src/cmd/compile/internal/arm/gsubr.go

// Derived from Inferno utils/5c/txt.c
// http://code.google.com/p/inferno-os/source/browse/utils/5c/txt.c
//
//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
//	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
//	Portions Copyright © 1997-1999 Vita Nuova Limited
//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
//	Portions Copyright © 2004,2006 Bruce Ellis
//	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
//	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
//	Portions Copyright © 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package arm

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

var resvd = []int{
	arm.REG_R9,  // formerly reserved for m; might be okay to reuse now; not sure about NaCl
	arm.REG_R10, // reserved for g
}

/*
 * return constant i node.
 * overwritten by next call, but useful in calls to gins.
 */

var ncon_n gc.Node

func ncon(i uint32) *gc.Node {
	if ncon_n.Type == nil {
		gc.Nodconst(&ncon_n, gc.Types[gc.TUINT32], 0)
	}
	ncon_n.SetInt(int64(i))
	return &ncon_n
}

var sclean [10]gc.Node

var nsclean int

/*
 * n is a 64-bit value.  fill in lo and hi to refer to its 32-bit halves.
 */
func split64(n *gc.Node, lo *gc.Node, hi *gc.Node) {
	if !gc.Is64(n.Type) {
		gc.Fatalf("split64 %v", n.Type)
	}

	if nsclean >= len(sclean) {
		gc.Fatalf("split64 clean")
	}
	sclean[nsclean].Op = gc.OEMPTY
	nsclean++
	switch n.Op {
	default:
		switch n.Op {
		default:
			var n1 gc.Node
			if !dotaddable(n, &n1) {
				gc.Igen(n, &n1, nil)
				sclean[nsclean-1] = n1
			}

			n = &n1

		case gc.ONAME, gc.OINDREG:
			// nothing
		}

		*lo = *n
		*hi = *n
		lo.Type = gc.Types[gc.TUINT32]
		if n.Type.Etype == gc.TINT64 {
			hi.Type = gc.Types[gc.TINT32]
		} else {
			hi.Type = gc.Types[gc.TUINT32]
		}
		hi.Xoffset += 4

	case gc.OLITERAL:
		var n1 gc.Node
		n.Convconst(&n1, n.Type)
		i := n1.Int64()
		gc.Nodconst(lo, gc.Types[gc.TUINT32], int64(uint32(i)))
		i >>= 32
		if n.Type.Etype == gc.TINT64 {
			gc.Nodconst(hi, gc.Types[gc.TINT32], int64(int32(i)))
		} else {
			gc.Nodconst(hi, gc.Types[gc.TUINT32], int64(uint32(i)))
		}
	}
}

func splitclean() {
	if nsclean <= 0 {
		gc.Fatalf("splitclean")
	}
	nsclean--
	if sclean[nsclean].Op != gc.OEMPTY {
		gc.Regfree(&sclean[nsclean])
	}
}

func gmove(f *gc.Node, t *gc.Node) {
	if gc.Debug['M'] != 0 {
		fmt.Printf("gmove %v -> %v\n", f, t)
	}

	ft := gc.Simsimtype(f.Type)
	tt := gc.Simsimtype(t.Type)
	cvt := t.Type

	if gc.Iscomplex[ft] || gc.Iscomplex[tt] {
		gc.Complexmove(f, t)
		return
	}

	// cannot have two memory operands;
	// except 64-bit, which always copies via registers anyway.
	var a obj.As
	var r1 gc.Node
	if !gc.Is64(f.Type) && !gc.Is64(t.Type) && gc.Ismem(f) && gc.Ismem(t) {
		goto hard
	}

	// convert constant to desired type
	if f.Op == gc.OLITERAL {
		var con gc.Node
		switch tt {
		default:
			f.Convconst(&con, t.Type)

		case gc.TINT16,
			gc.TINT8:
			var con gc.Node
			f.Convconst(&con, gc.Types[gc.TINT32])
			var r1 gc.Node
			gc.Regalloc(&r1, con.Type, t)
			gins(arm.AMOVW, &con, &r1)
			gmove(&r1, t)
			gc.Regfree(&r1)
			return

		case gc.TUINT16,
			gc.TUINT8:
			var con gc.Node
			f.Convconst(&con, gc.Types[gc.TUINT32])
			var r1 gc.Node
			gc.Regalloc(&r1, con.Type, t)
			gins(arm.AMOVW, &con, &r1)
			gmove(&r1, t)
			gc.Regfree(&r1)
			return
		}

		f = &con
		ft = gc.Simsimtype(con.Type)

		// constants can't move directly to memory
		if gc.Ismem(t) && !gc.Is64(t.Type) {
			goto hard
		}
	}

