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>
master
Ran Benita
parent
f9b95c06c1
commit
7c42945e04
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@ -55,20 +55,6 @@
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#include "ast-build.h"
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#include "include.h"
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ParseCommon *
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AppendStmt(ParseCommon *to, ParseCommon *append)
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{
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ParseCommon *iter;
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if (!to)
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return append;
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for (iter = to; iter->next; iter = iter->next);
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iter->next = append;
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return to;
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}
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static ExprDef *
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ExprCreate(enum expr_op_type op, enum expr_value_type type, size_t size)
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{
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@ -568,7 +554,7 @@ XkbFileFromComponents(struct xkb_context *ctx,
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enum xkb_file_type type;
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IncludeStmt *include = NULL;
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XkbFile *file = NULL;
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ParseCommon *defs = NULL;
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ParseCommon *defs = NULL, *defsLast = NULL;
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for (type = FIRST_KEYMAP_FILE_TYPE; type <= LAST_KEYMAP_FILE_TYPE; type++) {
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include = IncludeCreate(ctx, components[type], MERGE_DEFAULT);
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@ -581,7 +567,10 @@ XkbFileFromComponents(struct xkb_context *ctx,
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goto err;
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}
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defs = AppendStmt(defs, &file->common);
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if (!defs)
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defsLast = defs = &file->common;
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else
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defsLast = defsLast->next = &file->common;
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}
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file = XkbFileCreate(FILE_TYPE_KEYMAP, NULL, defs, 0);
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@ -27,9 +27,6 @@
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#ifndef XKBCOMP_AST_BUILD_H
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#define XKBCOMP_AST_BUILD_H
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ParseCommon *
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AppendStmt(ParseCommon *to, ParseCommon *append);
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ExprDef *
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ExprCreateString(xkb_atom_t str);
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@ -169,9 +169,13 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
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enum xkb_map_flags mapFlags;
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xkb_keysym_t keysym;
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ParseCommon *any;
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struct { ParseCommon *head; ParseCommon *last; } anyList;
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ExprDef *expr;
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struct { ExprDef *head; ExprDef *last; } exprList;
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VarDef *var;
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struct { VarDef *head; VarDef *last; } varList;
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VModDef *vmod;
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struct { VModDef *head; VModDef *last; } vmodList;
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InterpDef *interp;
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KeyTypeDef *keyType;
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SymbolsDef *syms;
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@ -183,6 +187,7 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
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KeyAliasDef *keyAlias;
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void *geom;
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XkbFile *file;
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struct { XkbFile *head; XkbFile *last; } fileList;
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}
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%type <num> INTEGER FLOAT
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@ -196,11 +201,15 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
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%type <str> MapName OptMapName
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%type <atom> FieldSpec Ident Element String
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%type <keysym> KeySym
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%type <any> DeclList Decl
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%type <expr> OptExprList ExprList Expr Term Lhs Terminal ArrayInit KeySyms
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%type <expr> OptKeySymList KeySymList Action ActionList Coord CoordList
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%type <var> VarDecl VarDeclList SymbolsBody SymbolsVarDecl
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%type <vmod> VModDecl VModDefList VModDef
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%type <any> Decl
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%type <anyList> DeclList
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%type <expr> Expr Term Lhs Terminal ArrayInit KeySyms
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%type <expr> OptKeySymList KeySymList Action Coord CoordList
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%type <exprList> OptExprList ExprList ActionList
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%type <var> VarDecl SymbolsVarDecl
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%type <varList> VarDeclList SymbolsBody
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%type <vmod> VModDef
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%type <vmodList> VModDefList VModDecl
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%type <interp> InterpretDecl InterpretMatch
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%type <keyType> KeyTypeDecl
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%type <syms> SymbolsDecl
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@ -213,15 +222,19 @@ resolve_keysym(const char *name, xkb_keysym_t *sym_rtrn)
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%type <geom> ShapeDecl SectionDecl SectionBody SectionBodyItem RowBody RowBodyItem
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%type <geom> Keys Key OverlayDecl OverlayKeyList OverlayKey OutlineList OutlineInList
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%type <geom> DoodadDecl
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%type <file> XkbFile XkbMapConfigList XkbMapConfig
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%type <file> XkbFile XkbMapConfig
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%type <fileList> XkbMapConfigList
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%type <file> XkbCompositeMap
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%destructor { FreeStmt((ParseCommon *) $$); }
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<any> <expr> <var> <vmod> <interp> <keyType> <syms> <modMask> <groupCompat>
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<ledMap> <ledName> <keyCode> <keyAlias>
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%destructor { FreeStmt((ParseCommon *) $$.head); }
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<anyList> <exprList> <varList> <vmodList>
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/* The destructor also runs on the start symbol when the parser *succeeds*.
