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Merge pull request #178 from urbit/revert-177-revert-175-eamsden/gc-top-frame
2stackz: gc top frame by flipping polarity (take 2)
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commit
4ff2f1e161
@ -2,7 +2,7 @@ use crate::jets::*;
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use crate::noun::{Atom, DirectAtom, IndirectAtom, Noun, D, T};
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use ares_macros::tas;
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use either::Either::{self, Left, Right};
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use std::ptr::null_mut;
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use std::ptr::{copy_nonoverlapping, null_mut};
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/** Root for Hoon %k.139
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*/
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@ -826,3 +826,27 @@ struct HotMem {
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jet: Jet,
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next: Hot,
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}
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impl Preserve for Hot {
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unsafe fn preserve(&mut self, stack: &mut NockStack) {
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let mut it = self;
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while !it.0.is_null() && stack.is_in_frame(it.0) {
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let dest_mem = stack.struct_alloc_in_previous_frame(1);
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copy_nonoverlapping(it.0, dest_mem, 1);
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it.0 = dest_mem;
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(*it.0).a_path.preserve(stack);
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(*it.0).axis.preserve(stack);
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it = &mut (*it.0).next;
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}
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}
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unsafe fn assert_in_stack(&self, stack: &NockStack) {
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let mut it = self;
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while !it.0.is_null() {
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stack.assert_struct_is_in(it.0, 1);
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(*it.0).a_path.assert_in_stack(stack);
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(*it.0).axis.assert_in_stack(stack);
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it = &mut (*it.0).next;
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}
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}
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}
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@ -75,7 +75,7 @@ impl NockStack {
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unsafe {
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*frame_pointer.sub(FRAME + 1) = ptr::null::<u64>() as u64; // "frame pointer" from "previous" frame
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*frame_pointer.sub(STACK + 1) = ptr::null::<u64>() as u64; // "stack pointer" from "previous" frame
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*frame_pointer.sub(ALLOC + 1) = ptr::null::<u64>() as u64; // "alloc pointer" from "previous" frame
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*frame_pointer.sub(ALLOC + 1) = start as u64; // "alloc pointer" from "previous" frame
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};
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NockStack {
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start,
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@ -88,7 +88,43 @@ impl NockStack {
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}
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}
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/** Resets the NockStack. */
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/** Resets the NockStack but flipping the top-frame polarity and unsetting PC. Sets the alloc
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* pointer to the "previous" alloc pointer stored in the top frame to keep things "preserved"
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* from the top frame. This allows us to do a copying GC on the top frame without erroneously
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* "popping" the top frame.
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*/
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pub unsafe fn flip_top_frame(&mut self, top_slots: usize) {
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// Assert that we are at the top
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assert!((*self.prev_frame_pointer_pointer()).is_null());
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assert!((*self.prev_stack_pointer_pointer()).is_null());
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let new_alloc_pointer = *(self.prev_alloc_pointer_pointer());
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if self.is_west() {
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// new top frame will be east
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let new_frame_pointer = self.start.add(self.size).sub(RESERVED + top_slots) as *mut u64;
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*new_frame_pointer.add(FRAME) = ptr::null::<u64>() as u64;
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*new_frame_pointer.add(STACK) = ptr::null::<u64>() as u64;
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*new_frame_pointer.add(ALLOC) = self.start.add(self.size) as u64;
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self.frame_pointer = new_frame_pointer;
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self.stack_pointer = new_frame_pointer;
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self.alloc_pointer = new_alloc_pointer;
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self.pc = false;
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assert!(!self.is_west());
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} else {
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// new top frame will be west
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let new_frame_pointer = self.start.add(RESERVED + top_slots) as *mut u64;
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*new_frame_pointer.sub(FRAME + 1) = ptr::null::<u64>() as u64;
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*new_frame_pointer.sub(STACK + 1) = ptr::null::<u64>() as u64;
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*new_frame_pointer.sub(ALLOC + 1) = self.start as u64;
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self.frame_pointer = new_frame_pointer;
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self.stack_pointer = new_frame_pointer;
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self.alloc_pointer = new_alloc_pointer;
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self.pc = false;
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assert!(self.is_west());
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}
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}
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/** Resets the NockStack. The top frame is west as in the initial creation of the NockStack. */
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pub fn reset(&mut self, top_slots: usize) {
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self.frame_pointer = unsafe { self.start.add(RESERVED + top_slots) } as *mut u64;
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self.stack_pointer = self.frame_pointer;
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@ -97,7 +133,8 @@ impl NockStack {
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unsafe {
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*self.frame_pointer.sub(FRAME + 1) = ptr::null::<u64>() as u64; // "frame pointer" from "previous" frame
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*self.frame_pointer.sub(STACK + 1) = ptr::null::<u64>() as u64; // "stack pointer" from "previous" frame
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*self.frame_pointer.sub(ALLOC + 1) = ptr::null::<u64>() as u64; // "alloc pointer" from "previous" frame
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*self.frame_pointer.sub(ALLOC + 1) = self.start as u64; // "alloc pointer" from "previous" frame
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assert!(self.is_west());
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};
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}
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@ -123,7 +160,17 @@ impl NockStack {
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let ptr_u64 = ptr as *const u64;
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let prev = *self.prev_stack_pointer_pointer();
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if self.is_west() {
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// If we are in a top/west frame, the stack pointer will be null, so our allocation
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// arena was the alloc pointer to the top of the NockStack arena
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if prev.is_null() {
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ptr_u64 >= self.alloc_pointer && ptr_u64 < self.start.add(self.size)
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} else {
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ptr_u64 >= self.alloc_pointer && ptr_u64 < prev
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}
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// If we are in a top/east frame, the stack pointer will be null, so our allocation arena
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// was the alloc pointer to the bottom of the NockStack arena
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} else if prev.is_null() {
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ptr_u64 >= self.start && ptr_u64 < self.alloc_pointer
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} else {
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ptr_u64 >= prev && ptr_u64 < self.alloc_pointer
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}
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@ -224,7 +224,6 @@ pub fn serf(constant_hot_state: &[HotEntry]) -> io::Result<()> {
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// Reset the local cache and scry handler stack
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context.nock_context.cache = Hamt::<Noun>::new();
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context.nock_context.scry_stack = D(0);
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context.nock_context.stack.frame_push(0);
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let tag = slot(writ, 2)?.as_direct().unwrap();
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match tag.data() {
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@ -269,13 +268,15 @@ pub fn serf(constant_hot_state: &[HotEntry]) -> io::Result<()> {
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clear_interrupt();
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// Persist data that should survive between events
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// XX: Such data should go in the PMA once that's available
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// XX: Such data should go in the PMA once that's available, except
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// the warm and hot state which should survive between events but not interpreter runs
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unsafe {
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let stack = &mut context.nock_context.stack;
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stack.preserve(&mut context.arvo);
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stack.preserve(&mut context.nock_context.cold);
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stack.preserve(&mut context.nock_context.warm);
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stack.frame_pop();
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stack.preserve(&mut context.nock_context.hot);
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stack.flip_top_frame(0);
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}
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}
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