User:Kmeisthax/Findings/2012/2/4/Malias2 Listing: Difference between revisions

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(Created page with "This is a listing of the disassembly for Malias2 Compression, marked up and annotated by me. ROM:0811E39C ; ---...")
 
(fixed error in disasm due to misinterpreting NEGS)
 
Line 86: Line 86:
     ROM:0811E412                MOVS    R2, #1
     ROM:0811E412                MOVS    R2, #1
     ROM:0811E414                NEGS    R2, R2
     ROM:0811E414                NEGS    R2, R2
     ROM:0811E416                MOV    R8, R2          ; R8=-2 or 0xFFFFFFFE
     ROM:0811E416                MOV    R8, R2          ; R8=-1 or 0xFFFFFFFF
     ROM:0811E418
     ROM:0811E418
     ROM:0811E418 DecompCore_ExecuteCmd                  ; CODE XREF: DecompCore+F0�j
     ROM:0811E418 DecompCore_ExecuteCmd                  ; CODE XREF: DecompCore+F0�j
Line 139: Line 139:
     ROM:0811E452                LSRS    R5, R5, #2      ; grab next command
     ROM:0811E452                LSRS    R5, R5, #2      ; grab next command
     ROM:0811E454                CMP    R1, R8
     ROM:0811E454                CMP    R1, R8
     ROM:0811E456                BEQ    DecompCore_LoopPostamble ; if (CopyLen == -2) break
     ROM:0811E456                BEQ    DecompCore_LoopPostamble ; if (CopyLen == -1) break
     ROM:0811E458                MOVS    R0, #1
     ROM:0811E458                MOVS    R0, #1
     ROM:0811E45A                NEGS    R0, R0
     ROM:0811E45A                NEGS    R0, R0
     ROM:0811E45C                MOV    R12, R0        ; R12 = 0xFFFFFFFE
     ROM:0811E45C                MOV    R12, R0        ; R12 = -1
     ROM:0811E45C                                        ; WTF I THOUGHT YOU ALREADY HAD ANOTHER
     ROM:0811E45C                                        ; WTF I THOUGHT YOU ALREADY HAD ANOTHER
     ROM:0811E45C                                        ; REGISTER WITH THIS CONSTANT IN IT
     ROM:0811E45C                                        ; REGISTER WITH THIS CONSTANT IN IT
Line 262: Line 262:
     ROM:0811E4F2                DCB    0
     ROM:0811E4F2                DCB    0
     ROM:0811E4F3                DCB    0
     ROM:0811E4F3                DCB    0
    ROM:0811E4F4
    ROM:0811E4F4 ; =============== S U B R O U T I N E =======================================
    ROM:0811E4F4
    ROM:0811E4F4 ; It's just DeCompCore, retasked to only do
    ROM:0811E4F4 ; 16-bit reads and writes, i.e. it RMWs all over
    ROM:0811E4F4 ; the place.
    ROM:0811E4F4
    ROM:0811E4F4 VolatileDeComp                          ; CODE XREF: ROM:0811E3E0�p

Latest revision as of 11:13, 4 February 2012

This is a listing of the disassembly for Malias2 Compression, marked up and annotated by me.

