cmd/internal/obj: make Prog.From3 a pointer

It is almost never set and Addr is large, so having the full struct
in the Prog wastes memory most of the time.

Before (on a 64-bit system):

$ sizeof -p cmd/internal/obj Addr Prog
Addr 80
Prog 376
$

After:

$ sizeof -p cmd/internal/obj Addr Prog
Addr 80
Prog 304
$

Change-Id: I491f201241f87543964a7d0f48b85830759be9d0
Reviewed-on: https://go-review.googlesource.com/10457Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/asm/internal/asm/asm.go

@@ -151,7 +151,7 @@ func (p *Parser) asmText(word string, operands [][]lex.Token) {
 		As:     obj.ATEXT,
 		Lineno: p.histLineNum,
 		From:   nameAddr,
-		From3: obj.Addr{
+		From3: &obj.Addr{
 			Type:   obj.TYPE_CONST,
 			Offset: flag,
 		},
@@ -205,7 +205,7 @@ func (p *Parser) asmData(word string, operands [][]lex.Token) {
 		As:     obj.ADATA,
 		Lineno: p.histLineNum,
 		From:   nameAddr,
-		From3: obj.Addr{
+		From3: &obj.Addr{
 			Offset: int64(scale),
 		},
 		To: valueAddr,
@@ -244,7 +244,7 @@ func (p *Parser) asmGlobl(word string, operands [][]lex.Token) {
 		As:     obj.AGLOBL,
 		Lineno: p.histLineNum,
 		From:   nameAddr,
-		From3: obj.Addr{
+		From3: &obj.Addr{
 			Offset: flag,
 		},
 		To: addr,
@@ -504,7 +504,7 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 			prog.To = a[2]
 		case '6', '8':
 			prog.From = a[0]
-			prog.From3 = a[1]
+			prog.From3 = newAddr(a[1])
 			prog.To = a[2]
 		case '9':
 			if arch.IsPPC64CMP(op) {
@@ -526,7 +526,7 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 				prog.To = a[2]
 			case obj.TYPE_CONST:
 				prog.From = a[0]
-				prog.From3 = a[1]
+				prog.From3 = newAddr(a[1])
 				prog.To = a[2]
 			default:
 				p.errorf("invalid addressing modes for %s instruction", obj.Aconv(op))
@@ -551,7 +551,7 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 		if p.arch.Thechar == '7' {
 			prog.From = a[0]
 			prog.Reg = p.getRegister(prog, op, &a[1])
-			prog.From3 = a[2]
+			prog.From3 = newAddr(a[2])
 			prog.To = a[3]
 			break
 		}
@@ -561,7 +561,7 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 			// That is, are there 4-operand instructions without this property?
 			prog.From = a[0]
 			prog.Reg = p.getRegister(prog, op, &a[1])
-			prog.From3 = a[2]
+			prog.From3 = newAddr(a[2])
 			prog.To = a[3]
 			break
 		}
@@ -579,7 +579,7 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 			} else {
 				mask = (^uint32(0) >> uint(mask2+1)) & (^uint32(0) << uint(31-(mask1-1)))
 			}
-			prog.From3 = obj.Addr{
+			prog.From3 = &obj.Addr{
 				Type:   obj.TYPE_CONST,
 				Offset: int64(mask),
 			}
@@ -615,6 +615,13 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 	p.append(prog, cond, true)
 }
 
+// newAddr returns a new(Addr) initialized to x.
+func newAddr(x obj.Addr) *obj.Addr {
+	p := new(obj.Addr)
+	*p = x
+	return p
+}
+
 var emptyProg obj.Prog
 
 // getConstantPseudo checks that addr represents a plain constant and returns its value.

