View source for Get Square root of r4 dealing with 4096

 Parameter : r4 = Input value
 
 Returns : r2 = 0x00 if r4 = 0x00
           if r4 > 0x1000 (4096) : r2 =  (Square root of (r4/4096) )*4096
           if r4 < 0x1000 : r2 =  Square root of (r4 * 4096)
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 0001c268: 4884f000 mtc2 r4,gtedr30_lzcs          |{{f/store|<nowiki>Move word to coprocessor register gtedr30_lzcs</nowiki>}}
 0001c26c: 00000000 nop                           |
 0001c270: 00000000 nop                           |{{f/std|<nowiki>From GTE notes: "Reading LZCR returns the leading 0 count of LZCS if LZCS is positive and the leading 1 count of LZCS if LZCS is negative."</nowiki>}}
 0001c274: 4802f800 mfc2 r2,gtedr31_lzcr          |{{f/load|<nowiki>r2 = r4 number of leading zeros </nowiki>}} (Move from coprocessor gtedr31_lzcr)
 0001c278: 24010020 addiu r1,r0,0x0020            |{{f/std|<nowiki>r1 = 32</nowiki>}}
 0001c27c: 1041001d beq r2,r1,0x0001c2f4          {{f/Cond|<nowiki>If r4 <> 0x00</nowiki>}} /Branch if there's 32 leading 0s (r4 = 0x00000000)
 0001c280: 00000000 nop                               |{{f/std|<nowiki> </nowiki>}}
 0001c284: 30480001 andi r8,r2,0x0001                 |{{f/std|<nowiki>r8 = 0s count and 0x01 (0x00 or 0x01)</nowiki>}}
 0001c288: 240afffe addiu r10,r0,-0x0002              |{{f/std|<nowiki>r10 = -0x02 (0xfffffffe)</nowiki>}}
 0001c28c: 004a5024 and r10,r2,r10                    |{{f/std|<nowiki>r10 = even 0s count (down rounded)</nowiki>}}
 0001c290: 24090013 addiu r9,r0,0x0013                |{{f/std|<nowiki>r9 = 0x13 (19)</nowiki>}}
 0001c294: 012a4822 sub r9,r9,r10                     |{{f/std|<nowiki>r9 = 19 - even 0s count</nowiki>}} {{f/std|<nowiki>(4096 = lowest value with 19 Even zeros)</nowiki>}}
 0001c298: 00094843 sra r9,r9,0x01                    |{{f/std|<nowiki>r9 = (19 - even 0s count)/2    </nowiki>}}
 0001c29c: 214bffe8 addi r11,r10,-0x0018              |{{f/std|<nowiki>r11 > 0x00 if there's more than 24 zeros  (r4 < 0xff)</nowiki>}}
 0001c2a0: 05600003 bltz r11,0x0001c2b0               {{f/Cond|<nowiki>If r4 <= 0xff</nowiki>}} / Branch if r4 > 0xff (less than 24 leading 0's)
 0001c2a4: 00000000 nop                                   |{{f/std|<nowiki> </nowiki>}}
 0001c2a8: 01646004 sllv r12,r4,r11                       |{{f/std|<nowiki>r12 = r4 shifted to let only 24 leading zeros</nowiki>}}
 0001c2ac: 10000003 beq r0,r0,0x0001c2bc                  {{f/Cond|<nowiki>Branch if 0 = 0 (why not a jump ?)</nowiki>}}
 0001c2b0: 240b0018 addiu r11,r0,0x0018               {{f/Cond|<nowiki>Else (r4 >= 0xff)</nowiki>}} {{f/std|<nowiki>r11 = 24</nowiki>}}
 0001c2b4: 016a5822 sub r11,r11,r10                       |{{f/std|<nowiki>r11 = 24 - even 0s count</nowiki>}}
 0001c2b8: 01646007 srav r12,r4,r11                       |{{f/std|<nowiki>r12 = r4 shifted to let 24 leading zeros (byted ?)</nowiki>}}
 0001c2bc: 218cffc0 addi r12,r12,-0x0040              |{{f/std|<nowiki>r12 = byted r4 - 0x40</nowiki>}}
 0001c2c0: 000c6040 sll r12,r12,0x01                  |
