/*
	Copyright 2019 flyinghead

	This file is part of reicast.

    reicast is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 2 of the License, or
    (at your option) any later version.

    reicast is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with reicast.  If not, see <https://www.gnu.org/licenses/>.
 */

#include "build.h"

#if	HOST_CPU == CPU_ARM64 && FEAT_AREC != DYNAREC_NONE

#include <sstream>
#include "arm7.h"
#include "arm_emitter/arm_coding.h"
#include "deps/vixl/aarch64/macro-assembler-aarch64.h"
using namespace vixl::aarch64;
//#include "deps/vixl/aarch32/disasm-aarch32.h"

extern void vmem_platform_flush_cache(void *icache_start, void *icache_end, void *dcache_start, void *dcache_end);
extern u32 arm_single_op(u32 opcode);
extern "C" void arm_dispatch();
extern "C" void arm_exit();

extern u8* icPtr;
extern u8* ICache;
extern const u32 ICacheSize;
extern reg_pair arm_Reg[RN_ARM_REG_COUNT];

MacroAssembler *assembler;

extern "C" void armFlushICache(void *bgn, void *end) {
	vmem_platform_flush_cache(bgn, end, bgn, end);
}

static MemOperand arm_reg_operand(u32 regn)
{
	return MemOperand(x28, (u8*)&arm_Reg[regn].I - (u8*)&arm_Reg[0].I);
}

//helpers ...
void LoadReg(ARM::eReg rd, u32 regn, ARM::ConditionCode cc = ARM::CC_AL)
{
	assembler->Ldr(Register::GetWRegFromCode(rd), arm_reg_operand(regn));
}
void StoreReg(ARM::eReg rd, u32 regn, ARM::ConditionCode cc = ARM::CC_AL)
{
	assembler->Str(Register::GetWRegFromCode(rd), arm_reg_operand(regn));
}

void *armv_start_conditional(ARM::ConditionCode cc)
{
	if (cc == ARM::CC_AL)
		return NULL;
	Label *label = new Label();
	verify(cc <= ARM::CC_LE);
	Condition condition = (Condition)((u32)cc ^ 1);
	assembler->B(label, condition);

	return label;
}

void armv_end_conditional(void *ref)
{
	if (ref != NULL)
	{
		Label *label = (Label *)ref;
		assembler->Bind(label);
		delete label;
	}
}

//For COND
void LoadFlags()
{
	//Load flags
	LoadReg(ARM::r0, RN_PSR_FLAGS);
	//move them to flags register
	assembler->Msr(NZCV, x0);
}

void StoreFlags()
{
	//get results from flags register
	assembler->Mrs(x1, NZCV);
	//Store flags
	StoreReg(ARM::r1, RN_PSR_FLAGS);
}

void armv_imm_to_reg(u32 regn, u32 imm)
{
	assembler->Mov(w0, imm);
	assembler->Str(w0, arm_reg_operand(regn));
}

void armv_call(void* loc)
{
	ptrdiff_t offset = reinterpret_cast<uintptr_t>(loc) - assembler->GetBuffer()->GetStartAddress<uintptr_t>();
	Label function_label;
	assembler->BindToOffset(&function_label, offset);
	assembler->Bl(&function_label);
}

void armv_setup()
{
	assembler = new MacroAssembler(icPtr, ICache + ICacheSize - icPtr);
}

void armv_intpr(u32 opcd)
{
	//Call interpreter
	assembler->Mov(w0, opcd);
	armv_call((void*)&arm_single_op);
}

void armv_end(void* codestart, u32 cycl)
{
	//Normal block end
	//cycle counter rv

	//pop registers & return
	assembler->Subs(w27, w27, cycl);
	ptrdiff_t offset = reinterpret_cast<uintptr_t>(arm_exit) - assembler->GetBuffer()->GetStartAddress<uintptr_t>();
	Label arm_exit_label;
	assembler->BindToOffset(&arm_exit_label, offset);
	assembler->B(&arm_exit_label, mi);	//statically predicted as not taken

	offset = reinterpret_cast<uintptr_t>(arm_dispatch) - assembler->GetBuffer()->GetStartAddress<uintptr_t>();
	Label arm_dispatch_label;
	assembler->BindToOffset(&arm_dispatch_label, offset);
	assembler->B(&arm_dispatch_label);

	assembler->FinalizeCode();
	verify(assembler->GetBuffer()->GetCursorOffset() <= assembler->GetBuffer()->GetCapacity());
	vmem_platform_flush_cache(
		codestart, assembler->GetBuffer()->GetEndAddress<void*>(),
		codestart, assembler->GetBuffer()->GetEndAddress<void*>());
	icPtr += assembler->GetBuffer()->GetSizeInBytes();

