// SPDX-FileCopyrightText: 2002-2024 PCSX2 Dev Team
// SPDX-License-Identifier: GPL-3.0+

/*
 * ix86 core v0.9.1
 *
 * Original Authors (v0.6.2 and prior):
 *		linuzappz <linuzappz@pcsx.net>
 *		alexey silinov
 *		goldfinger
 *		zerofrog(@gmail.com)
 *
 * Authors of v0.9.1:
 *		Jake.Stine(@gmail.com)
 *		cottonvibes(@gmail.com)
 *		sudonim(1@gmail.com)
 */

#include "common/emitter/internal.h"
#include <functional>

// ------------------------------------------------------------------------
// Notes on Thread Local Storage:
//  * TLS is pretty simple, and "just works" from a programmer perspective, with only
//    some minor additional computational overhead (see performance notes below).
//
//  * MSVC and GCC handle TLS differently internally, but behavior to the programmer is
//    generally identical.
//
// Performance Considerations:
//  * GCC's implementation involves an extra dereference from normal storage (possibly
//    applies to x86-32 only -- x86-64 is untested).
//
//  * MSVC's implementation involves *two* extra dereferences from normal storage because
//    it has to look up the TLS heap pointer from the Windows Thread Storage Area.  (in
//    generated ASM code, this dereference is denoted by access to the fs:[2ch] address),
//
//  * However, in either case, the optimizer usually optimizes it to a register so the
//    extra overhead is minimal over a series of instructions.
//
// MSVC Notes:
//  * Important!! the Full Optimization [/Ox] option effectively disables TLS optimizations
//    in MSVC 2008 and earlier, causing generally significant code bloat.  Not tested in
//    VC2010 yet.
//
//  * VC2010 generally does a superior job of optimizing TLS across inlined functions and
//    class methods, compared to predecessors.
//


thread_local u8* x86Ptr;
thread_local XMMSSEType g_xmmtypes[iREGCNT_XMM] = {XMMT_INT};

namespace x86Emitter
{

	template void xWrite<u8>(u8 val);
	template void xWrite<u16>(u16 val);
	template void xWrite<u32>(u32 val);
	template void xWrite<u64>(u64 val);
	template void xWrite<u128>(u128 val);

	__fi void xWrite8(u8 val)
	{
		xWrite(val);
	}

	__fi void xWrite16(u16 val)
	{
		xWrite(val);
	}

	__fi void xWrite32(u32 val)
	{
		xWrite(val);
	}

	__fi void xWrite64(u64 val)
	{
		xWrite(val);
	}

	// Empty initializers are due to frivolously pointless GCC errors (it demands the
	// objects be initialized even though they have no actual variable members).

	const xAddressIndexer<xIndirectVoid> ptr = {};
	const xAddressIndexer<xIndirectNative> ptrNative = {};
	const xAddressIndexer<xIndirect128> ptr128 = {};
	const xAddressIndexer<xIndirect64> ptr64 = {};
	const xAddressIndexer<xIndirect32> ptr32 = {};
	const xAddressIndexer<xIndirect16> ptr16 = {};
	const xAddressIndexer<xIndirect8> ptr8 = {};

	// ------------------------------------------------------------------------

	const xRegisterEmpty xEmptyReg = {};

	// clang-format off

const xRegisterSSE
    xmm0(0), xmm1(1),
    xmm2(2), xmm3(3),
    xmm4(4), xmm5(5),
    xmm6(6), xmm7(7),
    xmm8(8), xmm9(9),
    xmm10(10), xmm11(11),
    xmm12(12), xmm13(13),
    xmm14(14), xmm15(15);

const xRegisterSSE
    ymm0(0, xRegisterYMMTag()), ymm1(1, xRegisterYMMTag()),
    ymm2(2, xRegisterYMMTag()), ymm3(3, xRegisterYMMTag()),
    ymm4(4, xRegisterYMMTag()), ymm5(5, xRegisterYMMTag()),
    ymm6(6, xRegisterYMMTag()), ymm7(7, xRegisterYMMTag()),
    ymm8(8, xRegisterYMMTag()), ymm9(9, xRegisterYMMTag()),
    ymm10(10, xRegisterYMMTag()), ymm11(11, xRegisterYMMTag()),
    ymm12(12, xRegisterYMMTag()), ymm13(13, xRegisterYMMTag()),
    ymm14(14, xRegisterYMMTag()), ymm15(15, xRegisterYMMTag());

const xAddressReg
    rax(0), rbx(3),
    rcx(1), rdx(2),
    rsp(4), rbp(5),
    rsi(6), rdi(7),
    r8(8), r9(9),
    r10(10), r11(11),
    r12(12), r13(13),
    r14(14), r15(15);

const xRegister32
    eax(0), ebx(3),
    ecx(1), edx(2),
    esp(4), ebp(5),
    esi(6), edi(7),
    r8d(8), r9d(9),
    r10d(10), r11d(11),
    r12d(12), r13d(13),
    r14d(14), r15d(15);

const xRegister16
    ax(0), bx(3),
    cx(1), dx(2),
    sp(4), bp(5),
    si(6), di(7);

const xRegister8
    al(0),
    dl(2), bl(3),
    ah(4), ch(5),
    dh(6), bh(7),
    spl(4, true), bpl(5, true),
    sil(6, true), dil(7, true),
    r8b(8), r9b(9),
    r10b(10), r11b(11),
    r12b(12), r13b(13),
    r14b(14), r15b(15);

