From febbd998ee72054353e816e9b7b588c9ea2c0500 Mon Sep 17 00:00:00 2001
From: Shaojin Wen <swen@openjdk.org>
Date: Fri, 6 Sep 2024 12:01:01 +0000
Subject: [PATCH] 8339168: Optimize ClassFile Util slotSize

Reviewed-by: liach, redestad
---
 .../classfile/impl/DirectMethodBuilder.java   |  3 ++
 .../jdk/internal/classfile/impl/Util.java     | 33 ++++++++++---------
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/java.base/share/classes/jdk/internal/classfile/impl/DirectMethodBuilder.java b/src/java.base/share/classes/jdk/internal/classfile/impl/DirectMethodBuilder.java
index f79eb0af0cb..77b937eb74a 100644
--- a/src/java.base/share/classes/jdk/internal/classfile/impl/DirectMethodBuilder.java
+++ b/src/java.base/share/classes/jdk/internal/classfile/impl/DirectMethodBuilder.java
@@ -98,6 +98,9 @@ public final class DirectMethodBuilder
 
     @Override
     public int parameterSlot(int paramNo) {
+        if (paramNo == 0) {
+            return ((flags & ClassFile.ACC_STATIC) != 0) ? 0 : 1;
+        }
         if (parameterSlots == null)
             parameterSlots = Util.parseParameterSlots(methodFlags(), methodTypeSymbol());
         return parameterSlots[paramNo];
diff --git a/src/java.base/share/classes/jdk/internal/classfile/impl/Util.java b/src/java.base/share/classes/jdk/internal/classfile/impl/Util.java
index fee55249bbb..d4d91d9aab1 100644
--- a/src/java.base/share/classes/jdk/internal/classfile/impl/Util.java
+++ b/src/java.base/share/classes/jdk/internal/classfile/impl/Util.java
@@ -55,6 +55,10 @@ import java.lang.classfile.attribute.CodeAttribute;
 import java.lang.classfile.components.ClassPrinter;
 import java.util.function.Consumer;
 
+import static jdk.internal.constant.PrimitiveClassDescImpl.CD_double;
+import static jdk.internal.constant.PrimitiveClassDescImpl.CD_long;
+import static jdk.internal.constant.PrimitiveClassDescImpl.CD_void;
+
 /**
  * Helper to create and manipulate type descriptors, where type descriptors are
  * represented as JVM type descriptor strings and symbols are represented as
@@ -105,9 +109,11 @@ public class Util {
     }
 
     public static int parameterSlots(MethodTypeDesc mDesc) {
-        int count = 0;
-        for (int i = 0; i < mDesc.parameterCount(); i++) {
-            count += slotSize(mDesc.parameterType(i));
+        int count = mDesc.parameterCount();
+        for (int i = count - 1; i >= 0; i--) {
+            if (isDoubleSlot(mDesc.parameterType(i))) {
+                count++;
+            }
         }
         return count;
     }
@@ -117,17 +123,13 @@ public class Util {
         int count = ((flags & ACC_STATIC) != 0) ? 0 : 1;
         for (int i = 0; i < result.length; i++) {
             result[i] = count;
-            count += slotSize(mDesc.parameterType(i));
+            count += paramSlotSize(mDesc.parameterType(i));
         }
         return result;
     }
 
     public static int maxLocals(int flags, MethodTypeDesc mDesc) {
-        int count = ((flags & ACC_STATIC) != 0) ? 0 : 1;
-        for (int i = 0; i < mDesc.parameterCount(); i++) {
-            count += slotSize(mDesc.parameterType(i));
-        }
-        return count;
+        return parameterSlots(mDesc) + ((flags & ACC_STATIC) == 0 ? 1 : 0) ;
     }
 
     /**
@@ -252,16 +254,15 @@ public class Util {
     }
 
     public static int slotSize(ClassDesc desc) {
-        return switch (desc.descriptorString().charAt(0)) {
-            case 'V' -> 0;
-            case 'D','J' -> 2;
-            default -> 1;
-        };
+        return desc == CD_void ? 0 : isDoubleSlot(desc) ? 2 : 1;
+    }
+
+    public static int paramSlotSize(ClassDesc desc) {
+        return isDoubleSlot(desc) ? 2 : 1;
     }
 
     public static boolean isDoubleSlot(ClassDesc desc) {
-        char ch = desc.descriptorString().charAt(0);
-        return ch == 'D' || ch == 'J';
+        return desc == CD_double || desc == CD_long;
     }
 
     public static void dumpMethod(SplitConstantPool cp,