   ROM:0811E39C ; ---------------------------------------------------------------------------
   ROM:0811E39C                 CODE16
   ROM:0811E39C
   ROM:0811E39C DeCompress
   ROM:0811E39C                 PUSH    {R4,LR}
   ROM:0811E39E                 ADDS    R3, R0, #0      ; R3: Compression Source
   ROM:0811E3A0                 ADDS    R4, R1, #0      ; R4: Decompression Destination
   ROM:0811E3A2                 LDRB    R0, [R3]
   ROM:0811E3A4                 CMP     R0, #0x4C
   ROM:0811E3A6                 BNE     DeCompress_NoMagic ; ret false
   ROM:0811E3A8                 LDRB    R0, [R3,#1]
   ROM:0811E3AA                 CMP     R0, #0x65
   ROM:0811E3AC                 BEQ     DeCompress_MagicValid ; test for magic bytes 4C 65
   ROM:0811E3AE
   ROM:0811E3AE DeCompress_NoMagic                      ; CODE XREF: ROM:0811E3A6�j
   ROM:0811E3AE                 MOVS    R0, #0          ; ret false
   ROM:0811E3B0                 B       DeCompress_Return
   ROM:0811E3B2 ; ---------------------------------------------------------------------------
   ROM:0811E3B2
   ROM:0811E3B2 DeCompress_MagicValid                   ; CODE XREF: ROM:0811E3AC�j
   ROM:0811E3B2                 LDR     R0, =0xFBFFFFFF
   ROM:0811E3B4                 ADDS    R1, R4, R0      ; R1 = R4 - 0x4000001
   ROM:0811E3B6                 LDR     R0, =0x3FFFFFE
   ROM:0811E3B8                 CMP     R1, R0
   ROM:0811E3BA                 BLS     DeCompress_ToVolatile ; branch if (R4 - 0x4000001) <= 0x3FFFFFE
   ROM:0811E3BA                                         ; (if memory location in I/Oregs, palram, vram, or oam)
   ROM:0811E3BC                 LDRB    R2, [R3,#2]
   ROM:0811E3BE                 LDRB    R0, [R3,#3]
   ROM:0811E3C0                 LSLS    R0, R0, #8
   ROM:0811E3C2                 ORRS    R2, R0          ; unaligned little-endian 16 bit read
   ROM:0811E3C4                 LDRB    R0, [R3,#4]
   ROM:0811E3C6                 LSLS    R0, R0, #0x10
   ROM:0811E3C8                 ORRS    R2, R0          ; unaligned little-endian 24-bit read
   ROM:0811E3CA                 ADDS    R0, R3, #0
   ROM:0811E3CC                 ADDS    R1, R4, #0      ; Size (32-bit align, 24-bits used)
   ROM:0811E3CE                 BL      DecompCore      ; call(CmpSrc, CmpDst, Size)
   ROM:0811E3D2                 B       DeCompress_Return
   ROM:0811E3D2 ; ---------------------------------------------------------------------------
   ROM:0811E3D4 dword_811E3D4   DCD 0xFBFFFFFF          ; DATA XREF: ROM:DeCompress_MagicValid�r
   ROM:0811E3D8 dword_811E3D8   DCD 0x3FFFFFE           ; DATA XREF: ROM:0811E3B6�r
   ROM:0811E3DC ; ---------------------------------------------------------------------------
   ROM:0811E3DC
   ROM:0811E3DC DeCompress_ToVolatile                   ; CODE XREF: ROM:0811E3BA�j
   ROM:0811E3DC                 ADDS    R0, R3, #0
   ROM:0811E3DE                 ADDS    R1, R4, #0
   ROM:0811E3E0                 BL      VolatileDeComp  ; It's just DeCompCore, retasked to only do
   ROM:0811E3E0                                         ; 16-bit reads and writes, i.e. it RMWs all over
   ROM:0811E3E0                                         ; the place.
   ROM:0811E3E4
   ROM:0811E3E4 DeCompress_Return                       ; CODE XREF: ROM:0811E3B0�j
   ROM:0811E3E4                                         ; ROM:0811E3D2�j
   ROM:0811E3E4                 POP     {R4}
   ROM:0811E3E6                 POP     {R1}
   ROM:0811E3E8                 BX      R1
   ROM:0811E3E8 ; ---------------------------------------------------------------------------
   ROM:0811E3EA                 DCB    0
   ROM:0811E3EB                 DCB    0
   ROM:0811E3EC
   ROM:0811E3EC ; =============== S U B R O U T I N E =======================================
   ROM:0811E3EC
   ROM:0811E3EC
   ROM:0811E3EC DecompCore                              ; CODE XREF: ROM:0811E3CE�p
   ROM:0811E3EC                 PUSH    {R4-R7,LR}
   ROM:0811E3EE                 MOV     R7, R10
