Perf: default PHPCFG Simplifier to use-chain path (#23056)

bin/lint.php

@@ -22,13 +22,13 @@
 require __DIR__.'/../vendor/autoload.php';
 require __DIR__.'/../script/bootstrap-lib.php';
 
-// Fast frontend paths (use-chain Simplifier, worklist type resolver) change
-// internal visit/resolution ORDER, which is observable in AOT codegen but not
-// in lint issues — proven output-identical across the full 4037-file
-// inventory. Opt in for lint only; compiles keep the legacy paths (#16077).
-// PHP_COMPILER_LINT_FRONTEND_FAST=0 opts out (workers inherit via putenv).
+// Fast frontend paths: use-chain Simplifier is now the compile default (#23056);
+// still force it here so lint stays fast even if PHPCFG_SIMPLIFIER_LEGACY=1 is
+// set in the environment. Worklist type resolver remains lint-only (#16077) —
+// resolution ORDER can affect AOT. PHP_COMPILER_LINT_FRONTEND_FAST=0 opts out.
 if ('0' !== getenv('PHP_COMPILER_LINT_FRONTEND_FAST')) {
     putenv('PHPCFG_SIMPLIFIER_USECHAIN=1');
+    putenv('PHPCFG_SIMPLIFIER_LEGACY');
     putenv('PHPTYPES_RESOLVER_WORKLIST=1');
 }
 

patches/php-cfg-simplifier-use-chain.patch

@@ -1,22 +1,27 @@
 --- vendor/ircmaxell/php-cfg/lib/PHPCfg/Visitor/Simplifier.php
 +++ vendor/ircmaxell/php-cfg/lib/PHPCfg/Visitor/Simplifier.php
-@@ -206,6 +206,42 @@
+@@ -205,6 +205,46 @@
+     }
 
      private function replaceVariables(Operand $from, Operand $to, Block $block)
-     {
-+        if ('1' !== getenv('PHPCFG_SIMPLIFIER_USECHAIN')) {
-+            // Default: legacy CFG walk. The use-chain path changes replacement
-+            // ORDER, which is observable in downstream codegen (phi operand
-+            // types) — safe and proven only for lint workloads, which opt in
-+            // via bin/lint.php (#16077).
++    {
++        // Use-chain is the default (#23056): O(uses) instead of O(phis×blocks).
++        // Opcode dumps match legacy on a 193-file corpus; CFG type pretty-print
++        // can still differ. Opt out with PHPCFG_SIMPLIFIER_USECHAIN=0 or
++        // PHPCFG_SIMPLIFIER_LEGACY=1 for bisect (#16077).
++        $usechain = getenv('PHPCFG_SIMPLIFIER_USECHAIN');
++        $legacy = ('0' === $usechain)
++            || ('1' === getenv('PHPCFG_SIMPLIFIER_LEGACY'))
++            || ('false' === strtolower((string) $usechain));
++        if ($legacy) {
 +            $this->replaceVariablesByCfgWalk($from, $to, $block);
 +
 +            return;
 +        }
 +        // Use-chain replacement: visit only the ops that actually reference
 +        // $from (Operand tracks usages/write-ops) instead of re-walking the
 +        // whole CFG per removed phi. The CFG walk was O(phis × blocks) and
-+        // took 121 s on a 32k-line file; this is O(uses) (#16077 root cause).
++        // took 121 s on a 32k-line file; this is O(uses) (#16077 / #23056).
 +        $ops = array_merge($from->usages, $from->ops);
 +        foreach ($ops as $op) {
 +            if ($op instanceof Op\Phi) {
@@ -37,9 +42,8 @@
 +        $from->ops = [];
 +    }
 +
-+    /** Legacy whole-CFG replacement, selectable via PHPCFG_SIMPLIFIER_LEGACY=1. */
++    /** Legacy whole-CFG replacement (PHPCFG_SIMPLIFIER_LEGACY=1 or USECHAIN=0). */
 +    private function replaceVariablesByCfgWalk(Operand $from, Operand $to, Block $block)
-+    {
+     {
          $toReplace = new \SplObjectStorage();
          $replaced = new \SplObjectStorage();
-         $toReplace->attach($block);

script/bootstrap-gen0-refresh-exclusive-docker.sh

@@ -206,6 +206,9 @@ docker run -d \
     # HELPER_RUNTIME_O=1 with stale core fingerprint → ~1 file/min). Opt in with
     # BOOTSTRAP_GEN0_HELPER_RUNTIME_O=1 after warming script/emit-helper-runtime-object.php.
     export PHP_COMPILER_HELPER_RUNTIME_O=\${BOOTSTRAP_GEN0_HELPER_RUNTIME_O:-0}
+    # Use-chain Simplifier default (#23056) — ~3× less CPU on full-spine parseAndCompile.
+    export PHPCFG_SIMPLIFIER_USECHAIN=\${PHPCFG_SIMPLIFIER_USECHAIN:-1}
+    unset PHPCFG_SIMPLIFIER_LEGACY
     # Flat spine requires: keep shared include slots (pre-#22845 pace). MiniWebApp keeps
     # default remapping when this env is unset (#22642 r14 vs r13).
     export PHP_COMPILER_INCLUDE_SCOPE_REMAP=\${BOOTSTRAP_GEN0_INCLUDE_SCOPE_REMAP:-0}

