// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

#include "textflag.h"

// ABI0 JIT trampoline.  enterJIT switches from the Go stack to a prepared
// stack and jumps to the assembled function; when the function RETs, control
// lands in leaveJIT, which restores the Go stack and returns to the Go caller.
//
// The prepared stack must begin with the address of leaveJIT (the return
// address the JIT function will pop), followed by the function's ABI0
// argument area.
//
// Single-threaded: savedSP is a package global, so only one JIT call may be
// in flight at a time.  gasm verify runs sequentially.

// func enterJIT(fn uintptr, stack uintptr)
// Switches to the prepared stack and jumps to fn.  Does not return normally;
// the JIT function's RET transfers control to leaveJIT.
TEXT ·enterJIT(SB), NOSPLIT, $0-16
	MOVQ fn+0(FP), AX // target function address (before SP switch)
	MOVQ SP, ·savedSP(SB) // preserve the Go stack pointer
	MOVQ stack+8(FP), SP // switch to the prepared stack
	JMP  AX

	// func leaveJIT()
	// Restores the Go stack pointer and returns to enterJIT's caller.
TEXT ·leaveJIT(SB), NOSPLIT, $0-0
	MOVQ ·savedSP(SB), SP
	RET