Commit 7c42945e04a2107827a057245298dedc0475cc88
2019-11-13T22:41:38
parser: fix quadratic pointer chasing In the AST, lists (e.g. the list of statements in a file) are kept in singly-linked lists -- each AST node has a `next` pointer available for this purpose. Previously, a node was added to the list by starting from the head, chasing to the last, and appending. So creating a list of length N would take ~N^2/2 pointer dereferences. Now, we always (temporarily) keep the last as well, so appending is O(1) instead of O(N). Given a keymap xkb_keymap { xkb_keycodes { minimum = 8; minimum = 8; minimum = 8; minimum = 8; minimum = 8; [... repeated N times ...] }; xkb_types {}; xkb_compat {}; xkb_symbols {}; }; The compilation times are N | Before | After --------|----------|------- 10,000 | 0.407s | 0.006s 20,000 | 1.851s | 0.015s 30,000 | 5.737s | 0.021s 40,000 | 12.759s | 0.023s 50,000 | 21.489s | 0.035s 60,000 | 40.473s | 0.041s 70,000 | 53.336s | 0.039s 80,000 | 72.485s | 0.044s 90,000 | 94.703s | 0.048s 100,000 | 118.390s | 0.057s Another option is to ditch the linked lists and use arrays instead. I got it to work, but its more involved and allocation heavy so turns out to be worse without further optimizations. Signed-off-by: Ran Benita <ran@unusedvar.com>
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diff --git a/src/xkbcomp/ast-build.c b/src/xkbcomp/ast-build.c
index 64051c7..c2f095d 100644
--- a/src/xkbcomp/ast-build.c
+++ b/src/xkbcomp/ast-build.c
@@ -55,20 +55,6 @@
#include "ast-build.h"
#include "include.h"
-ParseCommon *
-AppendStmt(ParseCommon *to, ParseCommon *append)
-{
- ParseCommon *iter;
-
- if (!to)
- return append;
-
- for (iter = to; iter->next; iter = iter->next);
-
- iter->next = append;
- return to;
-}
-
static ExprDef *
ExprCreate(enum expr_op_type op, enum expr_value_type type, size_t size)
{
@@ -568,7 +554,7 @@ XkbFileFromComponents(struct xkb_context *ctx,
enum xkb_file_type type;
IncludeStmt *include = NULL;
XkbFile *file = NULL;
- ParseCommon *defs = NULL;
+ ParseCommon *defs = NULL, *defsLast = NULL;
for (type = FIRST_KEYMAP_FILE_TYPE; type <= LAST_KEYMAP_FILE_TYPE; type++) {
include = IncludeCreate(ctx, components[type], MERGE_DEFAULT);
@@ -581,7 +567,10 @@ XkbFileFromComponents(struct xkb_context *ctx,
goto err;
}
- defs = AppendStmt(defs, &file->common);
+ if (!defs)
+ defsLast = defs = &file->common;
+ else
+ defsLast = defsLast->next = &file->common;
}
file = XkbFileCreate(FILE_TYPE_KEYMAP, NULL, defs, 0);
diff --git a/src/xkbcomp/ast-build.h b/src/xkbcomp/ast-build.h
index 46c7fbb..3afb080 100644
--- a/src/xkbcomp/ast-build.h
+++ b/src/xkbcomp/ast-build.h
@@ -27,9 +27,6 @@
#ifndef XKBCOMP_AST_BUILD_H
#define XKBCOMP_AST_BUILD_H
-ParseCommon *
-AppendStmt(ParseCommon *to, ParseCommon *append);
-
ExprDef *
ExprCreateString(xkb_atom_t str);
diff --git a/src/xkbcomp/parser.y b/src/xkbcomp/parser.y
index 5a2f11e..9b16fc7 100644
--- a/src/xkbcomp/parser.y
+++ b/src/xkbcomp/parser.y
@@ -169,9 +169,13 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
enum xkb_map_flags mapFlags;
xkb_keysym_t keysym;
ParseCommon *any;
+ struct { ParseCommon *head; ParseCommon *last; } anyList;
ExprDef *expr;
+ struct { ExprDef *head; ExprDef *last; } exprList;
VarDef *var;
+ struct { VarDef *head; VarDef *last; } varList;
