//
//  Instruction.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 15/01/21.
//  Copyright © 2021 Thomas Harte. All rights reserved.
//

#ifndef InstructionSets_PowerPC_Instruction_h
#define InstructionSets_PowerPC_Instruction_h

#include <cstdint>

namespace InstructionSet {
namespace PowerPC {

enum class CacheLine: uint32_t {
	Instruction = 0b01100,
	Data = 0b1101,
	Minimum = 0b01110,
	Maximum = 0b01111,
};

enum class Condition: uint32_t {
	// CR0
	Negative = 0,				// LT
	Positive = 1,				// GT
	Zero = 2,					// EQ
	SummaryOverflow = 3,		// SO

	// CR1
	FPException = 4,			// FX
	FPEnabledException = 5,		// FEX
	FPInvalidException = 6,		// VX
	FPOverflowException = 7,	// OX

	// CRs2–7 fill out the condition register.
};

enum class BranchOption: uint32_t {
	// Naming convention:
	//
	//	Dec_ prefix => decrement the CTR;
	//	condition starting NotZero or Zero => test CTR;
	//	condition ending Set or Clear => test for condition bit.
	//
	// Numerical suffixes are present because there's some redundancy
	// in encodings.
	//
	// Note that the encodings themselves may suggest alternative means
	// of interpretation than mapping via this enum.
	Dec_NotZeroAndClear	= 0b0000,
	Dec_ZeroAndClear	= 0b0001,
	Clear 				= 0b0010,
	Dec_NotZeroAndSet	= 0b0100,
	Dec_ZeroAndSet 		= 0b0101,
	Set 				= 0b0110,
	Dec_NotZero 		= 0b1000,
	Dec_Zero			= 0b1001,
	Always 				= 0b1010,
};

enum class Operation: uint8_t {
	Undefined,

	//
	// MARK: - 601-exclusive instructions.
	//
	// A lot of them are carry-overs from POWER, left in place
	// due to the tight original development timeline.
	//
	// These are not part of the PowerPC architecture.

	/// Absolute.
	/// abs abs. abso abso.
	/// rA(), rD(), oe()
	///
	/// |rA| is placed into rD. If rA = 0x8000'0000 then 0x8000'0000 is placed into rD
	/// and XER[OV] is set if oe() indicates that overflow is enabled.
	absx,

	/// Cache line compute size.
	/// clcs
	/// rA(), rD()
	///
	/// The size of the cache line specified by rA is placed into rD. Cf. the CacheLine enum.
	/// As an aside: all cache lines are 64 bytes on the MPC601.
	clcs,

	/// Divide.
	/// div div. divo divo.
	/// rA(), rB(), rD(), rc(), oe()
	///
	/// Unsigned 64-bit divide. rA|MQ / rB is placed into rD and the
	/// remainder is placed into MQ. The ermainder has the same sign as the dividend
	/// such that remainder + divisor * quotient = dividend.
	///
	/// rc() != 0 => the LT, GT and EQ bits in CR are set as per the remainder.
	/// oe() != 0 => SO and OV are set if the quotient exceeds 32 bits.
	divx,

	/// Divide short.
	/// divs divs. divso divso.
	/// rA(), rB(), rD(), rc(), eo()
	///
	/// Signed 32-bit divide. rD = rA/rB; remainder is
	/// placed into MQ. The ermainder has the same sign as the dividend
	/// such that remainder + divisor * quotient = dividend.
	///
	/// rc() != 0 => the LT, GT and EQ bits in CR are set as per the remainder.
	/// oe() != 0 => SO and OV are set if the quotient exceeds 32 bits.
	divsx,

	/// Difference or zero.
	/// dozx
	/// rA(), rB(), rD()
	///
	/// if rA > rB then rD = 0; else rD = NOT(rA) + rB + 1.
	dozx,

	/// Difference or zero immediate.
	/// dozi
	/// rA(), rD(), simm()
	///
	/// if rA > simm() then rD = 0; else rD = NOT(rA) + simm() + 1.
	dozi,

	lscbxx, maskgx, maskirx,

	/// Multiply.
	/// mul mul. mulo mulo.
	/// rA(), rB(), rD()
	mulx,

	nabsx, rlmix, rribx, slex, sleqx, sliqx, slliqx, sllqx, slqx,
	sraiqx, sraqx, srex, sreax, sreqx, sriqx, srliqx, srlqx, srqx,

	//
	// MARK: - 32- and 64-bit PowerPC instructions.
	//

	/// Add.
	/// add add. addo addo.
	/// rA(), rB(), rD(), rc(), oe()
	///
	/// rD() = rA() + rB(). Carry is ignored, rD() may be equal to rA() or rB().
	addx,

