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Allow pass special constants to the write barrier

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Some GC implementations want to always know when an object is written to,
even if the written value is a special constant. Checking special constants
in rb_obj_written was a micro-optimization that made assumptions about
the GC implementation.
This commit is contained in:
Peter Zhu 2025-06-02 16:31:28 -04:00
parent 5f247416b6
commit ea8b53a539
Notes: git 2025-06-03 16:04:39 +00:00 
Merged: https://github.com/ruby/ruby/pull/13497
4 changed files with 6 additions and 5 deletions
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3
gc/default/default.c
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@ -6006,9 +6006,10 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
if (RGENGC_CHECK_MODE) { if (RGENGC_CHECK_MODE) {
if (SPECIAL_CONST_P(a)) rb_bug("rb_gc_writebarrier: a is special const: %"PRIxVALUE, a); if (SPECIAL_CONST_P(a)) rb_bug("rb_gc_writebarrier: a is special const: %"PRIxVALUE, a);
if (SPECIAL_CONST_P(b)) rb_bug("rb_gc_writebarrier: b is special const: %"PRIxVALUE, b);
} }
if (SPECIAL_CONST_P(b)) return;
GC_ASSERT(RB_BUILTIN_TYPE(a) != T_NONE); GC_ASSERT(RB_BUILTIN_TYPE(a) != T_NONE);
GC_ASSERT(RB_BUILTIN_TYPE(a) != T_MOVED); GC_ASSERT(RB_BUILTIN_TYPE(a) != T_MOVED);
GC_ASSERT(RB_BUILTIN_TYPE(a) != T_ZOMBIE); GC_ASSERT(RB_BUILTIN_TYPE(a) != T_ZOMBIE);

2
gc/mmtk/mmtk.c
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@ -750,6 +750,8 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
{ {
struct MMTk_ractor_cache *cache = rb_gc_get_ractor_newobj_cache(); struct MMTk_ractor_cache *cache = rb_gc_get_ractor_newobj_cache();
if (SPECIAL_CONST_P(b)) return;
mmtk_object_reference_write_post(cache->mutator, (MMTk_ObjectReference)a); mmtk_object_reference_write_post(cache->mutator, (MMTk_ObjectReference)a);
} }

2
include/ruby/internal/abi.h
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@ -24,7 +24,7 @@
* In released versions of Ruby, this number is not defined since teeny * In released versions of Ruby, this number is not defined since teeny
* versions of Ruby should guarantee ABI compatibility. * versions of Ruby should guarantee ABI compatibility.
*/ */
#define RUBY_ABI_VERSION 1 #define RUBY_ABI_VERSION 2
/* Windows does not support weak symbols so ruby_abi_version will not exist /* Windows does not support weak symbols so ruby_abi_version will not exist
* in the shared library. */ * in the shared library. */

2
include/ruby/internal/gc.h
View File

@ -785,9 +785,7 @@ rb_obj_written(
RGENGC_LOGGING_OBJ_WRITTEN(a, oldv, b, filename, line); RGENGC_LOGGING_OBJ_WRITTEN(a, oldv, b, filename, line);
#endif #endif
if (!RB_SPECIAL_CONST_P(b)) {
rb_gc_writebarrier(a, b); rb_gc_writebarrier(a, b);
}
return a; return a;
} }