Function CreateUnwindInfoWindows

source/common/scripting/jit/jit_runtime.cpp:84–254

#define UWOP_PUSH_MACHFRAME 10

static TArray<uint16_t> CreateUnwindInfoWindows(asmjit::CCFunc *func)
{
	using namespace asmjit;
	FuncFrameLayout layout;
	Error error = layout.init(func->getDetail(), func->getFrameInfo());
	if (error != kErrorOk)
		I_Error("FuncFrameLayout.init failed");

	// We need a dummy emitter for instruction size calculations
	CodeHolder code;
	code.init(GetHostCodeInfo());
	X86Assembler assembler(&code);
	X86Emitter *emitter = assembler.asEmitter();

	// Build UNWIND_CODE codes:

	TArray<uint16_t> codes;
	uint32_t opoffset, opcode, opinfo;

	// Note: this must match exactly what X86Internal::emitProlog does

	X86Gp zsp = emitter->zsp();   // ESP|RSP register.
	X86Gp zbp = emitter->zsp();   // EBP|RBP register.
	zbp.setId(X86Gp::kIdBp);
	X86Gp gpReg = emitter->zsp(); // General purpose register (temporary).
	X86Gp saReg = emitter->zsp(); // Stack-arguments base register.
	uint32_t gpSaved = layout.getSavedRegs(X86Reg::kKindGp);

	if (layout.hasPreservedFP())
	{
		// Emit: 'push zbp'
		//       'mov  zbp, zsp'.
		gpSaved &= ~Utils::mask(X86Gp::kIdBp);
		emitter->push(zbp);

		opoffset = (uint32_t)assembler.getOffset();
		opcode = UWOP_PUSH_NONVOL;
		opinfo = X86Gp::kIdBp;
		codes.Push(opoffset | (opcode << 8) | (opinfo << 12));

		emitter->mov(zbp, zsp);
	}

	if (gpSaved)
	{
		for (uint32_t i = gpSaved, regId = 0; i; i >>= 1, regId++)
		{
			if (!(i & 0x1)) continue;
			// Emit: 'push gp' sequence.
			gpReg.setId(regId);
			emitter->push(gpReg);

			opoffset = (uint32_t)assembler.getOffset();
			opcode = UWOP_PUSH_NONVOL;
			opinfo = regId;
			codes.Push(opoffset | (opcode << 8) | (opinfo << 12));
		}
	}