diff --git a/hat/backends/ffi/cuda/src/main/java/hat/backend/ffi/CudaBackend.java b/hat/backends/ffi/cuda/src/main/java/hat/backend/ffi/CudaBackend.java
index 88db7a801db..99c68677770 100644
--- a/hat/backends/ffi/cuda/src/main/java/hat/backend/ffi/CudaBackend.java
+++ b/hat/backends/ffi/cuda/src/main/java/hat/backend/ffi/CudaBackend.java
@@ -412,14 +412,7 @@ String createPTX(KernelCallGraph kernelCallGraph,  Object... args){
         builder.ptxHeader(major, minor, target, addressSize);
         out.append(builder.getTextAndReset());
 
-        if (CallGraph.usingModuleOp) {
-            System.out.println("Using ModuleOp for CudaBackend");
-            kernelCallGraph.moduleOp.functionTable().forEach((_, funcOp) -> {
-                CoreOp.FuncOp loweredFunc = OpTk.lower(funcOp);
-                loweredFunc = transformPTXPtrs(kernelCallGraph.computeContext.accelerator.lookup,loweredFunc, argsMap, usedMathFns);
-                invokedMethods.append(createFunction(new PTXHATKernelBuilder(addressSize).nl().nl(), loweredFunc, false));
-            });
-        } else {
+        if (CallGraph.noModuleOp) {
             System.out.println("NOT using ModuleOp for CudaBackend");
             for (KernelCallGraph.KernelReachableResolvedMethodCall k : kernelCallGraph.kernelReachableResolvedStream().toList()) {
                 CoreOp.FuncOp calledFunc = k.funcOp();
@@ -427,6 +420,13 @@ String createPTX(KernelCallGraph kernelCallGraph,  Object... args){
                 loweredFunc = transformPTXPtrs(kernelCallGraph.computeContext.accelerator.lookup,loweredFunc, argsMap, usedMathFns);
                 invokedMethods.append(createFunction(new PTXHATKernelBuilder(addressSize).nl().nl(), loweredFunc, false));
             }
+        } else {
+            System.out.println("Using ModuleOp for CudaBackend");
+            kernelCallGraph.moduleOp.functionTable().forEach((_, funcOp) -> {
+                CoreOp.FuncOp loweredFunc = OpTk.lower(funcOp);
+                loweredFunc = transformPTXPtrs(kernelCallGraph.computeContext.accelerator.lookup,loweredFunc, argsMap, usedMathFns);
+                invokedMethods.append(createFunction(new PTXHATKernelBuilder(addressSize).nl().nl(), loweredFunc, false));
+            });
         }
 
         lowered = transformPTXPtrs(kernelCallGraph.computeContext.accelerator.lookup,lowered, argsMap, usedMathFns);
diff --git a/hat/backends/ffi/mock/src/main/java/hat/backend/ffi/MockBackend.java b/hat/backends/ffi/mock/src/main/java/hat/backend/ffi/MockBackend.java
index 8fbc3929d30..e933622445e 100644
--- a/hat/backends/ffi/mock/src/main/java/hat/backend/ffi/MockBackend.java
+++ b/hat/backends/ffi/mock/src/main/java/hat/backend/ffi/MockBackend.java
@@ -56,14 +56,14 @@ public void dispatchKernel(KernelCallGraph kernelCallGraph, NDRange ndRange, Obj
         // Here we receive a callgraph from the kernel entrypoint
         // The first time we see this we need to convert the kernel entrypoint
         // and rechable methods to a form that our mock backend can execute.
-        if (CallGraph.usingModuleOp) {
-            System.out.println("Using ModuleOp for MockBackend");
-            kernelCallGraph.moduleOp.functionTable().forEach((_, funcOp) -> {
-            });
-        } else {
+        if (CallGraph.noModuleOp) {
             System.out.println("NOT using ModuleOp for MockBackend");
             kernelCallGraph.kernelReachableResolvedStream().forEach(kr -> {
 
