Specialize bytecode for pairs()/next() iterator. Speedup: 3.5x.

Parser predict pairs/next and emits specialized bytecode.
Bytecode is descpecialized at runtime if the prediction was wrong.
Store slot index in hidden control var to avoid key lookups.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/lj_bc.h b/src/lj_bc.h
index ba868283..837316d5 100644
--- a/src/lj_bc.h
+++ b/src/lj_bc.h
@@ -154,6 +154,8 @@
   _(CALLMT,     base,   ___,    lit,    call) \
   _(CALLT,      base,   ___,    lit,    call) \
   _(ITERC,      base,   lit,    lit,    call) \
+  _(ITERN,      base,   lit,    lit,    call) \
+  _(ISNEXT,     base,   ___,    jump,   ___) \
   _(VARG,       base,   lit,    lit,    ___) \
   \
   /* Returns. */ \
@@ -221,6 +223,9 @@ LJ_STATIC_ASSERT((int)BC_FUNCF + 2 == (int)BC_JFUNCF);
 LJ_STATIC_ASSERT((int)BC_FUNCV + 1 == (int)BC_IFUNCV);
 LJ_STATIC_ASSERT((int)BC_FUNCV + 2 == (int)BC_JFUNCV);
 
+/* This solves a circular dependency problem, change as needed. */
+#define FF_next_N       15
+
 /* Stack slots used by FORI/FORL, relative to operand A. */
 enum {
   FORL_IDX, FORL_STOP, FORL_STEP, FORL_EXT