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MIRROR: javascript for 🐜's, a tiny runtime with big ambitions ant.themackabu.dev
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1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465// meson test -C build code-unit-feedback//// Call-target feedback is weak: a function outside any code unit (script or// module code, never freed) may keep a target in a unit that dies. Majors// clear such targets for every function that has recorded one, whether or// not that major traced the function (code_units.fb_watch); otherwise the// target would point into freed unit memory for the JIT to read later.#include "internal.h"#include "gc.h"#include "silver/engine.h"#include "debug.h"#include <assert.h>#include <stdio.h>#include <string.h>
static void run(ant_t *js, const char *source) { ant_value_t result = js_eval_bytecode(js, source, strlen(source)); assert(!is_err(result));}
static int unit_targets(const sv_func_t *func) { int n = 0; for (int i = 0; i < func->call_target_fb_count; i++) { const sv_func_t *target = func->call_target_fb[i].target; if (target && target->unit) n++; } return n;}
int main(void) { char stack_base; // compiled code would make the unit immortal (sv_code_unit_make_immortal) sv_debug_enable(SV_DEBUG_JITLESS); ant_t *js = ant_create(nullptr); assert(js); js_setstackbase(js, &stack_base);
// inner is script code; it calls a function from a unit often enough to // record feedback, then everything that could reach inner is dropped run(js, "globalThis.outer = function () {" " return function inner(f) { let s = 0; for (let i = 0; i < 2000; i++) s += f(i); return s; };" "};" "globalThis.inner = outer();" "globalThis.dyn = new Function('x', 'return x + 1');" "inner(dyn); inner(dyn);");
sv_closure_t *closure = js_func_closure(js_get(js, js->global, "inner")); assert(closure && closure->func && !closure->func->unit); sv_func_t *inner = closure->func; assert(unit_targets(inner) == 1); assert(inner->fb_unit_watched);
run(js, "globalThis.outer = undefined; globalThis.inner = undefined; globalThis.dyn = undefined;"); size_t units_before = js->code_units.unit_count; for (int i = 0; i < 4; i++) gc_run(js); assert(js->code_units.unit_count < units_before);
// inner was not traced, and its unit target is gone with the unit assert(unit_targets(inner) == 0);
js_destroy(js); puts("PASS untraced functions drop feedback targets in freed code units");}