+            });
+        } else {
+            System.out.println("Using ModuleOp for MockBackend");
+            kernelCallGraph.moduleOp.functionTable().forEach((_, funcOp) -> {
             });
         }
     }
diff --git a/hat/backends/ffi/shared/src/main/java/hat/backend/ffi/C99FFIBackend.java b/hat/backends/ffi/shared/src/main/java/hat/backend/ffi/C99FFIBackend.java
index fbe1a6475aa..46e6fa52f53 100644
--- a/hat/backends/ffi/shared/src/main/java/hat/backend/ffi/C99FFIBackend.java
+++ b/hat/backends/ffi/shared/src/main/java/hat/backend/ffi/C99FFIBackend.java
@@ -233,14 +233,7 @@ public <T extends C99HATKernelBuilder<T>> String createCode(KernelCallGraph kern
                         kernelCallGraph.entrypoint.funcOp());
 
         // Sorting by rank ensures we don't need forward declarations
-        if (CallGraph.usingModuleOp) {
-            System.out.println("Using ModuleOp for C99FFIBackend");
-            kernelCallGraph.moduleOp.functionTable()
-                    .forEach((_, funcOp) -> builder
-                            .nl()
-                            .kernelMethod(buildContext,funcOp)
-                            .nl());
-        } else {
+        if (CallGraph.noModuleOp) {
             System.out.println("NOT using ModuleOp for C99FFIBackend");
             kernelCallGraph.kernelReachableResolvedStream().sorted((lhs, rhs) -> rhs.rank - lhs.rank)
                     .forEach(kernelReachableResolvedMethod ->
@@ -248,6 +241,13 @@ public <T extends C99HATKernelBuilder<T>> String createCode(KernelCallGraph kern
                                     .nl()
                                     .kernelMethod(buildContext,kernelReachableResolvedMethod.funcOp())
                                     .nl());
+        } else {
+          System.out.println("Using ModuleOp for C99FFIBackend");
+            kernelCallGraph.moduleOp.functionTable()
+                    .forEach((_, funcOp) -> builder
+                            .nl()
+                            .kernelMethod(buildContext,funcOp)
+                            .nl());
         }
 
