Add more details the --trace-deopt output

src/x64/deoptimizer-x64.cc

Index: src/x64/deoptimizer-x64.cc
===================================================================
--- src/x64/deoptimizer-x64.cc	(revision 7379)
+++ src/x64/deoptimizer-x64.cc	(working copy)
@@ -364,10 +364,19 @@
   for (int i = 0; ok && i < 4; i++) {
     intptr_t input_value = input_->GetFrameSlot(input_offset);
     if (FLAG_trace_osr) {
-      PrintF("    [esp + %d] <- 0x%08" V8PRIxPTR " ; [esp + %d] (fixed part)\n",
+      const char* name = "UNKNOWN";
+      switch (i) {
+        case 0: name = "caller's pc"; break;
+        case 1: name = "rbp"; break;
+        case 2: name = "context"; break;
+        case 3: name = "function"; break;
+      }
+      PrintF("    [rsp + %d] <- 0x%08" V8PRIxPTR " ; [rsp + %d] "
+             "(fixed part - %s)\n",
              output_offset,
              input_value,
-             input_offset);
+             input_offset,
+             name);
     }
     output_[0]->SetFrameSlot(output_offset, input_->GetFrameSlot(input_offset));
     input_offset -= kPointerSize;