From 89b7f41bd19e4a15099cb5214bfa0b2e0a3169ae Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 21 Dec 2025 06:13:53 +0000
Subject: [PATCH 1/2] Initial plan


From 52cb6f4dd3007a38da4927db6b23a994d1d3be83 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 21 Dec 2025 15:27:38 +0000
Subject: [PATCH 2/2] Add CodePointerLookupFrame class for interface dispatch

- Added CodePointerLookupFrame frame type to FrameTypes.h
- Defined CodePointerLookupFrame class in frames.h inheriting from TransitionFrame
- Implemented constructor and TraceFrame_Impl in frames.cpp
- This frame avoids double GC reporting by inheriting directly from TransitionFrame instead of FramedMethodFrame
- Built and verified CoreCLR compiles successfully

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>
---
 src/coreclr/vm/FrameTypes.h |  1 +
 src/coreclr/vm/frames.cpp   | 23 +++++++++++++
 src/coreclr/vm/frames.h     | 64 +++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)

diff --git a/src/coreclr/vm/FrameTypes.h b/src/coreclr/vm/FrameTypes.h
index 83a4e0aa6de455..af90d964bfd816 100644
--- a/src/coreclr/vm/FrameTypes.h
+++ b/src/coreclr/vm/FrameTypes.h
@@ -30,6 +30,7 @@ FRAME_TYPE_NAME(HijackFrame)
 FRAME_TYPE_NAME(PrestubMethodFrame)
 FRAME_TYPE_NAME(CallCountingHelperFrame)
 FRAME_TYPE_NAME(StubDispatchFrame)
+FRAME_TYPE_NAME(CodePointerLookupFrame)
 FRAME_TYPE_NAME(ExternalMethodFrame)
 FRAME_TYPE_NAME(DynamicHelperFrame)
 FRAME_TYPE_NAME(ProtectValueClassFrame)
diff --git a/src/coreclr/vm/frames.cpp b/src/coreclr/vm/frames.cpp
index 11b48a3f227908..a6257498a52f24 100644
--- a/src/coreclr/vm/frames.cpp
+++ b/src/coreclr/vm/frames.cpp
@@ -952,6 +952,29 @@ Frame::Interception StubDispatchFrame::GetInterception_Impl()
     return INTERCEPTION_NONE;
 }
 
+#ifndef DACCESS_COMPILE
+CodePointerLookupFrame::CodePointerLookupFrame(TransitionBlock * pTransitionBlock)
+    : TransitionFrame(FrameIdentifier::CodePointerLookupFrame), m_pTransitionBlock(dac_cast<TADDR>(pTransitionBlock))
+{
+    LIMITED_METHOD_CONTRACT;
+
+    m_pZapModule = NULL;
+    m_pIndirection = (TADDR)NULL;
+}
+#endif
+
+BOOL CodePointerLookupFrame::TraceFrame_Impl(Thread *thread, BOOL fromPatch,
+                                    TraceDestination *trace, REGDISPLAY *regs)
+{
+    WRAPPER_NO_CONTRACT;
+
+    // CodePointerLookupFrame is used for interface dispatch resolution and never directly calls managed code.
+    // Returning false instructs the debugger to step out of the call that erected this frame.
+    LOG((LF_CORDB, LL_INFO1000, "CodePointerLookupFrame::TraceFrame: return FALSE\n"));
+
+    return FALSE;
+}
+
 #ifndef DACCESS_COMPILE
 CallCountingHelperFrame::CallCountingHelperFrame(TransitionBlock *pTransitionBlock, MethodDesc *pMD)
     : FramedMethodFrame(FrameIdentifier::CallCountingHelperFrame, pTransitionBlock, pMD)
diff --git a/src/coreclr/vm/frames.h b/src/coreclr/vm/frames.h
index 5491e238918411..3810aa44386c35 100644
--- a/src/coreclr/vm/frames.h
+++ b/src/coreclr/vm/frames.h
@@ -1723,6 +1723,70 @@ struct cdac_data<StubDispatchFrame>
 
 typedef DPTR(class StubDispatchFrame) PTR_StubDispatchFrame;
 
+//------------------------------------------------------------------------
+// CodePointerLookupFrame is used for resolving interface dispatch calls.
+// Unlike StubDispatchFrame, it inherits directly from TransitionFrame to
+// avoid double GC reporting of argument registers. The calling code handles
+// GC reporting via the TransitionFrame base class.
+//------------------------------------------------------------------------
+
+class CodePointerLookupFrame : public TransitionFrame
+{
+    TADDR m_pTransitionBlock;
+
+    // Indirection cell and containing module.
+    PTR_Module      m_pZapModule;
+    TADDR           m_pIndirection;
+
+public:
+    CodePointerLookupFrame(TransitionBlock * pTransitionBlock);
+
+    TADDR GetTransitionBlock_Impl()
+    {
+        LIMITED_METHOD_DAC_CONTRACT;
+        return m_pTransitionBlock;
+    }
+
+#ifndef DACCESS_COMPILE
+    void SetCallSite(Module * pZapModule, TADDR pIndirection)
+    {
+        LIMITED_METHOD_CONTRACT;
+
+        m_pZapModule = pZapModule;
+        m_pIndirection = pIndirection;
+    }
+#endif
+
+    PCODE GetUnadjustedReturnAddress()
+    {
+        LIMITED_METHOD_DAC_CONTRACT;
+        return GetReturnAddress_Impl();
+    }
+
+    BOOL TraceFrame_Impl(Thread *thread, BOOL fromPatch,
+                    TraceDestination *trace, REGDISPLAY *regs);
+
+    int GetFrameType_Impl()
+    {
+        LIMITED_METHOD_CONTRACT;
+        return TYPE_CALL;
+    }
+
+    Interception GetInterception_Impl()
+    {
+        LIMITED_METHOD_DAC_CONTRACT;
+        return INTERCEPTION_NONE;
+    }
+
+    ETransitionType GetTransitionType_Impl()
+    {
+        LIMITED_METHOD_DAC_CONTRACT;
+        return TT_InternalCall;
+    }
+};
+
+typedef DPTR(class CodePointerLookupFrame) PTR_CodePointerLookupFrame;
+
 typedef DPTR(class CallCountingHelperFrame) PTR_CallCountingHelperFrame;
 
 class CallCountingHelperFrame : public FramedMethodFrame