         builder.nl().kernelEntrypoint(buildContext, args).nl();
diff --git a/hat/core/src/main/java/hat/BufferTagger.java b/hat/core/src/main/java/hat/BufferTagger.java
new file mode 100644
index 00000000000..f0341f9dc8a
--- /dev/null
+++ b/hat/core/src/main/java/hat/BufferTagger.java
@@ -0,0 +1,214 @@
+package hat;
+
+import hat.buffer.Buffer;
+import hat.ifacemapper.MappableIface;
+import jdk.incubator.code.*;
+import jdk.incubator.code.analysis.Inliner;
+import jdk.incubator.code.analysis.SSA;
+import jdk.incubator.code.dialect.core.CoreOp;
+import jdk.incubator.code.dialect.java.*;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Method;
+import java.util.*;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public class BufferTagger {
+    static HashMap<Value, AccessType> accessMap = new HashMap<>();
+    static HashMap<Value, Value> remappedVals = new HashMap<>(); // maps values to their "root" parameter/value
+    static HashMap<Block, List<Block.Parameter>> blockParams = new HashMap<>(); // holds block parameters for easy lookup
+
+    public enum AccessType {
+        NA(1),
+        RO(2),
+        WO(4),
+        RW(6),
+        NOT_BUFFER(0);
+
+        public final int value;
+        AccessType(int i) {
+            value = i;
+        }
+    }
+
+    // generates a list of AccessTypes matching the given FuncOp's parameter order
+    public static ArrayList<AccessType> getAccessList(MethodHandles.Lookup l, CoreOp.FuncOp f) {
+        CoreOp.FuncOp inlinedFunc = inlineLoop(l, f);
+        buildAccessMap(l, inlinedFunc);
+        ArrayList<AccessType> accessList = new ArrayList<>();
+        for (Block.Parameter p : inlinedFunc.body().entryBlock().parameters()) {
+            if (accessMap.containsKey(p)) {
+                accessList.add(accessMap.get(p)); // is an accessed buffer
+            } else if (getClass(l, p.type()) instanceof Class<?> c && MappableIface.class.isAssignableFrom(c)) {
+                accessList.add(AccessType.NA); // is a buffer but not accessed
+            } else {
+                accessList.add(AccessType.NOT_BUFFER); // is not a buffer
+            }
+        }
+        return accessList;
+    }
+
+    // inlines functions found in FuncOp f until no more inline-able functions are present
+    public static CoreOp.FuncOp inlineLoop(MethodHandles.Lookup l, CoreOp.FuncOp f) {
+        CoreOp.FuncOp ssaFunc = SSA.transform(f.transform(OpTransformer.LOWERING_TRANSFORMER));
+        AtomicBoolean changed = new AtomicBoolean(true);
+        while (changed.get()) { // loop until no more inline-able functions
+            changed.set(false);
+            ssaFunc = ssaFunc.transform((bb, op) -> {
+                if (op instanceof JavaOp.InvokeOp iop) {
+                    MethodRef methodRef = iop.invokeDescriptor();
+                    Method invokeOpCalledMethod;
+                    try {
+                        invokeOpCalledMethod = methodRef.resolveToMethod(l, iop.invokeKind());
+                    } catch (ReflectiveOperationException _) {
+                        throw new IllegalStateException("Could not resolve invokeOp to method");
+                    }
+                    if (invokeOpCalledMethod instanceof Method method) { // if method isn't a buffer access (is code reflected)
+                        if (Op.ofMethod(method).isPresent()) {
+                            CoreOp.FuncOp inline = Op.ofMethod(method).get(); // method to be inlined
+                            CoreOp.FuncOp ssaInline = SSA.transform(inline.transform(OpTransformer.LOWERING_TRANSFORMER));
+
+                            Block.Builder exit = Inliner.inline(bb, ssaInline, bb.context().getValues(iop.operands()), (_, v) -> {
+                                if (v != null) bb.context().mapValue(iop.result(), v);
+                            });
+
+                            if (!exit.parameters().isEmpty()) {
+                                bb.context().mapValue(iop.result(), exit.parameters().getFirst());
+                            }
+                            changed.set(true);
+                            return exit.rebind(bb.context(), bb.transformer()); // return exit in same context as block
+                        }
+                    }
+                }
+                bb.op(op);
+                return bb;
+            });
+        }
+        return ssaFunc;
+    }
+
+    // creates the access map
+    public static void buildAccessMap(MethodHandles.Lookup l, CoreOp.FuncOp f) {
+        // build blockParams so that we can map params to "root" params later
+        for (Body b : f.bodies()) {
+            for (Block block : b.blocks()) {
+                if (!block.parameters().isEmpty()) {
+                    blockParams.put(block, block.parameters());
+                }
+            }
+        }
+
+        f.traverse(null, (map, op) -> {
+            if (op instanceof CoreOp.BranchOp b) {
+                mapBranch(l, b.branch());
+            } else if (op instanceof  CoreOp.ConditionalBranchOp cb) {
+                mapBranch(l, cb.trueBranch()); // handle true branch
+                mapBranch(l, cb.falseBranch()); // handle false branch
+            } else if (op instanceof JavaOp.InvokeOp iop) { // (almost) all the buffer accesses happen here