src/cmd/compile/internal/arm64/peep.go

@@ -418,9 +418,9 @@ func copy1(v1 *obj.Addr, v2 *obj.Addr, r *gc.Flow, f int) bool {
 //	  can be rewritten independently)
 //	0 otherwise (not touched)
 func copyu(p *obj.Prog, v *obj.Addr, s *obj.Addr) int {
-	if p.From3.Type != obj.TYPE_NONE {
+	if p.From3Type() != obj.TYPE_NONE {
 		// 7g never generates a from3
-		fmt.Printf("copyu: from3 (%v) not implemented\n", gc.Ctxt.Dconv(&p.From3))
+		fmt.Printf("copyu: from3 (%v) not implemented\n", gc.Ctxt.Dconv(p.From3))
 	}
 	if p.RegTo2 != obj.REG_NONE {
 		// 7g never generates a to2

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

@@ -214,6 +214,7 @@ func ggloblnod(nam *Node) {
 	p.To.Sym = nil
 	p.To.Type = obj.TYPE_CONST
 	p.To.Offset = nam.Type.Width
+	p.From3 = new(obj.Addr)
 	if nam.Name.Readonly {
 		p.From3.Offset = obj.RODATA
 	}
@@ -233,6 +234,7 @@ func ggloblsym(s *Sym, width int32, flags int16) {
 	}
 	p.To.Type = obj.TYPE_CONST
 	p.To.Offset = int64(width)
+	p.From3 = new(obj.Addr)
 	p.From3.Offset = int64(flags)
 }
 

src/cmd/compile/internal/gc/obj.go

@@ -286,6 +286,7 @@ func dstringptr(s *Sym, off int, str string) int {
 	p.From.Name = obj.NAME_EXTERN
 	p.From.Sym = Linksym(s)
 	p.From.Offset = int64(off)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(Widthptr)
 
@@ -334,6 +335,7 @@ func dgostrlitptr(s *Sym, off int, lit *string) int {
 	p.From.Name = obj.NAME_EXTERN
 	p.From.Sym = Linksym(s)
 	p.From.Offset = int64(off)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(Widthptr)
 	datagostring(*lit, &p.To)
@@ -350,6 +352,7 @@ func dsname(s *Sym, off int, t string) int {
 	p.From.Name = obj.NAME_EXTERN
 	p.From.Offset = int64(off)
 	p.From.Sym = Linksym(s)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(len(t))
 
@@ -366,6 +369,7 @@ func dsymptr(s *Sym, off int, x *Sym, xoff int) int {
 	p.From.Name = obj.NAME_EXTERN
 	p.From.Sym = Linksym(s)
 	p.From.Offset = int64(off)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(Widthptr)
 	p.To.Type = obj.TYPE_ADDR
@@ -391,6 +395,7 @@ func gdata(nam *Node, nr *Node, wid int) {
 	}
 
 	p := Thearch.Gins(obj.ADATA, nam, nr)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(wid)
 }
@@ -400,12 +405,14 @@ func gdatacomplex(nam *Node, cval *Mpcplx) {
 	w = int(Types[w].Width)
 
 	p := Thearch.Gins(obj.ADATA, nam, nil)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(w)
 	p.To.Type = obj.TYPE_FCONST
 	p.To.Val = mpgetflt(&cval.Real)
 
 	p = Thearch.Gins(obj.ADATA, nam, nil)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(w)
 	p.From.Offset += int64(w)
@@ -418,6 +425,7 @@ func gdatastring(nam *Node, sval string) {
 
 	p := Thearch.Gins(obj.ADATA, nam, nil)
 	Datastring(sval, &p.To)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = Types[Tptr].Width
 	p.To.Type = obj.TYPE_ADDR
@@ -427,6 +435,7 @@ func gdatastring(nam *Node, sval string) {
 	Nodconst(&nod1, Types[TINT], int64(len(sval)))
 
 	p = Thearch.Gins(obj.ADATA, nam, &nod1)
+	p.From3 = new(obj.Addr)
 	p.From3.Type = obj.TYPE_CONST
 	p.From3.Offset = int64(Widthint)
 	p.From.Offset += int64(Widthptr)

src/cmd/compile/internal/gc/pgen.go

@@ -413,6 +413,7 @@ func compile(fn *Node) {
 		nam = nil
 	}
 	ptxt = Thearch.Gins(obj.ATEXT, nam, &nod1)
+	ptxt.From3 = new(obj.Addr)
 	if fn.Func.Dupok {
 		ptxt.From3.Offset |= obj.DUPOK
 	}