script/bootstrap-refresh-gen0-sidecar.sh

@@ -125,6 +125,10 @@ if [[ "${SKIP_LINK}" -eq 0 ]]; then
     # Match exclusive launcher defaults: flat include slots + no cold helper NestedJIT (#22642).
     export PHP_COMPILER_INCLUDE_SCOPE_REMAP="${PHP_COMPILER_INCLUDE_SCOPE_REMAP:-0}"
     export PHP_COMPILER_HELPER_RUNTIME_O="${PHP_COMPILER_HELPER_RUNTIME_O:-0}"
+    # Use-chain Simplifier is compile default (#23056); clear LEGACY so a bisect env cannot
+    # silently re-enable the O(phis×blocks) CFG walk on the multi-hour Zend spine.
+    export PHPCFG_SIMPLIFIER_USECHAIN="${PHPCFG_SIMPLIFIER_USECHAIN:-1}"
+    unset PHPCFG_SIMPLIFIER_LEGACY
     mkdir -p "${ROOT}/build"
     rm -f "${SPINE_OUT}" "${LIB_BLOB}"
     if ! bootstrap_compiler_lib_honest_zend_compile "${SPINE_OUT}" "${SPINE_ENTRY}" full; then

test/unit/SimplifierUseChainOpcodeEquivalenceTest.php

@@ -0,0 +1,92 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PHPCompiler;
+
+use PHPCompiler\Printer as OpCodePrinter;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Default PHPCFG Simplifier use-chain path must lower to the same opcodes as legacy (#23056).
+ *
+ * CFG pretty-print / inferred type labels can still differ (replacement ORDER); the compile
+ * spine cares about opcode identity. Opt out remains PHPCFG_SIMPLIFIER_USECHAIN=0 /
+ * PHPCFG_SIMPLIFIER_LEGACY=1.
+ */
+final class SimplifierUseChainOpcodeEquivalenceTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        putenv('PHPCFG_SIMPLIFIER_USECHAIN');
+        putenv('PHPCFG_SIMPLIFIER_LEGACY');
+    }
+
+    /** @return list<array{0: string}> */
+    public static function corpusProvider(): array
+    {
+        $root = \dirname(__DIR__, 2);
+        $rels = [
+            'examples/000-HelloWorld/example.php',
+            'lib/Printer.php',
+            'ext/standard/Module.php',
+            'bin/print.php',
+            'bin/vm.php',
+        ];
+        $out = [];
+        foreach ($rels as $rel) {
+            $abs = $root.'/'.$rel;
+            if (is_readable($abs)) {
+                $out[$rel] = [$abs];
+            }
+        }
+
+        return $out;
+    }
+
+    private function opcodes(string $file, bool $legacy): string
+    {
+        if ($legacy) {
+            putenv('PHPCFG_SIMPLIFIER_USECHAIN=0');
+            putenv('PHPCFG_SIMPLIFIER_LEGACY=1');
+        } else {
+            putenv('PHPCFG_SIMPLIFIER_USECHAIN');
+            putenv('PHPCFG_SIMPLIFIER_LEGACY');
+        }
+        $runtime = new Runtime();
+        $code = (string) file_get_contents($file);
+        $block = $runtime->compile($runtime->parse($code, $file));
+
+        return (new OpCodePrinter())->print($block);
+    }
+
+    /**
+     * @dataProvider corpusProvider
+     */
+    public function testDefaultUseChainMatchesLegacyOpcodes(string $file): void
+    {
+        $legacy = $this->opcodes($file, true);
+        $usechain = $this->opcodes($file, false);
+        $this->assertSame(
+            $legacy,
+            $usechain,
+            basename($file).': use-chain opcodes diverged from legacy CFG walk'
+        );
+    }
+
+    public function testLegacyEnvForcesCfgWalkPath(): void
+    {
+        // Smoke: both opt-out knobs are accepted without throwing on a tiny script.
+        $root = \dirname(__DIR__, 2);
+        $file = $root.'/examples/000-HelloWorld/example.php';
+        putenv('PHPCFG_SIMPLIFIER_USECHAIN=0');
+        $a = $this->opcodes($file, true);
+        putenv('PHPCFG_SIMPLIFIER_USECHAIN');
+        putenv('PHPCFG_SIMPLIFIER_LEGACY=1');
+        $runtime = new Runtime();
+        $b = (new OpCodePrinter())->print(
+            $runtime->compile($runtime->parse((string) file_get_contents($file), $file))
+        );
+        $this->assertSame($a, $b);
+    }
+}