#if defined(_WIN32)
const xAddressReg
    arg1reg = rcx,
    arg2reg = rdx,
    arg3reg = r8,
    arg4reg = r9,
    calleeSavedReg1 = rdi,
    calleeSavedReg2 = rsi;

const xRegister32
    arg1regd = ecx,
    arg2regd = edx,
    calleeSavedReg1d = edi,
    calleeSavedReg2d = esi;
#else
const xAddressReg
    arg1reg = rdi,
    arg2reg = rsi,
    arg3reg = rdx,
    arg4reg = rcx,
    calleeSavedReg1 = r12,
    calleeSavedReg2 = r13;

const xRegister32
    arg1regd = edi,
    arg2regd = esi,
    calleeSavedReg1d = r12d,
    calleeSavedReg2d = r13d;
#endif

	// clang-format on

	const xRegisterCL cl;

	const char* const x86_regnames_gpr8[] =
	{
		"al", "cl", "dl", "bl",
		"ah", "ch", "dh", "bh",
		"b8", "b9", "b10", "b11",
		"b12", "b13", "b14", "b15"
	};

	const char* const x86_regnames_gpr16[] =
	{
		"ax", "cx", "dx", "bx",
		"sp", "bp", "si", "di",
		"h8", "h9", "h10", "h11",
		"h12", "h13", "h14", "h15"
	};

	const char* const x86_regnames_gpr32[] =
	{
		"eax", "ecx", "edx", "ebx",
		"esp", "ebp", "esi", "edi",
		"e8", "e9", "e10", "e11",
		"e12", "e13", "e14", "e15"
	};

	const char* const x86_regnames_gpr64[] =
	{
		"rax", "rcx", "rdx", "rbx",
		"rsp", "rbp", "rsi", "rdi",
		"r8", "r9", "r10", "r11",
		"r12", "r13", "r14", "r15"
	};

	const char* const x86_regnames_sse[] =
	{
		"xmm0", "xmm1", "xmm2", "xmm3",
		"xmm4", "xmm5", "xmm6", "xmm7",
		"xmm8", "xmm9", "xmm10", "xmm11",
		"xmm12", "xmm13", "xmm14", "xmm15"
	};

	const char* xRegisterBase::GetName()
	{
		if (Id == xRegId_Invalid)
			return "invalid";
		if (Id == xRegId_Empty)
			return "empty";

		// bad error?  Return a "big" error string.  Might break formatting of register tables
		// but that's the least of your worries if you see this baby.
		if (Id >= (int)iREGCNT_GPR || Id < 0)
			return "!Register index out of range!";

		switch (GetOperandSize())
		{
			case 1:
				return x86_regnames_gpr8[Id];
			case 2:
				return x86_regnames_gpr16[Id];
			case 4:
				return x86_regnames_gpr32[Id];
			case 8:
				return x86_regnames_gpr64[Id];
			case 16:
				return x86_regnames_sse[Id];
		}

		return "oops?";
	}

	//////////////////////////////////////////////////////////////////////////////////////////
	// Performance note: VC++ wants to use byte/word register form for the following
	// ModRM/SibSB constructors when we use xWrite<u8>, and furthermore unrolls the
	// the shift using a series of ADDs for the following results:
	//   add cl,cl
	//   add cl,cl
	//   add cl,cl
	//   or  cl,bl
	//   add cl,cl
	//  ... etc.
	//
	// This is unquestionably bad optimization by Core2 standard, an generates tons of
	// register aliases and false dependencies. (although may have been ideal for early-
	// brand P4s with a broken barrel shifter?).  The workaround is to do our own manual
	// x86Ptr access and update using a u32 instead of u8.  Thanks to little endianness,
	// the same end result is achieved and no false dependencies are generated.  The draw-
	// back is that it clobbers 3 bytes past the end of the write, which could cause a
	// headache for someone who himself is doing some kind of headache-inducing amount of
	// recompiler SMC.  So we don't do a work-around, and just hope for the compiler to
	// stop sucking someday instead. :)
	//
	// (btw, I know this isn't a critical performance item by any means, but it's
	//  annoying simply because it *should* be an easy thing to optimize)

	static __fi void ModRM(uint mod, uint reg, uint rm)
	{
		xWrite8((mod << 6) | (reg << 3) | rm);
	}

	static __fi void SibSB(u32 ss, u32 index, u32 base)
	{
		xWrite8((ss << 6) | (index << 3) | base);
	}

	void EmitSibMagic(uint regfield, const void* address, int extraRIPOffset)
	{
		sptr displacement = (sptr)address;
		sptr ripRelative = (sptr)address - ((sptr)x86Ptr + sizeof(s8) + sizeof(s32) + extraRIPOffset);
		// Can we use a rip-relative address?  (Prefer this over eiz because it's a byte shorter)
		if (ripRelative == (s32)ripRelative)
		{
			ModRM(0, regfield, ModRm_UseDisp32);
			displacement = ripRelative;
		}
		else
		{
			pxAssertMsg(displacement == (s32)displacement, "SIB target is too far away, needs an indirect register");
			ModRM(0, regfield, ModRm_UseSib);
			SibSB(0, Sib_EIZ, Sib_UseDisp32);
		}

		xWrite<s32>((s32)displacement);
	}

	//////////////////////////////////////////////////////////////////////////////////////////
	// returns TRUE if this instruction requires SIB to be encoded, or FALSE if the
	// instruction ca be encoded as ModRm alone.
	static __fi bool NeedsSibMagic(const xIndirectVoid& info)
	{
		// no registers? no sibs!
		// (xIndirectVoid::Reduce always places a register in Index, and optionally leaves
		// Base empty if only register is specified)
		if (info.Index.IsEmpty())
			return false;