	// value -> value copy, only one memory operand.
	// figure out the instruction to use.
	// break out of switch for one-instruction gins.
	// goto rdst for "destination must be register".
	// goto hard for "convert to cvt type first".
	// otherwise handle and return.

	switch uint32(ft)<<16 | uint32(tt) {
	default:
		// should not happen
		gc.Fatalf("gmove %v -> %v", f, t)
		return

		/*
		 * integer copy and truncate
		 */
	case gc.TINT8<<16 | gc.TINT8: // same size
		if !gc.Ismem(f) {
			a = arm.AMOVB
			break
		}
		fallthrough

	case gc.TUINT8<<16 | gc.TINT8,
		gc.TINT16<<16 | gc.TINT8, // truncate
		gc.TUINT16<<16 | gc.TINT8,
		gc.TINT32<<16 | gc.TINT8,
		gc.TUINT32<<16 | gc.TINT8:
		a = arm.AMOVBS

	case gc.TUINT8<<16 | gc.TUINT8:
		if !gc.Ismem(f) {
			a = arm.AMOVB
			break
		}
		fallthrough

	case gc.TINT8<<16 | gc.TUINT8,
		gc.TINT16<<16 | gc.TUINT8,
		gc.TUINT16<<16 | gc.TUINT8,
		gc.TINT32<<16 | gc.TUINT8,
		gc.TUINT32<<16 | gc.TUINT8:
		a = arm.AMOVBU

	case gc.TINT64<<16 | gc.TINT8, // truncate low word
		gc.TUINT64<<16 | gc.TINT8:
		a = arm.AMOVBS

		goto trunc64

	case gc.TINT64<<16 | gc.TUINT8,
		gc.TUINT64<<16 | gc.TUINT8:
		a = arm.AMOVBU
		goto trunc64

	case gc.TINT16<<16 | gc.TINT16: // same size
		if !gc.Ismem(f) {
			a = arm.AMOVH
			break
		}
		fallthrough

	case gc.TUINT16<<16 | gc.TINT16,
		gc.TINT32<<16 | gc.TINT16, // truncate
		gc.TUINT32<<16 | gc.TINT16:
		a = arm.AMOVHS

	case gc.TUINT16<<16 | gc.TUINT16:
		if !gc.Ismem(f) {
			a = arm.AMOVH
			break
		}
		fallthrough

	case gc.TINT16<<16 | gc.TUINT16,
		gc.TINT32<<16 | gc.TUINT16,
		gc.TUINT32<<16 | gc.TUINT16:
		a = arm.AMOVHU

	case gc.TINT64<<16 | gc.TINT16, // truncate low word
		gc.TUINT64<<16 | gc.TINT16:
		a = arm.AMOVHS

		goto trunc64

	case gc.TINT64<<16 | gc.TUINT16,
		gc.TUINT64<<16 | gc.TUINT16:
		a = arm.AMOVHU
		goto trunc64

	case gc.TINT32<<16 | gc.TINT32, // same size
		gc.TINT32<<16 | gc.TUINT32,
		gc.TUINT32<<16 | gc.TINT32,
		gc.TUINT32<<16 | gc.TUINT32:
		a = arm.AMOVW

	case gc.TINT64<<16 | gc.TINT32, // truncate
		gc.TUINT64<<16 | gc.TINT32,
		gc.TINT64<<16 | gc.TUINT32,
		gc.TUINT64<<16 | gc.TUINT32:
		var flo gc.Node
		var fhi gc.Node
		split64(f, &flo, &fhi)

		var r1 gc.Node
		gc.Regalloc(&r1, t.Type, nil)
		gins(arm.AMOVW, &flo, &r1)
		gins(arm.AMOVW, &r1, t)
		gc.Regfree(&r1)
		splitclean()
		return

	case gc.TINT64<<16 | gc.TINT64, // same size
		gc.TINT64<<16 | gc.TUINT64,
		gc.TUINT64<<16 | gc.TINT64,
		gc.TUINT64<<16 | gc.TUINT64:
		var fhi gc.Node
		var flo gc.Node
		split64(f, &flo, &fhi)

		var tlo gc.Node
		var thi gc.Node
		split64(t, &tlo, &thi)
		var r1 gc.Node
		gc.Regalloc(&r1, flo.Type, nil)
		var r2 gc.Node
		gc.Regalloc(&r2, fhi.Type, nil)
		gins(arm.AMOVW, &flo, &r1)
		gins(arm.AMOVW, &fhi, &r2)
		gins(arm.AMOVW, &r1, &tlo)
		gins(arm.AMOVW, &r2, &thi)
		gc.Regfree(&r1)
		gc.Regfree(&r2)
		splitclean()
		splitclean()
		return