#if 0
	Instruction* instr_start = (Instruction *)codestart;
	Instruction* instr_end = assembler->GetBuffer()->GetEndAddress<Instruction*>();
	Decoder decoder;
	Disassembler disasm;
	decoder.AppendVisitor(&disasm);
	Instruction* instr;
	for (instr = instr_start; instr < instr_end; instr += kInstructionSize) {
		decoder.Decode(instr);
		DEBUG_LOG(AICA_ARM, "arm64 arec\t %p:\t%s",
				   reinterpret_cast<void*>(instr),
				   disasm.GetOutput());
	}
#endif
	delete assembler;
	assembler = NULL;
}

//Hook cus varm misses this, so x86 needs special code
void armv_MOV32(ARM::eReg regn, u32 imm)
{
	assembler->Mov(Register::GetWRegFromCode(regn), imm);
}

void armv_mov(ARM::eReg regd, ARM::eReg regn)
{
	assembler->Mov(Register::GetWRegFromCode(regd), Register::GetWRegFromCode(regn));
}

void armv_add(ARM::eReg regd, ARM::eReg regn, ARM::eReg regm)
{
	assembler->Add(Register::GetWRegFromCode(regd), Register::GetWRegFromCode(regn), Register::GetWRegFromCode(regm));
}

void armv_sub(ARM::eReg regd, ARM::eReg regn, ARM::eReg regm)
{
	assembler->Sub(Register::GetWRegFromCode(regd), Register::GetWRegFromCode(regn), Register::GetWRegFromCode(regm));
}

void armv_add(ARM::eReg regd, ARM::eReg regn, s32 imm)
{
	assembler->Add(Register::GetWRegFromCode(regd), Register::GetWRegFromCode(regn), imm);
}

void armv_lsl(ARM::eReg regd, ARM::eReg regn, u32 imm)
{
	assembler->Lsl(Register::GetWRegFromCode(regd), Register::GetWRegFromCode(regn), imm);
}

void armv_bic(ARM::eReg regd, ARM::eReg regn, u32 imm)
{
	assembler->Bic(Register::GetWRegFromCode(regd), Register::GetWRegFromCode(regn), imm);
}

class android_buf : public std::stringbuf
{
public:
    virtual int sync() override {
    	DEBUG_LOG(AICA_ARM, "ARM7: %s", this->str().c_str());
    	str("");

    	return 0;
    }
};

void armEmit32(u32 opcode)
{
#if 0
	if (opcode != 0x00011001)
	{
		android_buf buffer;
		std::ostream cout(&buffer);
		vixl::aarch32::PrintDisassembler disasm(cout, 0);
		disasm.DecodeA32(opcode);
		cout.flush();
	}
#endif

	const Register& rd = Register::GetWRegFromCode((opcode >> 12) & 15);
	const Register& rn = Register::GetWRegFromCode((opcode >> 16) & 15);
	bool set_flags = opcode & (1 << 20);
	Operand op2;
	int op_type = (opcode >> 21) & 15;
	bool logical_op = op_type == 0 || op_type == 1 || op_type == 8 || op_type == 9	// AND, EOR, TST, TEQ
			 || op_type == 12 || op_type == 13 || op_type == 15 || op_type == 14;	// ORR, MOV, MVN, BIC
	bool set_carry_bit = false;

	ARM::ConditionCode condition = (ARM::ConditionCode)(opcode >> 28);
	void *cond_op_label = armv_start_conditional(condition);

	if (opcode & (1 << 25))
	{
		// op2 is imm8r4
		u32 rotate = ((opcode >> 8) & 15) << 1;
		u32 imm8 = opcode & 0xff;
		op2 = Operand((imm8 >> rotate) | (imm8 << (32 - rotate)));
	}
	else
	{
		// op2 is register
		const Register& rm = Register::GetWRegFromCode(opcode & 15);

		Shift shift = (Shift)((opcode >> 5) & 3);

		if (opcode & (1 << 4))
		{
			// shift by register
			// FIXME Carry must be set based on shift/rotate
			//if (set_flags && logical_op)
			//	die("shift by register with set flags C - not implemented");
			const Register& shift_reg = Register::GetWRegFromCode((opcode >> 8) & 15);

