[wasm] OOB traps: build protected instruction list during codegen

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 56f6b70a6565444f4000e741e281cdd16b701851..9c17b1909daa91127f6e017bc6ec50a2fd0a2b5f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5421,6 +5421,10 @@ class Code: public HeapObject {
   // [source_position_table]: ByteArray for the source positions table.
   DECL_ACCESSORS(source_position_table, ByteArray)
 
+  // [protected_instructions]: Fixed array containing protected instruction and
+  // corresponding landing pad offsets.
+  DECL_ACCESSORS(protected_instructions, FixedArray)

[titzer, 2016/11/30 21:19:07]

Can you double check that the addition of this field didn't push the Code header
over 64 bytes? I think we have space, but if it overflows it will be a
significant regression.

[Eric Holk, 2016/11/30 21:55:54]

I played around with some static asserts, and it looks like without this field
we were already above 64 bytes, but with this field we are still less than 128,
so it seems like this change makes no difference in terms of multiples of 64
bytes.

+
   // [raw_type_feedback_info]: This field stores various things, depending on
   // the kind of the code object.
   //   FUNCTION           => type feedback information.
@@ -5800,7 +5804,12 @@ class Code: public HeapObject {
   static const int kConstantPoolOffset = kPrologueOffset + kIntSize;
   static const int kBuiltinIndexOffset =
       kConstantPoolOffset + kConstantPoolSize;
-  static const int kHeaderPaddingStart = kBuiltinIndexOffset + kIntSize;
+  static const int kProtectedInstructionOffset = kBuiltinIndexOffset + kIntSize;
+
+  enum TrapFields { kTrapCodeOffset, kTrapLandingOffset, kTrapDataSize };
+
+  static const int kHeaderPaddingStart =
+      kProtectedInstructionOffset + kPointerSize;
 
   // Add padding to align the instruction start following right after
   // the Code object header.