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f93d6bfbd2
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
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|---|---|---|
| .. | ||
| lxdialog | ||
| tests | ||
| .gitignore | ||
| conf.c | ||
| confdata.c | ||
| expr.c | ||
| expr.h | ||
| gconf-cfg.sh | ||
| gconf.c | ||
| gconf.glade | ||
| images.c | ||
| images.h | ||
| internal.h | ||
| lexer.l | ||
| lkc_proto.h | ||
| lkc.h | ||
| Makefile | ||
| mconf-cfg.sh | ||
| mconf.c | ||
| menu.c | ||
| merge_config.sh | ||
| mnconf-common.c | ||
| mnconf-common.h | ||
| nconf-cfg.sh | ||
| nconf.c | ||
| nconf.gui.c | ||
| nconf.h | ||
| parser.y | ||
| preprocess.c | ||
| preprocess.h | ||
| qconf-cfg.sh | ||
| qconf.cc | ||
| qconf.h | ||
| streamline_config.pl | ||
| symbol.c | ||
| util.c | ||