Adds a new command for move scripts, jumpifsubstituteblocks to Fire Red. Substitute does not block moves that are sound-based or coming from a Pokémon with the ability Infiltrator.
If necessary, change move_cmds in constants.s. The given address of this table is for MrDollSteak's patch, so if it is there, you will not need to modify this. This is the table of commands for move scripts (e.g. attackcanceler and attackstring).
Update ATK_JUMPIFSUBSTITUTEBLOCKS in constants.s. It will need an unused move script command id.
Sound-based moves only started bypassing Substitute in Gen VI. If you don't like that change, you can set SOUND_BYPASSES_SUBSTITUTE to false in src/global.h.
Change ABILITY_INFILTRATOR in src/defines/abilities.h to match what it is in your ROM. You should set this to 0xFFFF if you don't have Infiltrator in your ROM.
The build script will search for adequate free space, but if you need to insert the code in a particular place, you can tell it where to start looking by modifying free-space in config.ini. If the given address is acceptable (i.e. is word-aligned and has enough bytes of free space), it will be inserted there.
Click here for build instructions.
The syntax in your move script is just jumpifsubstituteblocks ptr. It'll be stepped over and do nothing if Substitute doesn't block; it it does block, script execution will continue from ptr.
In order to use it in BSP, you'll need to add #command jumpifbattleover ATK_JUMPIFSUBSTITUTEBLOCKS 0x1 "Offset to possibly jump to" 0x4 to BSP's commands.bsh. Don't literally include ATK_JUMPIFSUBSTITUTEBLOCKS here; replace it with whatever value you chose.
This also patches a number of existing functions that check for the Substitute status so that they instead check if Substitute should block the move instead. However, scripts for moves are untouched and may still check simply for whether Substitute is active (they should be updated to use jumpifsubstituteblocks instead).
Port of the same command in Egg's Pokeemerald Battle Engine.