		/*
		 * integer up-conversions
		 */
	case gc.TINT8<<16 | gc.TINT16, // sign extend int8
		gc.TINT8<<16 | gc.TUINT16,
		gc.TINT8<<16 | gc.TINT32,
		gc.TINT8<<16 | gc.TUINT32:
		a = arm.AMOVBS

		goto rdst

	case gc.TINT8<<16 | gc.TINT64, // convert via int32
		gc.TINT8<<16 | gc.TUINT64:
		cvt = gc.Types[gc.TINT32]

		goto hard

	case gc.TUINT8<<16 | gc.TINT16, // zero extend uint8
		gc.TUINT8<<16 | gc.TUINT16,
		gc.TUINT8<<16 | gc.TINT32,
		gc.TUINT8<<16 | gc.TUINT32:
		a = arm.AMOVBU

		goto rdst

	case gc.TUINT8<<16 | gc.TINT64, // convert via uint32
		gc.TUINT8<<16 | gc.TUINT64:
		cvt = gc.Types[gc.TUINT32]

		goto hard

	case gc.TINT16<<16 | gc.TINT32, // sign extend int16
		gc.TINT16<<16 | gc.TUINT32:
		a = arm.AMOVHS

		goto rdst

	case gc.TINT16<<16 | gc.TINT64, // convert via int32
		gc.TINT16<<16 | gc.TUINT64:
		cvt = gc.Types[gc.TINT32]

		goto hard

	case gc.TUINT16<<16 | gc.TINT32, // zero extend uint16
		gc.TUINT16<<16 | gc.TUINT32:
		a = arm.AMOVHU

		goto rdst

	case gc.TUINT16<<16 | gc.TINT64, // convert via uint32
		gc.TUINT16<<16 | gc.TUINT64:
		cvt = gc.Types[gc.TUINT32]

		goto hard

	case gc.TINT32<<16 | gc.TINT64, // sign extend int32
		gc.TINT32<<16 | gc.TUINT64:
		var tlo gc.Node
		var thi gc.Node
		split64(t, &tlo, &thi)

		var r1 gc.Node
		gc.Regalloc(&r1, tlo.Type, nil)
		var r2 gc.Node
		gc.Regalloc(&r2, thi.Type, nil)
		gmove(f, &r1)
		p1 := gins(arm.AMOVW, &r1, &r2)
		p1.From.Type = obj.TYPE_SHIFT
		p1.From.Offset = 2<<5 | 31<<7 | int64(r1.Reg)&15 // r1->31
		p1.From.Reg = 0

		//print("gmove: %v\n", p1);
		gins(arm.AMOVW, &r1, &tlo)

		gins(arm.AMOVW, &r2, &thi)
		gc.Regfree(&r1)
		gc.Regfree(&r2)
		splitclean()
		return

	case gc.TUINT32<<16 | gc.TINT64, // zero extend uint32
		gc.TUINT32<<16 | gc.TUINT64:
		var thi gc.Node
		var tlo gc.Node
		split64(t, &tlo, &thi)

		gmove(f, &tlo)
		var r1 gc.Node
		gc.Regalloc(&r1, thi.Type, nil)
		gins(arm.AMOVW, ncon(0), &r1)
		gins(arm.AMOVW, &r1, &thi)
		gc.Regfree(&r1)
		splitclean()
		return

		//	case CASE(TFLOAT64, TUINT64):
	/*
	* float to integer
	 */
	case gc.TFLOAT32<<16 | gc.TINT8,
		gc.TFLOAT32<<16 | gc.TUINT8,
		gc.TFLOAT32<<16 | gc.TINT16,
		gc.TFLOAT32<<16 | gc.TUINT16,
		gc.TFLOAT32<<16 | gc.TINT32,
		gc.TFLOAT32<<16 | gc.TUINT32,

		//	case CASE(TFLOAT32, TUINT64):

		gc.TFLOAT64<<16 | gc.TINT8,
		gc.TFLOAT64<<16 | gc.TUINT8,
		gc.TFLOAT64<<16 | gc.TINT16,
		gc.TFLOAT64<<16 | gc.TUINT16,
		gc.TFLOAT64<<16 | gc.TINT32,
		gc.TFLOAT64<<16 | gc.TUINT32:
		fa := arm.AMOVF

		a := arm.AMOVFW
		if ft == gc.TFLOAT64 {
			fa = arm.AMOVD
			a = arm.AMOVDW
		}

		ta := arm.AMOVW
		switch tt {
		case gc.TINT8:
			ta = arm.AMOVBS

		case gc.TUINT8:
			ta = arm.AMOVBU

		case gc.TINT16:
			ta = arm.AMOVHS

		case gc.TUINT16:
			ta = arm.AMOVHU
		}

		var r1 gc.Node
		gc.Regalloc(&r1, gc.Types[ft], f)
		var r2 gc.Node
		gc.Regalloc(&r2, gc.Types[tt], t)
		gins(fa, f, &r1)        // load to fpu
		p1 := gins(a, &r1, &r1) // convert to w
		switch tt {
		case gc.TUINT8,
			gc.TUINT16,
			gc.TUINT32:
			p1.Scond |= arm.C_UBIT
		}

		gins(arm.AMOVW, &r1, &r2) // copy to cpu
		gins(ta, &r2, t)          // store
		gc.Regfree(&r1)
		gc.Regfree(&r2)
		return

