[wasm] Rework encoding of local declarations.

src/wasm/wasm-macro-gen.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_MACRO_GEN_H_
 #define V8_WASM_MACRO_GEN_H_
 
 #include "src/wasm/wasm-opcodes.h"
 
 // Convenience macros for building Wasm bytecode directly into a byte array.
@@ skipping 264 matching lines @@
 
 #define SIG_INDEX(v) U16_LE(v)
 #define FUNC_INDEX(v) U16_LE(v)
 #define NAME_OFFSET(v) U32_LE(v)
 
 #define MASK_7 ((1 << 7) - 1)
 #define MASK_14 ((1 << 14) - 1)
 #define MASK_21 ((1 << 21) - 1)
 #define MASK_28 ((1 << 28) - 1)
 
-#define U32V_1(x) static_cast<byte>(x & MASK_7)
+#define U32V_1(x) static_cast<byte>((x)&MASK_7)

[bradnelson, 2016/03/02 21:51:15]

inconsistent spacing around operator

[titzer, 2016/03/02 22:43:41]

Somehow that's what git cl format has done. Fixed it and then it fixed it back.
:-/

 #define U32V_2(x) \
-  static_cast<byte>((x & MASK_7) | 0x80), static_cast<byte>((x >> 7) & MASK_7)
-#define U32V_3(x)                                    \
-  static_cast<byte>((x & MASK_7) | 0x80),            \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 14) & MASK_7)
-#define U32V_4(x)                                     \
-  static_cast<byte>((x & MASK_7) | 0x80),             \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80),  \
-      static_cast<byte>(((x >> 14) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 21) & MASK_7)
-#define U32V_5(x)                                     \
-  static_cast<byte>((x & MASK_7) | 0x80),             \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80),  \
-      static_cast<byte>(((x >> 14) & MASK_7) | 0x80), \
-      static_cast<byte>(((x >> 21) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 28) & 0xF)
+  static_cast<byte>(((x)&MASK_7) | 0x80), static_cast<byte>(((x) >> 7) & MASK_7)
+#define U32V_3(x)                                      \
+  static_cast<byte>(((x)&MASK_7) | 0x80),              \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80), \

[bradnelson, 2016/03/02 21:51:15]

yeah not having those parens was muy mal.

[titzer, 2016/03/02 22:43:41]

Acknowledged.

+      static_cast<byte>(((x) >> 14) & MASK_7)
+#define U32V_4(x)                                       \
+  static_cast<byte>(((x)&MASK_7) | 0x80),               \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80),  \
+      static_cast<byte>((((x) >> 14) & MASK_7) | 0x80), \
+      static_cast<byte>(((x) >> 21) & MASK_7)
+#define U32V_5(x)                                       \
+  static_cast<byte>(((x)&MASK_7) | 0x80),               \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80),  \
+      static_cast<byte>((((x) >> 14) & MASK_7) | 0x80), \
+      static_cast<byte>((((x) >> 21) & MASK_7) | 0x80), \
+      static_cast<byte>(((x) >> 28) & 0xF)
 
+#define WASM_NO_LOCALS 0
+
+#define WASM_DECL_LOCALS(count, type) \
+  static_cast<byte>(count), WasmOpcodes::LocalTypeCodeFor(type)
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+// A helper for encoding local declarations prepended to the body of a
+// function.
+class LocalDeclEncoder {
+ public:
+  // Prepend local declarations by creating a new buffer and copying data
+  // over. The new buffer must be delete[]'d by the caller.
+  void Prepend(const byte** start, const byte** end) const {
+    size_t size = (*end - *start);
+    byte* buffer = new byte[5 + 6 * local_decls.size() + size];

[binji, 2016/03/02 22:51:38]

name the magic numbers?

[titzer, 2016/03/02 23:03:28]

Fixed to use Size(), which should be more robust.

+    size_t pos = Emit(buffer);
+    memcpy(buffer + pos, *start, size);
+    pos += size;
+    *start = buffer;
+    *end = buffer + pos;
+  }
+
+  size_t Emit(byte* buffer) const {
+    size_t pos = 0;
+    pos = WriteUint32v(buffer, pos, static_cast<uint32_t>(local_decls.size()));
+    for (size_t i = 0; i < local_decls.size(); i++) {
+      pos = WriteUint32v(buffer, pos, local_decls[i].first);
+      buffer[pos++] = WasmOpcodes::LocalTypeCodeFor(local_decls[i].second);
+    }
+    return pos;
+  }
+
+  // Add locals declarations to this helper. Return the index of the newly added
+  // local(s), with an optional adjustment for the parameters.
+  uint32_t AddLocals(uint32_t count, LocalType type,
+                     FunctionSig* sig = nullptr) {
+    if (count == 0) return static_cast<uint32_t>(local_decls.size());

[binji, 2016/03/02 22:51:38]

include sig->parameter_count() if sig is non-null?

[titzer, 2016/03/02 23:03:28]

Done.

+    size_t pos = local_decls.size();
+    if (local_decls.size() > 0 && local_decls.back().second == type) {
+      count += local_decls.back().first;
+      local_decls.pop_back();
+    }
+    local_decls.push_back(std::pair<uint32_t, LocalType>(count, type));
+    return static_cast<uint32_t>(pos + (sig ? sig->parameter_count() : 0));
+  }
+
+  size_t Size() const {
+    size_t size = SizeofUint32v(local_decls.size());
+    for (auto p : local_decls) size += 1 + SizeofUint32v(p.first);
+    return size;
+  }
+
+ private:
+  std::vector<std::pair<uint32_t, LocalType>> local_decls;
+
+  size_t SizeofUint32v(size_t val) const {

[bradnelson, 2016/03/02 21:51:15]

This will move out too I assume?

[titzer, 2016/03/02 22:43:41]

Yeah, it needs to find a nice common home.

[binji, 2016/03/02 22:51:38]

should be uint32_t val, right?

[titzer, 2016/03/02 23:03:28]

Done.

+    size_t size = 1;
+    while (true) {
+      byte b = val & MASK_7;
+      if (b == val) return size;
+      size++;
+      val = val >> 7;
+    }
+  }
+
+  // TODO(titzer): lift encoding of u32v to a common place.
+  size_t WriteUint32v(byte* buffer, size_t pos, uint32_t val) const {
+    while (true) {
+      byte b = val & MASK_7;
+      if (b == val) {
+        buffer[pos++] = b;
+        break;
+      }
+      buffer[pos++] = 0x80 | b;
+      val = val >> 7;
+    }
+    return pos;
+  }
+};
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8
 #endif  // V8_WASM_MACRO_GEN_H_