[wasm] Master CL for Binary 0xC changes.

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 {
 
 const uint32_t kMaxNumWasmLocals = 8000000;
+struct WasmGlobal;
 
 // Helpers for decoding different kinds of operands which follow bytecodes.
 struct LocalIndexOperand {
   uint32_t index;
   LocalType type;
   unsigned length;
 
   inline LocalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "local index");
     type = kAstStmt;
@@ skipping 39 matching lines @@
   unsigned 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;
+  const WasmGlobal* global;
   unsigned length;
 
   inline GlobalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "global index");
+    global = nullptr;
     type = kAstStmt;
   }
 };
 
+struct BlockTypeOperand {
+  uint32_t arity;
+  const byte* types;  // pointer to encoded types for the block.
+  unsigned length;
+
+  inline BlockTypeOperand(Decoder* decoder, const byte* pc) {
+    uint8_t val = decoder->checked_read_u8(pc, 1, "block type");
+    LocalType type = kAstStmt;
+    length = 1;
+    arity = 0;
+    types = nullptr;
+    if (decode_local_type(val, &type)) {
+      arity = type == kAstStmt ? 0 : 1;
+      types = pc + 1;
+    } else {
+      // Handle multi-value blocks.
+      if (!FLAG_wasm_mv_prototype) {
+        decoder->error(pc, pc + 1, "invalid block arity > 1");
+        return;
+      }
+      if (val != kMultivalBlock) {
+        decoder->error(pc, pc + 1, "invalid block type");
+        return;
+      }
+      // Decode and check the types vector of the block.
+      unsigned len = 0;
+      uint32_t count = decoder->checked_read_u32v(pc, 2, &len, "block arity");
+      // {count} is encoded as {arity-2}, so that a {0} count here corresponds
+      // to a block with 2 values. This makes invalid/redundant encodings
+      // impossible.
+      arity = count + 2;
+      length = 1 + len + arity;
+      types = pc + 1 + 1 + len;
+
+      for (uint32_t i = 0; i < arity; i++) {
+        uint32_t offset = 1 + 1 + len + i;
+        val = decoder->checked_read_u8(pc, offset, "block type");
+        decode_local_type(val, &type);

[bradnelson, 2016/09/23 11:36:00]

This function has a weird calling convention.
Might be cleaner if decode_local_type just had unreachable for the one case it
doesn't grok and returns a LocalType and then all the callers check for
kMultivalBlock separately before calling it?

[titzer, 2016/09/23 12:07:30]

Yeah, it is weird. The problem is that it can't have UNREACHABLE, since it
should fail with some kind of decoder error on invalid user input, instead of
crashing.

[bradn, 2016/09/23 15:18:43]

Yeah true.
Many to few is hard.

+        if (type == kAstStmt) {
+          decoder->error(pc, pc + offset, "invalid block type");
+          return;
+        }
+      }
+    }
+  }
+  // Decode a byte representing a local type. Return {false} if the encoded
+  // byte was invalid.

[bradnelson, 2016/09/23 11:36:01]

Rather invalid or kMultivalBlock ?

[titzer, 2016/09/23 12:07:30]

Done.

+  bool decode_local_type(uint8_t val, LocalType* result) {
+    switch (static_cast<LocalTypeCode>(val)) {
+      case kLocalVoid:
+        *result = kAstStmt;
+        return true;
+      case kLocalI32:
+        *result = kAstI32;
+        return true;
+      case kLocalI64:
+        *result = kAstI64;
+        return true;
+      case kLocalF32:
+        *result = kAstF32;
+        return true;
+      case kLocalF64:
+        *result = kAstF64;
+        return true;
+      default:
+        *result = kAstStmt;
+        return false;
+    }
+  }
+  LocalType read_entry(unsigned index) {
+    DCHECK_LT(index, arity);
+    LocalType result;
+    CHECK(decode_local_type(types[index], &result));
+    return result;
+  }
+};
+
 struct Control;
 struct BreakDepthOperand {
-  uint32_t arity;
   uint32_t depth;
   Control* target;
   unsigned length;
   inline BreakDepthOperand(Decoder* decoder, const byte* pc) {
-    unsigned len1 = 0;
-    unsigned len2 = 0;
-    arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
-    depth = decoder->checked_read_u32v(pc, 1 + len1, &len2, "break depth");
-    length = len1 + len2;
+    depth = decoder->checked_read_u32v(pc, 1, &length, "break depth");
     target = nullptr;
   }
 };
 
 struct CallIndirectOperand {
-  uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
   unsigned length;
   inline CallIndirectOperand(Decoder* decoder, const byte* pc) {
     unsigned len1 = 0;
     unsigned len2 = 0;
-    arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "signature index");
     length = len1 + len2;
     sig = nullptr;
   }
 };
 
 struct CallFunctionOperand {
-  uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
   unsigned length;
   inline CallFunctionOperand(Decoder* decoder, const byte* pc) {
     unsigned len1 = 0;
     unsigned len2 = 0;
-    arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "function index");
     length = len1 + len2;
     sig = nullptr;
   }
 };
 
