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YJIT: Fallback setivar if the next shape is too complex #8152

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Aug 1, 2023
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YJIT: Fallback setivar if the next shape is too complex #8152

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109 changes: 60 additions & 49 deletions yjit/src/codegen.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2188,10 +2188,66 @@ fn gen_setinstancevariable(
gen_counter_incr(asm, Counter::num_setivar_megamorphic);
}

// Get the iv index
let shape_too_complex = comptime_receiver.shape_too_complex();
let ivar_index = if !shape_too_complex {
let shape_id = comptime_receiver.shape_id_of();
let shape = unsafe { rb_shape_get_shape_by_id(shape_id) };
let mut ivar_index: u32 = 0;
if unsafe { rb_shape_get_iv_index(shape, ivar_name, &mut ivar_index) } {
Some(ivar_index as usize)
} else {
None
}
} else {
None
};

// Get the next shape information if it needs transition
let new_shape = if !shape_too_complex && ivar_index.is_none() {
let shape = comptime_receiver.shape_of();

let current_capacity = unsafe { (*shape).capacity };
let new_capacity = current_capacity * 2;

// If the object doesn't have the capacity to store the IV,
// then we'll need to allocate it.
let needs_extension = unsafe { (*shape).next_iv_index >= current_capacity };

// We can write to the object, but we need to transition the shape
let ivar_index = unsafe { (*shape).next_iv_index } as usize;

let capa_shape = if needs_extension {
// We need to add an extended table to the object
// First, create an outgoing transition that increases the
// capacity
Some(unsafe { rb_shape_transition_shape_capa(shape, new_capacity) })
} else {
None
};

let dest_shape = if let Some(capa_shape) = capa_shape {
unsafe { rb_shape_get_next(capa_shape, comptime_receiver, ivar_name) }
} else {
unsafe { rb_shape_get_next(shape, comptime_receiver, ivar_name) }
};

let new_shape_id = unsafe { rb_shape_id(dest_shape) };
let needs_extension = if needs_extension {
Some((current_capacity, new_capacity))
} else {
None
};
Some((new_shape_id, needs_extension, ivar_index))
} else {
None
};
let new_shape_too_complex = matches!(new_shape, Some((OBJ_TOO_COMPLEX_SHAPE_ID, _, _)));

// If the receiver isn't a T_OBJECT, or uses a custom allocator,
// then just write out the IV write as a function call.
// too-complex shapes can't use index access, so we use rb_ivar_get for them too.
if !receiver_t_object || uses_custom_allocator || comptime_receiver.shape_too_complex() || megamorphic {
if !receiver_t_object || uses_custom_allocator || shape_too_complex || new_shape_too_complex || megamorphic {
asm.comment("call rb_vm_setinstancevariable()");

let ic = jit.get_arg(1).as_u64(); // type IVC
Expand All @@ -2215,18 +2271,6 @@ fn gen_setinstancevariable(
]
);
} else {
// Get the iv index
let ivar_index = unsafe {
let shape_id = comptime_receiver.shape_id_of();
let shape = rb_shape_get_shape_by_id(shape_id);
let mut ivar_index: u32 = 0;
if rb_shape_get_iv_index(shape, ivar_name, &mut ivar_index) {
Some(ivar_index as usize)
} else {
None
}
};

// Get the receiver
let mut recv = asm.load(Opnd::mem(64, CFP, RUBY_OFFSET_CFP_SELF));

Expand Down Expand Up @@ -2257,41 +2301,8 @@ fn gen_setinstancevariable(
// If we don't have an instance variable index, then we need to
// transition out of the current shape.
None => {
let shape = comptime_receiver.shape_of();

let current_capacity = unsafe { (*shape).capacity };
let new_capacity = current_capacity * 2;

// If the object doesn't have the capacity to store the IV,
// then we'll need to allocate it.
let needs_extension = unsafe { (*shape).next_iv_index >= current_capacity };

// We can write to the object, but we need to transition the shape
let ivar_index = unsafe { (*shape).next_iv_index } as usize;

let capa_shape = if needs_extension {
// We need to add an extended table to the object
// First, create an outgoing transition that increases the
// capacity
Some(unsafe { rb_shape_transition_shape_capa(shape, new_capacity) })
} else {
None
};

let dest_shape = if let Some(capa_shape) = capa_shape {
unsafe { rb_shape_get_next(capa_shape, comptime_receiver, ivar_name) }
} else {
unsafe { rb_shape_get_next(shape, comptime_receiver, ivar_name) }
};

let new_shape_id = unsafe { rb_shape_id(dest_shape) };

if new_shape_id == OBJ_TOO_COMPLEX_SHAPE_ID {
gen_counter_incr(asm, Counter::setivar_too_complex);
return None;
}

if needs_extension {
let (new_shape_id, needs_extension, ivar_index) = new_shape.unwrap();
if let Some((current_capacity, new_capacity)) = needs_extension {
// Generate the C call so that runtime code will increase
// the capacity and set the buffer.
asm.comment("call rb_ensure_iv_list_size");
Expand All @@ -2312,7 +2323,7 @@ fn gen_setinstancevariable(
}

write_val = asm.stack_pop(1);
gen_write_iv(asm, comptime_receiver, recv, ivar_index, write_val, needs_extension);
gen_write_iv(asm, comptime_receiver, recv, ivar_index, write_val, needs_extension.is_some());

asm.comment("write shape");

Expand Down
1 change: 0 additions & 1 deletion yjit/src/stats.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -323,7 +323,6 @@ make_counters! {
setivar_not_heap,
setivar_frozen,
setivar_megamorphic,
setivar_too_complex,

definedivar_not_heap,
definedivar_megamorphic,
Expand Down