[MIRROR] Optimize /atom/movable/Initialize with faster check for blocks_emissive [140ms on init] [MDB IGNORE] (#20293)

* Optimize /atom/movable/Initialize with faster check for blocks_emissive [140ms on init] (#74453)

Quoting the comment:

This one is incredible.
`if (x) else { /* code */ }` is surprisingly fast, and it's faster than
a switch, which is seemingly not a jump table.
From what I can tell, a switch case checks every single branch
individually, although sane, is slow in a hot proc like this.
So, we make the most common `blocks_emissive` value,
EMISSIVE_BLOCK_GENERIC, 0, getting to the fast else branch quickly.
If it fails, then we can check over every value it can be (here,
EMISSIVE_BLOCK_UNIQUE is the only one that matters).
This saves several hundred milliseconds of init time.

* Optimize /atom/movable/Initialize with faster check for blocks_emissive [140ms on init]

---------

Co-authored-by: Mothblocks <35135081+Mothblocks@users.noreply.github.com>

code/__DEFINES/lighting.dm

@@ -61,9 +61,11 @@
 
 // Emissive blocking.
 /// Uses vis_overlays to leverage caching so that very few new items need to be made for the overlay. For anything that doesn't change outline or opaque area much or at all.
-#define EMISSIVE_BLOCK_GENERIC 1
+#define EMISSIVE_BLOCK_GENERIC 0
 /// Uses a dedicated render_target object to copy the entire appearance in real time to the blocking layer. For things that can change in appearance a lot from the base state, like humans.
-#define EMISSIVE_BLOCK_UNIQUE 2
+#define EMISSIVE_BLOCK_UNIQUE 1
+/// Don't block any emissives. Useful for things like, pieces of paper?
+#define EMISSIVE_BLOCK_NONE 2
 
 /// The color matrix applied to all emissive overlays. Should be solely dependent on alpha and not have RGB overlap with [EM_BLOCK_COLOR].
 #define EMISSIVE_COLOR list(0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,1, 1,1,1,0)

code/controllers/admin.dm

@@ -1,7 +1,7 @@
 // Clickable stat() button.
 /obj/effect/statclick
 	name = "Initializing..."
-	blocks_emissive = NONE
+	blocks_emissive = EMISSIVE_BLOCK_NONE
 	var/target
 
 INITIALIZE_IMMEDIATE(/obj/effect/statclick)

code/game/atoms_movable.dm

@@ -73,8 +73,8 @@
 	///is the mob currently ascending or descending through z levels?
 	var/currently_z_moving
 
-	/// Either FALSE, [EMISSIVE_BLOCK_GENERIC], or [EMISSIVE_BLOCK_UNIQUE]
-	var/blocks_emissive = FALSE
+	/// Either [EMISSIVE_BLOCK_NONE], [EMISSIVE_BLOCK_GENERIC], or [EMISSIVE_BLOCK_UNIQUE]
+	var/blocks_emissive = EMISSIVE_BLOCK_NONE
 	///Internal holder for emissive blocker object, do not use directly use blocks_emissive
 	var/atom/movable/render_step/emissive_blocker/em_block
 
@@ -116,28 +116,19 @@
 		stack_trace("[type] blocks explosives, but does not have the managing element applied")
 #endif
 