		/*
		 * integer to float
		 */
	case gc.TINT8<<16 | gc.TFLOAT32,
		gc.TUINT8<<16 | gc.TFLOAT32,
		gc.TINT16<<16 | gc.TFLOAT32,
		gc.TUINT16<<16 | gc.TFLOAT32,
		gc.TINT32<<16 | gc.TFLOAT32,
		gc.TUINT32<<16 | gc.TFLOAT32,
		gc.TINT8<<16 | gc.TFLOAT64,
		gc.TUINT8<<16 | gc.TFLOAT64,
		gc.TINT16<<16 | gc.TFLOAT64,
		gc.TUINT16<<16 | gc.TFLOAT64,
		gc.TINT32<<16 | gc.TFLOAT64,
		gc.TUINT32<<16 | gc.TFLOAT64:
		fa := arm.AMOVW

		switch ft {
		case gc.TINT8:
			fa = arm.AMOVBS

		case gc.TUINT8:
			fa = arm.AMOVBU

		case gc.TINT16:
			fa = arm.AMOVHS

		case gc.TUINT16:
			fa = arm.AMOVHU
		}

		a := arm.AMOVWF
		ta := arm.AMOVF
		if tt == gc.TFLOAT64 {
			a = arm.AMOVWD
			ta = arm.AMOVD
		}

		var r1 gc.Node
		gc.Regalloc(&r1, gc.Types[ft], f)
		var r2 gc.Node
		gc.Regalloc(&r2, gc.Types[tt], t)
		gins(fa, f, &r1)          // load to cpu
		gins(arm.AMOVW, &r1, &r2) // copy to fpu
		p1 := gins(a, &r2, &r2)   // convert
		switch ft {
		case gc.TUINT8,
			gc.TUINT16,
			gc.TUINT32:
			p1.Scond |= arm.C_UBIT
		}

		gins(ta, &r2, t) // store
		gc.Regfree(&r1)
		gc.Regfree(&r2)
		return

	case gc.TUINT64<<16 | gc.TFLOAT32,
		gc.TUINT64<<16 | gc.TFLOAT64:
		gc.Fatalf("gmove UINT64, TFLOAT not implemented")
		return

		/*
		 * float to float
		 */
	case gc.TFLOAT32<<16 | gc.TFLOAT32:
		a = arm.AMOVF

	case gc.TFLOAT64<<16 | gc.TFLOAT64:
		a = arm.AMOVD

	case gc.TFLOAT32<<16 | gc.TFLOAT64:
		var r1 gc.Node
		gc.Regalloc(&r1, gc.Types[gc.TFLOAT64], t)
		gins(arm.AMOVF, f, &r1)
		gins(arm.AMOVFD, &r1, &r1)
		gins(arm.AMOVD, &r1, t)
		gc.Regfree(&r1)
		return

	case gc.TFLOAT64<<16 | gc.TFLOAT32:
		var r1 gc.Node
		gc.Regalloc(&r1, gc.Types[gc.TFLOAT64], t)
		gins(arm.AMOVD, f, &r1)
		gins(arm.AMOVDF, &r1, &r1)
		gins(arm.AMOVF, &r1, t)
		gc.Regfree(&r1)
		return
	}

	gins(a, f, t)
	return

	// TODO(kaib): we almost always require a register dest anyway, this can probably be
	// removed.
	// requires register destination
rdst:
	{
		gc.Regalloc(&r1, t.Type, t)

		gins(a, f, &r1)
		gmove(&r1, t)
		gc.Regfree(&r1)
		return
	}

	// requires register intermediate
hard:
	gc.Regalloc(&r1, cvt, t)

	gmove(f, &r1)
	gmove(&r1, t)
	gc.Regfree(&r1)
	return

	// truncate 64 bit integer
trunc64:
	var fhi gc.Node
	var flo gc.Node
	split64(f, &flo, &fhi)

	gc.Regalloc(&r1, t.Type, nil)
	gins(a, &flo, &r1)
	gins(a, &r1, t)
	gc.Regfree(&r1)
	splitclean()
	return
}

