//
//  AngelCode Scripting Library
//  Copyright (c) 2020-2020 Andreas Jonsson
//
//  This software is provided 'as-is', without any express or implied
//  warranty. In no event will the authors be held liable for any
//  damages arising from the use of this software.
//
//  Permission is granted to anyone to use this software for any
//  purpose, including commercial applications, and to alter it and
//  redistribute it freely, subject to the following restrictions:
//
//  1. The origin of this software must not be misrepresented// you
//     must not claim that you wrote the original software. If you use
//     this software in a product, an acknowledgment in the product
//     documentation would be appreciated but is not required.
//
//  2. Altered source versions must be plainly marked as such, and
//     must not be misrepresented as being the original software.
//
//  3. This notice may not be removed or altered from any source
//     distribution.
//
//  The original version of this library can be located at:
//  http://www.angelcode.com/angelscript/
//
//  Andreas Jonsson
//  andreas@angelcode.com
//


// Assembly routines for the ARM64/AArch64 call convention used for Linux
// Written by Max Waine in July 2020, based on as_callfunc_arm_msvc.asm,
// with assistance & guidance provided by Sir Kane

// Compile with GCC/GAS

.arch armv8-a
.text

.global GetHFAReturnDouble
.global GetHFAReturnFloat
.global CallARM64Ret128
.global CallARM64RetInMemory
.global CallARM64Double
.global CallARM64Float
.global CallARM64

.type GetHFAReturnDouble, %function
.type GetHFAReturnFloat, %function
.type CallARM64Ret128, %function
.type CallARM64RetInMemory, %function
.type CallARM64Double, %function
.type CallARM64Float, %function
.type CallARM64, %function

.align  2
GetHFAReturnDouble:
    adr     x9, populateDoubles
    sub     x9, x9, x1, lsr 1 // x9 -= returnSize >> 1; (/2 because double is 2x instruction size)
    br      x9

    str     d3, [x0, #0x18]
    str     d2, [x0, #0x10]
    str     d1, [x1]
    str     d0, [x0]
populateDoubles:

    ret

.align  2
GetHFAReturnFloat:
    adr     x9, populateFloats
    sub     x9, x9, x2 // x9 -= returnSize; (already 4 bytes per return)
    br      x9

    str     s3, [x1, #0x4]
    str     s2, [x1]
    str     s1, [x0, #0x4]
    str     s0, [x0]
populateFloats:

    ret


//[returnType] CallARM64[type](
//    const asQWORD *gpRegArgs,    asQWORD numGPRegArgs,
//    const asQWORD *floatRegArgs, asQWORD numFloatRegArgs,
//    const asQWORD *stackArgs,    asQWORD numStackArgs,
//    asFUNCTION_t func
//)
.align  2
CallARM64Double:
CallARM64Float:
CallARM64:
    .cfi_startproc
    stp     fp, lr, [sp,#-0x20]!
    str     x20, [sp,#0x10]
    .cfi_def_cfa_offset 0x20
    .cfi_offset 20,  0x10
    .cfi_offset fp, -0x20
    .cfi_offset lr, -0x18
    mov     fp, sp

    mov     x20, #0

    cbz     x5, stackArgsLoopEnd

    // Align count to 2, then multiply by 8, resulting in a size aligned to 16
    add x20, x5,  #1
    lsl x20, x20, #3
    and x20, x20, #-0x10
    // Multiply count by 8
    lsl x10, x5, #3
    sub sp, sp, x20
stackArgsLoopStart:
    ldp     x9,x11, [x4],#16
    stp     x9,x11, [sp],#16
    subs    x10, x10, #16
    bgt     stackArgsLoopStart
stackArgsLoopEnd:

    // Calculate amount to jump forward, avoiding pointless instructions
    adr     x9, populateFloatRegisterArgsEnd
    sub     x9, x9, x3, lsl 2 // x9 -= numFloatRegArgs * 4
    br      x9

    ldr     d7, [x2, #0x38]
    ldr     d6, [x2, #0x30]
    ldr     d5, [x2, #0x28]
    ldr     d4, [x2, #0x20]
    ldr     d3, [x2, #0x18]
    ldr     d2, [x2, #0x10]
    ldr     d1, [x2, #0x08]
    ldr     d0, [x2]
populateFloatRegisterArgsEnd:

    mov     x15, x6
    // Calculate amount to jump forward, avoiding pointless instructions
    adr     x9, populateGPRegisterArgsEnd
    sub     x9, x9, x1, lsl 2 // x9 -= numGPRegArgs * 4
    br      x9

    ldr     x7, [x0, #0x38]
    ldr     x6, [x0, #0x30]
    ldr     x5, [x0, #0x28]
    ldr     x4, [x0, #0x20]
    ldr     x3, [x0, #0x18]
    ldr     x2, [x0, #0x10]
    ldr     x1, [x0, #0x08]
    ldr     x0, [x0]
populateGPRegisterArgsEnd:

    // Actually call function
    sub     sp, sp, x20
    blr     x15
    add     sp, sp, x20

    ldr     x20, [sp,#0x10]
    ldp     fp, lr, [sp],#0x20

    .cfi_restore lr
	.cfi_restore fp
    .cfi_restore 20
	.cfi_def_cfa_offset 0
    ret
    .cfi_endproc

.align  2
CallARM64Ret128:
    .cfi_startproc
    stp     fp, lr, [sp,#-0x20]!
    str     x20, [sp,#0x10]
    .cfi_def_cfa_offset 0x20
    .cfi_offset 20,  0x10
    .cfi_offset fp, -0x20
    .cfi_offset lr, -0x18
    mov     fp, sp

    mov     x20, x6
    mov     x6, x7
    mov     x7, #0
    bl      CallARM64

    str     x1, [x20]

    ldr     x20, [sp,#0x10]
    ldp     fp, lr, [sp],#0x20

    .cfi_restore lr
	.cfi_restore fp
    .cfi_restore 20
	.cfi_def_cfa_offset 0
    ret
    .cfi_endproc

.align  2
CallARM64RetInMemory:
    .cfi_startproc
    stp     fp, lr, [sp,#-0x10]!
    mov     fp, sp
    .cfi_def_cfa_offset 0x10
    .cfi_offset fp, -0x10
    .cfi_offset lr, -0x08

    mov     x8, x6
    mov     x6, x7
    mov     x7, #0
    bl      CallARM64

    mov     x0, x8

    ldp     fp, lr, [sp],#0x10

    .cfi_restore lr
	.cfi_restore fp
	.cfi_def_cfa_offset 0
    ret
    .cfi_endproc