dos33fsprogs/tfv/OPTIMIZATION

Original implementation:
	Multiplying 1.0 * 2.0 = 2.0, took 707 cycles
	Multiplying ff.ff * ff.ff = 0.0, took 761 cycles

	Cycles: flying=               162
	Cycles: getkey=                46
	Cycles: page_flip=             26
	Cycles: multiply=          88,179
	Cycles: mode7=             76,077
	Cycles: lookup_map=        33,920
	Cycles: put_sprite=         2,561
	==================================
	Total =                   200,971
	Frame Rate = 4.98 fps

Update Multiply to use zero page addresses:
	Multiplying 1.0 * 2.0 = 2.0, took 616 cycles
	Multiplying ff.ff * ff.ff = 0.0, took 664 cycles

	Cycles: flying=              162
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         76,561
	Cycles: mode7=            76,077
	Cycles: lookup_map=       33,920
	Cycles: put_sprite=        2,561
	===================================
	Total =                  189,353
	Frame Rate = 5.28 fps

Update to use "fast multiply" w 2kB squares table lookup:
	Multiplying 1.0 * 2.0 = 2.0, took 228 cycles
	Multiplying ff.ff * ff.ff = 0.0, took 272 cycles

	Cycles: flying=              162
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         27,041
	Cycles: mode7=            76,077
	Cycles: lookup_map=       33,920
	Cycles: put_sprite=        2,561
	=================================
	Total =                  139,833
	Frame Rate = 7.15 fps

Update to optimize fast multiply (reusing NUM1H, return results in register)
	Multiplying 1.0 * 2.0 = 2.0, took 234 cycles
	Multiplying ff.ff * ff.ff = 0.0, took 278 cycles

	Cycles: flying=              162
	Cycles: getkey=               46
        Cycles: page_flip=            26
        Cycles: multiply=         24,935
        Cycles: mode7=            73,925
        Cycles: lookup_map=       33,920
        Cycles: put_sprite=        2,561
	=================================
        Total =                  135,575
	Frame Rate = 7.38 fps

Add a cache to lookup_map

	Cycles: flying=              162
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         24,935
	Cycles: mode7=            73,445
	Cycles: lookup_map=       24,649
	Cycles: put_sprite=        2,561
	=================================
	Total =                  125,824
	Frame Rate = 7.95 fps

Don't draw sky every frame

	Cycles: flying=              162
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         24,935
	Cycles: mode7=            69,099
	Cycles: lookup_map=       24,649
	Cycles: put_sprite=        2,561
	=================================
	Total =                  121,478
	Frame Rate = 8.23 fps

Move checking if over water out of critical section

	Cycles: flying=              187
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         24,935
	Cycles: mode7=            54,374
	Cycles: lookup_map=       24,712
	Cycles: put_sprite=        2,561
	=================================
	Total =                  106,841
	Frame Rate = 9.36 fps

Move to 40x40 mode

	Cycles: flying=              187
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         49,613
	Cycles: mode7=           123,701
	Cycles: lookup_map=       48,847
	Cycles: put_sprite=        2,561
	=================================
	Total =                  224,981
	Frame Rate = 4.44 fps

Remove some unnecessary zero page copies in the mode7 code
	Cycles: flying=              187
	Cycles: getkey=               46
	Cycles: page_flip=            26
	Cycles: multiply=         49,613
	Cycles: mode7=           141,269
	Cycles: lookup_map=       21,718
	Cycles: put_sprite=        2,561
	================================
	Total =                  215,420
	Frame Rate = 4.64 fps

A few more minor cleanups in the Y loop
	Cycles: flying=             187
	Cycles: getkey=              46
	Cycles: page_flip=           26
	Cycles: multiply=        49,613
	Cycles: mode7=          140,858
	Cycles: lookup_map=      21,718
	Cycles: put_sprite=       2,561
	===============================
	Total =                 215,009
	Frame Rate = 4.65 fps

Add some self-modifying code to inner loop:
	Cycles: flying=             187
	Cycles: getkey=              46
	Cycles: page_flip=           26
	Cycles: multiply=        49,613
	Cycles: mode7=          131,610
	Cycles: lookup_map=      21,718
	Cycles: put_sprite=       2,561
	================================
	Total =                 205,761
	Frame Rate = 4.86 fps

More self-modifying code, also move SCREEN_X to X register
	Cycles: flying=             187
	Cycles: getkey=              46
	Cycles: page_flip=           26
	Cycles: multiply=        49,613
	Cycles: mode7=          118,034
	Cycles: lookup_map=      22,747
	Cycles: put_sprite=       2,561
	================================
	Total =                 193,214
	Frame Rate = 5.18 fps

Each cycle removed from inner X loop saves
	32*40=1280 cycles