-struct CallImportOperand {
-  uint32_t arity;
-  uint32_t index;
-  FunctionSig* sig;
-  unsigned length;
-  inline CallImportOperand(Decoder* decoder, const byte* pc) {
+struct BranchTableOperand {
+  uint32_t table_count;
+  const byte* start;
+  const byte* table;
+  inline BranchTableOperand(Decoder* decoder, const byte* pc) {
+    DCHECK_EQ(kExprBrTable, decoder->checked_read_u8(pc, 0, "opcode"));
+    start = pc + 1;
     unsigned len1 = 0;
-    unsigned len2 = 0;
-    arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
-    index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "import index");
-    length = len1 + len2;
-    sig = nullptr;
-  }
-};
-
-struct BranchTableOperand {
-  uint32_t arity;
-  uint32_t table_count;
-  const byte* table;
-  unsigned length;
-  inline BranchTableOperand(Decoder* decoder, const byte* pc) {
-    unsigned len1 = 0;
-    unsigned len2 = 0;
-    arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
-    table_count =
-        decoder->checked_read_u32v(pc, 1 + len1, &len2, "table count");
+    table_count = decoder->checked_read_u32v(pc, 1, &len1, "table count");
     if (table_count > (UINT_MAX / sizeof(uint32_t)) - 1 ||
-        len1 + len2 > UINT_MAX - (table_count + 1) * sizeof(uint32_t)) {
+        len1 > UINT_MAX - (table_count + 1) * sizeof(uint32_t)) {
       decoder->error(pc, "branch table size overflow");
     }
-    length = len1 + len2 + (table_count + 1) * sizeof(uint32_t);
-
-    uint32_t table_start = 1 + len1 + len2;
-    if (decoder->check(pc, table_start, (table_count + 1) * sizeof(uint32_t),
-                       "expected <table entries>")) {
-      table = pc + table_start;
-    } else {
-      table = nullptr;
-    }
+    table = pc + 1 + len1;
   }
   inline uint32_t read_entry(Decoder* decoder, unsigned i) {
     DCHECK(i <= table_count);
     return table ? decoder->read_u32(table + i * sizeof(uint32_t)) : 0;
   }
 };
 
+// A helper to iterate over a branch table.
+class BranchTableIterator {
+ public:
+  unsigned cur_index() { return index_; }
+  bool has_next() { return index_ <= table_count_; }
+  uint32_t next() {
+    DCHECK(has_next());
+    index_++;
+    unsigned length = 0;
+    uint32_t result =
+        decoder_->checked_read_u32v(pc_, 0, &length, "branch table entry");
+    pc_ += length;
+    return result;
+  }
+  // length, including the length of the {BranchTableOperand}, but not the
+  // opcode.
+  unsigned length() {
+    while (has_next()) next();
+    return static_cast<unsigned>(pc_ - start_);
+  }
+  const byte* pc() { return pc_; }
+
+  BranchTableIterator(Decoder* decoder, BranchTableOperand& operand)
+      : decoder_(decoder),
+        start_(operand.start),
+        pc_(operand.table),
+        index_(0),
+        table_count_(operand.table_count) {}
+
+ private:
+  Decoder* decoder_;
+  const byte* start_;
+  const byte* pc_;
+  uint32_t index_;        // the current index.
+  uint32_t table_count_;  // the count of entries, not including default.
+};
+
 struct MemoryAccessOperand {
   uint32_t alignment;
   uint32_t offset;
   unsigned length;
   inline MemoryAccessOperand(Decoder* decoder, const byte* pc,
                              uint32_t max_alignment) {
     unsigned alignment_length;
     alignment =
         decoder->checked_read_u32v(pc, 1, &alignment_length, "alignment");
     if (max_alignment < alignment) {
       decoder->error(pc, pc + 1,
                      "invalid alignment; expected maximum alignment is %u, "
                      "actual alignment is %u",
                      max_alignment, alignment);
     }
     unsigned offset_length;
     offset = decoder->checked_read_u32v(pc, 1 + alignment_length,
                                         &offset_length, "offset");
     length = alignment_length + offset_length;
   }
 };
 
-struct ReturnArityOperand {
-  uint32_t arity;
-  unsigned length;
-
-  inline ReturnArityOperand(Decoder* decoder, const byte* pc) {
-    arity = decoder->checked_read_u32v(pc, 1, &length, "return count");
-  }
-};
-
 typedef compiler::WasmGraphBuilder TFBuilder;
 struct ModuleEnv;  // forward declaration of module interface.
 
 // All of the various data structures necessary to decode a function body.
 struct FunctionBody {
   ModuleEnv* module;  // module environment
   FunctionSig* sig;   // function signature
   const byte* base;   // base of the module bytes, for error reporting
   const byte* start;  // start of the function body
   const byte* end;    // end of the function body
@@ skipping 52 matching lines @@
       : decls_encoded_size(0), total_local_count(0), local_types(zone) {}
 };
 
 bool DecodeLocalDecls(AstLocalDecls& decls, const byte* start, const byte* end);
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end);
 
 // Computes the length of the opcode at the given address.
 unsigned OpcodeLength(const byte* pc, const byte* end);
 
-// Computes the arity (number of sub-nodes) of the opcode at the given address.
-unsigned OpcodeArity(const byte* pc, const byte* end);
-
 // A simple forward iterator for bytecodes.
 class BytecodeIterator : public Decoder {
  public:
   // If one wants to iterate over the bytecode without looking at {pc_offset()}.
   class iterator {
    public:
     inline iterator& operator++() {
       DCHECK_LT(ptr_, end_);
       ptr_ += OpcodeLength(ptr_, end_);
       return *this;
@@ skipping 38 matching lines @@
   }
 
   bool has_next() { return pc_ < end_; }
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_AST_DECODER_H_