Question

对ANTL4解析的性能进行了一些讨论，例如：

并且有一个开放的错误报告：

https://github.com/antlr/antlr4/issues/994

要求使用两阶段策略来提高ANTLR4的性能。为此，您首先在SLL模式下调用解析器，并且仅在失败时使用较慢的LL模式。

这适用于小问题，例如问题994中使用的语法：

grammar expr;

expr: ID
    | 'not' expr
    | expr 'and' expr
    | expr 'or' expr
    | expr 'between' expr 'and' expr
    ;

ID: [a-zA-Z_][a-zA-Z_0-9]*;
WS: [ \t\n\r\f]+ -> skip;
ERROR: .;

但是如果语法变得稍微复杂和含糊不清：

/**
 * see https://github.com/antlr/antlr4/issues/994
 */
grammar numexpr;

numexpr: if_statement EOF;

if_statement:
  if_part ( else_part ) ? 'endif';

if_part:
  'if' expr statement_list|
  'if' expr;

else_part:
  'else' statement_list |
  'else';

statement_list:
  statement +;  


statement: if_statement; 

expr: ID
    | VALUE
    | 'not' expr
    | expr '=' expr
    | expr 'and' expr
    | expr 'or' expr
    | expr 'between' expr 'and' expr
    ;

VALUE: [0-9]+;
ID: [a-zA-Z_][a-zA-Z_0-9]*;
WS: [ \t\n\r\f]+ -> skip;
ERROR: .;

使用两阶段策略不再适用。时间结果是：

  2    27 msecs   0,2
  3    95 msecs   3,5
  4    99 msecs   1,0
  5    64 msecs   0,6
  6    87 msecs   1,4
  7   181 msecs   2,1
  8   350 msecs   1,9
  9   822 msecs   2,3
 10  2912 msecs   3,5
 11  7134 msecs   2,4
 12 21420 msecs   3,0
ratio: 2,01

每个＆＃34;并且valuex = x＆＃34;表达部分从输入

开始添加

if Value=0  and not Value0=0 and not Value1=1 endif.

需要对语法进行一些工作才能使其适合SLL。

如何做到这一点？

How do I diagnose ambiguities in my ANTLR4 grammar?

询问相关问题。所以，如果我添加

if (mode.equals(PredictionMode.LL_EXACT_AMBIG_DETECTION)) {
  parserHolder.parser.addErrorListener(new DiagnosticErrorListener());
}

并将doTestParser行更改为：

doTestParser(parserHolder, PredictionMode.LL_EXACT_AMBIG_DETECTION, PredictionMode.LL);

我也没有任何含糊不清的界限，只有：

if Value=0  and not Value0=0 and not Value1=1 endif
line 1:20 reportAttemptingFullContext d=6 (expr), input='andnotValue0'
line 1:12 reportContextSensitivity d=6 (expr), input='and'
line 1:37 reportAttemptingFullContext d=6 (expr), input='andnotValue1'
line 1:29 reportContextSensitivity d=6 (expr), input='and'

请在下面找到显示问题的JUnit测试。它由两个类组成 - 一个抽象基类和一个显示

时序问题的测试类

JUnit Testcase

package com.bitplan.ruleparser;

import java.io.IOException;

import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.Lexer;
import org.antlr.v4.runtime.ParserRuleContext;
import org.junit.Test;

import com.bitplan.expr.exprLexer;
import com.bitplan.expr.exprParser;
import com.bitplan.numexpr.numexprLexer;
import com.bitplan.numexpr.numexprParser;

/**
 * Test the Issue 994 performance
 * 
 * @author wf
 *
 */
public class TestIssue994 extends TestTwoPhaseParser {

  public static class ExprParserHolderFactory extends ParserHolderFactory {

    @Override
    ParserHolder getParserHolder(int index) throws Exception {
      return new ExprParserHolder(index);
    }

  }

  /**
   * 
   * @author wf
   *
   */
  public static class ExprParserHolder extends ParserHolder {

    public ExprParserHolder(int index) throws IOException {
      super(index);
    }

    private exprParser mParser;

    @Override
    protected org.antlr.v4.runtime.Parser getParser(CommonTokenStream tokens) {
      mParser = new exprParser(tokens);
      return mParser;
    }

    @Override
    protected Lexer getLexer(ANTLRInputStream in) {
      return new exprLexer(in);
    }

    @Override
    protected ParserRuleContext parse() {
      return mParser.expr();
    }

    @Override
    protected String getInput(int index) {
      String andClause = "not X0";
      for (int i = 0; i <= index; i++) {
        if (i % 4 == 1) {
          andClause += " or X" + i;
        } else {
          andClause += " and not X" + i;
        }
      }
      return andClause;
    }
  }

  public static class NumExprParserHolderFactory extends ParserHolderFactory {

    @Override
    ParserHolder getParserHolder(int index) throws Exception {
      return new NumExprParserHolder(index);
    }