		// A scaled register needs a SIB
		if (info.Scale != 0)
			return true;

		// two registers needs a SIB
		if (!info.Base.IsEmpty())
			return true;

		return false;
	}

	//////////////////////////////////////////////////////////////////////////////////////////
	// Conditionally generates Sib encoding information!
	//
	// regfield - register field to be written to the ModRm.  This is either a register specifier
	//   or an opcode extension.  In either case, the instruction determines the value for us.
	//
	void EmitSibMagic(uint regfield, const xIndirectVoid& info, int extraRIPOffset)
	{
		// 3 bits also on x86_64 (so max is 8)
		// We might need to mask it on x86_64
		pxAssertMsg(regfield < 8, "Invalid x86 register identifier.");
		int displacement_size = (info.Displacement == 0) ? 0 :
                                                           ((info.IsByteSizeDisp()) ? 1 : 2);

		pxAssert(!info.Base.IsEmpty() || !info.Index.IsEmpty() || displacement_size == 2);
		// Displacement is only 64 bits for rip-relative addressing
		pxAssert(info.Displacement == (s32)info.Displacement || (info.Base.IsEmpty() && info.Index.IsEmpty()));

		if (!NeedsSibMagic(info))
		{
			// Use ModRm-only encoding, with the rm field holding an index/base register, if
			// one has been specified.  If neither register is specified then use Disp32 form,
			// which is encoded as "EBP w/o displacement" (which is why EBP must always be
			// encoded *with* a displacement of 0, if it would otherwise not have one).

			if (info.Index.IsEmpty())
			{
				EmitSibMagic(regfield, (void*)info.Displacement, extraRIPOffset);
				return;
			}
			else
			{
				if (info.Index == rbp && displacement_size == 0)
					displacement_size = 1; // forces [ebp] to be encoded as [ebp+0]!

				ModRM(displacement_size, regfield, info.Index.Id & 7);
			}
		}
		else
		{
			// In order to encode "just" index*scale (and no base), we have to encode
			// it as a special [index*scale + displacement] form, which is done by
			// specifying EBP as the base register and setting the displacement field
			// to zero. (same as ModRm w/o SIB form above, basically, except the
			// ModRm_UseDisp flag is specified in the SIB instead of the ModRM field).

			if (info.Base.IsEmpty())
			{
				ModRM(0, regfield, ModRm_UseSib);
				SibSB(info.Scale, info.Index.Id, Sib_UseDisp32);
				xWrite<s32>(info.Displacement);
				return;
			}
			else
			{
				if (info.Base == rbp && displacement_size == 0)
					displacement_size = 1; // forces [ebp] to be encoded as [ebp+0]!

				ModRM(displacement_size, regfield, ModRm_UseSib);
				SibSB(info.Scale, info.Index.Id & 7, info.Base.Id & 7);
			}
		}

		if (displacement_size != 0)
		{
			if (displacement_size == 1)
				xWrite<s8>(info.Displacement);
			else
				xWrite<s32>(info.Displacement);
		}
	}

	// Writes a ModRM byte for "Direct" register access forms, which is used for all
	// instructions taking a form of [reg,reg].
	void EmitSibMagic(uint reg1, const xRegisterBase& reg2, int)
	{
		xWrite8((Mod_Direct << 6) | (reg1 << 3) | (reg2.Id & 7));
	}

	void EmitSibMagic(const xRegisterBase& reg1, const xRegisterBase& reg2, int)
	{
		xWrite8((Mod_Direct << 6) | ((reg1.Id & 7) << 3) | (reg2.Id & 7));
	}

	void EmitSibMagic(const xRegisterBase& reg1, const void* src, int extraRIPOffset)
	{
		EmitSibMagic(reg1.Id & 7, src, extraRIPOffset);
	}

	void EmitSibMagic(const xRegisterBase& reg1, const xIndirectVoid& sib, int extraRIPOffset)
	{
		EmitSibMagic(reg1.Id & 7, sib, extraRIPOffset);
	}

	//////////////////////////////////////////////////////////////////////////////////////////
	__emitinline static void EmitRex(bool w, bool r, bool x, bool b, bool ext8bit = false)
	{
		const u8 rex = 0x40 | (w << 3) | (r << 2) | (x << 1) | (u8)b;
		if (rex != 0x40 || ext8bit)
			xWrite8(rex);
	}

	void EmitRex(uint regfield, const void* address)
	{
		pxAssert(0);
		bool w = false;
		bool r = false;
		bool x = false;
		bool b = false;
		EmitRex(w, r, x, b);
	}

	void EmitRex(uint regfield, const xIndirectVoid& info)
	{
		bool w = info.IsWide();
		bool r = false;
		bool x = info.Index.IsExtended();
		bool b = info.Base.IsExtended();
		if (!NeedsSibMagic(info))
		{
			b = x;
			x = false;
		}
		EmitRex(w, r, x, b);
	}