func samaddr(f *gc.Node, t *gc.Node) bool {
	if f.Op != t.Op {
		return false
	}

	switch f.Op {
	case gc.OREGISTER:
		if f.Reg != t.Reg {
			break
		}
		return true
	}

	return false
}

/*
 * generate one instruction:
 *	as f, t
 */
func gins(as obj.As, f *gc.Node, t *gc.Node) *obj.Prog {
	//	Node nod;
	//	int32 v;

	if f != nil && f.Op == gc.OINDEX {
		gc.Fatalf("gins OINDEX not implemented")
	}

	//		gc.Regalloc(&nod, &regnode, Z);
	//		v = constnode.vconst;
	//		gc.Cgen(f->right, &nod);
	//		constnode.vconst = v;
	//		idx.reg = nod.reg;
	//		gc.Regfree(&nod);
	if t != nil && t.Op == gc.OINDEX {
		gc.Fatalf("gins OINDEX not implemented")
	}

	//		gc.Regalloc(&nod, &regnode, Z);
	//		v = constnode.vconst;
	//		gc.Cgen(t->right, &nod);
	//		constnode.vconst = v;
	//		idx.reg = nod.reg;
	//		gc.Regfree(&nod);

	p := gc.Prog(as)
	gc.Naddr(&p.From, f)
	gc.Naddr(&p.To, t)

	switch as {
	case arm.ABL:
		if p.To.Type == obj.TYPE_REG {
			p.To.Type = obj.TYPE_MEM
		}

	case arm.ACMP, arm.ACMPF, arm.ACMPD:
		if t != nil {
			if f.Op != gc.OREGISTER {
				/* generate a comparison
				TODO(kaib): one of the args can actually be a small constant. relax the constraint and fix call sites.
				*/
				gc.Fatalf("bad operands to gcmp")
			}
			p.From = p.To
			p.To = obj.Addr{}
			raddr(f, p)
		}

	case arm.AMULU:
		if f != nil && f.Op != gc.OREGISTER {
			gc.Fatalf("bad operands to mul")
		}

	case arm.AMOVW:
		if (p.From.Type == obj.TYPE_MEM || p.From.Type == obj.TYPE_ADDR || p.From.Type == obj.TYPE_CONST) && (p.To.Type == obj.TYPE_MEM || p.To.Type == obj.TYPE_ADDR) {
			gc.Fatalf("gins double memory")
		}

	case arm.AADD:
		if p.To.Type == obj.TYPE_MEM {
			gc.Fatalf("gins arith to mem")
		}

	case arm.ARSB:
		if p.From.Type == obj.TYPE_NONE {
			gc.Fatalf("rsb with no from")
		}
	}

	if gc.Debug['g'] != 0 {
		fmt.Printf("%v\n", p)
	}
	return p
}

/*
 * insert n into reg slot of p
 */
func raddr(n *gc.Node, p *obj.Prog) {
	var a obj.Addr
	gc.Naddr(&a, n)
	if a.Type != obj.TYPE_REG {
		if n != nil {
			gc.Fatalf("bad in raddr: %v", n.Op)
		} else {
			gc.Fatalf("bad in raddr: <null>")
		}
		p.Reg = 0
	} else {
		p.Reg = a.Reg
	}
}

/* generate a constant shift
 * arm encodes a shift by 32 as 0, thus asking for 0 shift is illegal.
 */
func gshift(as obj.As, lhs *gc.Node, stype int32, sval int32, rhs *gc.Node) *obj.Prog {
	if sval <= 0 || sval > 32 {
		gc.Fatalf("bad shift value: %d", sval)
	}

	sval = sval & 0x1f

	p := gins(as, nil, rhs)
	p.From.Type = obj.TYPE_SHIFT
	p.From.Offset = int64(stype) | int64(sval)<<7 | int64(lhs.Reg)&15
	return p
}

/* generate a register shift
 */
func gregshift(as obj.As, lhs *gc.Node, stype int32, reg *gc.Node, rhs *gc.Node) *obj.Prog {
	p := gins(as, nil, rhs)
	p.From.Type = obj.TYPE_SHIFT
	p.From.Offset = int64(stype) | (int64(reg.Reg)&15)<<8 | 1<<4 | int64(lhs.Reg)&15
	return p
}

/*
 * return Axxx for Oxxx on type t.
 */
func optoas(op gc.Op, t *gc.Type) obj.As {
	if t == nil {
		gc.Fatalf("optoas: t is nil")
	}

