1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
3
4//go:build linux
5
6#include "textflag.h"
7#include "go_asm.h"
8#include "funcdata.h"
9
10// Stack usage:
11// 0(SP) - 56(SP): stack args a9-a15 (7 * 8 bytes = 56)
12// 56(SP) - 64(SP): saved RA (x1)
13// 64(SP) - 72(SP): saved X9 (s1)
14// 72(SP) - 80(SP): saved X18 (s2)
15// 80(SP) - 88(SP): saved args pointer (original X10)
16// 88(SP) - 96(SP): padding
17#define STACK_SIZE 96
18#define SAVE_RA 56
19#define SAVE_X9 64
20#define SAVE_X18 72
21#define SAVE_ARGP 80
22
23GLOBL ·syscall15XABI0(SB), NOPTR|RODATA, $8
24DATA ·syscall15XABI0(SB)/8, $syscall15X(SB)
25
26TEXT syscall15X(SB), NOSPLIT, $0
27 // Allocate stack frame (keeps 16-byte alignment)
28 SUB $STACK_SIZE, SP
29
30 // Save callee-saved regs we clobber + return address
31 MOV X1, SAVE_RA(SP)
32 MOV X9, SAVE_X9(SP)
33 MOV X18, SAVE_X18(SP)
34
35 // Save original args pointer (in a0/X10)
36 MOV X10, SAVE_ARGP(SP)
37
38 // X9 := args pointer (syscall15Args*)
39 MOV X10, X9
40
41 // Load float args into fa0-fa7 (F10-F17)
42 MOVD syscall15Args_f1(X9), F10
43 MOVD syscall15Args_f2(X9), F11
44 MOVD syscall15Args_f3(X9), F12
45 MOVD syscall15Args_f4(X9), F13
46 MOVD syscall15Args_f5(X9), F14
47 MOVD syscall15Args_f6(X9), F15
48 MOVD syscall15Args_f7(X9), F16
49 MOVD syscall15Args_f8(X9), F17
50
51 // Load integer args into a0-a7 (X10-X17)
52 MOV syscall15Args_a1(X9), X10
53 MOV syscall15Args_a2(X9), X11
54 MOV syscall15Args_a3(X9), X12
55 MOV syscall15Args_a4(X9), X13
56 MOV syscall15Args_a5(X9), X14
57 MOV syscall15Args_a6(X9), X15
58 MOV syscall15Args_a7(X9), X16
59 MOV syscall15Args_a8(X9), X17
60
61 // Spill a9-a15 onto the stack (C ABI)
62 MOV syscall15Args_a9(X9), X18
63 MOV X18, 0(SP)
64 MOV syscall15Args_a10(X9), X18
65 MOV X18, 8(SP)
66 MOV syscall15Args_a11(X9), X18
67 MOV X18, 16(SP)
68 MOV syscall15Args_a12(X9), X18
69 MOV X18, 24(SP)
70 MOV syscall15Args_a13(X9), X18
71 MOV X18, 32(SP)
72 MOV syscall15Args_a14(X9), X18
73 MOV X18, 40(SP)
74 MOV syscall15Args_a15(X9), X18
75 MOV X18, 48(SP)
76
77 // Call fn
78 // IMPORTANT: preserve RA across this call (we saved it above)
79 MOV syscall15Args_fn(X9), X18
80 CALL X18
81
82 // Restore args pointer (syscall15Args*) for storing results
83 MOV SAVE_ARGP(SP), X9
84
85 // Store results back
86 MOV X10, syscall15Args_a1(X9)
87 MOV X11, syscall15Args_a2(X9)
88
89 // Store back float return regs if used by your ABI contract
90 MOVD F10, syscall15Args_f1(X9)
91 MOVD F11, syscall15Args_f2(X9)
92 MOVD F12, syscall15Args_f3(X9)
93 MOVD F13, syscall15Args_f4(X9)
94
95 // Restore callee-saved regs and return address
96 MOV SAVE_X18(SP), X18
97 MOV SAVE_X9(SP), X9
98 MOV SAVE_RA(SP), X1
99
100 ADD $STACK_SIZE, SP
101 RET