forked from NUDT-compiler/nudt-compiler-cpp
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99 lines
1.4 KiB
99 lines
1.4 KiB
// SysY 子集语法：支持形如
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// int main() { int a = 1; int b = 2; return a + b; }
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// 的最小返回表达式编译。
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// 后续需要自行添加
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grammar SysY;
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/*===-------------------------------------------===*/
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/* Lexer rules */
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/*===-------------------------------------------===*/
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INT: 'int';
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RETURN: 'return';
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ASSIGN: '=';
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ADD: '+';
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LPAREN: '(';
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RPAREN: ')';
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LBRACE: '{';
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RBRACE: '}';
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SEMICOLON: ';';
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ID: [a-zA-Z_][a-zA-Z_0-9]*;
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ILITERAL: [0-9]+;
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WS: [ \t\r\n] -> skip;
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LINECOMMENT: '//' ~[\r\n]* -> skip;
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BLOCKCOMMENT: '/*' .*? '*/' -> skip;
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/*===-------------------------------------------===*/
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/* Syntax rules */
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/*===-------------------------------------------===*/
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compUnit
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: funcDef EOF
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;
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decl
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: btype varDef SEMICOLON
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;
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btype
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: INT
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;
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varDef
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: lValue (ASSIGN initValue)?
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;
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initValue
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: exp
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;
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funcDef
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: funcType ID LPAREN RPAREN blockStmt
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;
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funcType
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: INT
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;
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blockStmt
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: LBRACE blockItem* RBRACE
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;
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blockItem
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: decl
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| stmt
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;
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stmt
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: returnStmt
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;
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returnStmt
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: RETURN exp SEMICOLON
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;
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exp
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: LPAREN exp RPAREN # parenExp
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| var # varExp
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| number # numberExp
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| exp ADD exp # additiveExp
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;
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var
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: ID
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;
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lValue
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: ID
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;
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number
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: ILITERAL
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;
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