   ROM:0811E3F0                 MOV     R6, R9
   ROM:0811E3F2                 MOV     R5, R8
   ROM:0811E3F4                 PUSH    {R5-R7}         ; preamble: using R4-R10
   ROM:0811E3F6                 MOV     R10, R2         ; R10: Size
   ROM:0811E3F8                 MOV     R7, R10
   ROM:0811E3FA                 ADDS    R3, R1, #0      ; R3: Decompression Destination
   ROM:0811E3FC                 ADDS    R4, R0, #6      ; R4: Compression Source + 6
   ROM:0811E3FE                 MOV     R0, R10
   ROM:0811E400                 CMP     R0, #0
   ROM:0811E402                 BEQ     DecompCore_Return
   ROM:0811E404
   ROM:0811E404 DecompCore_ExecuteBundle                ; CODE XREF: DecompCore+F4�j
   ROM:0811E404                 LDRB    R5, [R4]        ; R5: Current bundle command list
   ROM:0811E406                 ADDS    R4, #1
   ROM:0811E408                 MOVS    R6, #0          ; R6: Number of commands in current bundle
   ROM:0811E40A                 CMP     R7, #0
   ROM:0811E40C                 BEQ     DecompCore_Return
   ROM:0811E40E                 MOVS    R1, #3
   ROM:0811E410                 MOV     R9, R1          ; R9=+3
   ROM:0811E412                 MOVS    R2, #1
   ROM:0811E414                 NEGS    R2, R2
   ROM:0811E416                 MOV     R8, R2          ; R8=-1 or 0xFFFFFFFF
   ROM:0811E418
   ROM:0811E418 DecompCore_ExecuteCmd                   ; CODE XREF: DecompCore+F0�j
   ROM:0811E418                 ADDS    R0, R5, #0
   ROM:0811E41A                 MOV     R1, R9
   ROM:0811E41C                 ANDS    R0, R1          ; *CmpSrc & 3
   ROM:0811E41E                 CMP     R0, #1
   ROM:0811E420                 BEQ     DecompCore_Mode1 ; Mode 1
   ROM:0811E422                 CMP     R0, #1
   ROM:0811E424                 BGT     DecompCore_UncompressedModes
   ROM:0811E426                 CMP     R0, #0
   ROM:0811E428                 BEQ     DecompCore_Mode0 ; Mode 0
   ROM:0811E42A                 B       DecompCore_Mode23_End ; You just &ed this with 3.
   ROM:0811E42A                                         ; There is no way to reach this code.
   ROM:0811E42A                                         ; What the hell compiled this swill?!
   ROM:0811E42C ; ---------------------------------------------------------------------------
   ROM:0811E42C
   ROM:0811E42C DecompCore_UncompressedModes            ; CODE XREF: DecompCore+38�j
   ROM:0811E42C                 CMP     R0, #2
   ROM:0811E42E                 BEQ     DecompCore_Mode2 ; Mode 2
   ROM:0811E42E                                         ; Copy 1 uncompressed byte.
   ROM:0811E430                 CMP     R0, #3
   ROM:0811E432                 BEQ     DecompCore_Mode3 ; Mode 3
   ROM:0811E432                                         ; Copy 3 uncompressed bytes.
   ROM:0811E434                 B       DecompCore_Mode23_End ; ANOTHER UNREACHABLE BRANCH
   ROM:0811E434                                         ; MAYBE YOU WOULDN'T NEED COMPRESSION
   ROM:0811E434                                         ; IF YOUR COMPILER ACTUALLY DID DEAD
   ROM:0811E434                                         ; CODE ELIMINATION
   ROM:0811E436 ; ---------------------------------------------------------------------------
   ROM:0811E436
   ROM:0811E436 DecompCore_Mode0                        ; CODE XREF: DecompCore+3C�j
   ROM:0811E436                 LDRB    R1, [R4]        ; LZ77 copy operation.
   ROM:0811E436                                         ;
   ROM:0811E436                                         ; The following 2 bytes are interpreted as a little
   ROM:0811E436                                         ; endian value. The low 12 bits are an offset from the
   ROM:0811E436                                         ; current copy head. The high 4 are the number of bytes
   ROM:0811E436                                         ; to copy, minus four. Bytes will be copied from the
   ROM:0811E436                                         ; offset to the output, byte-by-byte.
