Implement interpreter CEE_ADD_OVF and CEE_SUB_OVF opcodes

[janvorli]

These are needed for a couple of coreclr tests

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[Copilot]

Pull Request Overview

This PR adds overflow-checking support for the CEE_ADD_OVF and CEE_SUB_OVF IL opcodes by defining new internal opcodes, wiring them through the compiler, and handling them in the interpreter.

• Introduces signed and unsigned overflow variants for 32-bit and 64-bit adds/subtracts in interpexec.cpp.
• Registers new overflow opcodes in intops.def.
• Maps the IL overflow opcodes to the new internal opcodes in compiler.cpp.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/vm/interpexec.cpp	Implements safe-int overflow logic for add/sub ops
src/coreclr/interpreter/intops.def	Defines new INTOP_ADD_OVF* and INTOP_SUB_OVF* entries
src/coreclr/interpreter/compiler.cpp	Maps CEE_ADD_OVF* and CEE_SUB_OVF* to internal ops

Comments suppressed due to low confidence (2)

src/coreclr/vm/interpexec.cpp:983

• We should add dedicated interpreter tests for each new overflow variant (add/sub, 32-bit/64-bit, signed/unsigned) to verify both normal and overflow paths and prevent regressions.

case INTOP_ADD_OVF_I4:

src/coreclr/interpreter/compiler.cpp:3975

• Currently this always emits the 32-bit overflow opcode; double-check that for 64-bit integer operands the compiler emits INTOP_ADD_OVF_I8 (and similarly for subtraction) to match the interpreter’s handling.

case CEE_ADD_OVF:

[Copilot]

[nitpick] These four overflow handling blocks (signed/unsigned, 32/64) are nearly identical—consider extracting a templated helper or macro (e.g., HandleOverflowOp<T>(...)) to reduce duplication and keep future adjustments in sync.

Suggested change

	int32_t i1 = LOCAL_VAR(ip[2], int32_t);
	int32_t i2 = LOCAL_VAR(ip[3], int32_t);
	int32_t i3;
	if (!ClrSafeInt<int32_t>::addition(i1, i2, i3))
	COMPlusThrow(kOverflowException);
	LOCAL_VAR(ip[1], int32_t) = i3;
	ip += 4;
	break;
	}
	case INTOP_ADD_OVF_I8:
	{
	int64_t i1 = LOCAL_VAR(ip[2], int64_t);
	int64_t i2 = LOCAL_VAR(ip[3], int64_t);
	int64_t i3;
	if (!ClrSafeInt<int64_t>::addition(i1, i2, i3))
	COMPlusThrow(kOverflowException);
	LOCAL_VAR(ip[1], int64_t) = i3;
	HandleOverflowOp<int32_t>(ip, 2, 3, 1);
	ip += 4;
	break;
	}
	case INTOP_ADD_OVF_I8:
	{
	HandleOverflowOp<int64_t>(ip, 2, 3, 1);