# Every button mask the C_PAD_DECODER's update function applies, sub_8220B8C0
# (0x8220B8C0..0x8220CFA0, 1400 instructions). Two sources, both listed:
#   * pure masks  -- rlwinm rA,rS,0,MB,ME, the PPC idiom for 'test these bits'
#   * immediates  -- andi. / cmpli operands
# Bit values are XINPUT_GAMEPAD's, in their NATIVE positions: the decoder reads
# a 32-bit word at +12 of the C_PAD_RINGBUF (this+76) and masks its low 16 bits,
# verified 7/7 against /image/sylpheed.pe. There is no shift and no remap.

## SINGLE-BIT masks -- one XINPUT button each
  0x0001  DPAD_UP          rlwinm x21 0x8220BB9C  0x8220BC14  0x8220BE48  0x8220BEA8  0x8220BEEC  0x8220C28C   andi./cmpli x2
  0x0002  DPAD_DOWN        rlwinm x2  0x8220BC64  0x8220C864
  0x0004  DPAD_LEFT        rlwinm x3  0x8220B8E4  0x8220C858  0x8220C8D8
  0x0008  DPAD_RIGHT       rlwinm x1  0x8220BC50
  0x0010  START            rlwinm x5  0x8220BE64  0x8220C47C  0x8220C594  0x8220C6B0  0x8220C920
  0x0020  BACK             rlwinm x4  0x8220C498  0x8220C5A0  0x8220C6C8  0x8220C93C
  0x0040  LEFT_THUMB       rlwinm x2  0x8220BF98  0x8220C444
  0x0080  RIGHT_THUMB      rlwinm x2  0x8220C08C  0x8220C460
  0x0100  LEFT_SHOULDER    rlwinm x0  
  0x0200  RIGHT_SHOULDER   rlwinm x0  
  0x0400  (0x0400)         rlwinm x1  0x8220CBAC
  0x0800  (0x0800)         rlwinm x0  
  0x1000  A                rlwinm x2  0x8220C584  0x8220C608
  0x2000  B                rlwinm x1  0x8220C694
  0x4000  X                rlwinm x1  0x8220C66C
  0x8000  Y                rlwinm x1  0x8220C680

## GROUP masks -- the XINPUT groupings, which is what identifies these as buttons
  0x0003  x1   DPAD_UP,DPAD_DOWN
  0x000F  x1   DPAD_UP,DPAD_DOWN,DPAD_LEFT,DPAD_RIGHT
  0x0030  x1   START,BACK
  0x0060  x1   BACK,LEFT_THUMB
  0x00FF  x5   DPAD_UP,DPAD_DOWN,DPAD_LEFT,DPAD_RIGHT,START,BACK,LEFT_THUMB,RIGHT_THUMB
  0xE000  x18  B,X,Y
  0xF000  x1   A,B,X,Y

## Verified against the image (database used only as an index)
  0x8220C558 image=0x554A0426 expect=0x554A0426 OK  rlwinm r10,r10,0,16,19   mask A|B|X|Y  ("any face button")
  0x8220C680 image=0x556A0420 expect=0x556A0420 OK  rlwinm r10,r11,0,16,16   mask Y
  0x8220C66C image=0x556A0462 expect=0x556A0462 OK  rlwinm r10,r11,0,17,17   mask X
  0x8220C694 image=0x556B04A4 expect=0x556B04A4 OK  rlwinm r11,r11,0,18,18   mask B
  0x8220BB80 image=0x556B0424 expect=0x556B0424 OK  rlwinm r11,r11,0,16,18   mask B|X|Y
  0x8220C550 image=0x815F004C expect=0x815F004C OK  lwz r10,76(r31)   this+76 = the C_PAD_RINGBUF
  0x8220C554 image=0x814A000C expect=0x814A000C OK  lwz r10,12(r10)   +12 inside it = the button word