From 954259ee0489724155f5ae17c1d730dc5cdb5f53 Mon Sep 17 00:00:00 2001
From: Yiling Han <Yiling.Han@ibm.com>
Date: Mon, 3 Jun 2019 17:15:14 -0400
Subject: [PATCH] Add enumerateFields api to create a TypeLayout object

An enumerateFields api is added to create a TypeLayout object based
on given OpaqueClassBlock which iterates through each field to
construct a TypeLayoutEntry that contains DataType, offset and
field name information.

Signed-off-by: Yiling Han <Yiling.Han@ibm.com>
---
 runtime/compiler/env/J9ClassEnv.cpp | 56 +++++++++++++++++++++++++++++
 runtime/compiler/env/J9ClassEnv.hpp | 16 +++++++++
 2 files changed, 72 insertions(+)

diff --git a/runtime/compiler/env/J9ClassEnv.cpp b/runtime/compiler/env/J9ClassEnv.cpp
index db950ec1113..892ab239222 100644
--- a/runtime/compiler/env/J9ClassEnv.cpp
+++ b/runtime/compiler/env/J9ClassEnv.cpp
@@ -29,11 +29,13 @@
 #include "env/ClassEnv.hpp"
 #include "env/CompilerEnv.hpp"
 #include "env/jittypes.h"
+#include "env/TypeLayout.hpp"
 #include "env/VMJ9.h"
 #include "j9.h"
 #include "j9protos.h"
 #include "j9cp.h"
 #include "j9cfg.h"
+#include "j9fieldsInfo.h"
 #include "rommeth.h"
 
 
@@ -409,6 +411,60 @@ J9::ClassEnv::isAnonymousClass(TR::Compilation *comp, TR_OpaqueClassBlock *clazz
    return comp->fej9()->isAnonymousClass(clazz);
    }
 
+const TR::TypeLayout*
+J9::ClassEnv::enumerateFields(TR::Region& region, TR_OpaqueClassBlock * opaqueClazz, TR::Compilation *comp)
+   {  
+   J9Class *clazz = (J9Class*)opaqueClazz;
+   TR_VMFieldsInfo fieldsInfo(comp, clazz, 1, stackAlloc);
+   ListIterator<TR_VMField> iter(fieldsInfo.getFields());
+   TR::TypeLayoutBuilder tlb(region);
+   for (TR_VMField *field = iter.getFirst(); field; field = iter.getNext())
+      {
+      char *signature = field->signature;
+      char charSignature = *signature;
+      TR::DataType dataType;
+      switch(charSignature)
+         {
+         case 'Z': 
+         case 'B': 
+         case 'C': 
+         case 'S': 
+         case 'I':
+            {
+            dataType = TR::Int32;
+            break;
+            }
+         case 'J':
+            {
+            dataType = TR::Int64;
+            break;
+            }
+         case 'F':
+            {
+            dataType = TR::Float;
+            break;
+            }
+         case 'D':
+            {
+            dataType = TR::Double;
+            break;
+            }
+         case 'L': 
+         case '[':
+            {
+            dataType = TR::Address;
+            break;
+            }
+         }
+      size_t nameSize = strlen(field->name)+1;
+      char *fieldName = new (region) char[nameSize];
+      strncpy(fieldName, field->name, nameSize);
+      TR_ASSERT_FATAL(fieldName[nameSize-1] == '\0', "fieldName buffer was too small.");
+      int32_t offset = field->offset + TR::Compiler->om.objectHeaderSizeInBytes();
+      tlb.add(TR::TypeLayoutEntry(dataType, offset, fieldName));
+      }
+   return tlb.build();
+   }
 
 int32_t
 J9::ClassEnv::vTableSlot(TR::Compilation *comp, TR_OpaqueMethodBlock *method, TR_OpaqueClassBlock *clazz)
diff --git a/runtime/compiler/env/J9ClassEnv.hpp b/runtime/compiler/env/J9ClassEnv.hpp
index e7cf07aa092..e750f8510bb 100644
--- a/runtime/compiler/env/J9ClassEnv.hpp
+++ b/runtime/compiler/env/J9ClassEnv.hpp
@@ -41,6 +41,8 @@ namespace J9 { typedef J9::ClassEnv ClassEnvConnector; }
 #include "j9.h"
 
 namespace TR { class SymbolReference; }
+namespace TR { class TypeLayout; }
+namespace TR { class Region; }
 
 namespace J9
 {
@@ -102,6 +104,20 @@ class OMR_EXTENSIBLE ClassEnv : public OMR::ClassEnvConnector
    bool jitStaticsAreSame(TR::Compilation *comp, TR_ResolvedMethod * method1, int32_t cpIndex1, TR_ResolvedMethod * method2, int32_t cpIndex2);
    bool jitFieldsAreSame(TR::Compilation *comp, TR_ResolvedMethod * method1, int32_t cpIndex1, TR_ResolvedMethod * method2, int32_t cpIndex2, int32_t isStatic);
 
+   /** \brief
+    *	    Populates a TypeLayout object.
+    *
+    *  \param region
+    *     The region used to allocate TypeLayout.
+    * 
+    *  \param opaqueClazz
+    *     Class of the type whose layout needs to be populated.
+    * 
+    *  \return
+    *     Returns a pointer to the TypeLayout object populated.
+    */
+   const TR::TypeLayout* enumerateFields(TR::Region& region, TR_OpaqueClassBlock * clazz, TR::Compilation *comp);
+
    uintptrj_t getArrayElementWidthInBytes(TR::Compilation *comp, TR_OpaqueClassBlock* arrayClass);
 
    uintptrj_t persistentClassPointerFromClassPointer(TR::Compilation *comp, TR_OpaqueClassBlock *clazz);