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Rework inline cache handling #609

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merged 3 commits into from
Oct 20, 2024
Merged

Rework inline cache handling #609

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ae85f81
Rework inline cache handling
bnoordhuis Oct 19, 2024
1940c7a
squash! update ic offsets in bytecode
bnoordhuis Oct 19, 2024
51f24ec
test! assert that ic offset does not change
bnoordhuis Oct 19, 2024
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133 changes: 79 additions & 54 deletions quickjs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -602,21 +602,30 @@ typedef struct JSInlineCache {
uint32_t hash_bits;
JSInlineCacheHashSlot **hash;
JSInlineCacheRingSlot *cache;
uint32_t updated_offset;
BOOL updated;
} JSInlineCache;

#define INLINE_CACHE_MISS ((uint32_t)-1) // sentinel

// This is a struct so we don't tie up two argument registers in calls to
// JS_GetPropertyInternal2 and JS_SetPropertyInternal2 in the common case
// where there is no IC and therefore no offset to update.
typedef struct JSInlineCacheUpdate {
JSInlineCache *ic;
uint32_t offset;
} JSInlineCacheUpdate;

static JSInlineCache *init_ic(JSContext *ctx);
static int rebuild_ic(JSContext *ctx, JSInlineCache *ic);
static int resize_ic_hash(JSContext *ctx, JSInlineCache *ic);
static int free_ic(JSRuntime *rt, JSInlineCache *ic);
static uint32_t add_ic_slot(JSContext *ctx, JSInlineCache *ic, JSAtom atom, JSObject *object,
uint32_t prop_offset);
static void add_ic_slot(JSContext *ctx, JSInlineCacheUpdate *icu,
JSAtom atom, JSObject *object, uint32_t prop_offset);

static int32_t get_ic_prop_offset(JSInlineCache *ic, uint32_t cache_offset,
JSShape *shape)
static uint32_t get_ic_prop_offset(const JSInlineCacheUpdate *icu,
Comment on lines -616 to +624
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Offsets are stored as uint32_t so this should have been uint32_t from the start. Not that it matters in a practical sense, 2^31-1 is large enough by a wide margin. Still, bigger is better according to my girlfriend and 2^32 > 2^31.

JSShape *shape)
{
uint32_t i;
uint32_t i, cache_offset = icu->offset;
JSInlineCache *ic = icu->ic;
JSInlineCacheRingSlot *cr;
JSShape *shape_slot;
assert(cache_offset < ic->capacity);
Expand All @@ -635,7 +644,7 @@ static int32_t get_ic_prop_offset(JSInlineCache *ic, uint32_t cache_offset,
}
}

return -1;
return INLINE_CACHE_MISS;
}

static force_inline JSAtom get_ic_atom(JSInlineCache *ic, uint32_t cache_offset)
Expand Down Expand Up @@ -7283,7 +7292,8 @@ static int JS_AutoInitProperty(JSContext *ctx, JSObject *p, JSAtom prop,

static JSValue JS_GetPropertyInternal2(JSContext *ctx, JSValue obj,
JSAtom prop, JSValue this_obj,
JSInlineCache* ic, BOOL throw_ref_error)
JSInlineCacheUpdate *icu,
BOOL throw_ref_error)
{
JSObject *p;
JSProperty *pr;
Expand Down Expand Up @@ -7352,9 +7362,8 @@ static JSValue JS_GetPropertyInternal2(JSContext *ctx, JSValue obj,
continue;
}
} else {
if (ic && proto_depth == 0 && p->shape->is_hashed) {
ic->updated = TRUE;
ic->updated_offset = add_ic_slot(ctx, ic, prop, p, offset);
if (icu && proto_depth == 0 && p->shape->is_hashed) {
add_ic_slot(ctx, icu, prop, p, offset);
}
return js_dup(pr->u.value);
}
Expand Down Expand Up @@ -7444,20 +7453,20 @@ JSValue JS_GetProperty(JSContext *ctx, JSValue this_obj, JSAtom prop)