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* The `if` here catches this case. */
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%destructor { if (!param->rtrn) FreeXkbFile($$); } <file>
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%destructor { FreeXkbFile($$.head); } <fileList>
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%destructor { free($$); } <str>
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%%
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@ -249,7 +262,7 @@ XkbFile : XkbCompositeMap
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XkbCompositeMap : OptFlags XkbCompositeType OptMapName OBRACE
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XkbMapConfigList
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CBRACE SEMI
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{ $$ = XkbFileCreate($2, $3, (ParseCommon *) $5, $1); }
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{ $$ = XkbFileCreate($2, $3, (ParseCommon *) $5.head, $1); }
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;
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XkbCompositeType: XKB_KEYMAP { $$ = FILE_TYPE_KEYMAP; }
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@ -258,17 +271,16 @@ XkbCompositeType: XKB_KEYMAP { $$ = FILE_TYPE_KEYMAP; }
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;
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XkbMapConfigList : XkbMapConfigList XkbMapConfig
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{ $$ = (XkbFile *) AppendStmt((ParseCommon *) $1,
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(ParseCommon *) $2); }
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{ $$.head = $1.head; $$.last->common.next = &$2->common; $$.last = $2; }
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| XkbMapConfig
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{ $$ = $1; }
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{ $$.head = $$.last = $1; }
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;
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XkbMapConfig : OptFlags FileType OptMapName OBRACE
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DeclList
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CBRACE SEMI
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{
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$$ = XkbFileCreate($2, $3, $5, $1);
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$$ = XkbFileCreate($2, $3, $5.head, $1);
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}
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;
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@ -298,8 +310,27 @@ Flag : PARTIAL { $$ = MAP_IS_PARTIAL; }
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;
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DeclList : DeclList Decl
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{ $$ = AppendStmt($1, $2); }
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| { $$ = NULL; }
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{
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/*
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* TODO: This is needed because of VModDecl, which
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* is a list and is "inlined" into the DeclList.
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* Should change to avoid the O(N)-append behavior,
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* like we do in the other lists.
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*/
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if ($2) {
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if (!$1.head)
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$$.head = $2;
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else
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$$.head = $1.head;
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if (!$1.last)
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$$.last = $2;
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else
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$$.last = $1.last->next = $2;
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while ($$.last->next)
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$$.last = $$.last->next;
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}
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}
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| { $$.head = $$.last = NULL; }
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;
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Decl : OptMergeMode VarDecl
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@ -309,9 +340,9 @@ Decl : OptMergeMode VarDecl
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}
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| OptMergeMode VModDecl
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{
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for (VModDef *vmod = $2; vmod; vmod = (VModDef *) vmod->common.next)
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for (VModDef *vmod = $2.head; vmod; vmod = (VModDef *) vmod->common.next)
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vmod->merge = $1;
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$$ = (ParseCommon *) $2;
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$$ = (ParseCommon *) $2.head;
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}
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| OptMergeMode InterpretDecl
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{
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@ -389,10 +420,9 @@ VModDecl : VIRTUAL_MODS VModDefList SEMI
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;
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VModDefList : VModDefList COMMA VModDef
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{ $$ = (VModDef *) AppendStmt((ParseCommon *) $1,
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(ParseCommon *) $3); }
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{ $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
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| VModDef
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{ $$ = $1; }
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{ $$.head = $$.last = $1; }
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;
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VModDef : Ident
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@ -404,7 +434,7 @@ VModDef : Ident
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InterpretDecl : INTERPRET InterpretMatch OBRACE
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VarDeclList
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CBRACE SEMI
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{ $2->def = $4; $$ = $2; }
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{ $2->def = $4.head; $$ = $2; }
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;
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InterpretMatch : KeySym PLUS Expr
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@ -414,30 +444,28 @@ InterpretMatch : KeySym PLUS Expr
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;
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VarDeclList : VarDeclList VarDecl
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{ $$ = (VarDef *) AppendStmt((ParseCommon *) $1,
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(ParseCommon *) $2); }
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{ $$.head = $1.head; $$.last->common.next = &$2->common; $$.last = $2; }
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| VarDecl
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{ $$ = $1; }
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{ $$.head = $$.last = $1; }
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;