	/// Add carrying.
	/// addc addc. addco addco.
	/// rA(), rB(), rD(), rc(), oe()
	///
	/// rD() = rA() + rB().
	/// XER[CA] is updated with carry; if oe() is set then so are XER[SO] and XER[OV].
	/// if rc() is set, LT, GT, EQ and SO condition bits are updated.
	addcx,

	/// Add extended.
	/// adde adde. addeo addeo.
	/// rA(), rB(), rD(), rc(), eo()
	///
	/// rD() = rA() + rB() + XER[CA]; XER[CA] is set if further carry occurs.
	/// oe() and rc() apply.
	addex,

	/// Add immediate.
	/// addi
	/// rA(), rD(), simm()
	///
	/// rD() = (rA() | 0) + simm()
	addi,

	/// Add immediate carrying.
	/// addic
	/// rA(), rD(), simm()
	///
	/// rD() = (rA() | 0) + simm()
	/// XER[CA] is updated.
	addic,

	/// Add immediate carrying and record.
	/// addic.
	/// rA(), rD(), simm()
	///
	/// rD() = (rA() | 0) + simm()
	/// XER[CA] and the condition register are updated.
	addic_,

	/// Add immediate shifted.
	/// addis.
	/// rA(), rD(), simm()
	///
	/// rD() = (rA() | 0) + (simm() << 16)
	addis,

	/// Add to minus one.
	/// addme addme. addmeo addmeo.
	/// rA(), rD(), rc(), oe()
	///
	/// rD() = rA() + XER[CA] + 0xffff'ffff
	addmex,

	/// Add to zero extended.
	/// addze addze. addzeo addzeo.
	/// rA(), rD(), rc(), oe()
	///
	/// rD() = rA() + XER[CA]
	addzex,

	/// And.
	/// and, and.
	/// rA(), rB(), rD(), rc()
	andx,

	/// And with complement.
	/// andc, andc.
	/// rA(), rB(), rD(), rc()
	andcx,

	/// And immediate.
	/// andi.
	/// rA(), rD(), uimm()
	andi_,

	/// And immediate shifted.
	/// andis.
	/// rA(), rD(), uimm()
	andis_,

	/// Branch unconditional.
	/// b bl ba bla
	/// aa(), li(), lk()
	///
	/// Use li() to get the included immediate value.
	///
	/// Use aa() to determine whether it's a relative (aa() = 0) or absolute (aa() != 0) address.
	/// Also check lk() to determine whether to update the link register.
	bx,

	/// Branch conditional.
	/// bne bne+ beq bdnzt+ bdnzf bdnzt bdnzfla ...
	/// aa(), lk(), bd(), bi(), bo()
	///
	/// aa() determines whether the branch has a relative or absolute target.
	/// lk() determines whether to update the link register.
	/// bd() supplies a relative displacment or absolute address.
	/// bi() specifies which CR bit to use as a condition; cf. the Condition enum.
	/// bo() provides other branch options and a branch prediction hint as per (BranchOptions enum << 1) | hint.
	bcx,

	/// Branch conditional to count register.
	/// bctr bctrl bnectrl bnectrl bltctr blectr ...
	/// aa(), lk(), bi(), bo()
	///
	/// aa(), bi(), bo() and lk() are as per bcx.
	///
	/// On the MPC601, anything that decrements the count register will use the non-decremented
	/// version as the branch target. Other processors will use the decremented version.
	bcctrx,

	/// Branch conditional to link register.
	/// blr blrl bltlr blelrl bnelrl ...
	/// aa(), lk(), bi(), bo()
	///
	/// aa(), bi(), bo() and lk() are as per bcx.
	bclrx,

	cmp, cmpi, cmpl, cmpli,
	cntlzwx,

	/// Condition register and.
	/// crand
	/// crbA(), crbB(), crbD()
	crand,

	/// Condition register and with complement.
	/// crandc
	/// crbA(), crbB(), crbD()
	crandc,

	/// Condition register equivalent.
	/// creqv
	/// crbA(), crbB(), crbD()
	creqv,

	/// Condition register nand.
	/// crnand
	/// crbA(), crbB(), crbD()
	crnand,

	/// Condition register nor.
	/// crnor
	/// crbA(), crbB(), crbD()
	crnor,

	/// Condition register or.
	/// cror
	/// crbA(), crbB(), crbD()
	cror,

	/// Condition register or with complement.
	/// crorc
	/// crbA(), crbB(), crbD()
	crorc,