+                if (isAssignable(l, iop.invokeDescriptor().refType(), MappableIface.class)) {
+                    updateAccessType(getRootValue(iop), getAccessType(iop)); // update buffer access
+                    if (isAssignable(l, iop.invokeDescriptor().refType(), Buffer.class)
+                            && iop.result() != null && !(iop.resultType() instanceof PrimitiveType)
+                            && isAssignable(l, iop.resultType(), MappableIface.class)) {
+                        // if we access a struct/union from a buffer, we map the struct/union to the buffer root
+                        remappedVals.put(iop.result(), getRootValue(iop));
+                    }
+                }
+            } else if (op instanceof CoreOp.VarOp vop) { // map the new VarOp to the "root" param
+                if (isAssignable(l, vop.resultType().valueType(), Buffer.class)) {
+                    remappedVals.put(vop.initOperand(), getRootValue(vop));
+                }
+            } else if (op instanceof JavaOp.FieldAccessOp.FieldLoadOp flop) {
+                if (isAssignable(l, flop.fieldDescriptor().refType(), KernelContext.class)) {
+                    updateAccessType(getRootValue(flop), AccessType.RO); // handle kc access
+                }
+            }
+            return map;
+        });
+    }
+
+    // maps the parameters of a block to the values passed to a branch
+    public static void mapBranch(MethodHandles.Lookup l, Block.Reference b) {
+        List<Value> args = b.arguments();
+        for (int i = 0; i < args.size(); i++) {
+            Value key = blockParams.get(b.targetBlock()).get(i);
+            Value val = args.get(i);
+
+            if (val instanceof Op.Result) {
+                // either find root param or it doesnt exist (is a constant for example)
+                if (isAssignable(l, val.type(), MappableIface.class)) {
+                    val = getRootValue(((Op.Result) val).op());
+                    if (val instanceof Block.Parameter) {
+                        val = remappedVals.getOrDefault(val, val);
+                    }
+                }
+            }
+            remappedVals.put(key, val);
+        }
+    }
+
+    // checks if a TypeElement is assignable to a certain class
+    public static boolean isAssignable(MethodHandles.Lookup l, TypeElement type, Class<?> clazz) {
+        Class<?> fopClass = getClass(l, type);
+        return (fopClass != null && (clazz.isAssignableFrom(fopClass)));
+    }
+
+    // retrieves the class of a TypeElement
+    public static Class<?> getClass(MethodHandles.Lookup l, TypeElement type) {
+        if (type instanceof ClassType classType) {
+            try {
+                return (Class<?>) classType.resolve(l);
+            } catch (ReflectiveOperationException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return null;
+    }
+
+    // retrieves "root" value of an op, the origin of the parameter (or value) used by the op
+    public static Value getRootValue(Op op) {
+        if (op.operands().isEmpty()) {
+            return op.result();
+        }
+        if (op.operands().getFirst() instanceof Block.Parameter param) {
+            return param;
+        }
+        Value val = op.operands().getFirst();
+        while (!(val instanceof Block.Parameter)) {
+            // or if the "root VarOp" is an invoke (not sure how to tell)
+            // if (tempOp instanceof JavaOp.InvokeOp iop
+            //        && ((TypeElement) iop.resultType()) instanceof ClassType classType
+            //        && !hasOperandType(iop, classType)) return ((CoreOp.VarOp) op);
+            val = ((Op.Result) val).op().operands().getFirst();
+        }
+        return val;
+    }
+
+    // retrieves accessType based on return value of InvokeOp
+    public static AccessType getAccessType(JavaOp.InvokeOp iop) {
+        return iop.invokeDescriptor().type().returnType().equals(JavaType.VOID) ? AccessType.WO : AccessType.RO;
+    }
+
+    // updates accessMap
+    public static void updateAccessType(Value val, AccessType curAccess) {
+        Value remappedVal = remappedVals.getOrDefault(val, val);
+        AccessType storedAccess = accessMap.get(remappedVal);
+        if (storedAccess == null) {
+            accessMap.put(remappedVal, curAccess);
+        } else if (curAccess != storedAccess && storedAccess != AccessType.RW) {
+            accessMap.put(remappedVal, AccessType.RW);
+        }
+    }
+
+    public static void printAccessMap() {
+        System.out.println("access map output:");
+        for (Value val : accessMap.keySet()) {
+            if (val instanceof Block.Parameter param) {
+                System.out.println("\t" + ((CoreOp.FuncOp) param.declaringBlock().parent().parent()).funcName()
+                        + " param w/ idx " + param.index() + ": " + accessMap.get(val));
+            } else {
+                System.out.println("\t" + val.toString() + ": " + accessMap.get(val));
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/hat/core/src/main/java/hat/buffer/ArgArray.java b/hat/core/src/main/java/hat/buffer/ArgArray.java
index fb217c03b4d..e78f6729a54 100644
--- a/hat/core/src/main/java/hat/buffer/ArgArray.java
+++ b/hat/core/src/main/java/hat/buffer/ArgArray.java
@@ -25,6 +25,7 @@
 package hat.buffer;
 
