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py/gc: Rename gc_drain_stack to gc_mark_subtree and pass it first block.

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This saves a bit in code size:

minimal CROSS=1: -44
unix:            -96
This commit is contained in:
Ayke van Laethem 2018-02-15 17:10:13 +01:00 committed by Damien George
parent ea7cf2b738
commit 5c9e5618e0
1 changed files with 17 additions and 9 deletions
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26
py/gc.c
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@ -203,11 +203,13 @@ bool gc_is_locked(void) {
#endif
#endif
STATIC void gc_drain_stack(void) {
while (MP_STATE_MEM(gc_sp) > MP_STATE_MEM(gc_stack)) {
// pop the next block off the stack
size_t block = *--MP_STATE_MEM(gc_sp);
// Take the given block as the topmost block on the stack. Check all it's
// children: mark the unmarked child blocks and put those newly marked
// blocks on the stack. When all children have been checked, pop off the
// topmost block on the stack and repeat with that one.
STATIC void gc_mark_subtree(size_t block) {
// Start with the block passed in the argument.
for (;;) {
// work out number of consecutive blocks in the chain starting with this one
size_t n_blocks = 0;
do {
@ -233,6 +235,14 @@ STATIC void gc_drain_stack(void) {
}
}
}
// Are there any blocks on the stack?
if (MP_STATE_MEM(gc_sp) <= MP_STATE_MEM(gc_stack)) {
break; // No, stack is empty, we're done.
}
// pop the next block off the stack
block = *--MP_STATE_MEM(gc_sp);
}
}
@ -245,8 +255,7 @@ STATIC void gc_deal_with_stack_overflow(void) {
for (size_t block = 0; block < MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB; block++) {
// trace (again) if mark bit set
if (ATB_GET_KIND(block) == AT_MARK) {
*MP_STATE_MEM(gc_sp)++ = block;
gc_drain_stack();
gc_mark_subtree(block);
}
}
}
@ -339,8 +348,7 @@ void gc_collect_root(void **ptrs, size_t len) {
// an unmarked head, mark it, and push it on gc stack
TRACE_MARK(block, ptr);
ATB_HEAD_TO_MARK(block);
*MP_STATE_MEM(gc_sp)++ = block;
gc_drain_stack();
gc_mark_subtree(block);
}
}
}