	void EmitRex(uint reg1, const xRegisterBase& reg2)
	{
		bool w = reg2.IsWide();
		bool r = false;
		bool x = false;
		bool b = reg2.IsExtended();
		EmitRex(w, r, x, b, reg2.IsExtended8Bit());
	}

	void EmitRex(const xRegisterBase& reg1, const xRegisterBase& reg2)
	{
		bool w = reg1.IsWide() || reg2.IsWide();
		bool r = reg1.IsExtended();
		bool x = false;
		bool b = reg2.IsExtended();
		EmitRex(w, r, x, b, reg2.IsExtended8Bit());
	}

	void EmitRex(const xRegisterBase& reg1, const void* src)
	{
		pxAssert(0); //see fixme
		bool w = reg1.IsWide();
		bool r = reg1.IsExtended();
		bool x = false;
		bool b = false; // FIXME src.IsExtended();
		EmitRex(w, r, x, b, reg1.IsExtended8Bit());
	}

	void EmitRex(const xRegisterBase& reg1, const xIndirectVoid& sib)
	{
		bool w = reg1.IsWide() || sib.IsWide();
		bool r = reg1.IsExtended();
		bool x = sib.Index.IsExtended();
		bool b = sib.Base.IsExtended();
		if (!NeedsSibMagic(sib))
		{
			b = x;
			x = false;
		}
		EmitRex(w, r, x, b, reg1.IsExtended8Bit());
	}

	// For use by instructions that are implicitly wide
	void EmitRexImplicitlyWide(const xRegisterBase& reg)
	{
		bool w = false;
		bool r = false;
		bool x = false;
		bool b = reg.IsExtended();
		EmitRex(w, r, x, b);
	}

	void EmitRexImplicitlyWide(const xIndirectVoid& sib)
	{
		bool w = false;
		bool r = false;
		bool x = sib.Index.IsExtended();
		bool b = sib.Base.IsExtended();
		if (!NeedsSibMagic(sib))
		{
			b = x;
			x = false;
		}
		EmitRex(w, r, x, b);
	}


	// --------------------------------------------------------------------------------------
	//  xSetPtr / xAlignPtr / xGetPtr / xAdvancePtr
	// --------------------------------------------------------------------------------------

	// Assigns the current emitter buffer target address.
	// This is provided instead of using x86Ptr directly, since we may in the future find
	// a need to change the storage class system for the x86Ptr 'under the hood.'
	__emitinline void xSetPtr(void* ptr)
	{
		x86Ptr = (u8*)ptr;
	}

	// Retrieves the current emitter buffer target address.
	// This is provided instead of using x86Ptr directly, since we may in the future find
	// a need to change the storage class system for the x86Ptr 'under the hood.'
	__emitinline u8* xGetPtr()
	{
		return x86Ptr;
	}

	__emitinline void xAlignPtr(uint bytes)
	{
		// forward align
		x86Ptr = (u8*)(((uptr)x86Ptr + bytes - 1) & ~(uptr)(bytes - 1));
	}

	// Performs best-case alignment for the target CPU, for use prior to starting a new
	// function.  This is not meant to be used prior to jump targets, since it doesn't
	// add padding (additionally, speed benefit from jump alignment is minimal, and often
	// a loss).
	__emitinline void xAlignCallTarget()
	{
		// Core2/i7 CPUs prefer unaligned addresses.  Checking for SSSE3 is a decent filter.
		// (also align in debug modes for disasm convenience)

		if constexpr (IsDebugBuild)
		{
			// - P4's and earlier prefer 16 byte alignment.
			// - AMD Athlons and Phenoms prefer 8 byte alignment, but I don't have an easy
			//   heuristic for it yet.
			// - AMD Phenom IIs are unknown (either prefer 8 byte, or unaligned).

			xAlignPtr(16);
		}
	}

	__emitinline u8* xGetAlignedCallTarget()
	{
		xAlignCallTarget();
		return x86Ptr;
	}

	__emitinline void xAdvancePtr(uint bytes)
	{
		if (IsDevBuild)
		{
			// common debugger courtesy: advance with INT3 as filler.
			for (uint i = 0; i < bytes; i++)
				xWrite8(0xcc);
		}
		else
			x86Ptr += bytes;
	}

	// --------------------------------------------------------------------------------------
	//  xRegisterInt  (method implementations)
	// --------------------------------------------------------------------------------------
	xRegisterInt xRegisterInt::MatchSizeTo(xRegisterInt other) const
	{
		return other.GetOperandSize() == 1 ? xRegisterInt(xRegister8(*this)) : xRegisterInt(other.GetOperandSize(), Id);
	}

	// --------------------------------------------------------------------------------------
	//  xAddressReg  (operator overloads)
	// --------------------------------------------------------------------------------------
	xAddressVoid xAddressReg::operator+(const xAddressReg& right) const
	{
		pxAssertMsg(right.Id != -1 || Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(*this, right);
	}

	xAddressVoid xAddressReg::operator+(sptr right) const
	{
		pxAssertMsg(Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(*this, right);
	}

	xAddressVoid xAddressReg::operator+(const void* right) const
	{
		pxAssertMsg(Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(*this, (sptr)right);
	}

	xAddressVoid xAddressReg::operator-(sptr right) const
	{
		pxAssertMsg(Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(*this, -right);
	}

	xAddressVoid xAddressReg::operator-(const void* right) const
	{
		pxAssertMsg(Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(*this, -(sptr)right);
	}

	xAddressVoid xAddressReg::operator*(int factor) const
	{
		pxAssertMsg(Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(xEmptyReg, *this, factor);
	}

	xAddressVoid xAddressReg::operator<<(u32 shift) const
	{
		pxAssertMsg(Id != -1, "Uninitialized x86 register.");
		return xAddressVoid(xEmptyReg, *this, 1 << shift);
	}


