// Copyright 2008 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#include "Common/CommonTypes.h"
#include "Core/PowerPC/JitILCommon/JitILBase.h"


// The branches are known good, or at least reasonably good.
// No need for a disable-mechanism.

// If defined, clears CR0 at blr and bl-s. If the assumption that
// flags never carry over between functions holds, then the task for
// an optimizer becomes much easier.

// #define ACID_TEST

// Zelda and many more games seem to pass the Acid Test.

//#define NORMALBRANCH_START FallBackToInterpreter(inst); ibuild.EmitInterpreterBranch(); return;
#define NORMALBRANCH_START

void JitILBase::sc(UGeckoInstruction inst)
{
	ibuild.EmitSystemCall(ibuild.EmitIntConst(js.compilerPC));
}

void JitILBase::rfi(UGeckoInstruction inst)
{
	ibuild.EmitRFIExit();
}

void JitILBase::bx(UGeckoInstruction inst)
{
	NORMALBRANCH_START
	INSTRUCTION_START;

	// We must always process the following sentence
	// even if the blocks are merged by PPCAnalyst::Flatten().
	if (inst.LK)
		ibuild.EmitStoreLink(ibuild.EmitIntConst(js.compilerPC + 4));

	// If this is not the last instruction of a block,
	// we will skip the rest process.
	// Because PPCAnalyst::Flatten() merged the blocks.
	if (!js.isLastInstruction)
	{
		return;
	}

	u32 destination;
	if (inst.AA)
		destination = SignExt26(inst.LI << 2);
	else
		destination = js.compilerPC + SignExt26(inst.LI << 2);

	if (destination == js.compilerPC)
	{
		ibuild.EmitShortIdleLoop(ibuild.EmitIntConst(js.compilerPC));
		return;
	}

	ibuild.EmitBranchUncond(ibuild.EmitIntConst(destination));
}

static IREmitter::InstLoc EmitCRTest(IREmitter::IRBuilder& ibuild, UGeckoInstruction inst)
{
	IREmitter::InstLoc CRReg = ibuild.EmitLoadCR(inst.BI >> 2);
	IREmitter::InstLoc CRTest = nullptr;
	switch (3 - (inst.BI & 3))
	{
	case CR_SO_BIT:
		CRTest = ibuild.EmitFastCRSOSet(CRReg);
		break;
	case CR_EQ_BIT:
		CRTest = ibuild.EmitFastCREQSet(CRReg);
		break;
	case CR_GT_BIT:
		CRTest = ibuild.EmitFastCRGTSet(CRReg);
		break;
	case CR_LT_BIT:
		CRTest = ibuild.EmitFastCRLTSet(CRReg);
		break;
	}
	if (!(inst.BO & 8))
		CRTest = ibuild.EmitXor(CRTest, ibuild.EmitIntConst(1));
	return CRTest;
}

static IREmitter::InstLoc TestBranch(IREmitter::IRBuilder& ibuild, UGeckoInstruction inst)
{
	IREmitter::InstLoc CRTest = nullptr, CTRTest = nullptr;
	if ((inst.BO & 16) == 0)  // Test a CR bit
	{
		CRTest = EmitCRTest(ibuild, inst);
	}

	if ((inst.BO & 4) == 0)
	{
		IREmitter::InstLoc c = ibuild.EmitLoadCTR();
		c = ibuild.EmitSub(c, ibuild.EmitIntConst(1));
		ibuild.EmitStoreCTR(c);

		if (inst.BO & 2)
			CTRTest = ibuild.EmitICmpEq(c, ibuild.EmitIntConst(0));
		else
			CTRTest = c;
	}

