[wasm] Refactor handling of operands to bytecodes.

src/wasm/ast-decoder.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_AST_DECODER_H_
 #define V8_WASM_AST_DECODER_H_
 
 #include "src/signature.h"
+#include "src/wasm/decoder.h"
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
 
 namespace v8 {
 namespace internal {
 
 class BitVector;  // forward declaration
 
 namespace compiler {  // external declarations from compiler.
 class WasmGraphBuilder;
 }
 
 namespace wasm {
 
+// Helpers for decoding different kinds of operands which follow bytecodes.
+struct LocalIndexOperand {
+  uint32_t index;
+  LocalType type;
+  int length;
+
+  inline LocalIndexOperand(Decoder* decoder, const byte* pc) {
+    index = decoder->checked_read_u32v(pc, 1, &length, "local index");
+    type = kAstStmt;
+  }
+};
+
+struct ImmI8Operand {
+  int8_t value;
+  int length;
+  inline ImmI8Operand(Decoder* decoder, const byte* pc) {
+    value = bit_cast<int8_t>(decoder->checked_read_u8(pc, 1, "immi8"));
+    length = 1;
+  }
+};
+
+struct ImmI32Operand {
+  int32_t value;
+  int length;
+  inline ImmI32Operand(Decoder* decoder, const byte* pc) {
+    value = bit_cast<int32_t>(decoder->checked_read_u32(pc, 1, "immi32"));
+    length = 4;
+  }
+};
+
+struct ImmI64Operand {
+  int64_t value;
+  int length;
+  inline ImmI64Operand(Decoder* decoder, const byte* pc) {
+    value = bit_cast<int64_t>(decoder->checked_read_u64(pc, 1, "immi64"));
+    length = 8;
+  }
+};
+
+struct ImmF32Operand {
+  float value;
+  int length;
+  inline ImmF32Operand(Decoder* decoder, const byte* pc) {
+    value = bit_cast<float>(decoder->checked_read_u32(pc, 1, "immf32"));
+    length = 4;
+  }
+};
+
+struct ImmF64Operand {
+  double value;
+  int length;
+  inline ImmF64Operand(Decoder* decoder, const byte* pc) {
+    value = bit_cast<double>(decoder->checked_read_u64(pc, 1, "immf64"));
+    length = 8;
+  }
+};
+
+struct GlobalIndexOperand {
+  uint32_t index;
+  LocalType type;
+  MachineType machine_type;
+  int length;
+
+  inline GlobalIndexOperand(Decoder* decoder, const byte* pc) {
+    index = decoder->checked_read_u32v(pc, 1, &length, "global index");
+    type = kAstStmt;
+    machine_type = MachineType::None();
+  }
+};
+
+struct Block;
+struct BreakDepthOperand {
+  uint32_t depth;
+  Block* target;
+  int length;
+  inline BreakDepthOperand(Decoder* decoder, const byte* pc) {
+    depth = decoder->checked_read_u8(pc, 1, "break depth");
+    length = 1;
+    target = nullptr;
+  }
+};
+
+struct BlockCountOperand {
+  uint32_t count;
+  int length;
+  inline BlockCountOperand(Decoder* decoder, const byte* pc) {
+    count = decoder->checked_read_u8(pc, 1, "block count");
+    length = 1;
+  }
+};
+
+struct SignatureIndexOperand {
+  uint32_t index;
+  FunctionSig* sig;
+  int length;
+  inline SignatureIndexOperand(Decoder* decoder, const byte* pc) {
+    index = decoder->checked_read_u32v(pc, 1, &length, "signature index");
+    sig = nullptr;
+  }
+};
+
+struct FunctionIndexOperand {
+  uint32_t index;
+  FunctionSig* sig;
+  int length;
+  inline FunctionIndexOperand(Decoder* decoder, const byte* pc) {
+    index = decoder->checked_read_u32v(pc, 1, &length, "function index");
+    sig = nullptr;
+  }
+};
+
+struct TableSwitchOperand {
+  uint32_t case_count;
+  uint32_t table_count;
+  const byte* table;
+  int length;
+  inline TableSwitchOperand(Decoder* decoder, const byte* pc) {
+    case_count = decoder->checked_read_u16(pc, 1, "expected #cases");
+    table_count = decoder->checked_read_u16(pc, 3, "expected #entries");
+    length = 4 + table_count * 2;
+
+    if (decoder->check(pc, 5, table_count * 2, "expected <table entries>")) {
+      table = pc + 5;
+    } else {
+      table = nullptr;
+    }
+  }
+  inline uint16_t read_entry(Decoder* decoder, int i) {
+    DCHECK(i >= 0 && i < table_count);

[bradnelson, 2016/02/03 19:44:47]

compare sign mismatch

[titzer, 2016/02/04 09:34:08]

Yeah, dang it, for the 200th time. (This is one of my worst peeves with C++. The
code already checks for i >= 0, and even so, comparing integers on the same
number line is the obviously correct thing to do. So much for compilers.)

+    return table ? decoder->read_u16(table + i * sizeof(uint16_t)) : 0;
+  }
+};
+
+struct MemoryAccessOperand {
+  bool aligned;
+  uint32_t offset;
+  int length;
+  inline MemoryAccessOperand(Decoder* decoder, const byte* pc) {
+    byte bitfield = decoder->checked_read_u8(pc, 1, "memory access byte");
+    aligned = MemoryAccess::AlignmentField::decode(bitfield);
+    if (MemoryAccess::OffsetField::decode(bitfield)) {
+      offset = decoder->checked_read_u32v(pc, 2, &length, "memory offset");
+      length++;
+    } else {
+      offset = 0;
+      length = 1;
+    }
+  }
+};
+
 typedef compiler::WasmGraphBuilder TFBuilder;
 struct ModuleEnv;  // forward declaration of module interface.
 
 // Interface the function environment during decoding, include the signature
 // and number of locals.
 struct FunctionEnv {
   ModuleEnv* module;             // module environment
   FunctionSig* sig;              // signature of this function
   uint32_t local_int32_count;    // number of int32 locals
   uint32_t local_int64_count;    // number of int64 locals
   uint32_t local_float32_count;  // number of float32 locals
   uint32_t local_float64_count;  // number of float64 locals
   uint32_t total_locals;         // sum of parameters and all locals
 
-  bool IsValidLocal(uint32_t index) { return index < total_locals; }
   uint32_t GetLocalCount() { return total_locals; }
   LocalType GetLocalType(uint32_t index) {
     if (index < static_cast<uint32_t>(sig->parameter_count())) {
       return sig->GetParam(index);
     }
     index -= static_cast<uint32_t>(sig->parameter_count());
     if (index < local_int32_count) return kAstI32;
     index -= local_int32_count;
     if (index < local_int64_count) return kAstI64;
     index -= local_int64_count;
@@ skipping 57 matching lines @@
 
 enum ReadUnsignedLEB128ErrorCode { kNoError, kInvalidLEB128, kMissingLEB128 };
 
 ReadUnsignedLEB128ErrorCode ReadUnsignedLEB128Operand(const byte*, const byte*,
                                                       int*, uint32_t*);
 
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, FunctionEnv* env,
                                            const byte* start, const byte* end);
 
 // Computes the length of the opcode at the given address.
-int OpcodeLength(const byte* pc);
+int OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
-int OpcodeArity(FunctionEnv* env, const byte* pc);
+int OpcodeArity(FunctionEnv* env, const byte* pc, const byte* end);
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_AST_DECODER_H_