Conway's Game of Life

Pick a seed lasting over 1200 generations.

Keep state as two bits in a 64*16 buffer instead of the obvious way (as
characters in two 80x40 buffers). This will permit us to fit in the
available SRAM for the current HDL implementation on Spartan6.

This currently requires a separate object (linked last) to contain the
buffer, in order not to relocate code too far away for a type{0,1,2}
instruction to access. We should be able to rewrite accesses to use
type3 for data, but we can't control what other codes are going to do,
so we should trap the too-large relocation offsets in the assembler.
This remains to be done.

ex/Makefile

@@ -13,6 +13,7 @@ vpath %.tas.cpp $(TOP)/lib $(TOP)/lib/dword
 
 TARGETS = \
     bsearch_demo.texe   \
+    bm_conway.texe      \
     bm_snake.texe       \
     bm_mults.texe       \
     compare.texe        \
@@ -47,10 +48,11 @@ bsearch_demo.texe: puts.to
 qsort_demo.texe: qsort.to puts.to memcpy.to
 irc.texe: puts.to strcmp.to udiv.to umod.to strtol.to
 parse_hex.texe: strtol.to
-bm_snake.texe: rand.to
+bm_snake.texe bm_conway.texe: rand.to
 bm_fib.texe bm_mults.texe: putnum.to
 clock.texe: sleep.to
 trailz_demo.texe: puts.to trailz.to
+bm_conway.texe: bm_conway_buffer.to
 
 $(patsubst %.tas.cpp,%.tas,$(CPP_FILES)): %.tas: $(TOP)/lib/common.th
 

ex/bm_conway.tas.cpp

@@ -0,0 +1,187 @@
+#include "common.th"
+#include "vga.th"
+
+#define THRESHOLD 64
+
+// The operations later only work if INSET_{ROW,COL}S end up to be a power of 2
+#define OFFSET_ROWS 4
+#define OFFSET_COLS 8
+
+#define INSET_ROWS (ROWS - (OFFSET_ROWS * 2))
+#define INSET_COLS (COLS - (OFFSET_COLS * 2))
+
+_start:
+    bare_metal_init()   // TODO this shouldn't be necessary
+    prologue
+
+    call(init_display)
+    call(disable_cursor)
+
+    // m is generation
+    m <- 0
+
+    // i is global video base
+    i <- VGA_BASE
+    // g is global flip buffer
+    g <- rel(databuf)
+    // h is global flip buffer bit index
+    h <- 0
+
+    c <- i
+    d <- 0xa // in our font, a 50% greyscale
+    call(blank_area)
+
+    call(randomise_board)
+    call(flip)
+
+forever:
+    m -> [0x100]
+
+    call(compute)
+    call(flip)
+
+    m <- m + 1
+    goto(forever)
+
+blank_area:
+    pushall(j,n)
+    j <- COLS
+    j <- j * ROWS
+blank_area_loop:
+    j <- j - 1
+    d -> [c + j]
+    n <- j > 0
+    jnzrel(n,blank_area_loop)
+    popall_ret(j,n)
+
+randomise_board:
+    pushall(j,k,c,d,l,n)
+    c <- [rel(seed)]
+    call(srand)
+    j <- (INSET_ROWS - 1)
+randomise_board_rows:
+    k <- (INSET_COLS - 1)
+randomise_board_cols:
+    call(rand)
+    b <- b >> 23
+
+    l <- b >= THRESHOLD
+
+    b <- j * INSET_COLS + k
+    l -> [b + g] // write to buf0
+
+    k <- k - 1
+    n <- k >= 0
+    jnzrel(n,randomise_board_cols)
+    j <- j - 1
+    n <- j >= 0
+    jnzrel(n,randomise_board_rows)
+    popall_ret(j,k,c,d,l,n)
+
+flip:
+    pushall(j,k,n)
+    j <- (INSET_ROWS - 1)
+flip_rows:
+    k <- (INSET_COLS - 1)
+flip_cols:
+    b <- j * INSET_COLS + k
+    b <- [b + g] // read from buf0
+
+    b <- b @ h
+
+    n <- 'o' &  b
+    b <- ' ' &~ b
+    n <- b | n
+    c <- j
+    d <- k
+    call(get_real_offset)
+    n -> [b + i] // write to display
+
+    k <- k - 1
+    n <- k >= 0
+    jnzrel(n,flip_cols)
+    j <- j - 1
+    n <- j >= 0
+    jnzrel(n,flip_rows)
+
+    h <- h ^ 1
+    popall_ret(j,k,n)
+
+compute:
+    pushall(c,d,e,f,j,k,l)
+    j <- (INSET_ROWS - 1)
+compute_rows:
+    k <- (INSET_COLS - 1)
+compute_cols:
+
+    c <- j
+    d <- k
+    call(get_neighbour_count)
+    e <- b
+
+    b <- j * INSET_COLS + k
+    f <- [b + g] // read from buf1
+    // E is neighbour count, F is current state
+    c <- h ^ 1
+    n <- f @ c
+    n <- - n
+    // N is 1 if alive
+    e <- e | n // tricky
+    e <- e == 3
+    n <- 1 << h
+    e <- e & n
+    f <- f &~ n
+    f <- f |  e
+    f -> [b + g] // write to buf0
+
+    k <- k - 1
+    n <- k >= 0
+    jnzrel(n,compute_cols)
+    j <- j - 1
+    n <- j >= 0
+    jnzrel(n,compute_rows)
+    popall_ret(c,d,e,f,j,k,l)
+
+get_neighbour_count:
+    pushall(e,f,j,k,l,m,n)
+    m <- 0
+    j <- c
+    k <- d
+
+    e <- -1
+neighbour_loop_rows:
+    f <- -1
+neighbour_loop_cols:
+    // essentially doing `(a + 31) % 32` to get `a - 1` safely
+    c <- j + e + INSET_ROWS ; c <- c & (INSET_ROWS - 1)
+    d <- k + f + INSET_COLS ; d <- d & (INSET_COLS - 1)
+
+    b <- c * INSET_COLS + d
+    l <- [b + g]
+    n <- e | f
+    n <- n == 0
+    // skip case where e == f == 0 (self)
+
+    c <- h ^ 1
+    l <- l @ c ; l <- l &~ n
+
+    m <- m - l
+
+    f <- f + 1
+    n <- f <= 1
+    jnzrel(n,neighbour_loop_cols)
+    e <- e + 1
+    n <- e <= 1
+    jnzrel(n,neighbour_loop_rows)
+
+    b <- m
+    popall_ret(e,f,j,k,l,m,n)
+
+get_real_offset:
+    b <- c + OFFSET_ROWS
+    b <- b * COLS + d
+    b <- b + OFFSET_COLS
+    ret
+
+seed: .word 0x99999999
+

ex/bm_conway_buffer.tas.cpp

@@ -0,0 +1,13 @@
+#include "vga.th"
+
+#define THRESHOLD 64
+
+// The operations later only work if INSET_{ROW,COL}S end up to be a power of 2
+#define OFFSET_ROWS 4
+#define OFFSET_COLS 8
+
+#define INSET_ROWS (ROWS - (OFFSET_ROWS * 2))
+#define INSET_COLS (COLS - (OFFSET_COLS * 2))
+
+.global databuf
+databuf: .zero (INSET_ROWS * INSET_COLS)

lib/vga.th

@@ -0,0 +1,3 @@
+#define ROWS 40
+#define COLS 80
+#define VGA_BASE 0x10000