Masahiro Yamada f93d6bfbd2 kconfig: use hash table to reuse expressions ... Currently, every expression in Kconfig files produces a new abstract syntax tree (AST), even if it is identical to a previously encountered one. Consider the following code: config FOO bool "FOO" depends on (A || B) && C config BAR bool "BAR" depends on (A || B) && C config BAZ bool "BAZ" depends on A || B The "depends on" lines are similar, but currently a separate AST is allocated for each one. The current data structure looks like this: FOO->dep ==> AND BAR->dep ==> AND BAZ->dep ==> OR / \ / \ / \ OR C OR C A B / \ / \ A B A B This is redundant; FOO->dep and BAR->dep have identical ASTs but different memory instances. We can optimize this; FOO->dep and BAR->dep can share the same AST, and BAZ->dep can reference its sub tree. The optimized data structure looks like this: FOO->dep, BAR->dep ==> AND / \ BAZ->dep ==> OR C / \ A B This commit introduces a hash table to keep track of allocated expressions. If an identical expression is found, it is reused. This does not necessarily result in memory savings, as menu_finalize() transforms expressions without freeing up stale ones. This will be addressed later. One optimization that can be easily implemented is caching the expression's value. Once FOO's dependency, (A || B) && C, is calculated, it can be cached, eliminating the need to recalculate it for BAR. This commit also reverts commit e983b7b17a ("kconfig/menu.c: fix multiple references to expressions in menu_add_prop()"). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>		2024-09-20 09:21:52 +09:00
..
array_size.h
hash.h	kconfig: use hash table to reuse expressions	2024-09-20 09:21:52 +09:00
hashtable.h	scripts: import more hash table macros	2024-09-10 13:56:37 +09:00
list_types.h
list.h	scripts: import more hash table macros	2024-09-10 13:56:37 +09:00
xalloc.h	kbuild: split x*alloc() functions in kconfig to scripts/include/xalloc.h	2024-09-01 20:34:48 +09:00