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vm.c: add branch prediction hints for hot paths

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Add mrb_likely/mrb_unlikely hints to help CPU branch predictor:
- stack overflow checks (mrb_unlikely)
- exception checks (mrb_unlikely)
- integer type checks in arithmetic (mrb_likely)
- method dispatch fast path (mrb_likely)
- argument validation errors (mrb_unlikely)
- target class checks in method definition (mrb_unlikely)

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2026-01-21 16:55:12 +09:00
parent 7e3447b29a
commit 44f6cf4b4e
1 changed files with 48 additions and 30 deletions
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src/vm.c
+48 -30
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@@ -194,7 +194,7 @@ stack_extend_alloc(mrb_state *mrb, mrb_int room)
static inline void
stack_extend(mrb_state *mrb, mrb_int room)
{
if (!mrb->c->ci->stack || mrb->c->ci->stack + room >= mrb->c->stend) {
if (mrb_unlikely(!mrb->c->ci->stack || mrb->c->ci->stack + room >= mrb->c->stend)) {
stack_extend_alloc(mrb, room);
}
}
@@ -1691,7 +1691,7 @@ RETRY_TRY_BLOCK:
MRB_TRY(&c_jmp) {
if (mrb->exc) {
if (mrb_unlikely(mrb->exc)) {
mrb_gc_arena_restore(mrb, ai);
if (mrb->exc->tt == MRB_TT_BREAK)
goto L_BREAK;
@@ -2137,7 +2137,7 @@ RETRY_TRY_BLOCK:
CASE(OP_RAISEIF, B) {
mrb_value exc;
exc = regs[a];
if (mrb_nil_p(exc)) {
if (mrb_likely(mrb_nil_p(exc))) {
mrb->exc = NULL;
}
else if (mrb_break_p(exc)) {
@@ -2176,7 +2176,7 @@ RETRY_TRY_BLOCK:
struct mrb_context *c = mrb->c;
fiber_terminate(mrb, c, ci);
if (!c->vmexec) goto L_RAISE;
if (mrb_unlikely(!c->vmexec)) goto L_RAISE;
mrb->jmp = prev_jmp;
if (!prev_jmp) return mrb_obj_value(mrb->exc);
MRB_THROW(prev_jmp);
@@ -2195,7 +2195,7 @@ RETRY_TRY_BLOCK:
}
CASE(OP_MATCHERR, B) {
if (!mrb_test(regs[a])) {
if (mrb_unlikely(!mrb_test(regs[a]))) {
RAISE_LIT(mrb, mrb_exc_get_id(mrb, MRB_ERROR_SYM(NoMatchingPatternError)), "pattern not matched");
}
NEXT;
@@ -2229,7 +2229,7 @@ RETRY_TRY_BLOCK:
mrb_value recv, blk;
mrb_int bidx, new_bidx;
if (c < CALL_MAXARGS) {
if (mrb_likely(c < CALL_MAXARGS)) {
/* fast path limited to fixed length arguments of less than 15 */
bidx = a + c + 1 /* self */;
new_bidx = bidx;
@@ -2269,7 +2269,7 @@ RETRY_TRY_BLOCK:
recv = regs[0];
ci->u.target_class = (insn == OP_SUPER) ? CI_TARGET_CLASS(ci - 1)->super : mrb_class(mrb, recv);
m = mrb_vm_find_method(mrb, ci->u.target_class, &ci->u.target_class, mid);
if (MRB_METHOD_UNDEF_P(m)) {
if (mrb_unlikely(MRB_METHOD_UNDEF_P(m))) {
m = prepare_missing(mrb, ci, recv, mid, blk, (insn == OP_SUPER));
}
else {
@@ -2317,7 +2317,7 @@ RETRY_TRY_BLOCK:
/* cfunc epilogue */
mrb_gc_arena_shrink(mrb, ai);
if (mrb->exc) goto L_RAISE;
if (mrb_unlikely(mrb->exc)) goto L_RAISE;
ci = mrb->c->ci;
if (!ci->u.keep_context) { /* return from context modifying method (resume/yield) */
if (ci->cci == CINFO_RESUMED) {
@@ -2353,7 +2353,7 @@ RETRY_TRY_BLOCK:
if (MRB_PROC_CFUNC_P(p)) {
recv = MRB_PROC_CFUNC(p)(mrb, recv);
mrb_gc_arena_shrink(mrb, ai);
if (mrb->exc) goto L_RAISE;
if (mrb_unlikely(mrb->exc)) goto L_RAISE;
/* pop stackpos */
ci = cipop(mrb);
ci[1].stack[0] = recv;
@@ -2468,7 +2468,7 @@ RETRY_TRY_BLOCK:
/* no other args */
if ((a & ~0x7c0001) == 0 && argc < 15 && MRB_PROC_STRICT_P(ci->proc)) {
if (argc+(ci->nk==15) != m1) { /* count kdict too */
if (mrb_unlikely(argc+(ci->nk==15) != m1)) { /* count kdict too */
argnum_error(mrb, m1);
goto L_RAISE;
}
@@ -2533,7 +2533,7 @@ RETRY_TRY_BLOCK:
/* strict argument check */
if (ci->proc && MRB_PROC_STRICT_P(ci->proc)) {
if (argc < m1 + m2 || (r == 0 && argc > len)) {
if (mrb_unlikely(argc < m1 + m2 || (r == 0 && argc > len))) {
argnum_error(mrb, m1+m2);
goto L_RAISE;
}
@@ -2817,10 +2817,18 @@ RETRY_TRY_BLOCK:
#endif
#define TYPES2(a,b) ((((uint16_t)(a))<<8)|(((uint16_t)(b))&0xff))
