diff options
Diffstat (limited to 'Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_dce.c')
-rw-r--r-- | Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_dce.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_dce.c b/Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_dce.c new file mode 100644 index 00000000000..7f1faafe647 --- /dev/null +++ b/Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_dce.c @@ -0,0 +1,78 @@ +/* +** DCE: Dead Code Elimination. Pre-LOOP only -- ASM already performs DCE. +** Copyright (C) 2005-2015 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); + pchain[ir->o] = &ir->prev; + } else if (!ir_sideeff(ir)) { + *pchain[ir->o] = ir->prev; /* Reroute original instruction chain. */ + ir->t.irt = IRT_NIL; + ir->o = IR_NOP; /* Replace instruction with NOP. */ + ir->op1 = ir->op2 = 0; + ir->prev = 0; + continue; + } + 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 |