	// --------------------------------------------------------------------------------------
	//  xAddressVoid  (method implementations)
	// --------------------------------------------------------------------------------------

	xAddressVoid::xAddressVoid(const xAddressReg& base, const xAddressReg& index, int factor, sptr displacement)
	{
		Base = base;
		Index = index;
		Factor = factor;
		Displacement = displacement;

		pxAssertMsg(base.Id != xRegId_Invalid, "Uninitialized x86 register.");
		pxAssertMsg(index.Id != xRegId_Invalid, "Uninitialized x86 register.");
	}

	xAddressVoid::xAddressVoid(const xAddressReg& index, sptr displacement)
	{
		Base = xEmptyReg;
		Index = index;
		Factor = 0;
		Displacement = displacement;

		pxAssertMsg(index.Id != xRegId_Invalid, "Uninitialized x86 register.");
	}

	xAddressVoid::xAddressVoid(sptr displacement)
	{
		Base = xEmptyReg;
		Index = xEmptyReg;
		Factor = 0;
		Displacement = displacement;
	}

	xAddressVoid::xAddressVoid(const void* displacement)
	{
		Base = xEmptyReg;
		Index = xEmptyReg;
		Factor = 0;
		Displacement = (sptr)displacement;
	}

	xAddressVoid& xAddressVoid::Add(const xAddressReg& src)
	{
		if (src == Index)
		{
			Factor++;
		}
		else if (src == Base)
		{
			// Compound the existing register reference into the Index/Scale pair.
			Base = xEmptyReg;

			if (src == Index)
				Factor++;
			else
			{
				pxAssertMsg(Index.IsEmpty(), "x86Emitter: Only one scaled index register is allowed in an address modifier.");
				Index = src;
				Factor = 2;
			}
		}
		else if (Base.IsEmpty())
			Base = src;
		else if (Index.IsEmpty())
			Index = src;
		else
			pxAssumeMsg(false, "x86Emitter: address modifiers cannot have more than two index registers."); // oops, only 2 regs allowed per ModRm!

		return *this;
	}

	xAddressVoid& xAddressVoid::Add(const xAddressVoid& src)
	{
		Add(src.Base);
		Add(src.Displacement);

		// If the factor is 1, we can just treat index like a base register also.
		if (src.Factor == 1)
		{
			Add(src.Index);
		}
		else if (Index.IsEmpty())
		{
			Index = src.Index;
			Factor = src.Factor;
		}
		else if (Index == src.Index)
		{
			Factor += src.Factor;
		}
		else
			pxAssumeMsg(false, "x86Emitter: address modifiers cannot have more than two index registers."); // oops, only 2 regs allowed per ModRm!

		return *this;
	}

	xIndirectVoid::xIndirectVoid(const xAddressVoid& src)
	{
		Base = src.Base;
		Index = src.Index;
		Scale = src.Factor;
		Displacement = src.Displacement;

		Reduce();
	}

	xIndirectVoid::xIndirectVoid(sptr disp)
	{
		Base = xEmptyReg;
		Index = xEmptyReg;
		Scale = 0;
		Displacement = disp;

		// no reduction necessary :D
	}

	xIndirectVoid::xIndirectVoid(xAddressReg base, xAddressReg index, int scale, sptr displacement)
	{
		Base = base;
		Index = index;
		Scale = scale;
		Displacement = displacement;

		Reduce();
	}

	// Generates a 'reduced' ModSib form, which has valid Base, Index, and Scale values.
	// Necessary because by default ModSib compounds registers into Index when possible.
	//
	// If the ModSib is in illegal form ([Base + Index*5] for example) then an assertion
	// followed by an InvalidParameter Exception will be tossed around in haphazard
	// fashion.
	//
	// Optimization Note: Currently VC does a piss poor job of inlining this, even though
	// constant propagation *should* resove it to little or no code (VC's constprop fails
	// on C++ class initializers).  There is a work around [using array initializers instead]
	// but it's too much trouble for code that isn't performance critical anyway.
	// And, with luck, maybe VC10 will optimize it better and make it a non-issue. :D
	//
	void xIndirectVoid::Reduce()
	{
		if (Index.IsStackPointer())
		{
			// esp cannot be encoded as the index, so move it to the Base, if possible.
			// note: intentionally leave index assigned to esp also (generates correct
			// encoding later, since ESP cannot be encoded 'alone')

			pxAssert(Scale == 0); // esp can't have an index modifier!
			pxAssert(Base.IsEmpty()); // base must be empty or else!

