further locals optimization

lynglib/src/jvmTest/kotlin/LocalVarBenchmarkTest.kt

@@ -0,0 +1,76 @@
+/*
+ * Tiny JVM benchmark for local variable access performance.
+ */
+
+// import net.sergeych.tools.bm
+import kotlinx.coroutines.runBlocking
+import net.sergeych.lyng.PerfFlags
+import net.sergeych.lyng.Scope
+import net.sergeych.lyng.obj.ObjInt
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class LocalVarBenchmarkTest {
+    @Test
+    fun benchmarkLocalVarLoop() = runBlocking {
+        val n = 400_000 // keep under 1s even on CI
+        val code = """
+            var s = 0
+            var i = 0
+            while(i < $n) {
+                s = s + i
+                i = i + 1
+            }
+            s
+        """.trimIndent()
+
+        // Part 1: PIC off vs on for LocalVarRef
+        PerfFlags.EMIT_FAST_LOCAL_REFS = false
+
+        // Baseline: disable PIC
+        PerfFlags.LOCAL_SLOT_PIC = false
+        val scope1 = Scope()
+        val t0 = System.nanoTime()
+        val result1 = (scope1.eval(code) as ObjInt).value
+        val t1 = System.nanoTime()
+        println("[DEBUG_LOG] [BENCH] local-var loop $n iters [baseline PIC=OFF, EMIT=OFF]: ${(t1 - t0) / 1_000_000.0} ms")
+
+        // Optimized: enable PIC
+        PerfFlags.LOCAL_SLOT_PIC = true
+        val scope2 = Scope()
+        val t2 = System.nanoTime()
+        val result2 = (scope2.eval(code) as ObjInt).value
+        val t3 = System.nanoTime()
+        println("[DEBUG_LOG] [BENCH] local-var loop $n iters [baseline PIC=ON, EMIT=OFF]: ${(t3 - t2) / 1_000_000.0} ms")
+
+        // Verify correctness to avoid dead code elimination in future optimizations
+        val expected = (n.toLong() - 1L) * n / 2L
+        assertEquals(expected, result1)
+        assertEquals(expected, result2)
+
+        // Part 2: Enable compiler fast locals emission and measure
+        PerfFlags.EMIT_FAST_LOCAL_REFS = true
+        PerfFlags.LOCAL_SLOT_PIC = true
+
+        val code2 = """
+            fun sumN(n) {
+                var s = 0
+                var i = 0
+                while(i < n) {
+                    s = s + i
+                    i = i + 1
+                }
+                s
+            }
+            sumN($n)
+        """.trimIndent()
+
+        val scope3 = Scope()
+        val t4 = System.nanoTime()
+        val result3 = (scope3.eval(code2) as ObjInt).value
+        val t5 = System.nanoTime()
+        println("[DEBUG_LOG] [BENCH] local-var loop $n iters [EMIT=ON]: ${(t5 - t4) / 1_000_000.0} ms")
+
+        assertEquals(expected, result3)
+    }
+}