[groovy] branch master updated: Add option `groovy.antlr4.sll.threshold` for better parsing performance

[su...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

sunlan pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/groovy.git


The following commit(s) were added to refs/heads/master by this push:
     new be40582  Add option `groovy.antlr4.sll.threshold` for better parsing performance
be40582 is described below

commit be4058271cc538dabf607cef8052cc3f0df83419
Author: Daniel Sun <su...@apache.org>
AuthorDate: Sat Aug 28 20:20:43 2021 +0800

    Add option `groovy.antlr4.sll.threshold` for better parsing performance
---
 .../apache/groovy/parser/antlr4/AstBuilder.java    | 26 ++++++++++++++++------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/main/java/org/apache/groovy/parser/antlr4/AstBuilder.java b/src/main/java/org/apache/groovy/parser/antlr4/AstBuilder.java
index 14e2380..83d635f 100644
--- a/src/main/java/org/apache/groovy/parser/antlr4/AstBuilder.java
+++ b/src/main/java/org/apache/groovy/parser/antlr4/AstBuilder.java
@@ -210,6 +210,7 @@ import org.apache.groovy.parser.antlr4.internal.DescriptiveErrorStrategy;
 import org.apache.groovy.parser.antlr4.internal.atnmanager.AtnManager;
 import org.apache.groovy.parser.antlr4.util.StringUtils;
 import org.apache.groovy.util.Maps;
+import org.apache.groovy.util.SystemUtil;
 import org.codehaus.groovy.GroovyBugError;
 import org.codehaus.groovy.antlr.EnumHelper;
 import org.codehaus.groovy.ast.ASTNode;
@@ -404,14 +405,23 @@ public class AstBuilder extends GroovyParserBaseVisitor<Object> {
             // parsing have to wait util clearing is complete.
             AtnManager.READ_LOCK.lock();
             try {
-                result = buildCST(PredictionMode.SLL);
-            } catch (Throwable t) {
-                // if some syntax error occurred in the lexer, no need to retry the powerful LL mode
-                if (t instanceof GroovySyntaxError && GroovySyntaxError.LEXER == ((GroovySyntaxError) t).getSource()) {
-                    throw t;
-                }
+                if (SLL_THRESHOLD > 0 && parser.getInputStream().size() > SLL_THRESHOLD) {
+                    // The more tokens to parse, the more possibility SLL will fail and the more parsing time will waste.
+                    // The option `groovy.antlr4.sll.threshold` could be tuned for better parsing performance, but it is disabled by default.
+                    // if the token count is greater than `groovy.antlr4.sll.threshold`, use ALL directly.
+                    result = buildCST(PredictionMode.LL);
+                } else {
+                    try {
+                        result = buildCST(PredictionMode.SLL);
+                    } catch (Throwable t) {
+                        // if some syntax error occurred in the lexer, no need to retry the powerful LL mode
+                        if (t instanceof GroovySyntaxError && GroovySyntaxError.LEXER == ((GroovySyntaxError) t).getSource()) {
+                            throw t;
+                        }
 
-                result = buildCST(PredictionMode.LL);
+                        result = buildCST(PredictionMode.LL);
+                    }
+                }
             } finally {
                 AtnManager.READ_LOCK.unlock();
             }
@@ -5031,6 +5041,8 @@ public class AstBuilder extends GroovyParserBaseVisitor<Object> {
     private int visitingAssertStatementCount;
     private int visitingArrayInitializerCount;
 
+    private static final int SLL_THRESHOLD = SystemUtil.getIntegerSafe("groovy.antlr4.sll.threshold", -1);
+
     private static final String QUESTION_STR = "?";
     private static final String DOT_STR = ".";
     private static final String SUB_STR = "-";