	/// Condition register xor.
	/// crxor
	/// crbA(), crbB(), crbD()
	crxor,

	dcbf,
	dcbst, dcbt, dcbtst, dcbz, divwx, divwux, eciwx, ecowx, eieio, eqvx,
	extsbx, extshx, fabsx, faddx, faddsx, fcmpo, fcmpu, fctiwx, fctiwzx,
	fdivx, fdivsx, fmaddx, fmaddsx, fmrx, fmsubx, fmsubsx, fmulx, fmulsx,
	fnabsx, fnegx, fnmaddx, fnmaddsx, fnmsubx, fnmsubsx, frspx, fsubx, fsubsx,
	icbi, isync, lbz, lbzu,

	/// Load byte and zero with update indexed.
	/// lbzux
	///
	/// rD()[24, 31] = [ rA()|0 + rB() ]; and rA() is set to the calculated address
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	/// The rest of rD is set to 0.
	///
	/// PowerPC defines rA=0 and rA=rD to be invalid forms; the MPC601
	/// will suppress the update if rA=0 or rA=rD.
	lbzux,

	/// Load byte and zero indexed.
	/// lbzx
	///
	/// rD[24, 31] = [ (rA()|0) + rB() ]
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	/// The rest of rD is set to 0.
	lbzx,

	lfd, lfdu, lfdux, lfdx, lfs, lfsu,
	lfsux, lfsx, lha, lhau,

	/// Load half-word algebraic with update indexed.
	///
	/// rD()[16, 31] = [ rA()|0 + rB() ]; and rA() is set to the calculated address
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	/// The result in rD is sign extended.
	///
	/// PowerPC defines rA=0 and rA=rD to be invalid forms; the MPC601
	/// will suppress the update if rA=0 or rA=rD.
	lhaux,

	/// Load half-word algebraic indexed.
	///
	/// rD[16, 31] = [ (rA()|0) + rB() ]
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	/// The result in rD is sign extended.
	lhax,

	lhbrx, lhz, lhzu,

	/// Load half-word and zero with update indexed.
	///
	/// rD()[16, 31] = [ rA()|0 + rB() ]; and rA() is set to the calculated address
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	/// The rest of rD is set to 0.
	///
	/// PowerPC defines rA=0 and rA=rD to be invalid forms; the MPC601
	/// will suppress the update if rA=0 or rA=rD.
	lhzux,

	/// Load half-word and zero indexed.
	///
	/// rD[16, 31] = [ (rA()|0) + rB() ]
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	/// The rest of rD is set to 0.
	lhzx,

	lmw,
	lswi, lswx, lwarx, lwbrx, lwz, lwzu,

	/// Load word and zero with update indexed.
	/// lwzux
	///
	/// rD() = [ rA()|0 + rB() ]; and rA() is set to the calculated address
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	///
	/// PowerPC defines rA=0 and rA=rD to be invalid forms; the MPC601
	/// will suppress the update if rA=0 or rA=rD.
	lwzux,

	/// Load word and zero indexed.
	/// lwzx
	///
	/// rD() = [ (rA()|0) + rB() ]
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	lwzx,

	mcrf, mcrfs, mcrxr,
	mfcr, mffsx, mfmsr, mfspr, mfsr, mfsrin,

	/// Move to condition register fields.
	/// mtcrf
	/// rS(), crm()
	mtcrf,

	mtfsb0x, mtfsb1x, mtfsfx,
	mtfsfix, mtmsr, mtspr, mtsr, mtsrin,

	/// Multiply high word.
	/// mulhw mulgw.
	/// rD(), rA(), rB(), rc()
	mulhwx,

	/// Multiply high word unsigned.
	/// mulhwu mulhwu.
	/// rD(), rA(), rB(), rc()
	mulhwux,

	/// Multiply low immediate.
	///
	/// rD() = [low 32 bits of] rA() * simm()
	/// XER[OV] is set if, were the operands treated as signed, overflow occurred.
	mulli,

	/// Multiply low word.
	/// mullw mullw. mullwo mullwo.
	/// rA(), rB(), rD()
	mullwx,

	nandx, negx, norx, orx, orcx, ori, oris, rfi, rlwimix, rlwinmx, rlwnmx,
	sc, slwx, srawx, srawix, srwx, stb, stbu,

	/// Store byte with update indexed.
	///
	/// [ (ra()|0) + rB() ] = rS()[24, 31]; and rA() is updated with the calculated address.
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	///
	/// PowerPC defines rA=0 to an invalid form; the MPC601 will store to r0.
	stbux,

