone* zone, size_t initial = kInitialSize)
     25       : zone_(zone), buffer_(reinterpret_cast<byte*>(zone->New(initial))) {
     26     pos_ = buffer_;
     27     end_ = buffer_ + initial;
     28   }
     29 
     30   void write_u8(uint8_t x) {
     31     EnsureSpace(1);
     32     *(pos_++) = x;
     33   }
     34 
     35   void write_u16(uint16_t x) {
     36     EnsureSpace(2);
     37     WriteLittleEndianValue<uint16_t>(pos_, x);
     38     pos_ += 2;
     39   }
     40 
     41   void write_u32(uint32_t x) {
     42     EnsureSpace(4);
     43     WriteLittleEndianValue<uint32_t>(pos_, x);
     44     pos_ += 4;
     45   }
     46 
     47   void write_u32v(uint32_t val) {
     48     EnsureSpace(kMaxVarInt32Size);
     49     LEBHelper::write_u32v(&pos_, val);
     50   }
     51 
     52   void write_i32v(int32_t val) {
     53     EnsureSpace(kMaxVarInt32Size);
     54     LEBHelper::write_i32v(&pos_, val);
     55   }
     56 
     57   void write_size(size_t val) {
     58     EnsureSpace(kMaxVarInt32Size);
     59     DCHECK_EQ(val, static_cast<uint32_t>(val));
     60     LEBHelper::write_u32v(&pos_, static_cast<uint32_t>(val));
     61   }
     62 
     63   void write(const byte* data, size_t size) {
     64     EnsureSpace(size);
     65     memcpy(pos_, data, size);
     66     pos_ += size;
     67   }
     68 
     69   size_t reserve_u32v() {
     70     size_t off = offset();
     71     EnsureSpace(kMaxVarInt32Size);
     72     pos_ += kMaxVarInt32Size;
     73     return off;
     74   }
     75 
     76   // Patch a (padded) u32v at the given offset to be the given value.
     77   void patch_u32v(size_t offset, uint32_t val) {
     78     byte* ptr = buffer_ + offset;
     79     for (size_t pos = 0; pos != kPaddedVarInt32Size; ++pos) {
     80       uint32_t next = val >> 7;
     81       byte out = static_cast<byte>(val & 0x7f);
     82       if (pos != kPaddedVarInt32Size - 1) {
     83         *(ptr++) = 0x80 | out;
     84         val = next;
     85       } else {
     86         *(ptr++) = out;
     87       }
     88     }
     89   }
     90 
     91   size_t offset() const { return static_cast<size_t>(pos_ - buffer_); }
     92   size_t size() const { return static_cast<size_t>(pos_ - buffer_); }
     93   const byte* begin() const { return buffer_; }
     94   const byte* end() const { return pos_; }
     95 
     96   void EnsureSpace(size_t size) {
     97     if ((pos_ + size) > end_) {
     98       size_t new_size = 4096 + size + (end_ - buffer_) * 3;
     99       byte* new_buffer = reinterpret_cast<byte*>(zone_->New(new_size));
    100       memcpy(new_buffer, buffer_, (pos_ - buffer_));
    101       pos_ = new_buffer + (pos_ - buffer_);
    102       buffer_ = new_buffer;
    103       end_ = new_buffer + new_size;
    104     }
    105     DCHECK(pos_ + size <= end_);
    106   }
    107 
    108   byte** pos_ptr() { return &pos_; }
    109 
    110  private:
    111   Zone* zone_;
    112   byte* buffer_;
    113   byte* pos_;
    114   byte* end_;
    115 };
    116 
    117 class WasmModuleBuilder;
    118 
    119 class V8_EXPORT_PRIVATE WasmFunctionBuilder : public ZoneObject {
    120  public:
    121   // Building methods.
    122   void SetSignature(FunctionSig* sig);
    123   uint32_t AddLocal(LocalType type);
    124   void EmitVarInt(uint32_t val);
    125   void EmitCode(const byte* code, uint32_t code_size);
    126   void Emit(WasmOpcode opcode);
    127   void EmitGetLocal(uint32_t index);
    128   void EmitSetLocal(uint32_t index);
    129   void EmitTeeLocal(uint32_t index);
    130   void EmitI32Const(int32_t val);
    131   void EmitWithU8(WasmOpcode opcode, const byte immediate);
    132   void EmitWithU8U8(WasmOpcode opcode, const byte imm1, const byte imm2);
    133   void EmitWithVarInt(WasmOpcode opcode, uint32_t immediate);
    134   void EmitDirectCallIndex(uint32_t index);
    135   void Export();
    136   void ExportAs(Vector<const char> name);
    137   void SetName(Vector<const char> name);
    138   void AddAsmWasmOffset(int asm_position);
    139 
    140   void WriteSignature(ZoneBuffer& buffer) const;
    141   void WriteExport(ZoneBuffer& buffer) const;
    142   void WriteBody(ZoneBuffer& buffer) const;
    143   void WriteAsmWasmOffsetTable(ZoneBuffer& buffer) const;
    144 
    145   bool exported() { return exported_; }
    146   uint32_t func_index() { return func_index_; }
    147   FunctionSig* signature();
    148 
    149  private:
    150   explicit WasmFunctionBuilder(WasmModuleBuilder* builder);
    151   friend class WasmModuleBuilder;
    152   friend class WasmTemporary;
    153 
    154   struct DirectCallIndex {
    155     size_t offset;
    156     uint32_t direct_index;
    157   };
    158 
    159   WasmModuleBuilder* builder_;
    160   LocalDeclEncoder locals_;
    161   uint32_t signature_index_;
    162   bool exported_;
    163   uint32_t func_index_;
    164   ZoneVector<uint8_t> body_;
    165   ZoneVector<char> name_;
    166   ZoneVector<char> exported_name_;
    167   ZoneVector<uint32_t> i32_temps_;
    168   ZoneVector<uint32_t> i64_temps_;
    169   ZoneVector<uint32_t> f32_temps_;
    170   ZoneVector<uint32_t> f64_temps_;
    171   ZoneVector<DirectCallIndex> direct_calls_;
    172 
    173   // Delta-encoded mapping from wasm bytes to asm.js source positions.
