【新增】添加原版luajit版本v2.1代码

thirdPart/luajit/src/lj_opt_dce.c

@@ -0,0 +1,75 @@
+/*
+** DCE: Dead Code Elimination. Pre-LOOP only -- ASM already performs DCE.
+** Copyright (C) 2005-2023 Mike Pall. See Copyright Notice in luajit.h
+*/
+
+#define lj_opt_dce_c
+#define LUA_CORE
+
+#include "lj_obj.h"
+
+#if LJ_HASJIT
+
+#include "lj_ir.h"
+#include "lj_jit.h"
+#include "lj_iropt.h"
+
+/* Some local macros to save typing. Undef'd at the end. */
+#define IR(ref)		(&J->cur.ir[(ref)])
+
+/* Scan through all snapshots and mark all referenced instructions. */
+static void dce_marksnap(jit_State *J)
+{
+  SnapNo i, nsnap = J->cur.nsnap;
+  for (i = 0; i < nsnap; i++) {
+    SnapShot *snap = &J->cur.snap[i];
+    SnapEntry *map = &J->cur.snapmap[snap->mapofs];
+    MSize n, nent = snap->nent;
+    for (n = 0; n < nent; n++) {
+      IRRef ref = snap_ref(map[n]);
+      if (ref >= REF_FIRST)
+	irt_setmark(IR(ref)->t);
+    }
+  }
+}
+
+/* Backwards propagate marks. Replace unused instructions with NOPs. */
+static void dce_propagate(jit_State *J)
+{
+  IRRef1 *pchain[IR__MAX];
+  IRRef ins;
+  uint32_t i;
+  for (i = 0; i < IR__MAX; i++) pchain[i] = &J->chain[i];
+  for (ins = J->cur.nins-1; ins >= REF_FIRST; ins--) {
+    IRIns *ir = IR(ins);
+    if (irt_ismarked(ir->t)) {
+      irt_clearmark(ir->t);
+    } else if (!ir_sideeff(ir)) {
+      *pchain[ir->o] = ir->prev;  /* Reroute original instruction chain. */
+      lj_ir_nop(ir);
+      continue;
+    }
+    pchain[ir->o] = &ir->prev;
+    if (ir->op1 >= REF_FIRST) irt_setmark(IR(ir->op1)->t);
+    if (ir->op2 >= REF_FIRST) irt_setmark(IR(ir->op2)->t);
+  }
+}
+
+/* Dead Code Elimination.
+**
+** First backpropagate marks for all used instructions. Then replace
+** the unused ones with a NOP. Note that compressing the IR to eliminate
+** the NOPs does not pay off.
+*/
+void lj_opt_dce(jit_State *J)
+{
+  if ((J->flags & JIT_F_OPT_DCE)) {
+    dce_marksnap(J);
+    dce_propagate(J);
+    memset(J->bpropcache, 0, sizeof(J->bpropcache));  /* Invalidate cache. */
+  }
+}
+
+#undef IR
+
+#endif