   ROM:0811E438                 LDRB    R0, [R4,#1]
   ROM:0811E43A                 LSLS    R0, R0, #8
   ROM:0811E43C                 ADDS    R1, R1, R0
   ROM:0811E43E                 ADDS    R4, #2
   ROM:0811E440                 LDR     R0, =0xFFF
   ROM:0811E442                 ANDS    R0, R1
   ROM:0811E444                 ADDS    R0, #5
   ROM:0811E446                 SUBS    R2, R3, R0      ; CopySrc = Dest - (*((uint_16*)Src) & 0xFFF + 5)
   ROM:0811E448                 LSRS    R0, R1, #0xC
   ROM:0811E44A                 ADDS    R1, R0, #3
   ROM:0811E44C                 SUBS    R7, R7, R1      ; BytesLeft -= *((uint_16*)Src) >> 12 + 3
   ROM:0811E44E                 ADDS    R1, R0, #2      ; CopyLen = *((uint_16*)Src) >> 12 + 2
   ROM:0811E450                 ADDS    R6, #1
   ROM:0811E452                 LSRS    R5, R5, #2      ; grab next command
   ROM:0811E454                 CMP     R1, R8
   ROM:0811E456                 BEQ     DecompCore_LoopPostamble ; if (CopyLen == -1) break
   ROM:0811E458                 MOVS    R0, #1
   ROM:0811E45A                 NEGS    R0, R0
   ROM:0811E45C                 MOV     R12, R0         ; R12 = -1
   ROM:0811E45C                                         ; WTF I THOUGHT YOU ALREADY HAD ANOTHER
   ROM:0811E45C                                         ; REGISTER WITH THIS CONSTANT IN IT
   ROM:0811E45C                                         ; WHY ARE YOU REMATERIALIZING IT HERE
   ROM:0811E45E
   ROM:0811E45E DecompCore_Mode0CopyLoop                ; CODE XREF: DecompCore+7E�j
   ROM:0811E45E                 LDRB    R0, [R2]
   ROM:0811E460                 STRB    R0, [R3]
   ROM:0811E462                 ADDS    R2, #1
   ROM:0811E464                 ADDS    R3, #1
   ROM:0811E466                 SUBS    R1, #1
   ROM:0811E468                 CMP     R1, R12
   ROM:0811E46A                 BNE     DecompCore_Mode0CopyLoop
   ROM:0811E46C                 B       DecompCore_LoopPostamble
   ROM:0811E46C ; ---------------------------------------------------------------------------
   ROM:0811E46E                 DCB    0
   ROM:0811E46F                 DCB    0
   ROM:0811E470 dword_811E470   DCD 0xFFF               ; DATA XREF: DecompCore+54�r
   ROM:0811E474 ; ---------------------------------------------------------------------------
   ROM:0811E474
   ROM:0811E474 DecompCore_Mode1                        ; CODE XREF: DecompCore+34�j
   ROM:0811E474                 LDRB    R1, [R4]        ; LZ77 copy operation.
   ROM:0811E474                                         ;
   ROM:0811E474                                         ; The following byte is read. The low 2 bits are an
   ROM:0811E474                                         ; offset from the current copy head minus one. The
   ROM:0811E474                                         ; high 6 are the number of bytes to copy, minus three.
   ROM:0811E474                                         ; Bytes will be copied from the offset to the output,
   ROM:0811E474                                         ; byte-by-byte.
   ROM:0811E476                 ADDS    R4, #1
   ROM:0811E478                 ADDS    R0, R1, #0
   ROM:0811E47A                 MOV     R2, R9          ; +3
   ROM:0811E47C                 ANDS    R0, R2
   ROM:0811E47E                 ADDS    R0, #1
   ROM:0811E480                 SUBS    R2, R3, R0      ; CopySrc = Dest - (*Src & 3 + 1)
   ROM:0811E482                 LSRS    R0, R1, #2
   ROM:0811E484                 ADDS    R1, R0, #2
   ROM:0811E486                 SUBS    R7, R7, R1      ; BytesLeft -= *Src >> 2 + 2
   ROM:0811E488                 ADDS    R1, R0, #1      ; CopyLen = *Src >> 2 + 1
   ROM:0811E48A                 ADDS    R6, #1
   ROM:0811E48C                 LSRS    R5, R5, #2      ; grab next command
   ROM:0811E48E                 CMP     R1, R8
   ROM:0811E490                 BEQ     DecompCore_LoopPostamble
   ROM:0811E492                 MOVS    R0, #1
   ROM:0811E494                 NEGS    R0, R0
   ROM:0811E496                 MOV     R12, R0         ; another rematerialization of R8
   ROM:0811E496                                         ; THIS WAS WHY RISC WAS INVENTED
   ROM:0811E496                                         ;
   ROM:0811E496                                         ; MORANS
   ROM:0811E498
