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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"
- // S390X ELF ABI:
- // - Integer args: R2-R6 (5 registers)
- // - Float args: F0, F2, F4, F6 (4 registers, even-numbered)
- // - Return: R2 (integer), F0 (float)
- // - Stack pointer: R15
- // - Link register: R14
- // - Callee-saved: R6-R13, F8-F15 (but R6 is also used for 5th param)
- //
- // Stack frame layout (aligned to 8 bytes):
- // 0(R15) - back chain
- // 8(R15) - reserved
- // 16(R15) - reserved
- // ... - register save area (R6-R15 at 48(R15))
- // 160(R15) - parameter area start (args beyond registers)
- //
- // We need space for:
- // - 160 bytes standard frame (with register save area)
- // - Stack args a6-a15 (10 * 8 = 80 bytes)
- // - Saved args pointer (8 bytes)
- // - Padding for alignment
- // Total: 264 bytes (rounded to 8-byte alignment)
- #define STACK_SIZE 264
- #define STACK_ARGS 160
- #define ARGP_SAVE 248
- GLOBL ·syscall15XABI0(SB), NOPTR|RODATA, $8
- DATA ·syscall15XABI0(SB)/8, $syscall15X(SB)
- TEXT syscall15X(SB), NOSPLIT, $0
- // On entry, R2 contains the args pointer
- // Save callee-saved registers in caller's frame (per ABI)
- STMG R6, R15, 48(R15)
- // Allocate our stack frame
- MOVD R15, R1
- SUB $STACK_SIZE, R15
- MOVD R1, 0(R15) // back chain
- // Save args pointer
- MOVD R2, ARGP_SAVE(R15)
- // R9 := args pointer (syscall15Args*)
- MOVD R2, R9
- // Load float args into F0, F2, F4, F6 (s390x uses even-numbered FPRs)
- FMOVD syscall15Args_f1(R9), F0
- FMOVD syscall15Args_f2(R9), F2
- FMOVD syscall15Args_f3(R9), F4
- FMOVD syscall15Args_f4(R9), F6
- // Load integer args into R2-R6 (5 registers)
- MOVD syscall15Args_a1(R9), R2
- MOVD syscall15Args_a2(R9), R3
- MOVD syscall15Args_a3(R9), R4
- MOVD syscall15Args_a4(R9), R5
- MOVD syscall15Args_a5(R9), R6
- // Spill remaining args (a6-a15) onto the stack at 160(R15)
- MOVD ARGP_SAVE(R15), R9 // reload args pointer
- MOVD syscall15Args_a6(R9), R1
- MOVD R1, (STACK_ARGS+0*8)(R15)
- MOVD syscall15Args_a7(R9), R1
- MOVD R1, (STACK_ARGS+1*8)(R15)
- MOVD syscall15Args_a8(R9), R1
- MOVD R1, (STACK_ARGS+2*8)(R15)
- MOVD syscall15Args_a9(R9), R1
- MOVD R1, (STACK_ARGS+3*8)(R15)
- MOVD syscall15Args_a10(R9), R1
- MOVD R1, (STACK_ARGS+4*8)(R15)
- MOVD syscall15Args_a11(R9), R1
- MOVD R1, (STACK_ARGS+5*8)(R15)
- MOVD syscall15Args_a12(R9), R1
- MOVD R1, (STACK_ARGS+6*8)(R15)
- MOVD syscall15Args_a13(R9), R1
- MOVD R1, (STACK_ARGS+7*8)(R15)
- MOVD syscall15Args_a14(R9), R1
- MOVD R1, (STACK_ARGS+8*8)(R15)
- MOVD syscall15Args_a15(R9), R1
- MOVD R1, (STACK_ARGS+9*8)(R15)
- // Call function
- MOVD syscall15Args_fn(R9), R1
- BL (R1)
- // Restore args pointer for storing results
- MOVD ARGP_SAVE(R15), R9
- // Store integer results back (R2, R3)
- MOVD R2, syscall15Args_a1(R9)
- MOVD R3, syscall15Args_a2(R9)
- // Store float return values (F0, F2, F4, F6)
- FMOVD F0, syscall15Args_f1(R9)
- FMOVD F2, syscall15Args_f2(R9)
- FMOVD F4, syscall15Args_f3(R9)
- FMOVD F6, syscall15Args_f4(R9)
- // Deallocate stack frame
- ADD $STACK_SIZE, R15
- // Restore callee-saved registers from caller's save area
- LMG 48(R15), R6, R15
- RET
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