  }

  /**
   * 
   * @author wf
   *
   */
  public static class NumExprParserHolder extends ParserHolder {

    public NumExprParserHolder(int index) throws IOException {
      super(index);
    }

    private numexprParser mParser;

    @Override
    protected org.antlr.v4.runtime.Parser getParser(CommonTokenStream tokens) {
      mParser = new numexprParser(tokens);
      return mParser;
    }

    @Override
    protected Lexer getLexer(ANTLRInputStream in) {
      return new numexprLexer(in);
    }

    @Override
    protected ParserRuleContext parse() {
      return mParser.numexpr();
    }

    @Override
    protected String getInput(int index) {
      String andClause = "if Value=0 ";
      for (int i = 0; i <= index; i++) {
          andClause += " and not Value" + i+"="+i;
      }
      andClause+=" endif";
      return andClause;
    }
  }


  /**
   * see https://github.com/antlr/antlr4/issues/994
   * 
   * @throws Exception
   */
  @Test
  public void testIssue994() throws Exception {
    super.testDuration(new ExprParserHolderFactory(),60);
  }

  /**
   * see https://github.com/antlr/antlr4/issues/994
   * 
   * @throws Exception
   */
  @Test
  public void testIssue994NumExpr() throws Exception {
    debug=true;
    super.testDuration(new NumExprParserHolderFactory(),12);
  }

}

基础课程

package com.bitplan.ruleparser;

import static org.junit.Assert.assertTrue;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;

import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.BailErrorStrategy;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.Lexer;
import org.antlr.v4.runtime.ParserRuleContext;
import org.antlr.v4.runtime.RecognitionException;
import org.antlr.v4.runtime.atn.PredictionMode;
import org.antlr.v4.runtime.misc.ParseCancellationException;
import org.antlr.v4.runtime.Parser;

/**
 * 
 * @author wf
 *         see https://github.com/antlr/antlr4/issues/994
 */
public abstract class TestTwoPhaseParser {
  static boolean debug = false;

  public static abstract class ParserHolderFactory {
    abstract ParserHolder getParserHolder(int index) throws Exception;
  }

  /**
   * hold a parser and some input;
   */
  public static abstract class ParserHolder {
    ANTLRInputStream in;
    CommonTokenStream tokens;
    Parser parser;
    private Lexer lexer;
    private String input;

    /**
     * create a parser Holder for the given index
     * 
     * @param index
     * @throws IOException
     */
    public ParserHolder(int index) throws IOException {
      input = getInput(index);
      init(input);
    }

    /**
     * create a parser holder for the given input
     * 
     * @param input
     * @throws IOException
     */
    public void init(String input) throws IOException {
      if (debug)
        System.out.println(input);
      in = streamForText(input);
      lexer = getLexer(in);
      CommonTokenStream tokens = new CommonTokenStream(lexer);
      parser = getParser(tokens);
    }

    /**
     * get an input of the given index/size
     * 
     * @param index
     * @return a string to be tested
     */
    protected abstract String getInput(int index);

    protected abstract Parser getParser(CommonTokenStream tokens);

    protected abstract Lexer getLexer(ANTLRInputStream in);

    protected abstract ParserRuleContext parse();

    /**
     * get the ANTLRInputStream for the given text
     * 
     * @param text
     * @return
     * @throws IOException
     */
    public static ANTLRInputStream streamForText(String text)
        throws IOException {
      InputStream stream = new ByteArrayInputStream(
          text.getBytes(StandardCharsets.UTF_8));
      ANTLRInputStream in = new ANTLRInputStream(stream);
      return in;
    }
  }

  /**
   * test how long the parsing takes
   * 
   * @param parserHolderFactory
   * @throws Exception
   */
  public void testDuration(ParserHolderFactory parserHolderFactory, int max)
      throws Exception {
    long prevduration = 0;
    double ratiosum = 0;
    int ratiocount = 0;
    for (int i = 1; i <= max; i++) {
      long start = System.currentTimeMillis();
      ParserHolder parserHolder = parserHolderFactory.getParserHolder(i);
      doTestParser(parserHolder, PredictionMode.SLL, PredictionMode.LL);
      long stop = System.currentTimeMillis();
      long duration = stop - start;
      if (duration < 1)
        duration = 1;
      if (i >= 2) {
        double ratio = duration * 1.0 / (prevduration * 1.0);
        System.out.println(String.format("%3d %5d msecs %5.1f", i, duration,
            ratio));
        ratiosum += ratio;
        ratiocount++;
      }
      prevduration = duration;
    }
    double averageRatio = ratiosum / ratiocount;
    System.out.println(String.format("ratio: %3.2f", averageRatio));
    assertTrue("Performance issue https://github.com/antlr/antlr4/issues/994",
        averageRatio < 1.2);