   ROM:0811E498 DecompCore_Mode1CopyLoop                ; CODE XREF: DecompCore+B8�j
   ROM:0811E498                 LDRB    R0, [R2]
   ROM:0811E49A                 STRB    R0, [R3]
   ROM:0811E49C                 ADDS    R2, #1
   ROM:0811E49E                 ADDS    R3, #1
   ROM:0811E4A0                 SUBS    R1, #1
   ROM:0811E4A2                 CMP     R1, R12
   ROM:0811E4A4                 BNE     DecompCore_Mode1CopyLoop
   ROM:0811E4A6                 B       DecompCore_LoopPostamble
   ROM:0811E4A8 ; ---------------------------------------------------------------------------
   ROM:0811E4A8
   ROM:0811E4A8 DecompCore_Mode3                        ; CODE XREF: DecompCore+46�j
   ROM:0811E4A8                 LDRB    R0, [R4]
   ROM:0811E4AA                 STRB    R0, [R3]
   ROM:0811E4AC                 ADDS    R4, #1
   ROM:0811E4AE                 ADDS    R3, #1
   ROM:0811E4B0                 LDRB    R0, [R4]
   ROM:0811E4B2                 STRB    R0, [R3]
   ROM:0811E4B4                 ADDS    R4, #1
   ROM:0811E4B6                 ADDS    R3, #1
   ROM:0811E4B8                 LDRB    R0, [R4]
   ROM:0811E4BA                 STRB    R0, [R3]
   ROM:0811E4BC                 ADDS    R4, #1
   ROM:0811E4BE                 ADDS    R3, #1
   ROM:0811E4C0                 SUBS    R7, #3          ; for (int i = 0; i < 3; i++)
   ROM:0811E4C0                                         ;     *Dest++ = *CmpSrc++
   ROM:0811E4C0                                         ;
   ROM:0811E4C0                                         ; Size -= 3
   ROM:0811E4C2                 B       DecompCore_Mode23_End
   ROM:0811E4C4 ; ---------------------------------------------------------------------------
   ROM:0811E4C4
   ROM:0811E4C4 DecompCore_Mode2                        ; CODE XREF: DecompCore+42�j
   ROM:0811E4C4                 LDRB    R0, [R4]
   ROM:0811E4C6                 STRB    R0, [R3]
   ROM:0811E4C8                 ADDS    R4, #1
   ROM:0811E4CA                 ADDS    R3, #1
   ROM:0811E4CC                 SUBS    R7, #1
   ROM:0811E4CE
   ROM:0811E4CE DecompCore_Mode23_End                   ; CODE XREF: DecompCore+3E�j
   ROM:0811E4CE                                         ; DecompCore+48�j ...
   ROM:0811E4CE                 ADDS    R6, #1
   ROM:0811E4D0                 LSRS    R5, R5, #2      ; Grab next command
   ROM:0811E4D2
   ROM:0811E4D2 DecompCore_LoopPostamble                ; CODE XREF: DecompCore+6A�j
   ROM:0811E4D2                                         ; DecompCore+80�j ...
   ROM:0811E4D2                 LSLS    R0, R5, #0x18
   ROM:0811E4D4                 LSRS    R5, R0, #0x18   ; WTF THIS DOES NOTHING WHY DO YOU HAVE IT HERE
   ROM:0811E4D6                 CMP     R6, #3          ; Number of commands read in bundle
   ROM:0811E4D8                 BHI     DecompCore_LoopPostamble2
   ROM:0811E4DA                 CMP     R7, #0
   ROM:0811E4DC                 BNE     DecompCore_ExecuteCmd
   ROM:0811E4DE
   ROM:0811E4DE DecompCore_LoopPostamble2               ; CODE XREF: DecompCore+EC�j
   ROM:0811E4DE                 CMP     R7, #0
   ROM:0811E4E0                 BNE     DecompCore_ExecuteBundle ; R5: Current bundle command list
   ROM:0811E4E2
   ROM:0811E4E2 DecompCore_Return                       ; CODE XREF: DecompCore+16�j
   ROM:0811E4E2                                         ; DecompCore+20�j
   ROM:0811E4E2                 MOV     R0, R10
   ROM:0811E4E4                 POP     {R3-R5}
   ROM:0811E4E6                 MOV     R8, R3
   ROM:0811E4E8                 MOV     R9, R4
   ROM:0811E4EA                 MOV     R10, R5
   ROM:0811E4EC                 POP     {R4-R7}
   ROM:0811E4EE                 POP     {R1}
   ROM:0811E4F0                 BX      R1
   ROM:0811E4F0 ; End of function DecompCore
   ROM:0811E4F0
   ROM:0811E4F0 ; ---------------------------------------------------------------------------
   ROM:0811E4F2                 DCB    0
   ROM:0811E4F3                 DCB    0
   ROM:0811E4F4
   ROM:0811E4F4 ; =============== S U B R O U T I N E =======================================
   ROM:0811E4F4
   ROM:0811E4F4 ; It's just DeCompCore, retasked to only do
   ROM:0811E4F4 ; 16-bit reads and writes, i.e. it RMWs all over
   ROM:0811E4F4 ; the place.
   ROM:0811E4F4
   ROM:0811E4F4 VolatileDeComp                          ; CODE XREF: ROM:0811E3E0�p