	// avoid constant conversions in switches below
	const (
		OMINUS_ = uint32(gc.OMINUS) << 16
		OLSH_   = uint32(gc.OLSH) << 16
		ORSH_   = uint32(gc.ORSH) << 16
		OADD_   = uint32(gc.OADD) << 16
		OSUB_   = uint32(gc.OSUB) << 16
		OMUL_   = uint32(gc.OMUL) << 16
		ODIV_   = uint32(gc.ODIV) << 16
		OMOD_   = uint32(gc.OMOD) << 16
		OOR_    = uint32(gc.OOR) << 16
		OAND_   = uint32(gc.OAND) << 16
		OXOR_   = uint32(gc.OXOR) << 16
		OEQ_    = uint32(gc.OEQ) << 16
		ONE_    = uint32(gc.ONE) << 16
		OLT_    = uint32(gc.OLT) << 16
		OLE_    = uint32(gc.OLE) << 16
		OGE_    = uint32(gc.OGE) << 16
		OGT_    = uint32(gc.OGT) << 16
		OCMP_   = uint32(gc.OCMP) << 16
		OPS_    = uint32(gc.OPS) << 16
		OAS_    = uint32(gc.OAS) << 16
		OSQRT_  = uint32(gc.OSQRT) << 16
	)

	a := obj.AXXX
	switch uint32(op)<<16 | uint32(gc.Simtype[t.Etype]) {
	default:
		gc.Fatalf("optoas: no entry %v-%v etype %v simtype %v", op, t, gc.Types[t.Etype], gc.Types[gc.Simtype[t.Etype]])

		/*	case CASE(OADDR, TPTR32):
				a = ALEAL;
				break;

			case CASE(OADDR, TPTR64):
				a = ALEAQ;
				break;
		*/
	// TODO(kaib): make sure the conditional branches work on all edge cases
	case OEQ_ | gc.TBOOL,
		OEQ_ | gc.TINT8,
		OEQ_ | gc.TUINT8,
		OEQ_ | gc.TINT16,
		OEQ_ | gc.TUINT16,
		OEQ_ | gc.TINT32,
		OEQ_ | gc.TUINT32,
		OEQ_ | gc.TINT64,
		OEQ_ | gc.TUINT64,
		OEQ_ | gc.TPTR32,
		OEQ_ | gc.TPTR64,
		OEQ_ | gc.TFLOAT32,
		OEQ_ | gc.TFLOAT64:
		a = arm.ABEQ

	case ONE_ | gc.TBOOL,
		ONE_ | gc.TINT8,
		ONE_ | gc.TUINT8,
		ONE_ | gc.TINT16,
		ONE_ | gc.TUINT16,
		ONE_ | gc.TINT32,
		ONE_ | gc.TUINT32,
		ONE_ | gc.TINT64,
		ONE_ | gc.TUINT64,
		ONE_ | gc.TPTR32,
		ONE_ | gc.TPTR64,
		ONE_ | gc.TFLOAT32,
		ONE_ | gc.TFLOAT64:
		a = arm.ABNE

	case OLT_ | gc.TINT8,
		OLT_ | gc.TINT16,
		OLT_ | gc.TINT32,
		OLT_ | gc.TINT64,
		OLT_ | gc.TFLOAT32,
		OLT_ | gc.TFLOAT64:
		a = arm.ABLT

	case OLT_ | gc.TUINT8,
		OLT_ | gc.TUINT16,
		OLT_ | gc.TUINT32,
		OLT_ | gc.TUINT64:
		a = arm.ABLO

	case OLE_ | gc.TINT8,
		OLE_ | gc.TINT16,
		OLE_ | gc.TINT32,
		OLE_ | gc.TINT64,
		OLE_ | gc.TFLOAT32,
		OLE_ | gc.TFLOAT64:
		a = arm.ABLE

	case OLE_ | gc.TUINT8,
		OLE_ | gc.TUINT16,
		OLE_ | gc.TUINT32,
		OLE_ | gc.TUINT64:
		a = arm.ABLS

	case OGT_ | gc.TINT8,
		OGT_ | gc.TINT16,
		OGT_ | gc.TINT32,
		OGT_ | gc.TINT64,
		OGT_ | gc.TFLOAT32,
		OGT_ | gc.TFLOAT64:
		a = arm.ABGT

	case OGT_ | gc.TUINT8,
		OGT_ | gc.TUINT16,
		OGT_ | gc.TUINT32,
		OGT_ | gc.TUINT64:
		a = arm.ABHI

	case OGE_ | gc.TINT8,
		OGE_ | gc.TINT16,
		OGE_ | gc.TINT32,
		OGE_ | gc.TINT64,
		OGE_ | gc.TFLOAT32,
		OGE_ | gc.TFLOAT64:
		a = arm.ABGE

	case OGE_ | gc.TUINT8,
		OGE_ | gc.TUINT16,
		OGE_ | gc.TUINT32,
		OGE_ | gc.TUINT64:
		a = arm.ABHS