 import hat.Accelerator;
+import hat.BufferTagger;
 import hat.ComputeContext;
 import hat.callgraph.KernelCallGraph;
 import hat.ifacemapper.Schema;
@@ -34,6 +35,7 @@
 import java.lang.foreign.ValueLayout;
 import java.lang.invoke.MethodHandles;
 import java.nio.ByteOrder;
+import java.util.ArrayList;
 
 import static hat.buffer.ArgArray.Arg.Value.Buf.UNKNOWN_BYTE;
 import static java.lang.foreign.ValueLayout.JAVA_BYTE;
@@ -289,6 +291,8 @@ static ArgArray create(Accelerator accelerator, KernelCallGraph kernelCallGraph,
 
     static void update(ArgArray argArray, KernelCallGraph kernelCallGraph, Object... args) {
         Annotation[][] parameterAnnotations = kernelCallGraph.entrypoint.getMethod().getParameterAnnotations();
+        ArrayList<BufferTagger.AccessType> bufferAccessList = kernelCallGraph.bufferAccessList;
+
         for (int i = 0; i < args.length; i++) {
             Object argObject = args[i];
             Arg arg = argArray.arg(i); // this should be invariant, but if we are called from create it will be 0 for all
@@ -324,6 +328,8 @@ static void update(ArgArray argArray, KernelCallGraph kernelCallGraph, Object...
                     buf.address(segment);
                     buf.bytes(segment.byteSize());
                     buf.access(accessByte);
+
+                    assert bufferAccessList.get(i).value == accessByte;
                 }
                 default -> throw new IllegalStateException("Unexpected value: " + argObject);
             }
diff --git a/hat/core/src/main/java/hat/callgraph/CallGraph.java b/hat/core/src/main/java/hat/callgraph/CallGraph.java
index 5788e4fae2a..c3cf9ff6d47 100644
--- a/hat/core/src/main/java/hat/callgraph/CallGraph.java
+++ b/hat/core/src/main/java/hat/callgraph/CallGraph.java
@@ -42,7 +42,7 @@ public abstract class CallGraph<E extends Entrypoint> {
     public final Set<MethodCall> calls = new HashSet<>();
     public final Map<MethodRef, MethodCall> methodRefToMethodCallMap = new LinkedHashMap<>();
     public CoreOp.ModuleOp moduleOp;
-    public static boolean usingModuleOp = Boolean.getBoolean("moduleOp");
+    public static boolean noModuleOp = Boolean.getBoolean("noModuleOp");
     public Stream<MethodCall> callStream() {
         return methodRefToMethodCallMap.values().stream();
     }
diff --git a/hat/core/src/main/java/hat/callgraph/ComputeCallGraph.java b/hat/core/src/main/java/hat/callgraph/ComputeCallGraph.java
index 02d61c9c7ab..f1c29fb6a72 100644
--- a/hat/core/src/main/java/hat/callgraph/ComputeCallGraph.java
+++ b/hat/core/src/main/java/hat/callgraph/ComputeCallGraph.java
@@ -216,10 +216,10 @@ public void updateDag(ComputeReachableResolvedMethodCall computeReachableResolve
     }
 
     public void close() {
-        if (CallGraph.usingModuleOp) {
-            closeWithModuleOp(entrypoint);
-        } else {
+        if (CallGraph.noModuleOp) {
             updateDag(entrypoint);
+        } else {
+            closeWithModuleOp(entrypoint);
         }
     }
 
diff --git a/hat/core/src/main/java/hat/callgraph/KernelCallGraph.java b/hat/core/src/main/java/hat/callgraph/KernelCallGraph.java
index 26c63bc6430..3222233e494 100644
--- a/hat/core/src/main/java/hat/callgraph/KernelCallGraph.java
+++ b/hat/core/src/main/java/hat/callgraph/KernelCallGraph.java
@@ -24,6 +24,7 @@
  */
 package hat.callgraph;
 