src/cmd/compile/internal/gc/reg.go

@@ -1119,7 +1119,7 @@ func regopt(firstp *obj.Prog) {
 
 		// Currently we never generate three register forms.
 		// If we do, this will need to change.
-		if p.From3.Type != obj.TYPE_NONE {
+		if p.From3Type() != obj.TYPE_NONE {
 			Fatal("regopt not implemented for from3")
 		}
 

src/cmd/compile/internal/ppc64/peep.go

@@ -606,9 +606,9 @@ func copy1(v1 *obj.Addr, v2 *obj.Addr, r *gc.Flow, f int) bool {
 // 	  can be rewritten independently)
 //	0 otherwise (not touched)
 func copyu(p *obj.Prog, v *obj.Addr, s *obj.Addr) int {
-	if p.From3.Type != obj.TYPE_NONE {
+	if p.From3Type() != obj.TYPE_NONE {
 		// 9g never generates a from3
-		fmt.Printf("copyu: from3 (%v) not implemented\n", gc.Ctxt.Dconv(&p.From3))
+		fmt.Printf("copyu: from3 (%v) not implemented\n", gc.Ctxt.Dconv(p.From3))
 	}
 
 	switch p.As {

src/cmd/internal/obj/arm64/asm7.go

@@ -2040,7 +2040,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		rt := int(p.To.Reg)
 		var r int
 		var ra int
-		if p.From3.Type == obj.TYPE_REG {
+		if p.From3Type() == obj.TYPE_REG {
 			r = int(p.From3.Reg)
 			ra = int(p.Reg)
 			if ra == 0 {
@@ -2091,7 +2091,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		r := int(p.Reg)
 		var rf int
 		if r != 0 {
-			if p.From3.Type == obj.TYPE_NONE {
+			if p.From3Type() == obj.TYPE_NONE {
 				/* CINC/CINV/CNEG */
 				rf = r
 
@@ -2348,7 +2348,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 			ctxt.Diag("requires uimm16\n%v", p)
 		}
 		s := 0
-		if p.From3.Type != obj.TYPE_NONE {
+		if p.From3Type() != obj.TYPE_NONE {
 			if p.From3.Type != obj.TYPE_CONST {
 				ctxt.Diag("missing bit position\n%v", p)
 			}
@@ -2656,8 +2656,9 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 			ctxt.Diag("implausible condition\n%v", p)
 		}
 		rf := int(p.Reg)
-		if p.From3.Reg < REG_F0 || p.From3.Reg > REG_F31 {
+		if p.From3 == nil || p.From3.Reg < REG_F0 || p.From3.Reg > REG_F31 {
 			ctxt.Diag("illegal FCCMP\n%v", p)
+			break
 		}
 		rt := int(p.From3.Reg)
 		o1 |= uint32(rf&31)<<16 | uint32(cond)<<12 | uint32(rt&31)<<5 | uint32(nzcv)

src/cmd/internal/obj/go.go

@@ -55,7 +55,7 @@ func Nopout(p *Prog) {
 	p.As = ANOP
 	p.Scond = 0
 	p.From = Addr{}
-	p.From3 = Addr{}
+	p.From3 = nil
 	p.Reg = 0
 	p.To = Addr{}
 }

src/cmd/internal/obj/link.go

@@ -204,7 +204,7 @@ type Prog struct {
 	Ctxt     *Link
 	Link     *Prog
 	From     Addr
-	From3    Addr
+	From3    *Addr // optional
 	To       Addr
 	Opt      interface{}
 	Forwd    *Prog
@@ -231,6 +231,14 @@ type Prog struct {
 	Info ProgInfo
 }
 
+// From3Type returns From3.Type, or TYPE_NONE when From3 is nil.
+func (p *Prog) From3Type() int16 {
+	if p.From3 == nil {
+		return TYPE_NONE
+	}
+	return p.From3.Type
+}
+
 // ProgInfo holds information about the instruction for use
 // by clients such as the compiler. The exact meaning of this
 // data is up to the client and is not interpreted by the cmd/internal/obj/... packages.