-	switch(blocks_emissive)
-		if(EMISSIVE_BLOCK_GENERIC)
-			var/static/mutable_appearance/emissive_blocker/blocker = new()
-			blocker.icon = icon
-			blocker.icon_state = icon_state
-			blocker.dir = dir
-			blocker.appearance_flags |= appearance_flags
-			blocker.plane = GET_NEW_PLANE(EMISSIVE_PLANE, PLANE_TO_OFFSET(plane))
-			// Ok so this is really cursed, but I want to set with this blocker cheaply while
-			// Still allowing it to be removed from the overlays list later
-			// So I'm gonna flatten it, then insert the flattened overlay into overlays AND the managed overlays list, directly
-			// I'm sorry
-			var/mutable_appearance/flat = blocker.appearance
-			overlays += flat
-			if(managed_overlays)
-				if(islist(managed_overlays))
-					managed_overlays += flat
-				else
-					managed_overlays = list(managed_overlays, flat)
-			else
-				managed_overlays = flat
-		if(EMISSIVE_BLOCK_UNIQUE)
+#if EMISSIVE_BLOCK_GENERIC != 0
+	#error EMISSIVE_BLOCK_GENERIC is expected to be 0 to faciliate a weird optimization hack where we rely on it being the most common.
+	#error Read the comment in code/game/atoms_movable.dm for details.
+#endif
+
+	// This one is incredible.
+	// `if (x) else { /* code */ }` is surprisingly fast, and it's faster than a switch, which is seemingly not a jump table.
+	// From what I can tell, a switch case checks every single branch individually, although sane, is slow in a hot proc like this.
+	// So, we make the most common `blocks_emissive` value, EMISSIVE_BLOCK_GENERIC, 0, getting to the fast else branch quickly.
+	// If it fails, then we can check over every value it can be (here, EMISSIVE_BLOCK_UNIQUE is the only one that matters).
+	// This saves several hundred milliseconds of init time.
+	if (blocks_emissive)
+		if (blocks_emissive == EMISSIVE_BLOCK_UNIQUE)
 			render_target = ref(src)
 			em_block = new(src, render_target)
 			overlays += em_block
@@ -148,6 +139,27 @@
 					managed_overlays = list(managed_overlays, em_block)
 			else
 				managed_overlays = em_block
+	else
+		var/static/mutable_appearance/emissive_blocker/blocker = new()
+		blocker.icon = icon
+		blocker.icon_state = icon_state
+		blocker.dir = dir
+		blocker.appearance_flags |= appearance_flags
+		blocker.plane = GET_NEW_PLANE(EMISSIVE_PLANE, PLANE_TO_OFFSET(plane))
+		// Ok so this is really cursed, but I want to set with this blocker cheaply while
+		// Still allowing it to be removed from the overlays list later
+		// So I'm gonna flatten it, then insert the flattened overlay into overlays AND the managed overlays list, directly
+		// I'm sorry
+		var/mutable_appearance/flat = blocker.appearance
+		overlays += flat
+		if(managed_overlays)
+			if(islist(managed_overlays))
+				managed_overlays += flat
+			else
+				managed_overlays = list(managed_overlays, flat)
+		else
+			managed_overlays = flat
+
 	if(opacity)
 		AddElement(/datum/element/light_blocking)
 	switch(light_system)

code/game/machinery/doors/airlock.dm

@@ -102,7 +102,7 @@
 	smoothing_groups = SMOOTH_GROUP_AIRLOCK
 
 	interaction_flags_machine = INTERACT_MACHINE_WIRES_IF_OPEN | INTERACT_MACHINE_ALLOW_SILICON | INTERACT_MACHINE_OPEN_SILICON | INTERACT_MACHINE_OPEN
-	blocks_emissive = NONE // Custom emissive blocker. We don't want the normal behavior.
+	blocks_emissive = EMISSIVE_BLOCK_NONE // Custom emissive blocker. We don't want the normal behavior.
 
 	///The type of door frame to drop during deconstruction
 	var/assemblytype = /obj/structure/door_assembly

code/game/objects/effects/misc.dm

@@ -98,7 +98,7 @@
 	light_range = MINIMUM_USEFUL_LIGHT_RANGE
 	light_color = COLOR_WHITE
 	mouse_opacity = MOUSE_OPACITY_TRANSPARENT
-	blocks_emissive = NONE
+	blocks_emissive = EMISSIVE_BLOCK_NONE
 
 /obj/effect/dummy/lighting_obj/Initialize(mapload, _range, _power, _color, _duration)
 	. = ..()

code/modules/industrial_lift/industrial_lift.dm

@@ -18,7 +18,7 @@ GLOBAL_LIST_EMPTY(lifts)
 	obj_flags = CAN_BE_HIT | BLOCK_Z_OUT_DOWN
 	appearance_flags = PIXEL_SCALE|KEEP_TOGETHER //no TILE_BOUND since we're potentially multitile
 	// If we don't do this, we'll build our overlays early, and fuck up how we're rendered
-	blocks_emissive = NONE
+	blocks_emissive = EMISSIVE_BLOCK_NONE
 
 	///ID used to determine what lift types we can merge with
 	var/lift_id = BASIC_LIFT_ID

code/modules/mob/living/carbon/carbon_defines.dm

@@ -10,7 +10,7 @@
 	num_hands = 0 //Populated on init through list/bodyparts
 	usable_hands = 0 //Populated on init through list/bodyparts
 	mobility_flags = MOBILITY_FLAGS_CARBON_DEFAULT
-	blocks_emissive = NONE
+	blocks_emissive = EMISSIVE_BLOCK_NONE
 	///List of [/obj/item/organ/internal] in the mob. They don't go in the contents for some reason I don't want to know.
 	var/list/obj/item/organ/internal/organs = list()
 	///Same as [above][/mob/living/carbon/var/organs], but stores "slot ID" - "organ" pairs for easy access.