static JSValue JS_GetPropertyInternalWithIC(JSContext *ctx, JSValue obj,
JSAtom prop, JSValue this_obj,
JSInlineCache *ic, int32_t offset,
JSInlineCacheUpdate *icu,
BOOL throw_ref_error)
{
uint32_t tag;
uint32_t tag, offset;
JSObject *p;
tag = JS_VALUE_GET_TAG(obj);
if (unlikely(tag != JS_TAG_OBJECT))
goto slow_path;
p = JS_VALUE_GET_OBJ(obj);
offset = get_ic_prop_offset(ic, offset, p->shape);
if (likely(offset >= 0))
offset = get_ic_prop_offset(icu, p->shape);
if (likely(offset != INLINE_CACHE_MISS))
return js_dup(p->prop[offset].u.value);
slow_path:
return JS_GetPropertyInternal2(ctx, obj, prop, this_obj, ic, throw_ref_error);
return JS_GetPropertyInternal2(ctx, obj, prop, this_obj, icu, throw_ref_error);
}

static JSValue JS_ThrowTypeErrorPrivateNotFound(JSContext *ctx, JSAtom atom)
Expand Down Expand Up @@ -8611,9 +8620,9 @@ static void js_free_desc(JSContext *ctx, JSPropertyDescriptor *desc)
the new property is not added and an error is raised.
'obj' must be an object when obj != this_obj.
*/
static int JS_SetPropertyInternal2(JSContext *ctx, JSValue obj,
JSAtom prop, JSValue val, JSValue this_obj,
int flags, JSInlineCache *ic)
static int JS_SetPropertyInternal2(JSContext *ctx, JSValue obj, JSAtom prop,
JSValue val, JSValue this_obj, int flags,
JSInlineCacheUpdate *icu)
{
JSObject *p, *p1;
JSShapeProperty *prs;
Expand Down Expand Up @@ -8649,9 +8658,8 @@ static int JS_SetPropertyInternal2(JSContext *ctx, JSValue obj,
if (likely((prs->flags & (JS_PROP_TMASK | JS_PROP_WRITABLE |
JS_PROP_LENGTH)) == JS_PROP_WRITABLE)) {
/* fast case */
if (ic && p->shape->is_hashed) {
ic->updated = TRUE;
ic->updated_offset = add_ic_slot(ctx, ic, prop, p, offset);
if (icu && p->shape->is_hashed) {
add_ic_slot(ctx, icu, prop, p, offset);
}
set_value(ctx, &pr->u.value, val);
return TRUE;
Expand Down Expand Up @@ -8876,23 +8884,24 @@ int JS_SetProperty(JSContext *ctx, JSValue this_obj, JSAtom prop, JSValue val)
return JS_SetPropertyInternal2(ctx, this_obj, prop, val, this_obj, JS_PROP_THROW, NULL);
}

// XXX(bnoordhuis) only used by OP_put_field_ic, maybe inline at call site
static int JS_SetPropertyInternalWithIC(JSContext *ctx, JSValue this_obj,
JSAtom prop, JSValue val, int flags,
JSInlineCache *ic, int32_t offset) {
uint32_t tag;
JSInlineCacheUpdate *icu) {
uint32_t tag, offset;
JSObject *p;
tag = JS_VALUE_GET_TAG(this_obj);
if (unlikely(tag != JS_TAG_OBJECT))
goto slow_path;
p = JS_VALUE_GET_OBJ(this_obj);
offset = get_ic_prop_offset(ic, offset, p->shape);
if (likely(offset >= 0)) {
offset = get_ic_prop_offset(icu, p->shape);
if (likely(offset != INLINE_CACHE_MISS)) {
set_value(ctx, &p->prop[offset].u.value, val);
return TRUE;
}
slow_path:
return JS_SetPropertyInternal2(ctx, this_obj, prop, val, this_obj,
flags, ic);
flags, icu);
}