#define OP_MATH(op_name) \
#define OP_MATH(op_name) do { \
/* need to check if op is overridden */ \
switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) { \
OP_MATH_CASE_INTEGER(op_name); \
uint16_t tt = TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1])); \
if (mrb_likely(tt == TYPES2(MRB_TT_INTEGER, MRB_TT_INTEGER))) { \
mrb_int x = mrb_integer(regs[a]), y = mrb_integer(regs[a+1]), z; \
if (mrb_int_##op_name##_overflow(x, y, &z)) { \
OP_MATH_OVERFLOW_INT(op_name,x,y); \
} \
else \
SET_INT_VALUE(mrb,regs[a], z); \
} \
else switch (tt) { \
OP_MATH_CASE_FLOAT(op_name, integer, float); \
OP_MATH_CASE_FLOAT(op_name, float, integer); \
OP_MATH_CASE_FLOAT(op_name, float, float); \
@@ -2829,6 +2837,7 @@ RETRY_TRY_BLOCK:
mid = MRB_OPSYM(op_name); \
goto L_SEND_SYM; \
} \
} while(0); \
NEXT;
#define OP_MATH_CASE_INTEGER(op_name) \
case TYPES2(MRB_TT_INTEGER, MRB_TT_INTEGER): \
@@ -2922,16 +2931,24 @@ RETRY_TRY_BLOCK:
NEXT;
}
#define OP_MATHI(op_name) \
#define OP_MATHI(op_name) do { \
/* need to check if op is overridden */ \
switch (mrb_type(regs[a])) { \
OP_MATHI_CASE_INTEGER(op_name); \
if (mrb_likely(mrb_integer_p(regs[a]))) { \
mrb_int x = mrb_integer(regs[a]), y = (mrb_int)b, z; \
if (mrb_int_##op_name##_overflow(x, y, &z)) { \
OP_MATH_OVERFLOW_INT(op_name,x,y); \
} \
else \
SET_INT_VALUE(mrb,regs[a], z); \
} \
else switch (mrb_type(regs[a])) { \
OP_MATHI_CASE_FLOAT(op_name); \
default: \
SET_INT_VALUE(mrb,regs[a+1], b); \
mid = MRB_OPSYM(op_name); \
goto L_SEND_SYM; \
} \
} while(0); \
NEXT;
#define OP_MATHI_CASE_INTEGER(op_name) \
case MRB_TT_INTEGER: \
@@ -3014,12 +3031,12 @@ RETRY_TRY_BLOCK:
#ifdef MRB_NO_FLOAT
#define OP_CMP(op,sym) do {\
int result;\
/* need to check if - is overridden */\
switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) {\
case TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER):\
/* need to check if op is overridden */\
if (mrb_likely(TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1])) == \
TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER))) {\
result = OP_CMP_BODY(op,mrb_fixnum,mrb_fixnum);\
break;\
default:\
}\
else {\
mid = MRB_OPSYM(sym);\
goto L_SEND_SYM;\
}\
@@ -3033,11 +3050,12 @@ RETRY_TRY_BLOCK:
#else
#define OP_CMP(op, sym) do {\
int result;\
/* need to check if - is overridden */\
switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) {\
case TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER):\
/* need to check if op is overridden */\
uint16_t tt = TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]));\
if (mrb_likely(tt == TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER))) {\
result = OP_CMP_BODY(op,mrb_integer,mrb_integer);\
break;\
}\
else switch (tt) {\
case TYPES2(MRB_TT_INTEGER,MRB_TT_FLOAT):\
result = OP_CMP_BODY(op,mrb_integer,mrb_float);\
break;\
@@ -3398,7 +3416,7 @@ RETRY_TRY_BLOCK:
CASE(OP_TDEF, BBB) {
struct RClass *target = check_target_class(mrb);
if (!target) goto L_RAISE;
if (mrb_unlikely(!target)) goto L_RAISE;
struct RProc *p = mrb_proc_new(mrb, irep->reps[c]);
mrb_method_t m;
mrb_sym mid = irep->syms[b];
@@ -3440,7 +3458,7 @@ RETRY_TRY_BLOCK:
CASE(OP_TCLASS, B) {
struct RClass *target = check_target_class(mrb);
if (!target) goto L_RAISE;
if (mrb_unlikely(!target)) goto L_RAISE;
regs[a] = mrb_obj_value(target);
NEXT;
}
@@ -3448,7 +3466,7 @@ RETRY_TRY_BLOCK:
CASE(OP_ALIAS, BB) {
struct RClass *target = check_target_class(mrb);
if (!target) goto L_RAISE;
if (mrb_unlikely(!target)) goto L_RAISE;
mrb_alias_method(mrb, target, irep->syms[a], irep->syms[b]);
mrb_method_added(mrb, target, irep->syms[a]);
ci = mrb->c->ci;
@@ -3457,7 +3475,7 @@ RETRY_TRY_BLOCK:
CASE(OP_UNDEF, B) {
struct RClass *target = check_target_class(mrb);
if (!target) goto L_RAISE;
if (mrb_unlikely(!target)) goto L_RAISE;
mrb_undef_method_id(mrb, target, irep->syms[a]);
ci = mrb->c->ci;
NEXT;