			Label shift_by_32_label;

			switch (shift)
			{
			case LSL:
			case LSR:
				assembler->Mrs(x0, NZCV);
				assembler->Cmp(shift_reg, 32);
				if (shift == LSL)
					assembler->Lsl(w15, rm, shift_reg);
				else
					assembler->Lsr(w15, rm, shift_reg);
				assembler->Csel(w15, 0, w15, ge);		// LSL and LSR by 32 or more gives 0
				assembler->Msr(NZCV, x0);
				break;
			case ASR:
				assembler->Mrs(x0, NZCV);
				assembler->Cmp(shift_reg, 32);
				assembler->Asr(w15, rm, shift_reg);
				assembler->Sbfx(w13, rm, 31, 1);
				assembler->Csel(w15, w13, w15, ge);		// ASR by 32 or more gives 0 or -1 depending on operand sign
				assembler->Msr(NZCV, x0);
				break;
			case ROR:
				assembler->Ror(w15, rm, shift_reg);
				break;
			default:
				die("Invalid shift");
				break;
			}
			op2 = Operand(w15);
		}
		else
		{
			// shift by immediate
			u32 shift_imm = (opcode >> 7) & 0x1f;
			if (shift != ROR && shift_imm != 0 && !(set_flags && logical_op))
			{
				op2 = Operand(rm, shift, shift_imm);
			}
			else if (shift_imm == 0)
			{
				if (shift == LSL)
				{
					op2 = Operand(rm);		// LSL 0 is a no-op
				}
				else
				{
					// Shift by 32
					if (set_flags && logical_op)
						set_carry_bit = true;
					if (shift == LSR)
					{
						if (set_flags && logical_op)
							assembler->Ubfx(w14, rm, 31, 1);			// w14 = rm[31]
						assembler->Mov(w15, 0);							// w15 = 0
					}
					else if (shift == ASR)
					{
						if (set_flags && logical_op)
							assembler->Ubfx(w14, rm, 31, 1);			// w14 = rm[31]
						assembler->Sbfx(w15, rm, 31, 1);				// w15 = rm < 0 ? -1 : 0
					}
					else if (shift == ROR)
					{
						// RRX
						assembler->Cset(w14, cs);						// w14 = C
						assembler->Mov(w15, Operand(rm, LSR, 1));		// w15 = rm >> 1
						assembler->Bfi(w15, w14, 31, 1);				// w15[31] = C
						if (set_flags && logical_op)
							assembler->Ubfx(w14, rm, 0, 1);				// w14 = rm[0] (new C)
					}
					else
						die("Invalid shift");
					op2 = Operand(w15);
				}
			}
			else
			{
				// Carry must be preserved or Ror shift
				if (set_flags && logical_op)
					set_carry_bit = true;
				if (shift == LSL)
				{
					assembler->Ubfx(w14, rm, 32 - shift_imm, 1);	// w14 = rm[lsb]
					assembler->Lsl(w15, rm, shift_imm);				// w15 <<= shift
				}
				else
				{
					if (set_flags && logical_op)
						assembler->Ubfx(w14, rm, shift_imm - 1, 1);	// w14 = rm[msb]

					if (shift == LSR)
						assembler->Lsr(w15, rm, shift_imm);			// w15 >>= shift
					else if (shift == ASR)
						assembler->Asr(w15, rm, shift_imm);
					else if (shift == ROR)
						assembler->Ror(w15, rm, shift_imm);
					else
						die("Invalid shift");
				}
				op2 = Operand(w15);
			}
		}
	}
	if (!set_carry_bit
			&& (op_type == 8 || op_type == 9			// TST and TEQ always set flags
				|| (logical_op && set_flags)))
	{
		// Logical ops should only affect the carry bit based on the op2 shift
		// Here we're not shifting so the carry bit should be preserved
		set_carry_bit = true;
		assembler->Cset(w14, cs);
	}

