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Switched to faster unsigned ints for PPU memory

Andrew Alderwick authored on 20/09/2021 21:32:42
Showing 3 changed files
src/devices/ppu.c
History View file @ c0e42f1
... ... 
@@ -23,22 +23,22 @@ static void
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 ppu_clear(Ppu *p)
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 {
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 	int i;
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-	for(i = 0; i < p->width / 2 * p->height; ++i)
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+	for(i = 0; i < p->stride * p->height; ++i)
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 		p->dat[i] = 0;
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 }
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-int
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+unsigned int
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 ppu_pixel(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 color)
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 {
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-	unsigned int i = (x + y * p->width) / 2, shift = (x % 2) * 4;
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-	int ret = p->dat[i];
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+	unsigned int i = x / PPW + y * p->stride, shift = x % PPW * 4;
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+	unsigned int ret = p->dat[i];
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 	if(fg) shift += 2;
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 	p->dat[i] &= ~(3 << shift);
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 	p->dat[i] |= color << shift;
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 	return ret ^ p->dat[i];
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 }
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-int
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+unsigned int
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 ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)
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 {
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 	Uint16 v, h;
... ... 
@@ -56,7 +56,7 @@ ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 f
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 	return ret;
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 }
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-int
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+unsigned int
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 ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)
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 {
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 	Uint16 v, h;
... ... 
@@ -81,11 +81,10 @@ ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 f
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 int
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 ppu_set_size(Ppu *p, Uint16 width, Uint16 height)
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 {
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-	/* round width up to nearest multiple of 2 */
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-	width += width % 2;
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 	p->width = width;
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+	p->stride = (width + PPW - 1) / PPW;
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 	p->height = height;
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-	p->dat = realloc(p->dat, p->width / 2 * p->height);
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+	p->dat = realloc(p->dat, p->stride * p->height * sizeof(unsigned int));
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 	if(p->dat == NULL) return 0;
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 	ppu_clear(p);
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 	return 1;
src/devices/ppu.h
History View file @ c0e42f1
... ... 
@@ -13,16 +13,20 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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 WITH REGARD TO THIS SOFTWARE.
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 */
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+/* pixels per word in ppu.dat */
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+
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+#define PPW (sizeof(unsigned int) * 2)
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+
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 typedef unsigned char Uint8;
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 typedef unsigned short Uint16;
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 typedef unsigned int Uint32;
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 typedef struct Ppu {
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 	Uint16 width, height;
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-	Uint8 *dat;
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+	unsigned int *dat, stride;
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 } Ppu;
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 int ppu_set_size(Ppu *p, Uint16 width, Uint16 height);
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-int ppu_pixel(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 color);
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-int ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
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-int ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
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+unsigned int ppu_pixel(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 color);
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+unsigned int ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
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+unsigned int ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
src/uxnemu.c
History View file @ c0e42f1
... ... 
@@ -38,7 +38,8 @@ static Apu apu[POLYPHONY];
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 static Device *devsystem, *devscreen, *devmouse, *devctrl, *devaudio0, *devconsole;
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 static Uint32 *ppu_screen, stdin_event, audio0_event, palette[4];
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-static Uint8 zoom = 1, reqdraw = 0;
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+static Uint8 zoom = 1;
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+static unsigned int reqdraw = 0;
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 static Uint8 font[][8] = {
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 	{0x00, 0x7c, 0x82, 0x82, 0x82, 0x82, 0x82, 0x7c},
... ... 
@@ -114,7 +115,7 @@ inspect(Ppu *p, Uint8 *stack, Uint8 wptr, Uint8 rptr, Uint8 *memory)
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 static Uint8
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 get_pixel(int x, int y)
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 {
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-	unsigned int i = (x + y * ppu.width) / 2, shift = (x % 2) * 4;
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+	unsigned int i = x / PPW + y * ppu.stride, shift = x % PPW * 4;
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 	return (ppu.dat[i] >> shift) & 0xf;
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 }
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