import "cmd/compile/internal/base"

// tighten moves Values closer to the Blocks in which they are used.
// This can reduce the amount of register spilling required,
// if it doesn't also create more live values.
// A Value can be moved to any block that
// dominates all blocks in which it is used.
func tighten(f *Func) {
	if base.Flag.N != 0 && len(f.Blocks) < 10000 {
		// Skip the optimization in -N mode, except for huge functions.

		{name: "MOVBUreg", argLength: 1, reg: gp11, asm: "MOVBU"}, // move from arg0, unsign-extended from byte
		{name: "MOVHreg", argLength: 1, reg: gp11, asm: "MOVH"},   // move from arg0, sign-extended from half
		{name: "MOVHUreg", argLength: 1, reg: gp11, asm: "MOVHU"}, // move from arg0, unsign-extended from half

		{name: "MOVWgpfp", argLength: 1, reg: gpfp, asm: "MOVW"}, // move int32 to float32 (no conversion)

		// conversions
		{name: "MOVBreg", argLength: 1, reg: gp11, asm: "MOVB"},   // move from arg0, sign-extended from byte
		{name: "MOVBUreg", argLength: 1, reg: gp11, asm: "MOVBU"}, // move from arg0, unsign-extended from byte
		{name: "MOVHreg", argLength: 1, reg: gp11, asm: "MOVH"},   // move from arg0, sign-extended from half

		{name: "MOVBUreg", argLength: 1, reg: gp11, asm: "MOVBU"}, // move from arg0, unsign-extended from byte
		{name: "MOVHreg", argLength: 1, reg: gp11, asm: "MOVH"},   // move from arg0, sign-extended from half
		{name: "MOVHUreg", argLength: 1, reg: gp11, asm: "MOVHU"}, // move from arg0, unsign-extended from half
		{name: "MOVWreg", argLength: 1, reg: gp11, asm: "MOVW"},   // move from arg0, sign-extended from word

		}

		switch n {
		// Handle very small clears with move instructions.
		case 8, 4, 2, 1:
			ins := s390x.AMOVB
			switch n {
			case 8:
				ins = s390x.AMOVD
			case 4:
				ins = s390x.AMOVW
			case 2:
				ins = s390x.AMOVH
			}
			p = pp.Append(p, ins, obj.TYPE_CONST, 0, 0, obj.TYPE_MEM, reg, off)

		// Handle clears that would require multiple move instructions with CLEAR (assembled as XC).
		default:

	ANOALG         // implies ANOEQ, and in addition has a part that is marked Noalg
	AMEM           // Type can be compared/hashed as regular memory.
	AMEM0          // Specific subvariants of AMEM (TODO: move to ../reflectdata?)
	AMEM8
	AMEM16
	AMEM32
	AMEM64
	AMEM128
	ASTRING
	AINTER
	ANILINTER
	AFLOAT32
	AFLOAT64
	ACPLX64
	ACPLX128
	ASPECIAL // Type needs special comparison/hashing functions.
)

		{name: "MOVWreg", argLength: 1, reg: gp11, asm: "MOVW"},   // move from arg0, sign-extended from word
		{name: "MOVDreg", argLength: 1, reg: gp11, asm: "MOV"},    // move from arg0
		{name: "MOVBUreg", argLength: 1, reg: gp11, asm: "MOVBU"}, // move from arg0, unsign-extended from byte
		{name: "MOVHUreg", argLength: 1, reg: gp11, asm: "MOVHU"}, // move from arg0, unsign-extended from half

	// Parameter value feeds unmodified into a top level "switch"
	// statement or "if" statement simple expressions (see more on
	// "simple" expression classification below).
	ParamFeedsIfOrSwitch

	// Parameter value feeds unmodified into a "switch" or "if"
	// statement simple expressions (see more on "simple" expression
	// classification below), where the if/switch is
	// conditional/nested.
	ParamMayFeedIfOrSwitch
)

			v := b.Values[i]
			if opcodeTable[v.Op].argLen == 0 {
				key := vkey{v.Op, keyFor(v), v.Aux, v.Type}
				if vals[key] == nil {
					vals[key] = v
					if b != f.Entry {
						// Move v to the entry block so it will dominate every block
						// where we might use it. This prevents the need for any dominator
						// calculations in this pass.
						v.Block = f.Entry

	for i, b := range f.Blocks {
		idToIdx[b.ID] = i
	}

	// Set of blocks we're moving, by ID.
	move := map[ID]struct{}{}

	// Map from block ID to the moving blocks that should
	// come right after it.
	after := map[ID][]*Block{}

	// Check each loop header and decide if we want to move it.
	for _, loop := range loopnest.loops {
		b := loop.header
		var p *Block // b's in-loop predecessor