From fbe2629303bcee5855673b7e37d8c49f19dc9849 Mon Sep 17 00:00:00 2001
From: Shaojin Wen <swen@openjdk.org>
Date: Fri, 6 Sep 2024 18:37:29 +0000
Subject: [PATCH] 8339635: StringConcatFactory optimization for CompactStrings
 off

Reviewed-by: liach
---
 src/java.base/share/classes/java/lang/System.java          | 4 ++++
 .../classes/java/lang/invoke/StringConcatFactory.java      | 7 ++++++-
 .../share/classes/jdk/internal/access/JavaLangAccess.java  | 5 +++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/java.base/share/classes/java/lang/System.java b/src/java.base/share/classes/java/lang/System.java
index 368db1928f113..2521eb0149398 100644
--- a/src/java.base/share/classes/java/lang/System.java
+++ b/src/java.base/share/classes/java/lang/System.java
@@ -2642,6 +2642,10 @@ public Object stringConcat1(String[] constants) {
                 return new StringConcatHelper.Concat1(constants);
             }
 
+            public byte stringInitCoder() {
+                return String.COMPACT_STRINGS ? String.LATIN1 : String.UTF16;
+            }
+
             public int getCharsLatin1(long i, int index, byte[] buf) {
                 return StringLatin1.getChars(i, index, buf);
             }
diff --git a/src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java b/src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java
index 8486ede3a272c..6c8d72cec4e85 100644
--- a/src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java
+++ b/src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java
@@ -1196,9 +1196,14 @@ private static MethodTypeDesc prependArgs(MethodType concatArgs) {
 
         /**
          * Construct the MethodType of the coder method. The first parameter is the initialized coder.
-         * Only parameter types which can be UTF16 are added. Returns null if no such parameter exists.
+         * Only parameter types which can be UTF16 are added.
+         * Returns null if no such parameter exists or CompactStrings is off.
          */
         private static MethodTypeDesc coderArgsIfMaybeUTF16(MethodType concatArgs) {
+            if (JLA.stringInitCoder() != 0) {
+                return null;
+            }
+
             int parameterCount = concatArgs.parameterCount();
 
             int maybeUTF16Count = 0;
diff --git a/src/java.base/share/classes/jdk/internal/access/JavaLangAccess.java b/src/java.base/share/classes/jdk/internal/access/JavaLangAccess.java
index 98238af383174..dbe116599e099 100644
--- a/src/java.base/share/classes/jdk/internal/access/JavaLangAccess.java
+++ b/src/java.base/share/classes/jdk/internal/access/JavaLangAccess.java
@@ -459,6 +459,11 @@ public interface JavaLangAccess {
 
     Object stringConcat1(String[] constants);
 
+    /**
+     * Get the string initial coder, When COMPACT_STRINGS is on, it returns 0, and when it is off, it returns 1.
+     */
+    byte stringInitCoder();
+
     /**
      * Join strings
      */