  }

  /**
   * tes the parser
   * 
   * @param parserHolder
   * @param mode
   * @param fallBackMode
   * @return
   * @throws IOException
   */
  protected ParserRuleContext doTestParser(ParserHolder parserHolder,
      PredictionMode mode, PredictionMode fallBackMode) throws IOException {
    ParserRuleContext result;
    try {
      BailErrorStrategy errorHandler = new BailErrorStrategy();
      parserHolder.parser.setErrorHandler(errorHandler);
      // set PredictionMode
      parserHolder.parser.getInterpreter().setPredictionMode(mode);
      result = parserHolder.parse();
    } catch (Throwable th) {
      if (th instanceof ParseCancellationException) {
        ParseCancellationException pce = (ParseCancellationException) th;
        if (pce.getCause() instanceof RecognitionException) {
          RecognitionException re = (RecognitionException) pce.getCause();
          ParserRuleContext context = (ParserRuleContext) re.getCtx();
          throw context.exception;
        }
      }
      if (fallBackMode != null) {
        parserHolder.tokens.reset();
        parserHolder.parser.reset();
        parserHolder.parser.getInterpreter().setPredictionMode(fallBackMode);
        result = parserHolder.parse();
      } else {
        throw th;
      }
    }
    if (debug) {
      System.out.println(result.toStringTree());
    }
    return result;
  }