    174   ZoneBuffer asm_offsets_;
    175   uint32_t last_asm_byte_offset_ = 0;
    176   uint32_t last_asm_source_position_ = 0;
    177 };
    178 
    179 class WasmTemporary {
    180  public:
    181   WasmTemporary(WasmFunctionBuilder* builder, LocalType type) {
    182     switch (type) {
    183       case kAstI32:
    184         temporary_ = &builder->i32_temps_;
    185         break;
    186       case kAstI64:
    187         temporary_ = &builder->i64_temps_;
    188         break;
    189       case kAstF32:
    190         temporary_ = &builder->f32_temps_;
    191         break;
    192       case kAstF64:
    193         temporary_ = &builder->f64_temps_;
    194         break;
    195       default:
    196         UNREACHABLE();
    197         temporary_ = nullptr;
    198     }
    199     if (temporary_->size() == 0) {
    200       // Allocate a new temporary.
    201       index_ = builder->AddLocal(type);
    202     } else {
    203       // Reuse a previous temporary.
    204       index_ = temporary_->back();
    205       temporary_->pop_back();
    206     }
    207   }
    208   ~WasmTemporary() {
    209     temporary_->push_back(index_);  // return the temporary to the list.
    210   }
    211   uint32_t index() { return index_; }
    212 
    213  private:
    214   ZoneVector<uint32_t>* temporary_;
    215   uint32_t index_;
    216 };
    217 
    218 class V8_EXPORT_PRIVATE WasmModuleBuilder : public ZoneObject {
    219  public:
    220   explicit WasmModuleBuilder(Zone* zone);
    221 
    222   // Building methods.
    223   uint32_t AddImport(const char* name, int name_length, FunctionSig* sig);
    224   void SetImportName(uint32_t index, const char* name, int name_length) {
    225     imports_[index].name = name;
    226     imports_[index].name_length = name_length;
    227   }
    228   WasmFunctionBuilder* AddFunction(FunctionSig* sig = nullptr);
    229   uint32_t AddGlobal(LocalType type, bool exported, bool mutability = true,
    230                      const WasmInitExpr& init = WasmInitExpr());
    231   void AddDataSegment(const byte* data, uint32_t size, uint32_t dest);
    232   uint32_t AddSignature(FunctionSig* sig);
    233   void AddIndirectFunction(uint32_t index);
    234   void MarkStartFunction(WasmFunctionBuilder* builder);
    235 
    236   // Writing methods.
    237   void WriteTo(ZoneBuffer& buffer) const;
    238   void WriteAsmJsOffsetTable(ZoneBuffer& buffer) const;
    239 
    240   // TODO(titzer): use SignatureMap from signature-map.h here.
    241   // This signature map is zone-allocated, but the other is heap allocated.
    242   struct CompareFunctionSigs {
    243     bool operator()(FunctionSig* a, FunctionSig* b) const;
    244   };
    245   typedef ZoneMap<FunctionSig*, uint32_t, CompareFunctionSigs> SignatureMap;
    246 
    247   Zone* zone() { return zone_; }
    248 
    249   FunctionSig* GetSignature(uint32_t index) { return signatures_[index]; }
    250 
    251  private:
    252   struct WasmFunctionImport {
    253     uint32_t sig_index;
    254     const char* name;
    255     int name_length;
    256   };
    257 
    258   struct WasmGlobal {
    259     LocalType type;
    260     bool exported;
    261     bool mutability;
    262     WasmInitExpr init;
    263   };
    264 
    265   struct WasmDataSegment {
    266     ZoneVector<byte> data;
    267     uint32_t dest;
    268   };
    269 
    270   friend class WasmFunctionBuilder;
    271   Zone* zone_;
    272   ZoneVector<FunctionSig*> signatures_;
    273   ZoneVector<WasmFunctionImport> imports_;
    274   ZoneVector<WasmFunctionBuilder*> functions_;
    275   ZoneVector<WasmDataSegment> data_segments_;
    276   ZoneVector<uint32_t> indirect_functions_;
    277   ZoneVector<WasmGlobal> globals_;
    278   SignatureMap signature_map_;
    279   int start_function_index_;
    280 };
    281 
    282 inline FunctionSig* WasmFunctionBuilder::signature() {
    283   return builder_->signatures_[signature_index_];
    284 }
    285 
    286 }  // namespace wasm
    287 }  // namespace internal
    288 }  // namespace v8
    289 
    290 #endif  // V8_WASM_WASM_MODULE_BUILDER_H_
    291