Linux perf support - fix debug info.

This fixes support for debug info in perf. Thanks to Stephane Eranian for
identifying the problem - debug info event has to be emitted before the
code load event. It also seems that perf does not yet support the shorthand
for repeated source files in the debug info entry ("\xff\0"), so I changed
it to always write the script name.

Review URL: https://codereview.chromium.org/1843563002

Cr-Commit-Position: refs/heads/master@{#35092}

src/perf-jit.cc

@@ -171,6 +171,11 @@ void PerfJitLogger::LogRecordedBuffer(AbstractCode* abstract_code,
   Code* code = abstract_code->GetCode();
   DCHECK(code->instruction_start() == code->address() + Code::kHeaderSize);
 
+  // Debug info has to be emitted first.
+  if (FLAG_perf_prof_debug_info) {
+    LogWriteDebugInfo(code, shared);
+  }
+
   const char* code_name = name;
   uint8_t* code_pointer = reinterpret_cast<uint8_t*>(code->instruction_start());
   uint32_t code_size = code->is_crankshafted() ? code->safepoint_table_offset()
@@ -196,10 +201,6 @@ void PerfJitLogger::LogRecordedBuffer(AbstractCode* abstract_code,
   LogWriteBytes(code_name, length);
   LogWriteBytes(string_terminator, 1);
   LogWriteBytes(reinterpret_cast<const char*>(code_pointer), code_size);
-
-  if (FLAG_perf_prof_debug_info) {
-    LogWriteDebugInfo(code, shared);
-  }
 }
 
 void PerfJitLogger::LogWriteDebugInfo(Code* code, SharedFunctionInfo* shared) {
@@ -241,9 +242,7 @@ void PerfJitLogger::LogWriteDebugInfo(Code* code, SharedFunctionInfo* shared) {
   // Add the sizes of fixed parts of entries.
   size += entry_count * sizeof(PerfJitDebugEntry);
   // Add the size of the name after the first entry.
-  size += static_cast<uint32_t>(name_length) + 1;
-  // Add the sizes of the links to previous name (\0xff\0).
-  size += (entry_count - 1) * 2;
+  size += (static_cast<uint32_t>(name_length) + 1) * entry_count;
 
   int padding = ((size + 7) & (~7)) - size;
 
@@ -254,7 +253,6 @@ void PerfJitLogger::LogWriteDebugInfo(Code* code, SharedFunctionInfo* shared) {
   int script_line_offset = script->line_offset();
   Handle<FixedArray> line_ends(FixedArray::cast(script->line_ends()));
 
-  bool is_first = true;
   for (RelocIterator it(code, RelocInfo::kPositionMask); !it.done();
        it.next()) {
     int position = static_cast<int>(it.rinfo()->data());
@@ -276,13 +274,7 @@ void PerfJitLogger::LogWriteDebugInfo(Code* code, SharedFunctionInfo* shared) {
     entry.line_number_ = line_number;
     entry.column_ = column_offset;
     LogWriteBytes(reinterpret_cast<const char*>(&entry), sizeof(entry));
-
-    if (is_first) {
-      is_first = false;
-      LogWriteBytes(name_string.get(), name_length + 1);
-    } else {
-      LogWriteBytes("\xff", 2);
-    }
+    LogWriteBytes(name_string.get(), name_length + 1);
   }
   char padding_bytes[] = "\0\0\0\0\0\0\0\0";
   LogWriteBytes(padding_bytes, padding);