	case OCMP_ | gc.TBOOL,
		OCMP_ | gc.TINT8,
		OCMP_ | gc.TUINT8,
		OCMP_ | gc.TINT16,
		OCMP_ | gc.TUINT16,
		OCMP_ | gc.TINT32,
		OCMP_ | gc.TUINT32,
		OCMP_ | gc.TPTR32:
		a = arm.ACMP

	case OCMP_ | gc.TFLOAT32:
		a = arm.ACMPF

	case OCMP_ | gc.TFLOAT64:
		a = arm.ACMPD

	case OPS_ | gc.TFLOAT32,
		OPS_ | gc.TFLOAT64:
		a = arm.ABVS

	case OAS_ | gc.TBOOL:
		a = arm.AMOVB

	case OAS_ | gc.TINT8:
		a = arm.AMOVBS

	case OAS_ | gc.TUINT8:
		a = arm.AMOVBU

	case OAS_ | gc.TINT16:
		a = arm.AMOVHS

	case OAS_ | gc.TUINT16:
		a = arm.AMOVHU

	case OAS_ | gc.TINT32,
		OAS_ | gc.TUINT32,
		OAS_ | gc.TPTR32:
		a = arm.AMOVW

	case OAS_ | gc.TFLOAT32:
		a = arm.AMOVF

	case OAS_ | gc.TFLOAT64:
		a = arm.AMOVD

	case OADD_ | gc.TINT8,
		OADD_ | gc.TUINT8,
		OADD_ | gc.TINT16,
		OADD_ | gc.TUINT16,
		OADD_ | gc.TINT32,
		OADD_ | gc.TUINT32,
		OADD_ | gc.TPTR32:
		a = arm.AADD

	case OADD_ | gc.TFLOAT32:
		a = arm.AADDF

	case OADD_ | gc.TFLOAT64:
		a = arm.AADDD

	case OSUB_ | gc.TINT8,
		OSUB_ | gc.TUINT8,
		OSUB_ | gc.TINT16,
		OSUB_ | gc.TUINT16,
		OSUB_ | gc.TINT32,
		OSUB_ | gc.TUINT32,
		OSUB_ | gc.TPTR32:
		a = arm.ASUB

	case OSUB_ | gc.TFLOAT32:
		a = arm.ASUBF

	case OSUB_ | gc.TFLOAT64:
		a = arm.ASUBD

	case OMINUS_ | gc.TINT8,
		OMINUS_ | gc.TUINT8,
		OMINUS_ | gc.TINT16,
		OMINUS_ | gc.TUINT16,
		OMINUS_ | gc.TINT32,
		OMINUS_ | gc.TUINT32,
		OMINUS_ | gc.TPTR32:
		a = arm.ARSB

	case OAND_ | gc.TINT8,
		OAND_ | gc.TUINT8,
		OAND_ | gc.TINT16,
		OAND_ | gc.TUINT16,
		OAND_ | gc.TINT32,
		OAND_ | gc.TUINT32,
		OAND_ | gc.TPTR32:
		a = arm.AAND

	case OOR_ | gc.TINT8,
		OOR_ | gc.TUINT8,
		OOR_ | gc.TINT16,
		OOR_ | gc.TUINT16,
		OOR_ | gc.TINT32,
		OOR_ | gc.TUINT32,
		OOR_ | gc.TPTR32:
		a = arm.AORR

	case OXOR_ | gc.TINT8,
		OXOR_ | gc.TUINT8,
		OXOR_ | gc.TINT16,
		OXOR_ | gc.TUINT16,
		OXOR_ | gc.TINT32,
		OXOR_ | gc.TUINT32,
		OXOR_ | gc.TPTR32:
		a = arm.AEOR

	case OLSH_ | gc.TINT8,
		OLSH_ | gc.TUINT8,
		OLSH_ | gc.TINT16,
		OLSH_ | gc.TUINT16,
		OLSH_ | gc.TINT32,
		OLSH_ | gc.TUINT32,
		OLSH_ | gc.TPTR32:
		a = arm.ASLL

	case ORSH_ | gc.TUINT8,
		ORSH_ | gc.TUINT16,
		ORSH_ | gc.TUINT32,
		ORSH_ | gc.TPTR32:
		a = arm.ASRL

	case ORSH_ | gc.TINT8,
		ORSH_ | gc.TINT16,
		ORSH_ | gc.TINT32:
		a = arm.ASRA

	case OMUL_ | gc.TUINT8,
		OMUL_ | gc.TUINT16,
		OMUL_ | gc.TUINT32,
		OMUL_ | gc.TPTR32:
		a = arm.AMULU

