// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package arm

import (
	"cmd/compile/internal/gc"
	"cmd/compile/internal/ssa"
	"cmd/internal/obj"
	"cmd/internal/obj/arm"
)

var ssaRegToReg = []int16{
	arm.REG_R0,
	arm.REG_R1,
	arm.REG_R2,
	arm.REG_R3,
	arm.REGSP, // aka R13
}

func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
	s.SetLineno(v.Line)
	switch v.Op {
	case ssa.OpInitMem:
		// memory arg needs no code
	case ssa.OpArg:
		// input args need no code
	case ssa.OpSP, ssa.OpSB:
		// nothing to do
	case ssa.OpCopy:
	case ssa.OpLoadReg:
		// TODO: by type
		p := gc.Prog(arm.AMOVW)
		n, off := gc.AutoVar(v.Args[0])
		p.From.Type = obj.TYPE_MEM
		p.From.Node = n
		p.From.Sym = gc.Linksym(n.Sym)
		p.From.Offset = off
		if n.Class == gc.PPARAM || n.Class == gc.PPARAMOUT {
			p.From.Name = obj.NAME_PARAM
			p.From.Offset += n.Xoffset
		} else {
			p.From.Name = obj.NAME_AUTO
		}
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)

	case ssa.OpStoreReg:
		// TODO: by type
		p := gc.Prog(arm.AMOVW)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[0])
		n, off := gc.AutoVar(v)
		p.To.Type = obj.TYPE_MEM
		p.To.Node = n
		p.To.Sym = gc.Linksym(n.Sym)
		p.To.Offset = off
		if n.Class == gc.PPARAM || n.Class == gc.PPARAMOUT {
			p.To.Name = obj.NAME_PARAM
			p.To.Offset += n.Xoffset
		} else {
			p.To.Name = obj.NAME_AUTO
		}
	case ssa.OpARMADD:
		r := gc.SSARegNum(v)
		r1 := gc.SSARegNum(v.Args[0])
		r2 := gc.SSARegNum(v.Args[1])
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = r1
		p.Reg = r2
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r
	case ssa.OpARMADDconst:
		if v.Aux != nil {
			switch v.Aux.(type) {
			default:
				v.Fatalf("aux is of unknown type %T", v.Aux)
			case *ssa.ExternSymbol:
				reg := v.Args[0].Block.Func.RegAlloc[v.Args[0].ID].(*ssa.Register)
				if reg.Name() != "SB" {
					v.Fatalf("extern symbol with non-SB base register %s", reg.Name())
				}
			case *ssa.ArgSymbol,
				*ssa.AutoSymbol:
				reg := v.Args[0].Block.Func.RegAlloc[v.Args[0].ID].(*ssa.Register)
				if reg.Name() != "SP" {
					v.Fatalf("arg/auto symbol with non-SP base register %s", reg.Name())
				}
			}
			// MOVW $sym+off(base), R
			// the assembler expands it as the following:
			// - base is SP: add constant offset to SP (R13)
			//               when constant is large, tmp register (R11) may be used
			// - base is SB: load external address from constant pool (use relocation)
			p := gc.Prog(arm.AMOVW)
			p.From.Type = obj.TYPE_ADDR
			gc.AddAux(&p.From, v)
			p.To.Type = obj.TYPE_REG
			p.To.Reg = gc.SSARegNum(v)
			break
		}
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.Reg = gc.SSARegNum(v.Args[0])
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpARMMOVWconst:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpARMCMP:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		// Special layout in ARM assembly
		// Comparing to x86, the operands of ARM's CMP are reversed.
		p.From.Reg = gc.SSARegNum(v.Args[1])
		p.Reg = gc.SSARegNum(v.Args[0])
	case ssa.OpARMMOVWload:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.From, v)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpARMMOVWstore:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[1])
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.To, v)
	case ssa.OpARMCALLstatic:
		// TODO: deferreturn
		p := gc.Prog(obj.ACALL)
		p.To.Type = obj.TYPE_MEM
		p.To.Name = obj.NAME_EXTERN
		p.To.Sym = gc.Linksym(v.Aux.(*gc.Sym))
		if gc.Maxarg < v.AuxInt {
			gc.Maxarg = v.AuxInt
		}
	case ssa.OpVarDef:
		gc.Gvardef(v.Aux.(*gc.Node))
	case ssa.OpVarKill:
		gc.Gvarkill(v.Aux.(*gc.Node))
	case ssa.OpVarLive:
		gc.Gvarlive(v.Aux.(*gc.Node))
	case ssa.OpARMLessThan:
		v.Fatalf("pseudo-op made it to output: %s", v.LongString())
	default:
		v.Unimplementedf("genValue not implemented: %s", v.LongString())
	}
}

func ssaGenBlock(s *gc.SSAGenState, b, next *ssa.Block) {
	s.SetLineno(b.Line)

	switch b.Kind {
	case ssa.BlockCall:
		if b.Succs[0].Block() != next {
			p := gc.Prog(obj.AJMP)
			p.To.Type = obj.TYPE_BRANCH
			s.Branches = append(s.Branches, gc.Branch{P: p, B: b.Succs[0].Block()})
		}
	case ssa.BlockRet:
		gc.Prog(obj.ARET)
	case ssa.BlockARMLT:
		p := gc.Prog(arm.ABLT)
		p.To.Type = obj.TYPE_BRANCH
		s.Branches = append(s.Branches, gc.Branch{P: p, B: b.Succs[0].Block()})
		p = gc.Prog(obj.AJMP)
		p.To.Type = obj.TYPE_BRANCH
		s.Branches = append(s.Branches, gc.Branch{P: p, B: b.Succs[1].Block()})
	}
}