v0.14.0 - Forth-style SYS instruction

🚨 Breaking Changes

SYS instruction changed from IMM16 to NoImm opcode:

• Old format: SYS opcode (0x60) + 2-byte immediate operand = 3 bytes total
• New format: SYS opcode (0x60) only = 1 byte total
• SYS ID is now popped from the data stack instead of being encoded as an immediate

This enables dynamic SYS calls where the SYS ID can be computed at runtime.

Bytecode Example

Old bytecode: 60 01 00        (SYS with IMM16 = 0x0001)
New bytecode: 00 01 00 00 00 60  (LIT 1, SYS)

✨ Features

• Stack-based SYS: SYS ID is popped from the data stack
• Dynamic syscalls: Enable computed SYS IDs at runtime
• Smaller opcode: SYS opcode reduced from 3 bytes to 1 byte (immediates handled separately)

🔧 Changes

Core Changes

• opcodes.def: Changed SYS from IMM16 to NO_IMM
• opcodes.hpp: Updated comment to reflect SYS as NoImm
• core.cpp: Modified SYS handler to pop 16-bit ID from stack with validation (0-65535)

Test Updates

• Updated all 19 SYS test cases in test_sys.cpp
• Added emit16() helper function for test bytecode generation
• Changed test bytecode from IMM16 pattern to LIT+SYS pattern

✅ Testing

• All 11 V4-engine tests passing
• Tested with address sanitizer
• Tested with undefined behavior sanitizer
• GPIO, UART, Timer, System SYS calls verified

📦 Compatibility

• Requires V4-front v0.7.0 or later for correct Forth-style syntax
• Breaking change: Old bytecode with IMM16 SYS will not work
• Applications must be recompiled with new V4-front

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Full Changelog: v0.13.0...v0.14.0