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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
//go:build !cgo && (darwin || linux || freebsd)
/*
trampoline for emulating required C functions for cgo in go (see cgo.go)
(we convert cdecl calling convention to go and vice-versa)
Since we're called from go and call into C we can cheat a bit with the calling conventions:
- in go all the registers are caller saved
- in C we have a couple of callee saved registers
=> we can use BX, R12, R13, R14, R15 instead of the stack
C Calling convention cdecl used here (we only need integer args):
1. arg: DI
2. arg: SI
3. arg: DX
4. arg: CX
5. arg: R8
6. arg: R9
We don't need floats with these functions -> AX=0
return value will be in AX
*/
#include "textflag.h"
#include "go_asm.h"
// these trampolines map the gcc ABI to Go ABI and then calls into the Go equivalent functions.
TEXT x_cgo_init_trampoline(SB), NOSPLIT, $16
MOVQ DI, AX
MOVQ SI, BX
MOVQ ·x_cgo_init_call(SB), DX
MOVQ (DX), CX
CALL CX
RET
TEXT x_cgo_thread_start_trampoline(SB), NOSPLIT, $8
MOVQ DI, AX
MOVQ ·x_cgo_thread_start_call(SB), DX
MOVQ (DX), CX
CALL CX
RET
TEXT x_cgo_setenv_trampoline(SB), NOSPLIT, $8
MOVQ DI, AX
MOVQ ·x_cgo_setenv_call(SB), DX
MOVQ (DX), CX
CALL CX
RET
TEXT x_cgo_unsetenv_trampoline(SB), NOSPLIT, $8
MOVQ DI, AX
MOVQ ·x_cgo_unsetenv_call(SB), DX
MOVQ (DX), CX
CALL CX
RET
TEXT x_cgo_notify_runtime_init_done_trampoline(SB), NOSPLIT, $0
CALL ·x_cgo_notify_runtime_init_done(SB)
RET
TEXT x_cgo_bindm_trampoline(SB), NOSPLIT, $0
CALL ·x_cgo_bindm(SB)
RET
// func setg_trampoline(setg uintptr, g uintptr)
TEXT ·setg_trampoline(SB), NOSPLIT, $0-16
MOVQ G+8(FP), DI
MOVQ setg+0(FP), BX
XORL AX, AX
CALL BX
RET
TEXT threadentry_trampoline(SB), NOSPLIT, $16
MOVQ DI, AX
MOVQ ·threadentry_call(SB), DX
MOVQ (DX), CX
CALL CX
RET
TEXT ·call5(SB), NOSPLIT, $0-56
MOVQ fn+0(FP), BX
MOVQ a1+8(FP), DI
MOVQ a2+16(FP), SI
MOVQ a3+24(FP), DX
MOVQ a4+32(FP), CX
MOVQ a5+40(FP), R8
XORL AX, AX // no floats
PUSHQ BP // save BP
MOVQ SP, BP // save SP inside BP bc BP is callee-saved
SUBQ $16, SP // allocate space for alignment
ANDQ $-16, SP // align on 16 bytes for SSE
CALL BX
MOVQ BP, SP // get SP back
POPQ BP // restore BP
MOVQ AX, ret+48(FP)
RET
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