perf: optimize memory allocation

5 files changed, 103 insertions, 33 deletions

diff --git a/Makefile b/Makefile
index 7d1cdb4..6ff9576 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ bench:
 
 .PHONY: run
 run:
-	php -d zend.assertions=-1 -d memory_limit=256M -d opcache.enable_cli=on -d opcache.jit=on -d opcache.jit_buffer_size=1G examples/php-on-wasm/php-wasm.php
+	php -d zend.assertions=-1 -d memory_limit=512M -d opcache.enable_cli=on -d opcache.jit=on -d opcache.jit_buffer_size=1G examples/php-on-wasm/php-wasm.php
 
 .PHONY: test
 test:
diff --git a/benchmarks/20240314-2327.log b/benchmarks/20240314-2327.log
new file mode 100644
index 0000000..814c690
--- /dev/null
+++ b/benchmarks/20240314-2327.log
@@ -0,0 +1,4 @@
+Benchmark 1: make run
+  Time (mean ± σ):      3.088 s ±  0.049 s    [User: 3.021 s, System: 0.067 s]
+  Range (min … max):    3.041 s …  3.200 s    10 runs
+ 
diff --git a/src/Execution/MemInst.php b/src/Execution/MemInst.php
index e37bcd0..53414d7 100644
--- a/src/Execution/MemInst.php
+++ b/src/Execution/MemInst.php
@@ -9,13 +9,11 @@ use function assert;
 use function chr;
 use function count;
 use function ord;
+use function strlen;
 
 final class MemInst
 {
-    /**
-     * @var list<string>
-     */
-    private array $data;
+    private string $data;
 
     private const PAGE_SIZE = 64 * 1024;
 
@@ -25,12 +23,12 @@ final class MemInst
         $minSize = $type->limits->min;
         // @todo hack
         $minSize *= 8;
-        $this->data = array_fill(0, $minSize, str_repeat("\0", self::PAGE_SIZE));
+        $this->data = str_repeat("\0", $minSize * self::PAGE_SIZE);
     }
 
     public function size(): int
     {
-        return count($this->data) * self::PAGE_SIZE;
+        return strlen($this->data);
     }
 
     /**
@@ -56,8 +54,7 @@ final class MemInst
         if ($this->size() < $ptr) {
             return null;
         }
-        $page = $this->data[intdiv($ptr, self::PAGE_SIZE)];
-        $result = unpack('c', $page, $ptr % self::PAGE_SIZE);
+        $result = unpack('c', $this->data, $ptr);
         assert($result !== false);
         $c = $result[1];
         assert(-0x80 <= $c && $c <= 0x7F);
@@ -72,8 +69,7 @@ final class MemInst
         if ($this->size() < $ptr) {
             return null;
         }
-        $page = $this->data[intdiv($ptr, self::PAGE_SIZE)];
-        $result = unpack('C', $page, $ptr % self::PAGE_SIZE);
+        $result = unpack('C', $this->data, $ptr);
         assert($result !== false);
         $c = $result[1];
         assert(0x00 <= $c && $c <= 0xFF);
@@ -130,8 +126,7 @@ final class MemInst
         if ($this->size() < $ptr) {
             return null;
         }
-        $page = $this->data[intdiv($ptr, self::PAGE_SIZE)];
-        $result = unpack('c', $page, $ptr % self::PAGE_SIZE);
+        $result = unpack('c', $this->data, $ptr);
         assert($result !== false);
         $c = $result[1];
         assert(-0x80 <= $c && $c <= 0x7F);
@@ -146,8 +141,7 @@ final class MemInst
         if ($this->size() < $ptr) {
             return null;
         }
-        $page = $this->data[intdiv($ptr, self::PAGE_SIZE)];
-        $result = unpack('C', $page, $ptr % self::PAGE_SIZE);
+        $result = unpack('C', $this->data, $ptr);
         assert($result !== false);
         $c = $result[1];
         assert(0x00 <= $c && $c <= 0xFF);
@@ -260,8 +254,7 @@ final class MemInst
         if ($this->size() < $ptr) {
             return null;
         }
-        $page = $this->data[intdiv($ptr, self::PAGE_SIZE)];
-        $result = unpack('C', $page, $ptr % self::PAGE_SIZE);
+        $result = unpack('C', $this->data, $ptr);
         assert($result !== false);
         $c = $result[1];
         assert(0x00 <= $c && $c <= 0xFF);
@@ -277,8 +270,7 @@ final class MemInst
         if ($this->size() < $ptr) {
             return false;
         }
-        // @phpstan-ignore-next-line
-        $this->data[intdiv($ptr, self::PAGE_SIZE)][$ptr % self::PAGE_SIZE] = chr($c);
+        $this->data[$ptr] = chr($c);
         return true;
     }
 