			Base = Index;
			return;
		}

		// If no index reg, then load the base register into the index slot.
		if (Index.IsEmpty())
		{
			Index = Base;
			Scale = 0;
			if (!Base.IsStackPointer()) // prevent ESP from being encoded 'alone'
				Base = xEmptyReg;
			return;
		}

		// The Scale has a series of valid forms, all shown here:

		switch (Scale)
		{
			case 0:
				break;
			case 1:
				Scale = 0;
				break;
			case 2:
				Scale = 1;
				break;

			case 3: // becomes [reg*2+reg]
				pxAssertMsg(Base.IsEmpty(), "Cannot scale an Index register by 3 when Base is not empty!");
				Base = Index;
				Scale = 1;
				break;

			case 4:
				Scale = 2;
				break;

			case 5: // becomes [reg*4+reg]
				pxAssertMsg(Base.IsEmpty(), "Cannot scale an Index register by 5 when Base is not empty!");
				Base = Index;
				Scale = 2;
				break;

			case 6: // invalid!
				pxAssumeMsg(false, "x86 asm cannot scale a register by 6.");
				break;

			case 7: // so invalid!
				pxAssumeMsg(false, "x86 asm cannot scale a register by 7.");
				break;

			case 8:
				Scale = 3;
				break;
			case 9: // becomes [reg*8+reg]
				pxAssertMsg(Base.IsEmpty(), "Cannot scale an Index register by 9 when Base is not empty!");
				Base = Index;
				Scale = 3;
				break;

				jNO_DEFAULT
		}
	}

	xIndirectVoid& xIndirectVoid::Add(sptr imm)
	{
		Displacement += imm;
		return *this;
	}

	// ------------------------------------------------------------------------
	// Internal implementation of EmitSibMagic which has been custom tailored
	// to optimize special forms of the Lea instructions accordingly, such
	// as when a LEA can be replaced with a "MOV reg,imm" or "MOV reg,reg".
	//
	// preserve_flags - set to ture to disable use of SHL on [Index*Base] forms
	// of LEA, which alters flags states.
	//
	static void EmitLeaMagic(const xRegisterInt& to, const xIndirectVoid& src, bool preserve_flags)
	{
		int displacement_size = (src.Displacement == 0) ? 0 :
                                                          ((src.IsByteSizeDisp()) ? 1 : 2);

		// See EmitSibMagic for commenting on SIB encoding.

		if (!NeedsSibMagic(src) && src.Displacement == (s32)src.Displacement)
		{
			// LEA Land: means we have either 1-register encoding or just an offset.
			// offset is encodable as an immediate MOV, and a register is encodable
			// as a register MOV.

			if (src.Index.IsEmpty())
			{
				xMOV(to, src.Displacement);
				return;
			}
			else if (displacement_size == 0)
			{
				_xMovRtoR(to, src.Index.MatchSizeTo(to));
				return;
			}
			else if (!preserve_flags)
			{
				// encode as MOV and ADD combo.  Make sure to use the immediate on the
				// ADD since it can encode as an 8-bit sign-extended value.

				_xMovRtoR(to, src.Index.MatchSizeTo(to));
				xADD(to, src.Displacement);
				return;
			}
		}
		else
		{
			if (src.Base.IsEmpty())
			{
				if (!preserve_flags && (displacement_size == 0))
				{
					// Encode [Index*Scale] as a combination of Mov and Shl.
					// This is more efficient because of the bloated LEA format which requires
					// a 32 bit displacement, and the compact nature of the alternative.
					//
					// (this does not apply to older model P4s with the broken barrel shifter,
					//  but we currently aren't optimizing for that target anyway).

					_xMovRtoR(to, src.Index);
					xSHL(to, src.Scale);
					return;
				}
			}
			else
			{
				if (src.Scale == 0)
				{
					if (!preserve_flags)
					{
						if (src.Index == rsp)
						{
							// ESP is not encodable as an index (ix86 ignores it), thus:
							_xMovRtoR(to, src.Base.MatchSizeTo(to)); // will do the trick!
							if (src.Displacement)
								xADD(to, src.Displacement);
							return;
						}
						else if (src.Displacement == 0)
						{
							_xMovRtoR(to, src.Base.MatchSizeTo(to));
							_g1_EmitOp(G1Type_ADD, to, src.Index.MatchSizeTo(to));
							return;
						}
					}
					else if ((src.Index == rsp) && (src.Displacement == 0))
					{
						// special case handling of ESP as Index, which is replaceable with
						// a single MOV even when preserve_flags is set! :D

						_xMovRtoR(to, src.Base.MatchSizeTo(to));
						return;
					}
				}
			}
		}

		xOpWrite(0, 0x8d, to, src);
	}

	__emitinline void xLEA(xRegister64 to, const xIndirectVoid& src, bool preserve_flags)
	{
		EmitLeaMagic(to, src, preserve_flags);
	}

	__emitinline void xLEA(xRegister32 to, const xIndirectVoid& src, bool preserve_flags)
	{
		EmitLeaMagic(to, src, preserve_flags);
	}

	__emitinline void xLEA(xRegister16 to, const xIndirectVoid& src, bool preserve_flags)
	{
		xWrite8(0x66);
		EmitLeaMagic(to, src, preserve_flags);
	}

