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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
//go:build linux
#include "textflag.h"
#include "go_asm.h"
#include "funcdata.h"
#define STACK_SIZE 160
#define PTR_ADDRESS (STACK_SIZE - 4)
// syscall15X calls a function in libc on behalf of the syscall package.
// syscall15X takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// ...
// a32 uintptr
// f1 uintptr
// ...
// f16 uintptr
// arm64_r8 uintptr
// }
// syscall15X must be called on the g0 stack with the
// C calling convention (use libcCall).
//
// On i386 System V ABI, all arguments are passed on the stack.
// Return value is in EAX (and EDX for 64-bit values).
GLOBL ·syscall15XABI0(SB), NOPTR|RODATA, $4
DATA ·syscall15XABI0(SB)/4, $syscall15X(SB)
TEXT syscall15X(SB), NOSPLIT|NOFRAME, $0-0
// Called via C calling convention: argument pointer at 4(SP)
// NOT via Go calling convention
// On i386, the first argument is at 4(SP) after CALL pushes return address
MOVL 4(SP), AX // get pointer to syscall15Args
// Save callee-saved registers
PUSHL BP
PUSHL BX
PUSHL SI
PUSHL DI
MOVL AX, BX // save args pointer in BX
// Allocate stack space for C function arguments
// i386 SysV: all 32 args on stack = 32 * 4 = 128 bytes
// Plus 16 bytes for alignment and local storage
SUBL $STACK_SIZE, SP
MOVL BX, PTR_ADDRESS(SP) // save args pointer
// Load function pointer
MOVL syscall15Args_fn(BX), AX
MOVL AX, (PTR_ADDRESS-4)(SP) // save fn pointer
// Push all integer arguments onto the stack (a1-a32)
// i386 SysV ABI: arguments pushed right-to-left, but we're
// setting up the stack from low to high addresses
MOVL syscall15Args_a1(BX), AX
MOVL AX, 0(SP)
MOVL syscall15Args_a2(BX), AX
MOVL AX, 4(SP)
MOVL syscall15Args_a3(BX), AX
MOVL AX, 8(SP)
MOVL syscall15Args_a4(BX), AX
MOVL AX, 12(SP)
MOVL syscall15Args_a5(BX), AX
MOVL AX, 16(SP)
MOVL syscall15Args_a6(BX), AX
MOVL AX, 20(SP)
MOVL syscall15Args_a7(BX), AX
MOVL AX, 24(SP)
MOVL syscall15Args_a8(BX), AX
MOVL AX, 28(SP)
MOVL syscall15Args_a9(BX), AX
MOVL AX, 32(SP)
MOVL syscall15Args_a10(BX), AX
MOVL AX, 36(SP)
MOVL syscall15Args_a11(BX), AX
MOVL AX, 40(SP)
MOVL syscall15Args_a12(BX), AX
MOVL AX, 44(SP)
MOVL syscall15Args_a13(BX), AX
MOVL AX, 48(SP)
MOVL syscall15Args_a14(BX), AX
MOVL AX, 52(SP)
MOVL syscall15Args_a15(BX), AX
MOVL AX, 56(SP)
MOVL syscall15Args_a16(BX), AX
MOVL AX, 60(SP)
MOVL syscall15Args_a17(BX), AX
MOVL AX, 64(SP)
MOVL syscall15Args_a18(BX), AX
MOVL AX, 68(SP)
MOVL syscall15Args_a19(BX), AX
MOVL AX, 72(SP)
MOVL syscall15Args_a20(BX), AX
MOVL AX, 76(SP)
MOVL syscall15Args_a21(BX), AX
MOVL AX, 80(SP)
MOVL syscall15Args_a22(BX), AX
MOVL AX, 84(SP)
MOVL syscall15Args_a23(BX), AX
MOVL AX, 88(SP)
MOVL syscall15Args_a24(BX), AX
MOVL AX, 92(SP)
MOVL syscall15Args_a25(BX), AX
MOVL AX, 96(SP)
MOVL syscall15Args_a26(BX), AX
MOVL AX, 100(SP)
MOVL syscall15Args_a27(BX), AX
MOVL AX, 104(SP)
MOVL syscall15Args_a28(BX), AX
MOVL AX, 108(SP)
MOVL syscall15Args_a29(BX), AX
MOVL AX, 112(SP)
MOVL syscall15Args_a30(BX), AX
MOVL AX, 116(SP)
MOVL syscall15Args_a31(BX), AX
MOVL AX, 120(SP)
MOVL syscall15Args_a32(BX), AX
MOVL AX, 124(SP)
// Call the C function
MOVL (PTR_ADDRESS-4)(SP), AX
CALL AX
// Get args pointer back and save results
MOVL PTR_ADDRESS(SP), BX
MOVL AX, syscall15Args_a1(BX) // return value r1
MOVL DX, syscall15Args_a2(BX) // return value r2 (for 64-bit returns)
// Save x87 FPU return value (ST0) to f1 field
// On i386 System V ABI, float/double returns are in ST(0)
// We save as float64 (8 bytes) to preserve precision
FMOVDP F0, syscall15Args_f1(BX)
// Clean up stack
ADDL $STACK_SIZE, SP
// Restore callee-saved registers
POPL DI
POPL SI
POPL BX
POPL BP
RET
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