VModDef *vmod;
+ struct { VModDef *head; VModDef *last; } vmodList;
InterpDef *interp;
KeyTypeDef *keyType;
SymbolsDef *syms;
@@ -183,6 +187,7 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
KeyAliasDef *keyAlias;
void *geom;
XkbFile *file;
+ struct { XkbFile *head; XkbFile *last; } fileList;
}
%type <num> INTEGER FLOAT
@@ -196,11 +201,15 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
%type <str> MapName OptMapName
%type <atom> FieldSpec Ident Element String
%type <keysym> KeySym
-%type <any> DeclList Decl
-%type <expr> OptExprList ExprList Expr Term Lhs Terminal ArrayInit KeySyms
-%type <expr> OptKeySymList KeySymList Action ActionList Coord CoordList
-%type <var> VarDecl VarDeclList SymbolsBody SymbolsVarDecl
-%type <vmod> VModDecl VModDefList VModDef
+%type <any> Decl
+%type <anyList> DeclList
+%type <expr> Expr Term Lhs Terminal ArrayInit KeySyms
+%type <expr> OptKeySymList KeySymList Action Coord CoordList
+%type <exprList> OptExprList ExprList ActionList
+%type <var> VarDecl SymbolsVarDecl
+%type <varList> VarDeclList SymbolsBody
+%type <vmod> VModDef
+%type <vmodList> VModDefList VModDecl
%type <interp> InterpretDecl InterpretMatch
%type <keyType> KeyTypeDecl
%type <syms> SymbolsDecl
@@ -213,15 +222,19 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
%type <geom> ShapeDecl SectionDecl SectionBody SectionBodyItem RowBody RowBodyItem
%type <geom> Keys Key OverlayDecl OverlayKeyList OverlayKey OutlineList OutlineInList
%type <geom> DoodadDecl
-%type <file> XkbFile XkbMapConfigList XkbMapConfig
+%type <file> XkbFile XkbMapConfig
+%type <fileList> XkbMapConfigList
%type <file> XkbCompositeMap
%destructor { FreeStmt((ParseCommon *) $$); }
<any> <expr> <var> <vmod> <interp> <keyType> <syms> <modMask> <groupCompat>
<ledMap> <ledName> <keyCode> <keyAlias>
+%destructor { FreeStmt((ParseCommon *) $$.head); }
+ <anyList> <exprList> <varList> <vmodList>
/* The destructor also runs on the start symbol when the parser *succeeds*.
* The `if` here catches this case. */
%destructor { if (!param->rtrn) FreeXkbFile($$); } <file>
+%destructor { FreeXkbFile($$.head); } <fileList>
%destructor { free($$); } <str>
%%
@@ -249,7 +262,7 @@ XkbFile : XkbCompositeMap
XkbCompositeMap : OptFlags XkbCompositeType OptMapName OBRACE
XkbMapConfigList
CBRACE SEMI
- { $$ = XkbFileCreate($2, $3, (ParseCommon *) $5, $1); }
+ { $$ = XkbFileCreate($2, $3, (ParseCommon *) $5.head, $1); }
;
XkbCompositeType: XKB_KEYMAP { $$ = FILE_TYPE_KEYMAP; }
@@ -258,17 +271,16 @@ XkbCompositeType: XKB_KEYMAP { $$ = FILE_TYPE_KEYMAP; }
;
XkbMapConfigList : XkbMapConfigList XkbMapConfig
- { $$ = (XkbFile *) AppendStmt((ParseCommon *) $1,
- (ParseCommon *) $2); }
+ { $$.head = $1.head; $$.last->common.next = &$2->common; $$.last = $2; }
| XkbMapConfig
- { $$ = $1; }
+ { $$.head = $$.last = $1; }
;
XkbMapConfig : OptFlags FileType OptMapName OBRACE
DeclList
CBRACE SEMI
{
- $$ = XkbFileCreate($2, $3, $5, $1);
+ $$ = XkbFileCreate($2, $3, $5.head, $1);
}
;
@@ -298,8 +310,27 @@ Flag : PARTIAL { $$ = MAP_IS_PARTIAL; }
;
DeclList : DeclList Decl
- { $$ = AppendStmt($1, $2); }
- | { $$ = NULL; }
+ {
+ /*
+ * TODO: This is needed because of VModDecl, which
+ * is a list and is "inlined" into the DeclList.
+ * Should change to avoid the O(N)-append behavior,
+ * like we do in the other lists.
