Initial support for emitting unwinding information in perf jitdump.

src/ia32/assembler-ia32.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 314 matching lines @@
   // that we are still not overlapping instructions and relocation info).
   reloc_info_writer.Finish();
   DCHECK(pc_ <= reloc_info_writer.pos());  // No overlap.
   // Set up code descriptor.
   desc->buffer = buffer_;
   desc->buffer_size = buffer_size_;
   desc->instr_size = pc_offset();
   desc->reloc_size = (buffer_ + buffer_size_) - reloc_info_writer.pos();
   desc->origin = this;
   desc->constant_pool_size = 0;
+  desc->unwinding_info_size = 0;
+  desc->unwinding_info = nullptr;
 }
 
 
 void Assembler::Align(int m) {
   DCHECK(base::bits::IsPowerOfTwo32(m));
   int mask = m - 1;
   int addr = pc_offset();
   Nop((m - (addr & mask)) & mask);
 }
 
@@ skipping 2727 matching lines @@
     fflush(coverage_log);
   }
 }
 
 #endif
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32