	case OMUL_ | gc.TINT8,
		OMUL_ | gc.TINT16,
		OMUL_ | gc.TINT32:
		a = arm.AMUL

	case OMUL_ | gc.TFLOAT32:
		a = arm.AMULF

	case OMUL_ | gc.TFLOAT64:
		a = arm.AMULD

	case ODIV_ | gc.TUINT8,
		ODIV_ | gc.TUINT16,
		ODIV_ | gc.TUINT32,
		ODIV_ | gc.TPTR32:
		a = arm.ADIVU

	case ODIV_ | gc.TINT8,
		ODIV_ | gc.TINT16,
		ODIV_ | gc.TINT32:
		a = arm.ADIV

	case OMOD_ | gc.TUINT8,
		OMOD_ | gc.TUINT16,
		OMOD_ | gc.TUINT32,
		OMOD_ | gc.TPTR32:
		a = arm.AMODU

	case OMOD_ | gc.TINT8,
		OMOD_ | gc.TINT16,
		OMOD_ | gc.TINT32:
		a = arm.AMOD

		//	case CASE(OEXTEND, TINT16):
	//		a = ACWD;
	//		break;

	//	case CASE(OEXTEND, TINT32):
	//		a = ACDQ;
	//		break;

	//	case CASE(OEXTEND, TINT64):
	//		a = ACQO;
	//		break;

	case ODIV_ | gc.TFLOAT32:
		a = arm.ADIVF

	case ODIV_ | gc.TFLOAT64:
		a = arm.ADIVD

	case OSQRT_ | gc.TFLOAT64:
		a = arm.ASQRTD
	}

	return a
}

const (
	ODynam = 1 << 0
	OPtrto = 1 << 1
)

var clean [20]gc.Node

var cleani int = 0

func sudoclean() {
	if clean[cleani-1].Op != gc.OEMPTY {
		gc.Regfree(&clean[cleani-1])
	}
	if clean[cleani-2].Op != gc.OEMPTY {
		gc.Regfree(&clean[cleani-2])
	}
	cleani -= 2
}

func dotaddable(n *gc.Node, n1 *gc.Node) bool {
	if n.Op != gc.ODOT {
		return false
	}

	var oary [10]int64
	var nn *gc.Node
	o := gc.Dotoffset(n, oary[:], &nn)
	if nn != nil && nn.Addable && o == 1 && oary[0] >= 0 {
		*n1 = *nn
		n1.Type = n.Type
		n1.Xoffset += oary[0]
		return true
	}

	return false
}

/*
 * generate code to compute address of n,
 * a reference to a (perhaps nested) field inside
 * an array or struct.
 * return 0 on failure, 1 on success.
 * on success, leaves usable address in a.
 *
 * caller is responsible for calling sudoclean
 * after successful sudoaddable,
 * to release the register used for a.
 */
func sudoaddable(as obj.As, n *gc.Node, a *obj.Addr) bool {
	if n.Type == nil {
		return false
	}

	*a = obj.Addr{}

	switch n.Op {
	case gc.OLITERAL:
		if !gc.Isconst(n, gc.CTINT) {
			break
		}
		v := n.Int64()
		if v >= 32000 || v <= -32000 {
			break
		}
		switch as {
		default:
			return false

		case arm.AADD,
			arm.ASUB,
			arm.AAND,
			arm.AORR,
			arm.AEOR,
			arm.AMOVB,
			arm.AMOVBS,
			arm.AMOVBU,
			arm.AMOVH,
			arm.AMOVHS,
			arm.AMOVHU,
			arm.AMOVW:
			break
		}

		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		gc.Naddr(a, n)
		return true

	case gc.ODOT,
		gc.ODOTPTR:
		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		var nn *gc.Node
		var oary [10]int64
		o := gc.Dotoffset(n, oary[:], &nn)
		if nn == nil {
			sudoclean()
			return false
		}

		if nn.Addable && o == 1 && oary[0] >= 0 {
			// directly addressable set of DOTs
			n1 := *nn

			n1.Type = n.Type
			n1.Xoffset += oary[0]
			gc.Naddr(a, &n1)
			return true
		}

		gc.Regalloc(reg, gc.Types[gc.Tptr], nil)
		n1 := *reg
		n1.Op = gc.OINDREG
		if oary[0] >= 0 {
			gc.Agen(nn, reg)
			n1.Xoffset = oary[0]
		} else {
			gc.Cgen(nn, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[0] + 1)
		}

		for i := 1; i < o; i++ {
			if oary[i] >= 0 {
				gc.Fatalf("can't happen")
			}
			gins(arm.AMOVW, &n1, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[i] + 1)
		}

		a.Type = obj.TYPE_NONE
		a.Name = obj.NAME_NONE
		n1.Type = n.Type
		gc.Naddr(a, &n1)
		return true

	case gc.OINDEX:
		return false
	}

	return false
}