+ */
+ if ($2) {
+ if (!$1.head)
+ $$.head = $2;
+ else
+ $$.head = $1.head;
+ if (!$1.last)
+ $$.last = $2;
+ else
+ $$.last = $1.last->next = $2;
+ while ($$.last->next)
+ $$.last = $$.last->next;
+ }
+ }
+ | { $$.head = $$.last = NULL; }
;
Decl : OptMergeMode VarDecl
@@ -309,9 +340,9 @@ Decl : OptMergeMode VarDecl
}
| OptMergeMode VModDecl
{
- for (VModDef *vmod = $2; vmod; vmod = (VModDef *) vmod->common.next)
+ for (VModDef *vmod = $2.head; vmod; vmod = (VModDef *) vmod->common.next)
vmod->merge = $1;
- $$ = (ParseCommon *) $2;
+ $$ = (ParseCommon *) $2.head;
}
| OptMergeMode InterpretDecl
{
@@ -389,10 +420,9 @@ VModDecl : VIRTUAL_MODS VModDefList SEMI
;
VModDefList : VModDefList COMMA VModDef
- { $$ = (VModDef *) AppendStmt((ParseCommon *) $1,
- (ParseCommon *) $3); }
+ { $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
| VModDef
- { $$ = $1; }
+ { $$.head = $$.last = $1; }
;
VModDef : Ident
@@ -404,7 +434,7 @@ VModDef : Ident
InterpretDecl : INTERPRET InterpretMatch OBRACE
VarDeclList
CBRACE SEMI
- { $2->def = $4; $$ = $2; }
+ { $2->def = $4.head; $$ = $2; }
;
InterpretMatch : KeySym PLUS Expr
@@ -414,30 +444,28 @@ InterpretMatch : KeySym PLUS Expr
;
VarDeclList : VarDeclList VarDecl
- { $$ = (VarDef *) AppendStmt((ParseCommon *) $1,
- (ParseCommon *) $2); }
+ { $$.head = $1.head; $$.last->common.next = &$2->common; $$.last = $2; }
| VarDecl
- { $$ = $1; }
+ { $$.head = $$.last = $1; }
;
KeyTypeDecl : TYPE String OBRACE
VarDeclList
CBRACE SEMI
- { $$ = KeyTypeCreate($2, $4); }
+ { $$ = KeyTypeCreate($2, $4.head); }
;
SymbolsDecl : KEY KEYNAME OBRACE
SymbolsBody
CBRACE SEMI
- { $$ = SymbolsCreate($2, $4); }
+ { $$ = SymbolsCreate($2, $4.head); }
;
SymbolsBody : SymbolsBody COMMA SymbolsVarDecl
- { $$ = (VarDef *) AppendStmt((ParseCommon *) $1,
- (ParseCommon *) $3); }
+ { $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
| SymbolsVarDecl
- { $$ = $1; }
- | { $$ = NULL; }
+ { $$.head = $$.last = $1; }
+ | { $$.head = $$.last = NULL; }
;
SymbolsVarDecl : Lhs EQUALS Expr { $$ = VarCreate($1, $3); }
@@ -450,7 +478,7 @@ SymbolsVarDecl : Lhs EQUALS Expr { $$ = VarCreate($1, $3); }
ArrayInit : OBRACKET OptKeySymList CBRACKET
{ $$ = $2; }
| OBRACKET ActionList CBRACKET
- { $$ = ExprCreateActionList($2); }
+ { $$ = ExprCreateActionList($2.head); }
;
GroupCompatDecl : GROUP Integer EQUALS Expr SEMI
@@ -458,11 +486,11 @@ GroupCompatDecl : GROUP Integer EQUALS Expr SEMI
;
ModMapDecl : MODIFIER_MAP Ident OBRACE ExprList CBRACE SEMI
- { $$ = ModMapCreate($2, $4); }
+ { $$ = ModMapCreate($2, $4.head); }
;
LedMapDecl: INDICATOR String OBRACE VarDeclList CBRACE SEMI
- { $$ = LedMapCreate($2, $4); }
+ { $$ = LedMapCreate($2, $4.head); }
;
LedNameDecl: INDICATOR Integer EQUALS Expr SEMI
@@ -513,7 +541,7 @@ Keys : Keys COMMA Key { $$ = NULL; }
Key : KEYNAME
{ $$ = NULL; }
| OBRACE ExprList CBRACE
- { FreeStmt((ParseCommon *) $2); $$ = NULL; }
+ { FreeStmt((ParseCommon *) $2.head); $$ = NULL; }
;
OverlayDecl : OVERLAY String OBRACE OverlayKeyList CBRACE SEMI
@@ -552,7 +580,7 @@ Coord : OBRACKET SignedNumber COMMA SignedNumber CBRACKET
;
DoodadDecl : DoodadType String OBRACE VarDeclList CBRACE SEMI
- { FreeStmt((ParseCommon *) $4); $$ = NULL; }
+ { FreeStmt((ParseCommon *) $4.head); $$ = NULL; }
;
DoodadType : TEXT { $$ = 0; }
@@ -608,14 +636,13 @@ MergeMode : INCLUDE { $$ = MERGE_DEFAULT; }
;
OptExprList : ExprList { $$ = $1; }
- | { $$ = NULL; }
+ | { $$.head = $$.last = NULL; }
;
ExprList : ExprList COMMA Expr
- { $$ = (ExprDef *) AppendStmt((ParseCommon *) $1,
- (ParseCommon *) $3); }
+ { $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
| Expr
- { $$ = $1; }
+ { $$.head = $$.last = $1; }
;
Expr : Expr DIVIDE Expr
@@ -643,7 +670,7 @@ Term : MINUS Term
| Lhs
{ $$ = $1; }
| FieldSpec OPAREN OptExprList CPAREN %prec OPAREN
- { $$ = ExprCreateAction($1, $3); }
+ { $$ = ExprCreateAction($1, $3.head); }
| Terminal
{ $$ = $1; }
| OPAREN Expr CPAREN
@@ -651,14 +678,13 @@ Term : MINUS Term
;
ActionList : ActionList COMMA Action
- { $$ = (ExprDef *) AppendStmt((ParseCommon *) $1,
- (ParseCommon *) $3); }
+ { $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
| Action
- { $$ = $1; }
+ { $$.head = $$.last = $1; }
;
Action : FieldSpec OPAREN OptExprList CPAREN
- { $$ = ExprCreateAction($1, $3); }
+ { $$ = ExprCreateAction($1, $3.head); }
;
Lhs : FieldSpec