/* flags can be JS_PROP_THROW or JS_PROP_THROW_STRICT */
Expand Down Expand Up @@ -16129,16 +16138,17 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValue func_obj,
{
JSValue val;
JSAtom atom;
JSInlineCacheUpdate icu;
atom = get_u32(pc);
pc += 4;
sf->cur_pc = pc;
val = JS_GetPropertyInternal2(ctx, sp[-1], atom, sp[-1], ic, FALSE);
icu = (JSInlineCacheUpdate){ic, INLINE_CACHE_MISS};
val = JS_GetPropertyInternal2(ctx, sp[-1], atom, sp[-1], &icu, FALSE);
if (unlikely(JS_IsException(val)))
goto exception;
if (ic && ic->updated == TRUE) {
ic->updated = FALSE;
if (icu.offset != INLINE_CACHE_MISS) {
put_u8(pc - 5, OP_get_field_ic);
put_u32(pc - 4, ic->updated_offset);
put_u32(pc - 4, icu.offset);
JS_FreeAtom(ctx, atom);
}
JS_FreeValue(ctx, sp[-1]);
Expand All @@ -16150,33 +16160,39 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValue func_obj,
{
JSValue val;
JSAtom atom;
int32_t ic_offset;
uint32_t ic_offset;
JSInlineCacheUpdate icu;
ic_offset = get_u32(pc);
atom = get_ic_atom(ic, ic_offset);
pc += 4;
sf->cur_pc = pc;
val = JS_GetPropertyInternalWithIC(ctx, sp[-1], atom, sp[-1], ic, ic_offset, FALSE);
ic->updated = FALSE;
icu = (JSInlineCacheUpdate){ic, ic_offset};
val = JS_GetPropertyInternalWithIC(ctx, sp[-1], atom, sp[-1], &icu, FALSE);
if (unlikely(JS_IsException(val)))
goto exception;
if (icu.offset != ic_offset) {
put_u32(pc - 4, icu.offset);
}
JS_FreeValue(ctx, sp[-1]);
sp[-1] = val;
}
BREAK;

CASE(OP_get_field2):
{
JSValue val;
JSAtom atom;
JSInlineCacheUpdate icu;
atom = get_u32(pc);
pc += 4;
sf->cur_pc = pc;
val = JS_GetPropertyInternal2(ctx, sp[-1], atom, sp[-1], NULL, FALSE);
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Note how this was passing NULL instead of ic. Looks like another bug to me because a few lines below it is acting on ic->updated.

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Is there a way to have a test for that?

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Not at the moment (or not easily anyway) but I'm thinking about adding a debug module that would make it easier to inspect the textual representation of the bytecode (basically by using the existing bytecode printer to dump to a string.)

You can technically do that already with bjson.write and grubbing through the binary output but that's super fragile.

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A la the dis module in Python? That's cool!