	IREmitter::InstLoc Test = CRTest;
	if (CTRTest)
	{
		if (Test)
			Test = ibuild.EmitAnd(Test, CTRTest);
		else
			Test = CTRTest;
	}

	if (!Test)
	{
		Test = ibuild.EmitIntConst(1);
	}

	return Test;
}

void JitILBase::bcx(UGeckoInstruction inst)
{
	NORMALBRANCH_START
	if (inst.LK)
		ibuild.EmitStoreLink(ibuild.EmitIntConst(js.compilerPC + 4));

	IREmitter::InstLoc Test = TestBranch(ibuild, inst);

	u32 destination;
	if (inst.AA)
		destination = SignExt16(inst.BD << 2);
	else
		destination = js.compilerPC + SignExt16(inst.BD << 2);

	// Idle skipping:
	// The main Idle skipping is done in the LoadStore code, but there is an optimization here.
	// If idle skipping is enabled, then this branch will only be reached when the branch is not
	// taken.
	// TODO: We shouldn't use debug reads here.
	if (SConfig::GetInstance().m_LocalCoreStartupParameter.bSkipIdle &&
		inst.hex == 0x4182fff8 &&
		(PowerPC::HostRead_U32(js.compilerPC - 8) & 0xFFFF0000) == 0x800D0000 &&
		(PowerPC::HostRead_U32(js.compilerPC - 4) == 0x28000000 ||
		(SConfig::GetInstance().m_LocalCoreStartupParameter.bWii && PowerPC::HostRead_U32(js.compilerPC - 4) == 0x2C000000))
		)
	{
		// Uh, Do nothing.
	}
	else
	{
		ibuild.EmitBranchCond(Test, ibuild.EmitIntConst(destination));
	}
	ibuild.EmitBranchUncond(ibuild.EmitIntConst(js.compilerPC + 4));
}

void JitILBase::bcctrx(UGeckoInstruction inst)
{
	NORMALBRANCH_START
	if ((inst.BO & 4) == 0)
	{
		IREmitter::InstLoc c = ibuild.EmitLoadCTR();
		c = ibuild.EmitSub(c, ibuild.EmitIntConst(1));
		ibuild.EmitStoreCTR(c);
	}

	IREmitter::InstLoc test;
	if ((inst.BO & 16) == 0)  // Test a CR bit
	{
		test = EmitCRTest(ibuild, inst);
	}
	else
	{
		test = ibuild.EmitIntConst(1);
	}
	test = ibuild.EmitICmpEq(test, ibuild.EmitIntConst(0));
	ibuild.EmitBranchCond(test, ibuild.EmitIntConst(js.compilerPC + 4));

	IREmitter::InstLoc destination = ibuild.EmitLoadCTR();
	destination = ibuild.EmitAnd(destination, ibuild.EmitIntConst(-4));
	if (inst.LK)
		ibuild.EmitStoreLink(ibuild.EmitIntConst(js.compilerPC + 4));
	ibuild.EmitBranchUncond(destination);
}

void JitILBase::bclrx(UGeckoInstruction inst)
{
	NORMALBRANCH_START

	if (!js.isLastInstruction &&
	    (inst.BO & (1 << 4)) && (inst.BO & (1 << 2)))
	{
		if (inst.LK)
			ibuild.EmitStoreLink(ibuild.EmitIntConst(js.compilerPC + 4));
		return;
	}

	if (inst.hex == 0x4e800020)
	{
		ibuild.EmitBranchUncond(ibuild.EmitLoadLink());
		return;
	}

	IREmitter::InstLoc test = TestBranch(ibuild, inst);
	test = ibuild.EmitICmpEq(test, ibuild.EmitIntConst(0));
	ibuild.EmitBranchCond(test, ibuild.EmitIntConst(js.compilerPC + 4));

	IREmitter::InstLoc destination = ibuild.EmitLoadLink();
	destination = ibuild.EmitAnd(destination, ibuild.EmitIntConst(-4));
	if (inst.LK)
		ibuild.EmitStoreLink(ibuild.EmitIntConst(js.compilerPC + 4));
	ibuild.EmitBranchUncond(destination);
}