	/// Store byte indexed.
	///
	/// [ (ra()|0) + rB() ] = rS()[24, 31]
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	stbx,

	stfd, stfdu,
	stfdux, stfdx, stfs, stfsu, stfsux, stfsx, sth, sthbrx, sthu,

	/// Store half-word with update indexed.
	///
	/// [ (ra()|0) + rB() ] = rS()[16, 31]; and rA() is updated with the calculated address.
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	///
	/// PowerPC defines rA=0 to an invalid form; the MPC601 will store to r0.
	sthux,

	/// Store half-word indexed.
	///
	/// [ (ra()|0) + rB() ] = rS()[16, 31]
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	sthx,

	stmw, stswi, stswx, stw, stwbrx, stwcx_, stwu,

	/// Store word with update indexed.
	///
	/// [ (ra()|0) + rB() ] = rS(); and rA() is updated with the calculated address.
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	///
	/// PowerPC defines rA=0 to an invalid form; the MPC601 will store to r0.
	stwux,

	/// Store word indexed.
	///
	/// [ (ra()|0) + rB() ] = rS()
	/// i.e. if rA() is 0 then the value 0 is used, not the contents of r0.
	stwx,

	subfx,

	/// Subtract from carrying.
	/// subfc subfc. subfco subfco.
	///
	/// rD() = -rA() +rB() + 1
	///
	/// oe(), rc() apply.
	subfcx,
	subfex,

	/// Subtract from immediate carrying
	///
	/// rD() = ~rA() + simm() + 1
	subfic,

	subfmex, subfzex, sync, tw, twi, xorx, xori, xoris, mftb,

	//
	// MARK: - 32-bit, supervisor level.
	//
	dcbi,

	//
	// MARK: - Supervisor, optional.
	//
	tlbia, tlbie, tlbsync,

	//
	// MARK: - Optional.
	//
	fresx, frsqrtex, fselx, fsqrtx, slbia, slbie, stfiwx,

	//
	// MARK: - 64-bit only PowerPC instructions.
	//
	cntlzdx, divdx, divdux, extswx, fcfidx, fctidx, fctidzx, tdi, mulhdux,
	ldx, sldx, ldux, td, mulhdx, ldarx, stdx, stdux, mulld, lwax, lwaux,
	sradix, srdx, sradx, extsw, fsqrtsx, std, stdu, stdcx_,
};

/*!
	Holds a decoded PowerPC instruction.

	Implementation note: because the PowerPC encoding is particularly straightforward,
	only the operation has been decoded ahead of time; all other fields are decoded on-demand.

	It would be possible to partition the ordering of Operations into user followed by supervisor,
	eliminating the storage necessary for a flag, but it wouldn't save anything due to alignment.
*/
struct Instruction {
	Operation operation = Operation::Undefined;
	bool is_supervisor = false;
	uint32_t opcode = 0;

	Instruction() noexcept {}
	Instruction(uint32_t opcode) noexcept : opcode(opcode) {}
	Instruction(Operation operation, uint32_t opcode, bool is_supervisor = false) noexcept : operation(operation), is_supervisor(is_supervisor), opcode(opcode) {}

	// Instruction fields are decoded below; naming is a compromise between
	// Motorola's documentation and IBM's.
	//
	// I've dutifully implemented various synonyms with unique entry points,
	// in order to capture that information here rather than thrusting it upon
	// the reader of whatever implementation may follow.

	// Currently omitted: OPCD and XO, which I think are unnecessary given that
	// full decoding has already occurred.

	/// Immediate field used to specify an unsigned 16-bit integer.
	uint16_t uimm() const	{	return uint16_t(opcode & 0xffff);	}
	/// Immediate field used to specify a signed 16-bit integer.
	int16_t simm() const	{	return int16_t(opcode & 0xffff);	}
	/// Immediate field used to specify a signed 16-bit integer.
	int16_t d() const		{	return int16_t(opcode & 0xffff);	}
	/// Immediate field used to specify a signed 14-bit integer [64-bit only].
	int16_t ds() const		{	return int16_t(opcode & 0xfffc);	}
	/// Immediate field used as data to be placed into a field in the floating point status and condition register.
	int32_t imm() const		{	return (opcode >> 12) & 0xf;		}

	/// Specifies the conditions on which to trap.
	int32_t to() const	 	{	return (opcode >> 21) & 0x1f;		}

