Initial support for emitting unwinding information in perf jitdump.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index a5da88a0b3b2e0b5e44b17e0918d17655ea38e09..d448bcb0e124e9d45f437164e2cf4d659f291380 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -13473,6 +13473,21 @@ void Code::CopyFrom(const CodeDesc& desc) {
   CopyBytes(instruction_start(), desc.buffer,
             static_cast<size_t>(desc.instr_size));
 
+  // copy unwinding info, if any
+  if (desc.unwinding_info && desc.unwinding_info_size > 0) {
+    // pad to 2**3 boundary

[rmcilroy, 2016/06/21 13:47:43]

please write number of bytes instead of 2**3.

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+    static const byte padding[8] = {0};
+    int padding_size = ((desc.instr_size + 7) & (~7)) - desc.instr_size;

[rmcilroy, 2016/06/21 13:47:43]

I don't think it's necessary to copy zero's into the padding here, just leave it
as it is since it should never be read.

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+    CopyBytes(instruction_end(), padding, padding_size);
+
+    uint64_t unwinding_info_size = desc.unwinding_info_size;
+    CopyBytes(RoundUp(instruction_end(), kInt64Size),

[rmcilroy, 2016/06/21 13:47:43]

Just use set_unwinding_size

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+              reinterpret_cast<byte*>(&unwinding_info_size),
+              sizeof(unwinding_info_size));
+    CopyBytes(unwinding_info_start(), desc.unwinding_info,
+              static_cast<size_t>(desc.unwinding_info_size));
+  }
+
   // copy reloc info
   CopyBytes(relocation_start(),
             desc.buffer + desc.buffer_size - desc.reloc_size,