[clr-interp] Add User Breakpoint Support for Interpreter Debugging

[matouskozak]

This PR implements support for setting and handling user breakpoints (System.Diagnostics.Debugger.Break()) in interpreted code. Regular breakpoints, stepping, etc. are not covered by these changes.

Key Changes

Execution Control Abstraction (executioncontrol.h/cpp)

• Introduced IExecutionControl interface to abstract breakpoint operations across different execution strategies. Currently just for interpreter but will be extended to other codegens.
• Implemented InterpreterExecutionControl class for interpreter-specific bytecode patching
• ApplyPatch(): Replaces bytecode instruction with INTOP_BREAKPOINT opcode
• UnapplyPatch(): Restores original bytecode instruction

Patch Mechanism:

• Interpreter breakpoints work by patching bytecode directly with INTOP_BREAKPOINT instruction
• Original opcode is saved in the patch structure for restoration

Breakpoint Flow:

1. Interpreter hits INTOP_BREAKPOINT opcode
2. Interpreter context is prepared and is called FirstChanceNativeException()
3. Debugger controller dispatches to appropriate breakpoint handler
4. Original opcode is restored during patch skip activation

Notes

• JITComplete notification handling needs revisiting for interpreter code. I've disabled it for now as it wasn't needed for user breakpoints and when left enabled it would break the execution, likely due to patches being applied to interpreter execution loop code.

Testing

• Verified locally (macOS m2) using debugger tests that no new regressions are introduced for debugging with JIT
• For interpreter, debugger tests do not bring any meaningful results as of now due to missing regular breakpoint support.
• Validated using a sample console app running with interpreter

---

Future work

• Interpreter support for regular breakpoints and stepping
• Implement JIT execution control to avoid the interpreter’s conditional branches
• Tracking issue [clr-interp] Implement interpreter debugging support in CoreCLR #120842

[Copilot]

Pull request overview

This PR implements support for user breakpoints (System.Diagnostics.Debugger.Break()) in interpreted code by introducing an execution control abstraction layer. The implementation uses bytecode patching to replace interpreter instructions with INTOP_BREAKPOINT opcodes.

Key Changes

• Introduced IExecutionControl interface and InterpreterExecutionControl implementation for bytecode patching
• Modified debugger controller to delegate patch operations to execution control for interpreter code
• Implemented GetFunctionSize for InterpreterCodeManager to support debugger operations
• Disabled JITComplete notification for interpreter code as a temporary workaround
• Added frame filtering to prevent interpreter frames from being treated as managed frames during stack walks

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/coreclr/debug/ee/executioncontrol.h	Defines IExecutionControl interface and InterpreterExecutionControl class for bytecode patching abstraction
src/coreclr/debug/ee/executioncontrol.cpp	Implements bytecode patch application/removal by replacing opcodes with INTOP_BREAKPOINT
src/coreclr/debug/ee/controller.h	Adds include for execution control header
src/coreclr/debug/ee/controller.cpp	Modifies ApplyPatch/UnapplyPatch to delegate to execution control for interpreter code
src/coreclr/debug/ee/frameinfo.cpp	Filters out interpreter frames from debugger stack walks
src/coreclr/debug/ee/CMakeLists.txt	Adds new execution control source files to build
src/coreclr/vm/codeman.h	Adds virtual GetExecutionControl() method to IJitManager and overrides for InterpreterJitManager
src/coreclr/vm/codeman.cpp	Implements GetExecutionControl() and includes execution control header
src/coreclr/vm/jitinterface.cpp	Temporarily disables JITComplete notification for interpreter code
src/coreclr/vm/interpexec.cpp	Implements InterpBreakpoint handler that notifies debugger of breakpoint via exception mechanism
src/coreclr/vm/eetwain.cpp	Implements GetFunctionSize for interpreter code manager using GC info decoder

[janvorli]

LGTM, thank you!

[matouskozak]

Merging, future work is tracked in #120842