	/// Register source A or destination.
	uint32_t rA() const 	{	return (opcode >> 16) & 0x1f;		}
	/// Register source B.
	uint32_t rB() const 	{	return (opcode >> 11) & 0x1f;		}
	/// Register destination.
	uint32_t rD() const 	{	return (opcode >> 21) & 0x1f;		}
	/// Register source.
	uint32_t rS() const 	{	return (opcode >> 21) & 0x1f;		}

	/// Floating point register source A.
	uint32_t frA() const 	{	return (opcode >> 16) & 0x1f;		}
	/// Floating point register source B.
	uint32_t frB() const 	{	return (opcode >> 11) & 0x1f;		}
	/// Floating point register source C.
	uint32_t frC() const 	{	return (opcode >> 6) & 0x1f;		}
	/// Floating point register source.
	uint32_t frS() const 	{	return (opcode >> 21) & 0x1f;		}
	/// Floating point register destination.
	uint32_t frD() const 	{	return (opcode >> 21) & 0x1f;		}

	/// Branch conditional options as per PowerPC spec, i.e. options + branch-prediction flag.
	uint32_t bo() const 	{	return (opcode >> 21) & 0x1f;		}
	/// Just the branch options, with the branch prediction flag severed.
	BranchOption branch_options() const {
		return BranchOption((opcode >> 22) & 0xf);
	}
	/// Just the branch-prediction hint; @c 0 => expect untaken; @c non-0 => expect take.
	uint32_t branch_prediction_hint() const {
		return opcode & 0x200000;
	}
	/// Source condition register bit for branch conditionals.
	uint32_t bi() const 	{	return (opcode >> 16) & 0x1f;		}
	/// Branch displacement; provided as already sign extended.
	int16_t bd() const		{	return int16_t(opcode & 0xfffc);	}

	/// Specifies the first 1 bit of a 32/64-bit mask for rotate operations.
	uint32_t mb() const		{	return (opcode >> 6) & 0x1f;		}
	/// Specifies the first 1 bit of a 32/64-bit mask for rotate operations.
	uint32_t me() const		{	return (opcode >> 1) & 0x1f;		}

	/// Condition register source bit A.
	uint32_t crbA() const	{	return (opcode >> 16) & 0x1f;		}
	/// Condition register source bit B.
	uint32_t crbB() const	{	return (opcode >> 11) & 0x1f;		}
	/// Condition register (or floating point status & condition register) destination bit.
	uint32_t crbD() const	{	return (opcode >> 21) & 0x1f;		}

	/// Condition register (or floating point status & condition register) destination field.
	uint32_t crfD() const	{	return (opcode >> 23) & 0x07;		}
	/// Condition register (or floating point status & condition register) source field.
	uint32_t crfS() const	{	return (opcode >> 18) & 0x07;		}

	/// Mask identifying fields to be updated by mtcrf.
	uint32_t crm() const	{	return (opcode >> 12) & 0xff;		}

	/// Mask identifying fields to be updated by mtfsf.
	uint32_t fm() const		{	return (opcode >> 17) & 0xff;		}

	/// Specifies the number of bytes to move in an immediate string load or store.
	uint32_t nb() const		{	return (opcode >> 11) & 0x1f;		}

	/// Specifies a shift amount.
	/// TODO: possibly bit 30 is also used in 64-bit mode, find out.
	uint32_t sh() const		{	return (opcode >> 11) & 0x1f;		}

	/// Specifies one of the 16 segment registers [32-bit only].
	uint32_t sr() const		{	return (opcode >> 16) & 0xf;		}

	/// A 24-bit signed number; provided as already sign extended.
	int32_t li() const {
		constexpr uint32_t extensions[2] = {
			0x0000'0000,
			0xfc00'0000
		};
		const uint32_t value = (opcode & 0x03ff'fffc) | extensions[(opcode >> 25) & 1];
		return int32_t(value);
	}

	/// Absolute address bit; @c 0 or @c non-0.
	uint32_t aa() const	{	return opcode & 0x02;		}
	/// Link bit; @c 0 or @c non-0.
	uint32_t lk() const	{	return opcode & 0x01;		}
	/// Record bit; @c 0 or @c non-0.
	uint32_t rc() const	{	return opcode & 0x01;		}
	/// Whether to compare 32-bit or 64-bit numbers [for 64-bit implementations only]; @c 0 or @c non-0.
	uint32_t l() const	{	return opcode & 0x200000;	}
	/// Enables setting of OV and SO in the XER; @c 0 or @c non-0.
	uint32_t oe() const	{	return opcode & 0x400;		}
};

// Sanity check on Instruction size.
static_assert(sizeof(Instruction) <= 8);

}
}

#endif /* InstructionSets_PowerPC_Instruction_h */