icu = (JSInlineCacheUpdate){ic, INLINE_CACHE_MISS};
val = JS_GetPropertyInternal2(ctx, sp[-1], atom, sp[-1], &icu, FALSE);
if (unlikely(JS_IsException(val)))
goto exception;
if (ic != NULL && ic->updated == TRUE) {
ic->updated = FALSE;
if (icu.offset != INLINE_CACHE_MISS) {
put_u8(pc - 5, OP_get_field2_ic);
put_u32(pc - 4, ic->updated_offset);
put_u32(pc - 4, icu.offset);
JS_FreeAtom(ctx, atom);
}
*sp++ = val;
Expand All @@ -16187,15 +16203,19 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValue func_obj,
{
JSValue val;
JSAtom atom;
int32_t ic_offset;
uint32_t ic_offset;
JSInlineCacheUpdate icu;
ic_offset = get_u32(pc);
atom = get_ic_atom(ic, ic_offset);
pc += 4;
sf->cur_pc = pc;
val = JS_GetPropertyInternalWithIC(ctx, sp[-1], atom, sp[-1], ic, ic_offset, FALSE);
ic->updated = FALSE;
icu = (JSInlineCacheUpdate){ic, ic_offset};
val = JS_GetPropertyInternalWithIC(ctx, sp[-1], atom, sp[-1], &icu, FALSE);
if (unlikely(JS_IsException(val)))
goto exception;
if (icu.offset != ic_offset) {
put_u32(pc - 4, icu.offset);
}
*sp++ = val;
}
BREAK;
Expand All @@ -16204,21 +16224,22 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValue func_obj,
{
int ret;
JSAtom atom;
JSInlineCacheUpdate icu;
atom = get_u32(pc);
pc += 4;
sf->cur_pc = pc;
icu = (JSInlineCacheUpdate){ic, INLINE_CACHE_MISS};
ret = JS_SetPropertyInternal2(ctx,
sp[-2], atom,
sp[-1], sp[-2],
JS_PROP_THROW_STRICT, ic);
JS_PROP_THROW_STRICT, &icu);
JS_FreeValue(ctx, sp[-2]);
sp -= 2;
if (unlikely(ret < 0))
goto exception;
if (ic != NULL && ic->updated == TRUE) {
ic->updated = FALSE;
if (icu.offset != INLINE_CACHE_MISS) {
put_u8(pc - 5, OP_put_field_ic);
put_u32(pc - 4, ic->updated_offset);
put_u32(pc - 4, icu.offset);
JS_FreeAtom(ctx, atom);
}
}
Expand All @@ -16228,17 +16249,22 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValue func_obj,
{
int ret;
JSAtom atom;
int32_t ic_offset;
uint32_t ic_offset;
JSInlineCacheUpdate icu;
ic_offset = get_u32(pc);
atom = get_ic_atom(ic, ic_offset);
pc += 4;
sf->cur_pc = pc;
ret = JS_SetPropertyInternalWithIC(ctx, sp[-2], atom, sp[-1], JS_PROP_THROW_STRICT, ic, ic_offset);
ic->updated = FALSE;
icu = (JSInlineCacheUpdate){ic, ic_offset};
ret = JS_SetPropertyInternalWithIC(ctx, sp[-2], atom, sp[-1],
JS_PROP_THROW_STRICT, &icu);
JS_FreeValue(ctx, sp[-2]);
sp -= 2;
if (unlikely(ret < 0))
goto exception;
if (icu.offset != ic_offset) {
put_u32(pc - 4, icu.offset);
}
}
BREAK;

Expand Down Expand Up @@ -54433,8 +54459,6 @@ JSInlineCache *init_ic(JSContext *ctx)
if (unlikely(!ic->hash))
goto fail;
ic->cache = NULL;
ic->updated = FALSE;
ic->updated_offset = 0;
return ic;
fail:
js_free(ctx, ic);
Expand Down Expand Up @@ -54517,11 +54541,12 @@ int free_ic(JSRuntime* rt, JSInlineCache *ic)
return 0;
}

uint32_t add_ic_slot(JSContext *ctx, JSInlineCache *ic, JSAtom atom, JSObject *object,
uint32_t prop_offset)
static void add_ic_slot(JSContext *ctx, JSInlineCacheUpdate *icu,
JSAtom atom, JSObject *object, uint32_t prop_offset)
{
int32_t i;
uint32_t h;
JSInlineCache *ic = icu->ic;
JSInlineCacheHashSlot *ch;
JSInlineCacheRingSlot *cr;
JSShape *sh;
Expand Down Expand Up @@ -54550,7 +54575,7 @@ uint32_t add_ic_slot(JSContext *ctx, JSInlineCache *ic, JSAtom atom, JSObject *o
js_free_shape_null(ctx->rt, sh);
cr->prop_offset[i] = prop_offset;
end:
return ch->index;
icu->offset = ch->index;
}

/* CallSite */
Expand Down
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