	__emitinline u32* xLEA_Writeback(xAddressReg to)
	{
		xOpWrite(0, 0x8d, to, ptr[(void*)(0xdcdcdcd + (uptr)xGetPtr() + 7)]);

		return (u32*)xGetPtr() - 1;
	}

	// =====================================================================================================
	//  TEST / INC / DEC
	// =====================================================================================================
	void xImpl_Test::operator()(const xRegisterInt& to, const xRegisterInt& from) const
	{
		pxAssert(to.GetOperandSize() == from.GetOperandSize());
		xOpWrite(to.GetPrefix16(), to.Is8BitOp() ? 0x84 : 0x85, from, to);
	}

	void xImpl_Test::operator()(const xIndirect64orLess& dest, int imm) const
	{
		xOpWrite(dest.GetPrefix16(), dest.Is8BitOp() ? 0xf6 : 0xf7, 0, dest, dest.GetImmSize());
		dest.xWriteImm(imm);
	}

	void xImpl_Test::operator()(const xRegisterInt& to, int imm) const
	{
		if (to.IsAccumulator())
		{
			xOpAccWrite(to.GetPrefix16(), to.Is8BitOp() ? 0xa8 : 0xa9, 0, to);
		}
		else
		{
			xOpWrite(to.GetPrefix16(), to.Is8BitOp() ? 0xf6 : 0xf7, 0, to);
		}
		to.xWriteImm(imm);
	}

	void xImpl_BitScan::operator()(const xRegister16or32or64& to, const xRegister16or32or64& from) const
	{
		pxAssert(to->GetOperandSize() == from->GetOperandSize());
		xOpWrite0F(from->GetPrefix16(), Opcode, to, from);
	}
	void xImpl_BitScan::operator()(const xRegister16or32or64& to, const xIndirectVoid& sibsrc) const
	{
		xOpWrite0F(to->GetPrefix16(), Opcode, to, sibsrc);
	}

	void xImpl_IncDec::operator()(const xRegisterInt& to) const
	{
		if (to.Is8BitOp())
		{
			u8 regfield = isDec ? 1 : 0;
			xOpWrite(to.GetPrefix16(), 0xfe, regfield, to);
		}
		else
		{
			xOpWrite(to.GetPrefix16(), 0xff, isDec ? 1 : 0, to);
		}
	}

	void xImpl_IncDec::operator()(const xIndirect64orLess& to) const
	{
		to.prefix16();
		xWrite8(to.Is8BitOp() ? 0xfe : 0xff);
		EmitSibMagic(isDec ? 1 : 0, to);
	}

	void xImpl_DwordShift::operator()(const xRegister16or32or64& to, const xRegister16or32or64& from, const xRegisterCL& /* clreg */) const
	{
		pxAssert(to->GetOperandSize() == from->GetOperandSize());
		xOpWrite0F(from->GetPrefix16(), OpcodeBase + 1, to, from);
	}

	void xImpl_DwordShift::operator()(const xRegister16or32or64& to, const xRegister16or32or64& from, u8 shiftcnt) const
	{
		pxAssert(to->GetOperandSize() == from->GetOperandSize());
		if (shiftcnt != 0)
			xOpWrite0F(from->GetPrefix16(), OpcodeBase, to, from, shiftcnt);
	}

	void xImpl_DwordShift::operator()(const xIndirectVoid& dest, const xRegister16or32or64& from, const xRegisterCL& /* clreg */) const
	{
		xOpWrite0F(from->GetPrefix16(), OpcodeBase + 1, from, dest);
	}

	void xImpl_DwordShift::operator()(const xIndirectVoid& dest, const xRegister16or32or64& from, u8 shiftcnt) const
	{
		if (shiftcnt != 0)
			xOpWrite0F(from->GetPrefix16(), OpcodeBase, from, dest, shiftcnt);
	}

	const xImpl_Test xTEST = {};

	const xImpl_BitScan xBSF = {0xbc};
	const xImpl_BitScan xBSR = {0xbd};

	const xImpl_IncDec xINC = {false};
	const xImpl_IncDec xDEC = {true};

	const xImpl_DwordShift xSHLD = {0xa4};
	const xImpl_DwordShift xSHRD = {0xac};

	//////////////////////////////////////////////////////////////////////////////////////////
	// Push / Pop Emitters
	//
	// Note: pushad/popad implementations are intentionally left out.  The instructions are
	// invalid in x64, and are super slow on x32.  Use multiple Push/Pop instructions instead.

	__emitinline void xPOP(const xIndirectVoid& from)
	{
		EmitRexImplicitlyWide(from);
		xWrite8(0x8f);
		EmitSibMagic(0, from);
	}

	__emitinline void xPUSH(const xIndirectVoid& from)
	{
		EmitRexImplicitlyWide(from);
		xWrite8(0xff);
		EmitSibMagic(6, from);
	}

	__fi void xPOP(xRegister32or64 from)
	{
		EmitRexImplicitlyWide(from);
		xWrite8(0x58 | (from->Id & 7));
	}

	__fi void xPUSH(u32 imm)
	{
		if (is_s8(imm))
		{
			xWrite8(0x6a);
			xWrite8(imm);
		}
		else
		{
			xWrite8(0x68);
			xWrite32(imm);
		}
	}
	__fi void xPUSH(xRegister32or64 from)
	{
		EmitRexImplicitlyWide(from);
		xWrite8(0x50 | (from->Id & 7));
	}

	// pushes the EFLAGS register onto the stack
	__fi void xPUSHFD() { xWrite8(0x9C); }
	// pops the EFLAGS register from the stack
	__fi void xPOPFD() { xWrite8(0x9D); }


	//////////////////////////////////////////////////////////////////////////////////////////
	//