 0001c2c4: 3c0d8003 lui r13,0x8003                    |{{f/std|<nowiki>r13 = 0x80030000</nowiki>}}
 0001c2c8: 01ac6821 addu r13,r13,r12                  |{{f/std|<nowiki>r13 = 0x80030000 + offset (from r4)</nowiki>}}
 0001c2cc: 85adb8b8 lh r13,-0x4748(r13)               |{{f/load|<nowiki>r13 = root square mod</nowiki>}}    see [[Square_Root_Mods_Table]]
 0001c2d0: 00000000 nop                               |
 0001c2d4: 05200004 bltz r9,0x0001c2e8                {{f/Cond|<nowiki>if r9 >= 0</nowiki>}} {{f/Cond|<nowiki>r4  >= 4096 (sign a value * 4096 ?)</nowiki>}}
 0001c2d8: 00000000 nop                                   |{{f/std|<nowiki> </nowiki>}}
 0001c2dc: 012d1004 sllv r2,r13,r9                        |{{f/std|<nowiki>r2 = Increased Root square mod  (left shift 19 - r4 leadind 0's count)/2</nowiki>}} {{f/std|<nowiki>Half the leading zero before * 4096 (leading 0/2 matches the square root)</nowiki>}}
 0001c2e0: 03e00008 jr r31                                {{f/jump|<nowiki>Exit</nowiki>}}
 0001c2e4: 00000000 nop                                   |
 0001c2e8: 00094822 sub r9,r0,r9                      {{f/Cond|<nowiki>Else (r9 < 0)</nowiki>}} {{f/std|<nowiki>r9 = abs(r9)</nowiki>}} {{f/std|<nowiki>r4 < 4096</nowiki>}}
 0001c2ec: 03e00008 jr r31                                 {{f/jump|<nowiki>Exit </nowiki>}}
 0001c2f0: 012d1006 srlv r2,r13,r9                         |{{f/std|<nowiki>r2 = Decrease Root square mod (right shift r4 leading zeros count - 19)/2 </nowiki>}}
 0001c2f4: 03e00008 jr r31                         {{f/Cond|<nowiki>Else (r4 = 0x00) </nowiki>}} Exit
 0001c2f8: 24020000 addiu r2,r0,0x0000             |{{f/std|<nowiki>r2 = 0x00</nowiki>}}
=== Notes ===
 Count the leading zeros of the binary value of r4 (via coprocessor 2)
 Down round the count to an even value (look after the first couple of bit that hold a value)
 Force r4 to 24(25 if uneven count) leading zeros (so the most left values fit in a byte) - eventually loose the  bits to the right
 Use this value to pick up the square root mod
 Increase the square root mod if r4 > 0x1000 (by half the leading zeros > 19 (19 zeros is 0x1000))
   #Else decrease the square root mod by half the difference of leading 0 between r4 and 0x1000
=== Return locations ===
 '''Battle.bin'''
 0006a89c: [[0006a7c0 - 0006aa7c]]
 0006a8e4: [[0006a7c0 - 0006aa7c]]
 0006ab48: [[0006aa80 - 0006ad14]]
 0006adb0: [[0006ad18 - 0006af78]]
 0006adf8: [[0006ad18 - 0006af78]]
 00089e70: [[00089e20 - 00089f20]]
 00089ea4: [[00089e20 - 00089f20]]
 0008a3dc: [[0008a35c - 0008a4a8]]
 0008b174: [[0008b0c8 - 0008b230]]
 001af520: 001af3dc - 001af598	[[Maths For Arcing Trajectory]]
 001af760: 001af734 - 001af76c	[[Give Gravity Impact]]
 001afe78: [[001afd90 - 001aff14]]
 001b00e8: 001aff18 - 001b045c	[[Set and Validate Arc Trajectory]] - r4 = ((Delta Xmod)^2 + (Delta Y mod)^2)*4096   ((distance between attacker and target)^2)*4096
 001b07e0: [[001b06d0 - 001b0814]]
 001b0a3c: [[001b0818 - 001b0a8c]]
 001b0c4c: [[001b0a90 - 001b0c84]]
 001b10d0: 001b0ffc - 001b1538	[[Bow Arrow Secondary Effect]]
 001b3a1c: 001b3938 - 001b40f4	[[Linear Projectile secondary effect]]