src/cmd/internal/obj/pass.go

@@ -157,7 +157,9 @@ func linkpatch(ctxt *Link, sym *LSym) {
 
 	for p := sym.Text; p != nil; p = p.Link {
 		checkaddr(ctxt, p, &p.From)
-		checkaddr(ctxt, p, &p.From3)
+		if p.From3 != nil {
+			checkaddr(ctxt, p, p.From3)
+		}
 		checkaddr(ctxt, p, &p.To)
 
 		if ctxt.Arch.Progedit != nil {

src/cmd/internal/obj/ppc64/asm9.go

@@ -724,10 +724,13 @@ func oplook(ctxt *obj.Link, p *obj.Prog) *Optab {
 	}
 
 	a1--
-	a3 := int(p.From3.Class)
-	if a3 == 0 {
-		a3 = aclass(ctxt, &p.From3) + 1
-		p.From3.Class = int8(a3)
+	a3 := C_NONE
+	if p.From3 != nil {
+		a3 = int(p.From3.Class)
+		if a3 == 0 {
+			a3 = aclass(ctxt, p.From3) + 1
+			p.From3.Class = int8(a3)
+		}
 	}
 
 	a3--
@@ -1703,7 +1706,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		if r == 0 {
 			r = int(p.To.Reg)
 		}
-		d := vregoff(ctxt, &p.From3)
+		d := vregoff(ctxt, p.From3)
 		var mask [2]uint8
 		maskgen64(ctxt, p, mask[:], uint64(d))
 		var a int
@@ -1916,7 +1919,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		o2 = AOP_IRR(OP_ADDI, uint32(p.To.Reg), REGTMP, uint32(v))
 
 	case 27: /* subc ra,$simm,rd => subfic rd,ra,$simm */
-		v := regoff(ctxt, &p.From3)
+		v := regoff(ctxt, p.From3)
 
 		r := int(p.From.Reg)
 		o1 = AOP_IRR(uint32(opirr(ctxt, int(p.As))), uint32(p.To.Reg), uint32(r), uint32(v))
@@ -1925,7 +1928,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		if p.To.Reg == REGTMP || p.From.Reg == REGTMP {
 			ctxt.Diag("can't synthesize large constant\n%v", p)
 		}
-		v := regoff(ctxt, &p.From3)
+		v := regoff(ctxt, p.From3)
 		o1 = AOP_IRR(OP_ADDIS, REGTMP, REGZERO, uint32(v)>>16)
 		o2 = LOP_IRR(OP_ORI, REGTMP, REGTMP, uint32(v))
 		o3 = AOP_RRR(uint32(oprrr(ctxt, int(p.As))), uint32(p.To.Reg), uint32(p.From.Reg), REGTMP)
@@ -1938,7 +1941,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 	case 29: /* rldic[lr]? $sh,s,$mask,a -- left, right, plain give different masks */
 		v := regoff(ctxt, &p.From)
 
-		d := vregoff(ctxt, &p.From3)
+		d := vregoff(ctxt, p.From3)
 		var mask [2]uint8
 		maskgen64(ctxt, p, mask[:], uint64(d))
 		var a int
@@ -1978,7 +1981,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 	case 30: /* rldimi $sh,s,$mask,a */
 		v := regoff(ctxt, &p.From)
 
-		d := vregoff(ctxt, &p.From3)
+		d := vregoff(ctxt, p.From3)
 		var mask [2]uint8
 		maskgen64(ctxt, p, mask[:], uint64(d))
 		if int32(mask[1]) != (63 - v) {
@@ -2069,10 +2072,10 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		o1 = uint32(regoff(ctxt, &p.From))
 
 	case 41: /* stswi */
-		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(p.From.Reg), uint32(p.To.Reg), 0) | (uint32(regoff(ctxt, &p.From3))&0x7F)<<11
+		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(p.From.Reg), uint32(p.To.Reg), 0) | (uint32(regoff(ctxt, p.From3))&0x7F)<<11
 
