forked from Lephenixnoir/gint
203 lines
3.2 KiB
ArmAsm
203 lines
3.2 KiB
ArmAsm
.global _topti_glyph_fg_bg
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.global _topti_glyph_fg
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.global _topti_glyph_bg
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.section .pretext
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# Glyph rendering functions.
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# These are pretty naive, using only word accesses to index the VRAM and
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# absolute positions to index the glyph data, instead of shiting a single
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# longword to real all bits in order. This is because we only render a subglyph
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# (for clipping) so there'a non-zero stride in glyph data.
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# Parameters:
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# r4: vram
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# r5: data
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# r6: color (either fg, bg, or (fg << 16) | bg)
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# r7: height
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# @(4,r15): width
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# @(8,r15): dataw - width (stride)
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# @(12,r15): starting index in data
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# Stack:
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# @(0,r15): r8 save
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# Register allocation:
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# r0: (temporary)
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# r1: (temporary)
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# r2: x counter
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# r3: glyph data index
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# r4: vram pointer
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# r5: glyph pointer
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# r6: color
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# r7: y counter
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# Callee-saved registers:
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# r8: vram stride
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# Opaque foreground, opaque background
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_topti_glyph_fg_bg:
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# Compute VRAM stride 2 * (396-width)
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mov.l r8, @-r15
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mov.l 1f, r8
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mov.l @(4, r15), r3
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shll r3
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sub r3, r8
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# Load the starting index
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mov.l @(12, r15), r3
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.fg_bg_y:
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# Initialize width counter
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mov.l @(4, r15), r2
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.fg_bg_x:
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# Load one bit of data in T
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mov r3, r0
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mov #-5, r1
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shld r1, r0
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shll2 r0
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mov.l @(r0, r5), r1
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mov r3, r0
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and #31, r0
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shld r0, r1
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shll r1
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# Select the correct 16 bits or r6
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bf/s .fg_bg_zero
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mov r6, r1
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swap.w r6, r1
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.fg_bg_zero:
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# Write color to VRAM
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mov.w r1, @r4
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add #2, r4
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# Leave the x-loop if x counter reaches 0
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dt r2
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bf/s .fg_bg_x
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add #1, r3
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# Move to next row, leave the y-loop if height reaches 0
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dt r7
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mov.l @(8, r15), r0
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add r0, r3
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bf/s .fg_bg_y
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add r8, r4
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rts
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mov.l @r15+, r8
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# Opaque foreground, transparent background
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_topti_glyph_fg:
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# Compute VRAM stride 2 * (396-width)
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mov.l r8, @-r15
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mov.l 1f, r8
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mov.l @(4, r15), r3
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shll r3
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sub r3, r8
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# Load the starting index
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mov.l @(12, r15), r3
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.fg_y:
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# Initialize width counter
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mov.l @(4, r15), r2
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.fg_x:
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# Load one bit of data in T
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mov r3, r0
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mov #-5, r1
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shld r1, r0
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shll2 r0
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mov.l @(r0, r5), r1
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mov r3, r0
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and #31, r0
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shld r0, r1
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shll r1
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# Write color to VRAM only if it's a 1 bit
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bf .fg_next
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mov.w r6, @r4
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.fg_next:
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# Leave the x-loop if x counter reaches 0
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add #2, r4
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dt r2
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bf/s .fg_x
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add #1, r3
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# Move to next row, leave the y-loop if height reaches 0
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dt r7
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mov.l @(8, r15), r0
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add r0, r3
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bf/s .fg_y
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add r8, r4
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rts
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mov.l @r15+, r8
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# Transparent foreground, opaque background
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_topti_glyph_bg:
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# Compute VRAM stride 2 * (396-width)
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mov.l r8, @-r15
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mov.l 1f, r8
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mov.l @(4, r15), r3
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shll r3
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sub r3, r8
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# Load the starting index
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mov.l @(12, r15), r3
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.bg_y:
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# Initialize width counter
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mov.l @(4, r15), r2
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.bg_x:
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# Load one bit of data in T
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mov r3, r0
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mov #-5, r1
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shld r1, r0
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shll2 r0
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mov.l @(r0, r5), r1
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mov r3, r0
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and #31, r0
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shld r0, r1
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shll r1
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# Write color to VRAM only if it's a 0 bit
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bt .bg_next
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mov.w r6, @r4
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.bg_next:
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# Leave the x-loop if x counter reaches 0
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add #2, r4
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dt r2
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bf/s .bg_x
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add #1, r3
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# Move to next row, leave the y-loop if height reaches 0
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dt r7
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mov.l @(8, r15), r0
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add r0, r3
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bf/s .bg_y
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add r8, r4
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rts
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mov.l @r15+, r8
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# Data
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.align 4
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1: .long 396*2
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