Use Specific Action Hit Percentage

#   ROUTINE: USE SPECIFIC ACTION HIT PERCENTAGE            Alternative notes Uses_HP_damage_as_Action_hit%

#       This routine uses the value in the HP Damage field of the Action struct as a temporary Hit percentage value input
#       and sets the Action to miss if it fails a random roll against the input percentage value.  It also multiplies the 
#       input Hit percentage value into the Action's already calculated Hit Percentage (from evasion) to get an accurate
#       displayed Hit % value.   

80187510: 3c068019 lui r6,0x8019       
80187514: 8cc62d90 lw r6,0x2d90(r6)            #   action
80187518: 27bdffe8 addiu r29,r29,-0x0018        
8018751c: afbf0010 sw r31,0x0010(r29)      
80187520: 84c50004 lh r5,0x0004(r6)            #   action.HPDamage
80187524: 00000000 nop         
80187528: 28a20064 slti r2,r5,0x0064       
8018752c: 14400003 bne r2,r0,0x8018753c        #   if (action.HPDamage >= 100) {
80187530: 00000000 nop             
80187534: 08061d6b j 0x801875ac            
80187538: a4c00004 sh r0,0x0004(r6)            #       action.HPDamage = 0; return;
                                               #   }
8018753c: 84c2002a lh r2,0x002a(r6)            #   action.HitPercentage
80187540: 00000000 nop             
80187544: 00a20018 mult r5,r2              
80187548: 00001812 mflo r3                     #   action.HPDamage * action.HitPercentage
8018754c: 3c0251eb lui r2,0x51eb       
80187550: 3442851f ori r2,r2,0x851f            #   0.32
80187554: 00620018 mult r3,r2                  #   action.HPDamage * action.HitPercentage * 0.32
80187558: 3c048019 lui r4,0x8019       
8018755c: 8c84f5fc lw r4,-0x0a04(r4)           #   actionConsiderationStatus
80187560: a4c00004 sh r0,0x0004(r6)            #   action.HPDamage = 0
80187564: 00031fc3 sra r3,r3,0x1f      
80187568: 00001010 mfhi r2                     #   action.HPDamage * action.HitPercentage * 0.32
8018756c: 00021143 sra r2,r2,0x05              #   action.HPDamage * action.HitPercentage / 100    (action.HPDamage * action.HitPercentage * 0.32 / 32)
80187570: 00431023 subu r2,r2,r3       
80187574: 10800003 beq r4,r0,0x80187584        
80187578: a4c2002a sh r2,0x002a(r6)            #   action.HitPercentage = action.HPDamage * action.HitPercentage / 100
8018757c: 14a0000b bne r5,r0,0x801875ac        #   if ((actionConsiderationStatus == ACTION_EXECUTING) or (action.HPDamage >= 0)) {
80187580: 00000000 nop             
80187584: 0c017833 jal 0x0005e0cc              #       rollResult = Pass/Fail Roll (100, action.HPDamage);
80187588: 34040064 ori r4,r0,0x0064                   
8018758c: 10400007 beq r2,r0,0x801875ac        #       if (rollResult != 0) {              // Action fails roll
80187590: 00000000 nop             
80187594: 0c0610cf jal 0x0018433c              #           Cause Action Miss ();
80187598: 00000000 nop             
8018759c: 3c028019 lui r2,0x8019       
801875a0: 8c422d90 lw r2,0x2d90(r2)            #           action
801875a4: 00000000 nop             
801875a8: a4400004 sh r0,0x0004(r2)            #           action.HPDamage = 0
                                               #       }
                                               #   }
801875ac: 8fbf0010 lw r31,0x0010(r29)
801875b0: 27bd0018 addiu r29,r29,0x0018
801875b4: 03e00008 jr r31
801875b8: 00000000 nop

Notes

Rather than using a div op, the code is actually doing

HPDamage * HitPercentage * 0.32 / 32

Multiplication by 0.32 done by multiplying by (0.32 * 2^32) and using mfhi to take only the upper 32 bits, effectively right shifting 32. (R3000_instruction_set#mult)

Return locations

Battle.bin
001886f4: Routine_used_in_formula_2B
00188830: MA_+_X
0018893c: Golem Accuracy
001889fc: Calculate_Accuracy_for_Magical_Spells
00188a5c: Calculate_Accuracy_for_Magical
00188ab4: MA_+_X_without_faith
00188b3c: Physical_Routine_for_Hit_%_abilities
00189038: Formula 0e : Dmg (Y)% Hit F(MA+X)% 100% Status Hide Status
001892f4: 1A_Hit_F(MA+Y)%_//_-PA/MA/SP_(X)
001898c8: Formula 28 : StealExp (Lowest of TarCurExp & SP+Y) Hit (SP+X)%
00189938: Formula 29 : OppositeSex: Hit (MA+X)%
00189a5c: Formula 2A : Hit (MA+X)% // AffectBraveOrFaith(Y)
00189e60: Formula 33 : Hit (PA+X)%
00189f38: Formula 35 : Heal (Y)% Hit (PA+X)%
0018a054: Formula 3f : Hit (SP+X)%
0018a0b0: Formula 40 : Undead: Hit (SP+X)%
0018a520: Formula 51 : Hit (MA+X)%
0018a85c: Formula 58 : Generic: Set Morbol: Hit(MA+X)%