	switch (op_type)
	{
	case 0:		// AND
		if (set_flags)
			assembler->Ands(rd, rn, op2);
		else
			assembler->And(rd, rn, op2);
		break;
	case 1:		// EOR
		assembler->Eor(rd, rn, op2);
		if (set_flags)
			assembler->Tst(rd, rd);
		break;
	case 2:		// SUB
		if (set_flags)
			assembler->Subs(rd, rn, op2);
		else
			assembler->Sub(rd, rn, op2);
		break;
	case 3:		// RSB
		assembler->Neg(w0, rn);
		if (set_flags)
			assembler->Adds(rd, w0, op2);
		else
			assembler->Add(rd, w0, op2);
		break;
	case 4:		// ADD
		if (set_flags)
			assembler->Adds(rd, rn, op2);
		else
			assembler->Add(rd, rn, op2);
		break;
	case 12:	// ORR
		assembler->Orr(rd, rn, op2);
		if (set_flags)
			assembler->Tst(rd, rd);
		break;
	case 14:	// BIC
		if (set_flags)
			assembler->Bics(rd, rn, op2);
		else
			assembler->Bic(rd, rn, op2);
		break;
	case 5:		// ADC
		if (set_flags)
			assembler->Adcs(rd, rn, op2);
		else
			assembler->Adc(rd, rn, op2);
		break;
	case 6:		// SBC
		if (set_flags)
			assembler->Sbcs(rd, rn, op2);
		else
			assembler->Sbc(rd, rn, op2);
		break;
	case 7:		// RSC
		assembler->Ngc(w0, rn);
		if (set_flags)
			assembler->Adds(rd, w0, op2);
		else
			assembler->Add(rd, w0, op2);
		break;
	case 8:		// TST
		assembler->Tst(rn, op2);
		break;
	case 9:		// TEQ
		assembler->Eor(w0, rn, op2);
		assembler->Tst(w0, w0);
		break;
	case 10:	// CMP
		assembler->Cmp(rn, op2);
		break;
	case 11:	// CMN
		assembler->Cmn(rn, op2);
		break;
	case 13:	// MOV
		assembler->Mov(rd, op2);
		if (set_flags)
			assembler->Tst(rd, rd);
		break;
	case 15:	// MVN
		assembler->Mvn(rd, op2);
		if (set_flags)
			assembler->Tst(rd, rd);
		break;
	}
	if (set_carry_bit)
	{
		assembler->Mrs(x0, NZCV);
		assembler->Bfi(x0, x14, 29, 1);		// C is bit 29 in NZCV
		assembler->Msr(NZCV, x0);
	}
	armv_end_conditional(cond_op_label);
}

//
// Dynarec main loop
//
// w25 is used for temp mem save (post increment op2)
// x26 is the entry points table
// w27 is the cycle counter
// x28 points to the arm7 registers base
__asm__ (
		".globl arm_compilecode				\n\t"
		".hidden arm_compilecode			\n"
	"arm_compilecode:						\n\t"
		"bl CompileCode						\n\t"
		"b arm_dispatch						\n\t"

		".globl arm_mainloop				\n\t"
		".hidden arm_mainloop				\n"
	"arm_mainloop:							\n\t"	//  arm_mainloop(cycles, regs, entry points)
		"stp x25, x26, [sp, #-48]!			\n\t"
		"stp x27, x28, [sp, #16]			\n\t"
		"stp x29, x30, [sp, #32]			\n\t"

		"mov x28, x1						\n\t"	// arm7 registers
		"mov x26, x2						\n\t"	// lookup base

		"ldr w27, [x28, #192]				\n\t"	// cycle count
		"add w27, w27, w0					\n\t"	// add cycles for this timeslice

		".globl arm_dispatch				\n\t"
		".hidden arm_dispatch				\n"
	"arm_dispatch:							\n\t"
		"ldp w0, w1, [x28, #184]			\n\t"	// load Next PC, interrupt
		"ubfx w2, w0, #2, #21				\n\t"	// w2 = pc >> 2. Note: assuming address space == 8 MB (23 bits)
		"cbnz w1, arm_dofiq					\n\t"	// if interrupt pending, handle it

		"add x2, x26, x2, lsl #3			\n\t"	// x2 = EntryPoints + pc << 1
		"ldr x3, [x2]						\n\t"
		"br x3								\n"

	"arm_dofiq:								\n\t"
		"bl CPUFiq							\n\t"
		"b arm_dispatch						\n\t"

		".globl arm_exit					\n\t"
		".hidden arm_exit					\n"
	"arm_exit:								\n\t"
		"str w27, [x28, #192]				\n\t"	// if timeslice is over, save remaining cycles
		"ldp x29, x30, [sp, #32]			\n\t"
		"ldp x27, x28, [sp, #16]			\n\t"
		"ldp x25, x26, [sp], #48			\n\t"
		"ret								\n"
);
#endif // ARM64
