Ivar Fatland
115 lines
3.1 KiB
ArmAsm
115 lines
3.1 KiB
ArmAsm
// SPDX-License-Identifier: Apache-2.0
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// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
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//go:build linux
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#include "textflag.h"
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#include "go_asm.h"
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#include "funcdata.h"
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// S390X ELF ABI:
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// - Integer args: R2-R6 (5 registers)
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// - Float args: F0, F2, F4, F6 (4 registers, even-numbered)
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// - Return: R2 (integer), F0 (float)
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// - Stack pointer: R15
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// - Link register: R14
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// - Callee-saved: R6-R13, F8-F15 (but R6 is also used for 5th param)
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//
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// Stack frame layout (aligned to 8 bytes):
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// 0(R15) - back chain
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// 8(R15) - reserved
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// 16(R15) - reserved
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// ... - register save area (R6-R15 at 48(R15))
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// 160(R15) - parameter area start (args beyond registers)
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//
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// We need space for:
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// - 160 bytes standard frame (with register save area)
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// - Stack args a6-a15 (10 * 8 = 80 bytes)
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// - Saved args pointer (8 bytes)
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// - Padding for alignment
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// Total: 264 bytes (rounded to 8-byte alignment)
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#define STACK_SIZE 264
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#define STACK_ARGS 160
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#define ARGP_SAVE 248
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GLOBL ·syscall15XABI0(SB), NOPTR|RODATA, $8
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DATA ·syscall15XABI0(SB)/8, $syscall15X(SB)
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TEXT syscall15X(SB), NOSPLIT, $0
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// On entry, R2 contains the args pointer
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// Save callee-saved registers in caller's frame (per ABI)
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STMG R6, R15, 48(R15)
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// Allocate our stack frame
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MOVD R15, R1
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SUB $STACK_SIZE, R15
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MOVD R1, 0(R15) // back chain
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// Save args pointer
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MOVD R2, ARGP_SAVE(R15)
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// R9 := args pointer (syscall15Args*)
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MOVD R2, R9
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// Load float args into F0, F2, F4, F6 (s390x uses even-numbered FPRs)
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FMOVD syscall15Args_f1(R9), F0
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FMOVD syscall15Args_f2(R9), F2
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FMOVD syscall15Args_f3(R9), F4
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FMOVD syscall15Args_f4(R9), F6
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// Load integer args into R2-R6 (5 registers)
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MOVD syscall15Args_a1(R9), R2
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MOVD syscall15Args_a2(R9), R3
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MOVD syscall15Args_a3(R9), R4
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MOVD syscall15Args_a4(R9), R5
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MOVD syscall15Args_a5(R9), R6
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// Spill remaining args (a6-a15) onto the stack at 160(R15)
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MOVD ARGP_SAVE(R15), R9 // reload args pointer
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MOVD syscall15Args_a6(R9), R1
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MOVD R1, (STACK_ARGS+0*8)(R15)
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MOVD syscall15Args_a7(R9), R1
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MOVD R1, (STACK_ARGS+1*8)(R15)
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MOVD syscall15Args_a8(R9), R1
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MOVD R1, (STACK_ARGS+2*8)(R15)
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MOVD syscall15Args_a9(R9), R1
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MOVD R1, (STACK_ARGS+3*8)(R15)
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MOVD syscall15Args_a10(R9), R1
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MOVD R1, (STACK_ARGS+4*8)(R15)
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MOVD syscall15Args_a11(R9), R1
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MOVD R1, (STACK_ARGS+5*8)(R15)
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MOVD syscall15Args_a12(R9), R1
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MOVD R1, (STACK_ARGS+6*8)(R15)
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MOVD syscall15Args_a13(R9), R1
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MOVD R1, (STACK_ARGS+7*8)(R15)
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MOVD syscall15Args_a14(R9), R1
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MOVD R1, (STACK_ARGS+8*8)(R15)
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MOVD syscall15Args_a15(R9), R1
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MOVD R1, (STACK_ARGS+9*8)(R15)
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// Call function
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MOVD syscall15Args_fn(R9), R1
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BL (R1)
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// Restore args pointer for storing results
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MOVD ARGP_SAVE(R15), R9
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// Store integer results back (R2, R3)
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MOVD R2, syscall15Args_a1(R9)
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MOVD R3, syscall15Args_a2(R9)
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// Store float return values (F0, F2, F4, F6)
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FMOVD F0, syscall15Args_f1(R9)
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FMOVD F2, syscall15Args_f2(R9)
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FMOVD F4, syscall15Args_f3(R9)
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FMOVD F6, syscall15Args_f4(R9)
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// Deallocate stack frame
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ADD $STACK_SIZE, R15
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// Restore callee-saved registers from caller's save area
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LMG 48(R15), R6, R15
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RET
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