perf(compiler): bypass dynamic dispatch for known-array appends (#97)

benchmark/array-append/README.md

@@ -0,0 +1,35 @@
+# Known-array append benchmark
+
+This benchmark appends a function result to a known array, 1,000 times per
+round, and accumulates a checksum. It isolates the append fallback that must
+materialize its RHS before writing. It does not represent every PHP workload.
+
+With PHP 8.5 and a matching PHPX/embed installation, from this directory:
+
+```sh
+php run.php 100000
+php ../../bin/tpc.php project.yml --no-progress -o array_append_benchmark
+./array_append_benchmark 100000
+```
+
+The checksum must be `200000000`. Build baseline and candidate revisions into
+separate build directories and binary paths. Keep PHPX, PHP, compiler flags,
+and machine fixed. Alternate binary execution order, discard a warm-up pair,
+and compare medians across multiple runs; exclude compilation time.
+
+## Sample result
+
+Linux ARM64 in Docker, PHP 8.5.10 ZTS, PHPX `6a68f38`, GCC `-O2`, no LTO;
+baseline TypePHP `692841a6` versus direct known-array append lowering.
+Nine measured runs per binary after one discarded pair, 100,000 rounds:
+
+| Build | Median | Range |
+| --- | ---: | ---: |
+| Baseline | 980.88 ms | 970.47–1018.14 ms |
+| Direct append | 563.60 ms | 558.99–582.68 ms |
+
+Elapsed time decreased by 42.54% for this append-heavy microbenchmark; all
+nine paired runs were faster. This is not an application-wide speedup or a
+comparison against native PHP. Measurements include process startup and were
+collected on a shared development machine. Raw times in seconds are in
+`results-arm64.json`; its `count` field is the number of rounds.

benchmark/array-append/benchmark.php

@@ -0,0 +1,15 @@
+<?php
+function makeAppendValue(int $value): int { return $value + 1; }
+function main(int $argc, array $argv): void
+{
+    $rounds = $argc > 1 ? (int) $argv[1] : 10000;
+    $checksum = 0;
+    for ($r = 0; $r < $rounds; ++$r) {
+        $items = [];
+        for ($i = 0; $i < 1000; ++$i) {
+            $items[] = makeAppendValue($i);
+        }
+        $checksum += count($items) + $items[999];
+    }
+    echo $checksum, "\n";
+}

benchmark/array-append/project.yml

@@ -0,0 +1,5 @@
+name: array-append-benchmark
+build-mode: bin
+optimize: 2
+sources:
+  - benchmark.php

benchmark/array-append/results-arm64.json

@@ -0,0 +1,28 @@
+{
+    "count": 100000,
+    "checksum": "200000000",
+    "samples": {
+        "candidate": [
+            0.571479212,
+            0.582684347,
+            0.558988057,
+            0.561899686,
+            0.564578895,
+            0.560435413,
+            0.559544357,
+            0.563601629,
+            0.566580885
+        ],
+        "baseline": [
+            0.970465081,
+            0.979752269,
+            0.98223335,
+            0.983323284,
+            0.99910999,
+            0.976687971,
+            0.977219854,
+            0.980881162,
+            1.018139124
+        ]
+    }
+}

benchmark/array-append/run.php

@@ -0,0 +1,5 @@
+<?php
+
+require __DIR__ . '/benchmark.php';
+
+main($argc, $argv);

phpunit/code/hot-path-codegen.php

@@ -13,6 +13,8 @@ function hotPathCodegen(int $limit): int
 
     $items[0] = $value;
     $items[] = $value;
+    $items[] = hotPathTrace('append');
+    $appendResult = ($items[] = $value);
     $items[0] += $value;
     $items[0] += $other[0];
     $items[2] = $other[0];

phpunit/src/HotPathCodegenTest.php

@@ -16,6 +16,14 @@ final class HotPathCodegenTest extends \BaseTest
         self::assertStringContainsString('items.offsetSet(0L,', $code);
     }
 
+    public function testKnownArrayAppendFallbackAvoidsDynamicDispatch(): void
+    {
+        $code = $this->compileFixture();
+
+        self::assertStringNotContainsString('items.offsetSet(php::null,', $code);
+        self::assertMatchesRegularExpression('/items\.append\(tmp_var_\d+\)/', $code);
+    }
+
     public function testSafeTwoOperandConcatAndExactStringArgumentStayUnboxed(): void
     {
         $code = $this->compileFixture();

src/Parser/AssignOpTrait.php

@@ -76,6 +76,9 @@ trait AssignOpTrait
                 return $code . $array . '.appendValue(' . $value . ')';
             }
             $tmp = $this->addTmpVar(Type::VAR);
+            if ($arrayType === Type::ARRAY) {
+                return $code . '((' . $tmp . ' = ' . $value . ', ' . "{$array}.append({$tmp})" . '), ' . $tmp . ')';
+            }
             return $code . '((' . $tmp . ' = ' . $value . ', ' . "{$array}.offsetSet(" . self::VALUE_NULL . ", {$tmp})" . '), ' . $tmp . ')';
         }
         $dim = $this->parseIdentifier($left->dim);

tests/compiler/operator/array-append-expression.phpt

@@ -0,0 +1,72 @@
+--TEST--
+Known-array append expressions preserve values, references and RHS mutations
+--FILE--
+<?php
+function nextValue(array &$items): int
+{
+    $items[] = 10;
+    return count($items);
+}
+function main(): void
+{
+    $source = std::any(1);
+    $reference =& $source;
+    $items = [];
+    $result = ($items[] = $reference);
+    $reference = 2;
+    var_dump($items, $result);
+    $items[] =& $reference;
+    $reference = 3;
+    var_dump($items, $result);
+    $copy = $items;
+    $value = ($items[] = nextValue($items));
+    var_dump($items, $copy, $value);
+    $nested = [&$reference];
+    $last = ($items[] = $nested[0]);
+    $reference = 4;
+    var_dump($items, $last);
+}
+?>
+--EXPECT--
+array(1) {
+  [0]=>
+  int(1)
+}
+int(1)
+array(2) {
+  [0]=>
+  int(1)
+  [1]=>
+  &int(3)
+}
+int(1)
+array(4) {
+  [0]=>
+  int(1)
+  [1]=>
+  &int(3)
+  [2]=>
+  int(10)
+  [3]=>
+  int(3)
+}
+array(2) {
+  [0]=>
+  int(1)
+  [1]=>
+  &int(3)
+}
+int(3)
+array(5) {
+  [0]=>
+  int(1)
+  [1]=>
+  &int(4)
+  [2]=>
+  int(10)
+  [3]=>
+  int(3)
+  [4]=>
+  int(3)
+}
+int(3)