[wasm] Add support and unittests for decoding signed LEB128.

src/wasm/wasm-macro-gen.h

Index: src/wasm/wasm-macro-gen.h
diff --git a/src/wasm/wasm-macro-gen.h b/src/wasm/wasm-macro-gen.h
index 7e50d03fd6335563b9a2de5cabf5b5e3bd1a59a8..1d188c2b5d7030e06b4c6c1abeb5f03849ffadff 100644
--- a/src/wasm/wasm-macro-gen.h
+++ b/src/wasm/wasm-macro-gen.h
@@ -277,4 +277,28 @@
 #define FUNC_INDEX(v) U16_LE(v)
 #define NAME_OFFSET(v) U32_LE(v)
 
+#define MASK_7 ((1 << 7) - 1)

[bradn, 2016/02/29 06:30:00]

These are only used in one test, move them there? / inline the values?

[titzer, 2016/02/29 16:51:46]

The plan is to use U32V_1, U32V_2, etc in more tests, e.g. when I32Const and
I64Const are using SLEB's.

+#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_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)
+
 #endif  // V8_WASM_MACRO_GEN_H_