@@ -424,18 +416,6 @@ final class MemInst
         if ($this->size() < $ptr + $len) {
             return null;
         }
-        $buf = '';
-        $idx = $ptr % self::PAGE_SIZE;
-        for ($p = intdiv($ptr, self::PAGE_SIZE); ; $p++) {
-            $page = $this->data[$p];
-            $readLen = min(self::PAGE_SIZE - $idx, $len);
-            $buf .= substr($page, $idx, $readLen);
-            $len -= $readLen;
-            if ($len === 0) {
-                break;
-            }
-            $idx = 0;
-        }
-        return $buf;
+        return substr($this->data, $ptr, $len);
     }
 }
diff --git a/test.sh b/test.sh
index a87065a..23552a8 100644
--- a/test.sh
+++ b/test.sh
@@ -1,4 +1,4 @@
-result=$(php -d zend.assertions=-1 -d memory_limit=256M -d opcache.enable_cli=on -d opcache.jit=on -d opcache.jit_buffer_size=1G examples/php-on-wasm/php-wasm.php 2>/dev/null)
+result=$(php -d zend.assertions=-1 -d memory_limit=512M -d opcache.enable_cli=on -d opcache.jit=on -d opcache.jit_buffer_size=1G examples/php-on-wasm/php-wasm.php 2>/dev/null)
 if [[ "$result" == 'Hello, World!' ]]; then
   echo "Test passed"
   exit 0
diff --git a/traces/20240314-2329.stderr.log b/traces/20240314-2329.stderr.log
new file mode 100644
index 0000000..d466331
--- /dev/null
+++ b/traces/20240314-2329.stderr.log
@@ -0,0 +1,86 @@
+Decoding...
+Instantiating...
+Executing...
+
+Exit code: 0
+Memory peak usage: 323143064
+
+
+i64.rot_l: 6733 1 6733.000000
+i32.rem_u: 7305 1 7305.000000
+i64.eq: 4999 2 2499.500000
+f64.gt: 5540 2 2770.000000
+f64.load: 21272 2 10636.000000
+f64.mul: 25499 2 12749.500000
+f64.add: 6744 4 1686.000000
+f64.convert_i32_s: 7746 4 1936.500000
+i64.sub: 361953 16 22622.062500
+i64.extend_i32_s: 432682 16 27042.625000
+i64.lt_u: 641791 17 37752.411765
+f64.store: 744168 24 31007.000000
+f64.const: 464155 26 17852.115385
+i32.wrap_i64: 379227 32 11850.843750
+i64.eqz: 585563 42 13941.976190
+i64.gt_u: 471056 46 10240.347826
+i64.or: 478944 46 10411.826087
+i64.shl: 709743 47 15100.914894
+i32.le_s: 748959 49 15284.877551
+i64.xor: 471435 62 7603.790323
+i64.ne: 568949 70 8127.842857
+i32.extend8_s: 571592 78 7328.102564
+i32.load16_s: 813987 81 10049.222222
+memory.size: 701997 130 5399.976923
+i32.ge_s: 692009 134 5164.246269
+i32.ctz: 1094624 155 7062.090323
+i64.and: 602053 226 2663.951327
+i64.shr_u: 489889 239 2049.744770
+i32.extend16_s: 1199617 256 4686.003906
+i32.div_u: 1127920 284 3971.549296
+i64.add: 634539 323 1964.517028
+i32.load16_u: 1136275 426 2667.312207
+i64.extend_i32_u: 1249506 592 2110.652027
+i32.gt_s: 1223292 613 1995.582382
+i64.mul: 1275671 842 1515.048694
+i32.store16: 3287890 1998 1645.590591
+i32.lt_s: 2220142 2161 1027.367885
+i32.rot_l: 3532538 2203 1603.512483
+i32.clz: 4060905 5130 791.599415
+br_table: 3369007 6061 555.850025
+i64.const: 3895103 9965 390.878374
+call_indirect: 8815409968 12643 697256.186665
+i64.load: 9421807 12927 728.847142
+drop: 5123431 15033 340.812280
+i32.xor: 12436555 18826 660.605280
+return: 4770944 19633 243.006367
+i32.le_u: 13365637 25404 526.123327
+global.get: 10376406 25951 399.846095
+select: 13704301 29114 470.711719
+i32.ge_u: 16656897 33468 497.696217
+i32.store8: 18854855 42849 440.030222
+loop: 8725293963 44110 197807.616482
+global.set: 17362896 51161 339.377573
+i32.shr_u: 20238266 51699 391.463394
+i32.load8_s: 20337339 54242 374.937115
+i32.sub: 21552487 64081 336.331939
+i32.eq: 24843378 66100 375.845356
+br: 12245021 66911 183.004603
+i32.mul: 24502465 68122 359.685050
+call: 32674053681 70579 462942.995523
+i32.or: 39856224 71541 557.110244
+i32.shl: 36052558 86408 417.236344
+i32.ne: 30718539 92660 331.518875
+i32.lt_u: 38327762 101169 378.848877
+i32.gt_u: 40061428 117828 339.999219
+i32.load8_u: 63571082 159431 398.737272
+i32.eqz: 52743788 198278 266.009280
+i32.and: 101568221 249884 406.461482
+i64.store: 177976102 306534 580.608030
+i32.store: 183780629 362806 506.553445
+local.set: 99181624 439632 225.601467
+i32.load: 220094856 564315 390.021275
+block: 70106961183 723450 96906.436081
+br_if: 152340418 732305 208.028647
+local.tee: 169203732 758661 223.029432
+i32.add: 196169743 812466 241.449787
+i32.const: 261492311 1589717 164.489850
+local.get: 533212586 3135728 170.044272