optimize stack monitoring

Stepping over large functions is slow due to recent changes,
this optimizes some aspects with a 3-4x speed up.

lua/osv/init.lua

@@ -29,6 +29,11 @@ local log_filename
 
 local lock_debug_loop = false
 
+local skip_monitor = false
+local skip_monitor_same_depth = false
+
+local head_start_depth = -1
+
 local exit_autocmd
 
 local auto_nvim
@@ -278,6 +283,9 @@ function M.attach()
   		M.stop()
   	end
 
+    skip_monitor = false
+    skip_monitor_same_depth = false
+
     running = true
 
     limit = 0
@@ -523,13 +531,17 @@ function M.attach()
       end
       off = off + 1
     end
+    head_start_depth = off - 1
 
     depth = (off - 1) - surface
     stack_level = depth
 
     next = true
     monitor_stack = true
 
+    skip_monitor = false
+    skip_monitor_same_depth = false
+
     running = true
 
     sendProxyDAP(make_response(request, {}))
@@ -783,6 +795,9 @@ function M.attach()
     step_out = true
     monitor_stack = true
 
+    skip_monitor = false
+    skip_monitor_same_depth = false
+
     local depth = 0
     local surface = 0
     local off = 0
@@ -807,6 +822,7 @@ function M.attach()
       end
       off = off + 1
     end
+    head_start_depth = off - 1
 
     depth = (off - 1) - surface
     stack_level = depth
@@ -931,8 +947,13 @@ function M.attach()
     M.server_messages = {}
 
 
-    local depth = 0
-    if monitor_stack then
+    local depth = -1
+    if (event == "call" or event == "return") and monitor_stack and next then
+    	skip_monitor_same_depth = true
+    	skip_monitor = false
+    end
+
+    if monitor_stack and not skip_monitor then
       local surface = 0
       local off = 0
       while true do
@@ -956,8 +977,13 @@ function M.attach()
         end
         off = off + 1
       end
+      head_start_depth = off - 1
 
       depth = (off - 1) - surface
+      if next and event == "line" and skip_monitor_same_depth then
+      	skip_monitor = true
+      end
+
     end
 
     local bps = breakpoints[line]
@@ -1292,7 +1318,7 @@ function M.attach()
 
     	end
 
-    elseif event == "line" and next and depth <= stack_level then
+    elseif event == "line" and next and depth >= 0 and depth <= stack_level then
       local msg = make_event("stopped")
       msg.body = {
         reason = "step",
@@ -1329,7 +1355,7 @@ function M.attach()
       end
 
 
-    elseif event == "line" and step_out and stack_level-1 == depth then
+    elseif event == "line" and step_out and depth >= 0 and stack_level-1 == depth then
       local msg = make_event("stopped")
       msg.body = {
         reason = "step",
@@ -1650,6 +1676,9 @@ function M.stop()
     nvim_server = nil
   end
 
+  skip_monitor = false
+  skip_monitor_same_depth = false
+
   running = true
 
   limit = 0

src/handlers/attach.lua.t

@@ -9,9 +9,11 @@ debug.sethook(function(event, line)
   @handle_new_messages
   @clear_messages
 
-  local depth = 0
-  if monitor_stack then
+  local depth = -1
+  @speedup_stack_monitor
+  if monitor_stack and not skip_monitor then
     @get_stack_depth_with_debug_getinfo
+    @disable_monitor_for_speedup
   end
 
   @check_if_breakpoint_hit

src/handlers/next.lua.t

@@ -26,7 +26,7 @@ next = false
 monitor_stack = false
 
 @check_if_next+=
-elseif event == "line" and next and depth <= stack_level then
+elseif event == "line" and next and depth >= 0 and depth <= stack_level then
   @send_stopped_event_step
   @disable_next
 
@@ -48,5 +48,5 @@ while true do
   end
   off = off + 1
 end
-
+@save_for_next_head_start
 depth = (off - 1) - surface

src/handlers/step_out.lua.t

@@ -25,7 +25,7 @@ step_out = false
 monitor_stack = false
 
 @check_if_step_out+=
-elseif event == "line" and step_out and stack_level-1 == depth then
+elseif event == "line" and step_out and depth >= 0 and stack_level-1 == depth then
   @send_stopped_event_step
   @disable_step_out
 

src/optimizations/optimize_stack_monitor.lua.t

@@ -0,0 +1,45 @@
+##../lua-debug
+@script_variables+=
+local skip_monitor = false
+local skip_monitor_same_depth = false
+
+@reset_internal_states+=
+skip_monitor = false
+skip_monitor_same_depth = false
+
+@set_next_variable+=
+skip_monitor = false
+skip_monitor_same_depth = false
+
+@set_step_out+=
+skip_monitor = false
+skip_monitor_same_depth = false
+
+@speedup_stack_monitor+=
+if (event == "call" or event == "return") and monitor_stack and next then
+	skip_monitor_same_depth = true
+	skip_monitor = false
+end
+
+@disable_monitor_for_speedup+=
+if next and event == "line" and skip_monitor_same_depth then
+	skip_monitor = true
+end
+
+@script_variables+=
+local head_start_depth = -1
+
+@save_for_next_head_start+=
+head_start_depth = off - 1
+
+@head_start_for_monitoring+=
+if head_start_depth >= 0 then
+  local info = debug.getinfo(head_start_depth, "S")
+  if info then
+		local inside_osv = false
+		@check_if_inside_osv
+		if inside_osv then
+			off = head_start_depth+1
+		end
+  end
+end