From cd7f11eda240bb28b3648efcaee2a29c8ed1d609 Mon Sep 17 00:00:00 2001
From: Ashelyn Rose <git@tempest.dev>
Date: Sun, 3 Sep 2023 01:19:07 -0600
Subject: [PATCH] wasm optimizations

---
 scripts/wasm-life-2/game.wat | 173 +++++++++++++++++++++++++++++------
 1 file changed, 143 insertions(+), 30 deletions(-)

diff --git a/scripts/wasm-life-2/game.wat b/scripts/wasm-life-2/game.wat
index c0a8813..e9223f0 100644
--- a/scripts/wasm-life-2/game.wat
+++ b/scripts/wasm-life-2/game.wat
@@ -154,9 +154,71 @@
     i32.store8
   )
 
+  (func $setNewValueAtPosition (param $row i32) (param $column i32) (param $value i32)
+    (local $position i32)
+    local.get $row
+    local.get $column
+    call $getIndexForPosition
+
+    local.tee $position
+    i32.const 0
+    i32.lt_s
+
+    if
+      return
+    end
+
+    global.get $boardBufferLength
+    call $getBoardPtr
+    i32.xor
+    local.get $position
+    i32.add
+    local.get $value
+    i32.store8
+  )
+
   (func $getNewValueAtPosition (param $row i32) (param $column i32) (result i32)
     (local $count i32)
+    (local $current i32)
+    local.get $row
+    i32.const 1
+    i32.lt_u
 
+    local.get $row
+    global.get $boardHeight
+    i32.const 1
+    i32.sub
+    i32.ge_u
+
+    local.get $column
+    i32.const 1
+    i32.lt_u
+
+    local.get $column
+    global.get $boardWidth
+    i32.const 1
+    i32.sub
+    i32.ge_u
+
+    ;; if any of the boundary conditions are true
+    i32.or
+    i32.or
+    i32.or
+
+    if (result i32 i32)
+      local.get $row
+      local.get $column
+      call $getNeighborCountBoundary
+    else
+      local.get $row
+      local.get $column
+      call $getNeighborCountCenter
+    end
+
+    call $getOutcomeFromCountAndCurrent
+  )
+
+  (func $getNeighborCountBoundary (param $row i32) (param $column i32) (result i32 i32)
     local.get $row
     i32.const 1
     i32.sub
@@ -213,6 +275,7 @@
     i32.add
     call $getValueAtPosition
 
+    ;; sum neightbor count
     i32.add
     i32.add
     i32.add
@@ -221,39 +284,91 @@
     i32.add
     i32.add
 
-    ;; Exactly 3 neighbors
-    local.tee $count
-    i32.const 3
-    i32.eq
+    ;; get current
+    local.get $row
+    local.get $column
+    call $getValueAtPosition
+  )
 
-    if
-      ;; becomes or stays alive
-      i32.const 1
-      return
-    end
+  (func $getNeighborCountCenter (param $row i32) (param $column i32) (result i32 i32) ;; neighborCount, currentValue
+    (local $origIndex i32)
+    (local $rowAbove i32)
+    (local $rowCenter i32)
+    (local $rowBelow i32)
 
-    ;; If currently dead
+    ;; store current cell's memory position
+    call $getBoardPtr
     local.get $row
     local.get $column
-    call $getValueAtPosition
-    i32.eqz
-    if
-      ;; Stay dead
-      i32.const 0
-      return
-    end
+    call $getIndexForPosition
+    i32.add
+    local.tee $origIndex
 
-    ;; 2 neighbors
-    local.get $count
-    i32.const 2
-    i32.eq
-    if
-      i32.const 1
-      return
-    end
+    ;; load the three rows
+    i32.const 1
+    i32.sub
+    i32.load
+    local.set $rowCenter
 
-    i32.const 0
-    return
+    local.get $origIndex
+    i32.const 1
+    i32.sub
+    global.get $boardWidth
+    i32.sub
+    i32.load
+    local.set $rowAbove
+
+    local.get $origIndex
+    i32.const 1
+    i32.sub
+    global.get $boardWidth
+    i32.add
+    i32.load
+    local.set $rowBelow
+
+    ;; count the number of alive neighbors in each row
+    local.get $rowAbove
+    i32.const 0x00_01_01_01
+    i32.and
+    i32.popcnt
+
+    local.get $rowCenter
+    i32.const 0x00_01_00_01
+    i32.and
+    i32.popcnt
+
+
+    local.get $rowBelow
+    i32.const 0x00_01_01_01
+    i32.and
+    i32.popcnt
+
+    ;; sum neighbor count
+    i32.add
+    i32.add
+
+    ;; get current
+    local.get $rowCenter
+    i32.const 0x00_00_01_00
+    i32.and
+    i32.popcnt
+  )
+
+  (func $getOutcomeFromCountAndCurrent (param $neighborCount i32) (param $current i32) (result i32)
+    ;; get sentinal value for current count
+    i32.const 1
+    local.get $neighborCount
+    i32.shl
+
+    ;; get value mask for current state
+    i32.const 0xC ;;alive mask (1100, 3 or 2 neighbors)
+    i32.const 0x8 ;;dead mask  (1000, exactly three neighbors)
+    local.get $current
+    select
+
+    ;; mask out to see if we still have a bit
+    i32.and
+    i32.popcnt
   )
 
   (func $tick (export "tick")
@@ -280,12 +395,10 @@
         local.set $value
 
         ;; place in next board
-        call $swapBoards
         local.get $row
         local.get $column
         local.get $value
-        call $setValueAtPosition
-        call $swapBoards
+        call $setNewValueAtPosition
 
         ;; increment column
         local.get $column