+import hat.BufferTagger;
 import hat.buffer.Buffer;
 import hat.optools.OpTk;
 import jdk.incubator.code.Op;
@@ -38,6 +39,7 @@
 public class KernelCallGraph extends CallGraph<KernelEntrypoint> {
     public final ComputeCallGraph computeCallGraph;
     public final Map<MethodRef, MethodCall> bufferAccessToMethodCallMap = new LinkedHashMap<>();
+    public final ArrayList<BufferTagger.AccessType> bufferAccessList;
 
     public interface KernelReachable {
     }
@@ -77,6 +79,7 @@ public Stream<KernelReachableResolvedMethodCall> kernelReachableResolvedStream()
         super(computeCallGraph.computeContext, new KernelEntrypoint(null, methodRef, method, funcOp));
         entrypoint.callGraph = this;
         this.computeCallGraph = computeCallGraph;
+        bufferAccessList = BufferTagger.getAccessList(computeContext.accelerator.lookup, entrypoint.funcOp());
     }
 
     void updateDag(KernelReachableResolvedMethodCall kernelReachableResolvedMethodCall) {
diff --git a/hat/hat/Script.java b/hat/hat/Script.java
index e2f38e863c0..c542118e41a 100644
--- a/hat/hat/Script.java
+++ b/hat/hat/Script.java
@@ -1284,7 +1284,7 @@ public static final class JavaBuilder extends JavaToolBuilder<JavaBuilder> {
         public StringList args = new StringList();
         public StringList nativeAccessModules = new StringList();
         private boolean headless;
-        public boolean moduleOp;
+        public boolean noModuleOp;
 
 
         public JavaBuilder enable_native_access(String module) {
@@ -1344,8 +1344,8 @@ public void headless() {
             this.headless = true;
         }
 
-        public void moduleOp() {
-            this.moduleOp = true;
+        public void noModuleOp() {
+            this.noModuleOp = true;
         }
     }
 
@@ -1378,8 +1378,8 @@ public static JavaBuilder java(JavaBuilder javaBuilder) {
         if (javaBuilder.headless) {
             result.opts.add("-Dheadless=true");
         }
-        if (javaBuilder.moduleOp) {
-            result.opts.add("-DmoduleOp=true");
+        if (javaBuilder.noModuleOp) {
+            result.opts.add("-DnoModuleOp=true");
         }
         if (javaBuilder.startOnFirstThread) {
             result.opts.add("-XstartOnFirstThread");
diff --git a/hat/hat/run.java b/hat/hat/run.java
index f8d620bea4b..5bd02353596 100644
--- a/hat/hat/run.java
+++ b/hat/hat/run.java
@@ -28,7 +28,7 @@
 
 class Config{
      boolean headless=false;
-     boolean moduleOp = false;
+     boolean noModuleOp = false;
      boolean verbose = false;
      boolean startOnFirstThread = false;
      boolean justShowCommandline = false;
@@ -72,7 +72,7 @@ class Config{
             }else{
                 switch (args[arg]) {
                    case "headless" -> headless = true;
-                   case "moduleOp" -> moduleOp = true;
+                   case "noModuleOp" -> noModuleOp = true;
                    case "verbose" -> verbose = true;
                    case "justShowCommandLine" -> justShowCommandline = true;
                    case "startOnFirstThread" -> startOnFirstThread = true;
@@ -172,7 +172,7 @@ class name is assumed to be package.Main  (i.e. mandel.main)
               }
               default -> {}
           }
-          if (config.moduleOp) System.out.println("Using ModuleOp for CallGraphs");
+          if (config.noModuleOp) System.out.println("NOT using ModuleOp for CallGraphs");
       }
       Script.java(java -> java
               .enable_preview()
@@ -180,7 +180,7 @@ class name is assumed to be package.Main  (i.e. mandel.main)
               .enable_native_access("ALL-UNNAMED")
               .library_path(buildDir)
               .when(config.headless, Script.JavaBuilder::headless)
-              .when(config.moduleOp, Script.JavaBuilder::moduleOp)
+              .when(config.noModuleOp, Script.JavaBuilder::noModuleOp)
               .when(config.startOnFirstThread, Script.JavaBuilder::start_on_first_thread)
               .class_path(config.classpath)
               .vmargs(config.vmargs)