	__fi void xLEAVE() { xWrite8(0xC9); }
	__fi void xRET() { xWrite8(0xC3); }
	__fi void xCBW() { xWrite16(0x9866); }
	__fi void xCWD() { xWrite8(0x98); }
	__fi void xCDQ() { xWrite8(0x99); }
	__fi void xCWDE() { xWrite8(0x98); }
	__fi void xCDQE() { xWrite16(0x9848); }

	__fi void xLAHF() { xWrite8(0x9f); }
	__fi void xSAHF() { xWrite8(0x9e); }

	__fi void xSTC() { xWrite8(0xF9); }
	__fi void xCLC() { xWrite8(0xF8); }

	// NOP 1-byte
	__fi void xNOP() { xWrite8(0x90); }

	__fi void xINT(u8 imm)
	{
		if (imm == 3)
			xWrite8(0xcc);
		else
		{
			xWrite8(0xcd);
			xWrite8(imm);
		}
	}

	__fi void xINTO() { xWrite8(0xce); }

	__emitinline void xBSWAP(const xRegister32or64& to)
	{
		xWrite8(0x0F);
		xWrite8(0xC8 | to->Id);
	}

	alignas(16) static u64 xmm_data[iREGCNT_XMM * 2];

	__emitinline void xStoreReg(const xRegisterSSE& src)
	{
		xMOVDQA(ptr[&xmm_data[src.Id * 2]], src);
	}

	__emitinline void xRestoreReg(const xRegisterSSE& dest)
	{
		xMOVDQA(dest, ptr[&xmm_data[dest.Id * 2]]);
	}

//////////////////////////////////////////////////////////////////////////////////////////
// Helper object to handle ABI frame
// All x86-64 calling conventions ensure/require stack to be 16 bytes aligned
// I couldn't find documentation on when, but compilers would indicate it's before the call: https://gcc.godbolt.org/z/KzTfsz
#define ALIGN_STACK(v) xADD(rsp, v)

	static void stackAlign(int offset, bool moveDown)
	{
		int needed = (16 - (offset % 16)) % 16;
		if (moveDown)
		{
			needed = -needed;
		}
		ALIGN_STACK(needed);
	}

	xScopedStackFrame::xScopedStackFrame(bool base_frame, bool save_base_pointer, int offset)
	{
		m_base_frame = base_frame;
		m_save_base_pointer = save_base_pointer;
		m_offset = offset;

		m_offset += sizeof(void*); // Call stores the return address (4 bytes)

		// Note rbp can surely be optimized in 64 bits
		if (m_base_frame)
		{
			xPUSH(rbp);
			xMOV(rbp, rsp);
			m_offset += sizeof(void*);
		}
		else if (m_save_base_pointer)
		{
			xPUSH(rbp);
			m_offset += sizeof(void*);
		}

		xPUSH(rbx);
		xPUSH(r12);
		xPUSH(r13);
		xPUSH(r14);
		xPUSH(r15);
		m_offset += 40;
#ifdef _WIN32
		xPUSH(rdi);
		xPUSH(rsi);
		xSUB(rsp, 32); // Windows calling convention specifies additional space for the callee to spill registers
		m_offset += 48;
#endif

		stackAlign(m_offset, true);
	}

	xScopedStackFrame::~xScopedStackFrame()
	{
		stackAlign(m_offset, false);

		// Restore the register context
#ifdef _WIN32
		xADD(rsp, 32);
		xPOP(rsi);
		xPOP(rdi);
#endif
		xPOP(r15);
		xPOP(r14);
		xPOP(r13);
		xPOP(r12);
		xPOP(rbx);

		// Destroy the frame
		if (m_base_frame)
		{
			xLEAVE();
		}
		else if (m_save_base_pointer)
		{
			xPOP(rbp);
		}
	}

	xScopedSavedRegisters::xScopedSavedRegisters(std::initializer_list<std::reference_wrapper<const xAddressReg>> regs)
		: regs(regs)
	{
		for (auto reg : regs)
		{
			const xAddressReg& regRef = reg;
			xPUSH(regRef);
		}
		stackAlign(regs.size() * wordsize, true);
	}

	xScopedSavedRegisters::~xScopedSavedRegisters()
	{
		stackAlign(regs.size() * wordsize, false);
		for (auto it = regs.rbegin(); it < regs.rend(); ++it)
		{
			const xAddressReg& regRef = *it;
			xPOP(regRef);
		}
	}

	xAddressVoid xComplexAddress(const xAddressReg& tmpRegister, void* base, const xAddressVoid& offset)
	{
		if ((sptr)base == (s32)(sptr)base)
		{
			return offset + base;
		}
		else
		{
			xLEA(tmpRegister, ptr[base]);
			return offset + tmpRegister;
		}
	}

	void xLoadFarAddr(const xAddressReg& dst, void* addr)
	{
		sptr iaddr = (sptr)addr;
		sptr rip = (sptr)xGetPtr() + 7; // LEA will be 7 bytes
		sptr disp = iaddr - rip;
		if (disp == (s32)disp)
		{
			xLEA(dst, ptr[addr]);
		}
		else
		{
			xMOV64(dst, iaddr);
		}
	}

	void xWriteImm64ToMem(u64* addr, const xAddressReg& tmp, u64 imm)
	{
		xImm64Op(xMOV, ptr64[addr], tmp, imm);
	}

} // End namespace x86Emitter