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KeyTypeDecl : TYPE String OBRACE
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VarDeclList
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CBRACE SEMI
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{ $$ = KeyTypeCreate($2, $4); }
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{ $$ = KeyTypeCreate($2, $4.head); }
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;
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SymbolsDecl : KEY KEYNAME OBRACE
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SymbolsBody
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CBRACE SEMI
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{ $$ = SymbolsCreate($2, $4); }
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{ $$ = SymbolsCreate($2, $4.head); }
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;
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SymbolsBody : SymbolsBody COMMA SymbolsVarDecl
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{ $$ = (VarDef *) AppendStmt((ParseCommon *) $1,
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(ParseCommon *) $3); }
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{ $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
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| SymbolsVarDecl
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{ $$ = $1; }
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| { $$ = NULL; }
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{ $$.head = $$.last = $1; }
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| { $$.head = $$.last = NULL; }
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;
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SymbolsVarDecl : Lhs EQUALS Expr { $$ = VarCreate($1, $3); }
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@ -450,7 +478,7 @@ SymbolsVarDecl : Lhs EQUALS Expr { $$ = VarCreate($1, $3); }
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ArrayInit : OBRACKET OptKeySymList CBRACKET
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{ $$ = $2; }
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| OBRACKET ActionList CBRACKET
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{ $$ = ExprCreateActionList($2); }
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{ $$ = ExprCreateActionList($2.head); }
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;
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GroupCompatDecl : GROUP Integer EQUALS Expr SEMI
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@ -458,11 +486,11 @@ GroupCompatDecl : GROUP Integer EQUALS Expr SEMI
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;
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ModMapDecl : MODIFIER_MAP Ident OBRACE ExprList CBRACE SEMI
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{ $$ = ModMapCreate($2, $4); }
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{ $$ = ModMapCreate($2, $4.head); }
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;
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LedMapDecl: INDICATOR String OBRACE VarDeclList CBRACE SEMI
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{ $$ = LedMapCreate($2, $4); }
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{ $$ = LedMapCreate($2, $4.head); }
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;
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LedNameDecl: INDICATOR Integer EQUALS Expr SEMI
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@ -513,7 +541,7 @@ Keys : Keys COMMA Key { $$ = NULL; }
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Key : KEYNAME
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{ $$ = NULL; }
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| OBRACE ExprList CBRACE
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{ FreeStmt((ParseCommon *) $2); $$ = NULL; }
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{ FreeStmt((ParseCommon *) $2.head); $$ = NULL; }
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;
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OverlayDecl : OVERLAY String OBRACE OverlayKeyList CBRACE SEMI
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@ -552,7 +580,7 @@ Coord : OBRACKET SignedNumber COMMA SignedNumber CBRACKET
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;
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DoodadDecl : DoodadType String OBRACE VarDeclList CBRACE SEMI
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{ FreeStmt((ParseCommon *) $4); $$ = NULL; }
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{ FreeStmt((ParseCommon *) $4.head); $$ = NULL; }
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;
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DoodadType : TEXT { $$ = 0; }
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@ -608,14 +636,13 @@ MergeMode : INCLUDE { $$ = MERGE_DEFAULT; }
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;
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OptExprList : ExprList { $$ = $1; }
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| { $$ = NULL; }
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| { $$.head = $$.last = NULL; }
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;
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ExprList : ExprList COMMA Expr
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{ $$ = (ExprDef *) AppendStmt((ParseCommon *) $1,
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(ParseCommon *) $3); }
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{ $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
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| Expr
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{ $$ = $1; }
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{ $$.head = $$.last = $1; }
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;
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Expr : Expr DIVIDE Expr
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@ -643,7 +670,7 @@ Term : MINUS Term
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| Lhs
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{ $$ = $1; }
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| FieldSpec OPAREN OptExprList CPAREN %prec OPAREN
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{ $$ = ExprCreateAction($1, $3); }
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{ $$ = ExprCreateAction($1, $3.head); }
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| Terminal
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{ $$ = $1; }
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| OPAREN Expr CPAREN
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@ -651,14 +678,13 @@ Term : MINUS Term
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;
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ActionList : ActionList COMMA Action
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{ $$ = (ExprDef *) AppendStmt((ParseCommon *) $1,
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(ParseCommon *) $3); }
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{ $$.head = $1.head; $$.last->common.next = &$3->common; $$.last = $3; }
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| Action
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{ $$ = $1; }
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{ $$.head = $$.last = $1; }
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;
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Action : FieldSpec OPAREN OptExprList CPAREN
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{ $$ = ExprCreateAction($1, $3); }
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{ $$ = ExprCreateAction($1, $3.head); }
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;
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Lhs : FieldSpec
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