Perf: typed int **94 / pow(n,94) chained smul omit llvm.pow.f64 (#36386)

[PurHur]

Summary

• Part of Performance: v2.0 targets and the codegen roadmap to reach them — typed code ≥ 3x Zend, untyped ≤ 1.5x slower, web request ≥ php-fpm: inline caches for property/method access, escape analysis for arrays/strings, guarded speculation, per-function O1 by default (lib/JIT.php, lib/JIT/Builtin/Type/Object_.php, lib/JIT/Analyzer.php) #36386 (lane overflow: CI: php-llvm-structgep-assert.patch fails to apply — blocks north-star5-verify-fast and all bootstrap gates #36143–VM: 1M-iteration loops exit 255 silently — restore compute-suite headroom on bin/vm.php #36148 closed; continued Split-TU: extract JitPowIntegerEmitExponents80to91 for exponents 80–91 (#36387) #37655 Exponents80to91 → merged).
• Lower compile-time exponent **94 / pow(n,94) via (ninetythird×n) chained smul.with.overflow in JitPowIntegerEmitHigh — omit llvm.pow.f64.
• Even: (-1)**94 === 1. Append-only (keeps **92/**93 intact).
• No new C ABI. php-src: Zend/zend_operators.c pow_function / zend_pow / mul_function; ext/standard/math.c PHP_FUNCTION(pow).

Test plan

• php -l High + NativeLongPowFolds
• php script/check-size-budgets.php → OK
• ./script/opcode-corpus-md5.sh --update
• script/differential-sweep.sh --aot --repeat 3 on pow_ninetyfourth_smul_36386.php → 1/1 (3/3)
• ./script/phpunit.sh --filter NoThrowPowNinetyfourthMulAotTest → OK (4 tests)
• ./script/aot-smoke.sh → 9/9
• make north-star5-verify-fast → OK (spine 8592/8592)

Closes nothing (Part of #36386).

Made with Cursor

[PurHur]

Duplicate of already-merged #37658 (same **94 smul slice). Closing; gates on that merge cover this work.