}

调试输出

if Value=0  and not Value0=0 and not Value1=1 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] Value) = ([52 12 12 28 17 14] 0)) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value0)) = ([52 55 12 28 17 14] 0))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value1)) = ([52 55 28 17 14] 1)))) endif) <EOF>)
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] Value) = ([52 12 12 12 28 17 14] 0)) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value0)) = ([52 55 12 12 28 17 14] 0))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value1)) = ([52 55 12 28 17 14] 1))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value2)) = ([52 55 28 17 14] 2)))) endif) <EOF>)
  2    27 msecs   0,2
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 28 17 14] 0))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value1)) = ([52 55 12 12 28 17 14] 1))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value2)) = ([52 55 12 28 17 14] 2))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value3)) = ([52 55 28 17 14] 3)))) endif) <EOF>)
  3    96 msecs   3,6
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 28 17 14] 1))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value2)) = ([52 55 12 12 28 17 14] 2))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value3)) = ([52 55 12 28 17 14] 3))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value4)) = ([52 55 28 17 14] 4)))) endif) <EOF>)
  4    99 msecs   1,0
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 12 28 17 14] 1))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value2)) = ([52 55 12 12 12 28 17 14] 2))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value3)) = ([52 55 12 12 28 17 14] 3))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value4)) = ([52 55 12 28 17 14] 4))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value5)) = ([52 55 28 17 14] 5)))) endif) <EOF>)
  5    65 msecs   0,7
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 and not Value6=6 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 12 12 28 17 14] 1))) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value2)) = ([52 55 12 12 12 12 28 17 14] 2))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value3)) = ([52 55 12 12 12 28 17 14] 3))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value4)) = ([52 55 12 12 28 17 14] 4))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value5)) = ([52 55 12 28 17 14] 5))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value6)) = ([52 55 28 17 14] 6)))) endif) <EOF>)
  6    90 msecs   1,4
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 and not Value6=6 and not Value7=7 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 12 12 12 28 17 14] 1))) and ([55 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 28 17 14] Value2)) = ([52 55 12 12 12 12 12 28 17 14] 2))) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value3)) = ([52 55 12 12 12 12 28 17 14] 3))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value4)) = ([52 55 12 12 12 28 17 14] 4))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value5)) = ([52 55 12 12 28 17 14] 5))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value6)) = ([52 55 12 28 17 14] 6))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value7)) = ([52 55 28 17 14] 7)))) endif) <EOF>)
  7   185 msecs   2,1
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 and not Value6=6 and not Value7=7 and not Value8=8 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 12 12 12 12 28 17 14] 1))) and ([55 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 28 17 14] Value2)) = ([52 55 12 12 12 12 12 12 28 17 14] 2))) and ([55 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 28 17 14] Value3)) = ([52 55 12 12 12 12 12 28 17 14] 3))) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value4)) = ([52 55 12 12 12 12 28 17 14] 4))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value5)) = ([52 55 12 12 12 28 17 14] 5))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value6)) = ([52 55 12 12 28 17 14] 6))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value7)) = ([52 55 12 28 17 14] 7))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value8)) = ([52 55 28 17 14] 8)))) endif) <EOF>)
  8   358 msecs   1,9
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 and not Value6=6 and not Value7=7 and not Value8=8 and not Value9=9 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 12 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 12 12 12 12 12 28 17 14] 1))) and ([55 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 28 17 14] Value2)) = ([52 55 12 12 12 12 12 12 12 28 17 14] 2))) and ([55 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 28 17 14] Value3)) = ([52 55 12 12 12 12 12 12 28 17 14] 3))) and ([55 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 28 17 14] Value4)) = ([52 55 12 12 12 12 12 28 17 14] 4))) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value5)) = ([52 55 12 12 12 12 28 17 14] 5))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value6)) = ([52 55 12 12 12 28 17 14] 6))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value7)) = ([52 55 12 12 28 17 14] 7))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value8)) = ([52 55 12 28 17 14] 8))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value9)) = ([52 55 28 17 14] 9)))) endif) <EOF>)
  9   837 msecs   2,3
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 and not Value6=6 and not Value7=7 and not Value8=8 and not Value9=9 and not Value10=10 endif
...
 11  7346 msecs   2,5
if Value=0  and not Value0=0 and not Value1=1 and not Value2=2 and not Value3=3 and not Value4=4 and not Value5=5 and not Value6=6 and not Value7=7 and not Value8=8 and not Value9=9 and not Value10=10 and not Value11=11 and not Value12=12 endif
([] ([14] ([17 14] if ([28 17 14] ([12 28 17 14] ([12 12 28 17 14] ([12 12 12 28 17 14] ([12 12 12 12 28 17 14] ([12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 12 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] Value) = ([52 12 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] 0)) and ([55 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] Value0)) = ([52 55 12 12 12 12 12 12 12 12 12 12 12 12 28 17 14] 0))) and ([55 12 12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 12 12 12 28 17 14] Value1)) = ([52 55 12 12 12 12 12 12 12 12 12 12 12 28 17 14] 1))) and ([55 12 12 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 12 12 28 17 14] Value2)) = ([52 55 12 12 12 12 12 12 12 12 12 12 28 17 14] 2))) and ([55 12 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 12 28 17 14] Value3)) = ([52 55 12 12 12 12 12 12 12 12 12 28 17 14] 3))) and ([55 12 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 12 28 17 14] Value4)) = ([52 55 12 12 12 12 12 12 12 12 28 17 14] 4))) and ([55 12 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 12 28 17 14] Value5)) = ([52 55 12 12 12 12 12 12 12 28 17 14] 5))) and ([55 12 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 12 28 17 14] Value6)) = ([52 55 12 12 12 12 12 12 28 17 14] 6))) and ([55 12 12 12 12 12 28 17 14] ([12 55 12 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 12 28 17 14] Value7)) = ([52 55 12 12 12 12 12 28 17 14] 7))) and ([55 12 12 12 12 28 17 14] ([12 55 12 12 12 12 28 17 14] not ([47 12 55 12 12 12 12 28 17 14] Value8)) = ([52 55 12 12 12 12 28 17 14] 8))) and ([55 12 12 12 28 17 14] ([12 55 12 12 12 28 17 14] not ([47 12 55 12 12 12 28 17 14] Value9)) = ([52 55 12 12 12 28 17 14] 9))) and ([55 12 12 28 17 14] ([12 55 12 12 28 17 14] not ([47 12 55 12 12 28 17 14] Value10)) = ([52 55 12 12 28 17 14] 10))) and ([55 12 28 17 14] ([12 55 12 28 17 14] not ([47 12 55 12 28 17 14] Value11)) = ([52 55 12 28 17 14] 11))) and ([55 28 17 14] ([12 55 28 17 14] not ([47 12 55 28 17 14] Value12)) = ([52 55 28 17 14] 12)))) endif) <EOF>)
 12 21790 msecs   3,0
ratio: 2,01

Answer 1

您应该按照in my article描述的非递归或原始递归规则拆分左递归expr规则。

Answer 2

这是@KvanTTT

建议的分割后的语法

/**
 * see https://github.com/antlr/antlr4/issues/994
 */
grammar primrecexpr;

primrecexpr: if_statement EOF;

if_statement:
  if_part ( else_part ) ? 'endif';

if_part:
  'if' expr statement_list|
  'if' expr;

else_part:
  'else' statement_list |
  'else';

statement_list:
  statement +;  

statement: if_statement; 


expr:
    notexpr
    | expr 'and' expr
    | expr 'or' expr
    ;    

notexpr: 
    'not' notexpr
    | equalexpr;

equalexpr: 
    atomexpr |   
    equalexpr '=' equalexpr
    ;

atomexpr:
   ID
    | VALUE;

VALUE: [0-9]+;
ID: [a-zA-Z_][a-zA-Z_0-9]*;
WS: [ \t\n\r\f]+ -> skip;
ERROR: .;

ANTLR4性能问题

2 个答案: