[RFA] Remap variable table entries

[Keith Seitz <keiths at redhat dot com>]

Hi,

For some time now I've been noticing a discrepancy between variables 
that should be in scope and when Eclipse actually displays them in 
scope. Very, very irritating.

Turns out that we were blindly using the bytecode offsets from the debug 
info without ever taking into consideration that we were compiling the 
methods. As a result, the variable tables never were quite right...

The attached patch fixes this by converting the variable table entries 
when the method is compiled. I've also reworked _Jv_VarLineTableEntry to 
be more like _Jv_LineTableEntry, with the union for the bytecode pc and 
the direct-threaded pc.

QCC?

Keith

ChangeLog
2007-06-08  Keith Seitz  <keiths@redhat.com>

        * include/java-interp.h (_Jv_LocalVarTableEntry): Add union
        for bytecode_pc and direct-threaded pc.
        Add field descriptions inline.
        * defineclass.cc (read_one_code_attribute): Change from
        bytecode_start_pc to bytecode_pc.
        Remove unused variable "len".
        * interpret.cc (compile): Remap the variable table, too.
        (get_local_var_table) [DIRECT_THREADED]: Use insn_index on the
        start location to map from pc_t to code index.

Index: include/java-interp.h
===================================================================
--- include/java-interp.h	(revision 125581)
+++ include/java-interp.h	(working copy)
@@ -138,17 +138,27 @@
 };
 
 // This structure holds local variable information.
-// The pc value is the first pc where the variable must have a value and it
-// must continue to have a value until (start_pc + length).
-// The name is the variable name, and the descriptor contains type information.
-// The slot is the index in the local variable array of this method, long and
-// double occupy slot and slot+1.
+// Like _Jv_LineTableEntry above, it is remapped when the method is
+// compiled for direct threading.
 struct _Jv_LocalVarTableEntry
 {
-  int bytecode_start_pc;
+  // First PC value at which variable is live
+  union
+  {
+    pc_t pc;
+    int bytecode_pc;
+  };
+
+  // length of visibility of variable
   int length;
+
+  // variable name
   char *name;
+
+  // type description
   char *descriptor;
+
+  // stack slot number (long and double occupy slot and slot + 1)
   int slot;
 };
 
Index: defineclass.cc
===================================================================
--- defineclass.cc	(revision 125581)
+++ defineclass.cc	(working copy)
@@ -1009,11 +1009,10 @@
                                
       for (int i = 0; i < table_len; i++)
         {
-          table[i].bytecode_start_pc = read2u ();
+          table[i].bytecode_pc = read2u ();
           table[i].length = read2u ();
-          int len;
-          len = pool_Utf8_to_char_arr (read2u (), &table[i].name);
-          len = pool_Utf8_to_char_arr (read2u (), &table[i].descriptor);
+          pool_Utf8_to_char_arr (read2u (), &table[i].name);
+          pool_Utf8_to_char_arr (read2u (), &table[i].descriptor);
           table[i].slot = read2u ();
           
           if (table[i].slot > method->max_locals || table[i].slot < 0)
Index: interpret.cc
===================================================================
--- interpret.cc	(revision 125581)
+++ interpret.cc	(working copy)
@@ -947,6 +947,25 @@
 
   prepared = insns;
 
+  // Now remap the variable table for this method.
+  for (int i = 0; i < local_var_table_len; ++i)
+    {
+      int start_byte = local_var_table[i].bytecode_pc;
+      if (start_byte < 0 || start_byte >= code_length)
+	start_byte = 0;
+      jlocation start =  pc_mapping[start_byte];
+
+      int end_byte = start_byte + local_var_table[i].length;
+      if (end_byte < 0)
+	end_byte = 0;
+      jlocation end = ((end_byte >= code_length)
+		       ? number_insn_slots
+		       : pc_mapping[end_byte]);
+
+      local_var_table[i].pc = &insns[start];
+      local_var_table[i].length = end - start + 1;
+    }
+  
   if (breakpoint_insn == NULL)
     {
       bp_insn_slot.insn = const_cast<void *> (insn_targets[op_breakpoint]);
@@ -1526,12 +1545,15 @@
       *sig = local_var_table[table_slot].descriptor;
       *generic_sig = local_var_table[table_slot].descriptor;
 
-      *startloc = static_cast<jlong> 
-                    (local_var_table[table_slot].bytecode_start_pc);
+#ifdef DIRECT_THREADED
+      *startloc = insn_index (local_var_table[table_slot].pc);
+#else
+      *startloc = static_cast<jlong> (local_var_table[table_slot].bytecode_pc);
+#endif
       *length = static_cast<jint> (local_var_table[table_slot].length);
       *slot = static_cast<jint> (local_var_table[table_slot].slot);
     }
-  return local_var_table_len - table_slot -1;
+  return local_var_table_len - table_slot - 1;
 }
 
 pc_t