 	case 42: /* lswi */
-		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(p.To.Reg), uint32(p.From.Reg), 0) | (uint32(regoff(ctxt, &p.From3))&0x7F)<<11
+		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(p.To.Reg), uint32(p.From.Reg), 0) | (uint32(regoff(ctxt, p.From3))&0x7F)<<11
 
 	case 43: /* unary indexed source: dcbf (b); dcbf (a+b) */
 		o1 = AOP_RRR(uint32(oprrr(ctxt, int(p.As))), 0, uint32(p.From.Index), uint32(p.From.Reg))
@@ -2242,21 +2245,21 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		v := regoff(ctxt, &p.From)
 
 		var mask [2]uint8
-		maskgen(ctxt, p, mask[:], uint32(regoff(ctxt, &p.From3)))
+		maskgen(ctxt, p, mask[:], uint32(regoff(ctxt, p.From3)))
 		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(p.Reg), uint32(p.To.Reg), uint32(v))
 		o1 |= (uint32(mask[0])&31)<<6 | (uint32(mask[1])&31)<<1
 
 	case 63: /* rlwmi b,s,$mask,a */
 		var mask [2]uint8
-		maskgen(ctxt, p, mask[:], uint32(regoff(ctxt, &p.From3)))
+		maskgen(ctxt, p, mask[:], uint32(regoff(ctxt, p.From3)))
 
 		o1 = AOP_RRR(uint32(opirr(ctxt, int(p.As))), uint32(p.Reg), uint32(p.To.Reg), uint32(p.From.Reg))
 		o1 |= (uint32(mask[0])&31)<<6 | (uint32(mask[1])&31)<<1
 
 	case 64: /* mtfsf fr[, $m] {,fpcsr} */
 		var v int32
-		if p.From3.Type != obj.TYPE_NONE {
-			v = regoff(ctxt, &p.From3) & 255
+		if p.From3Type() != obj.TYPE_NONE {
+			v = regoff(ctxt, p.From3) & 255
 		} else {
 			v = 255
 		}
@@ -2307,11 +2310,11 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 
 	case 69: /* mtcrf CRM,rS */
 		var v int32
-		if p.From3.Type != obj.TYPE_NONE {
+		if p.From3Type() != obj.TYPE_NONE {
 			if p.To.Reg != 0 {
 				ctxt.Diag("can't use both mask and CR(n)\n%v", p)
 			}
-			v = regoff(ctxt, &p.From3) & 0xff
+			v = regoff(ctxt, p.From3) & 0xff
 		} else {
 			if p.To.Reg == 0 {
 				v = 0xff /* CR */
@@ -2408,7 +2411,9 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 
 func vregoff(ctxt *obj.Link, a *obj.Addr) int64 {
 	ctxt.Instoffset = 0
-	aclass(ctxt, a)
+	if a != nil {
+		aclass(ctxt, a)
+	}
 	return ctxt.Instoffset
 }
 

src/cmd/internal/obj/util.go

@@ -315,12 +315,12 @@ func (p *Prog) String() string {
 		fmt.Fprintf(&buf, "%s%v", sep, Rconv(int(p.Reg)))
 		sep = ", "
 	}
-	if p.From3.Type != TYPE_NONE {
+	if p.From3Type() != TYPE_NONE {
 		if p.From3.Type == TYPE_CONST && (p.As == ADATA || p.As == ATEXT || p.As == AGLOBL) {
 			// Special case - omit $.
 			fmt.Fprintf(&buf, "%s%d", sep, p.From3.Offset)
 		} else {
-			fmt.Fprintf(&buf, "%s%v", sep, Dconv(p, &p.From3))
+			fmt.Fprintf(&buf, "%s%v", sep, Dconv(p, p.From3))
 		}
 		sep = ", "
 	}

src/cmd/internal/obj/x86/asm6.go

@@ -2945,6 +2945,7 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
 	// Similarly SHRQ CX, AX:DX is really SHRQ CX(DX*0), AX.
 	// Change encoding generated by assemblers and compilers and remove.
 	if (p.From.Type == obj.TYPE_CONST || p.From.Type == obj.TYPE_REG) && p.From.Index != REG_NONE && p.From.Scale == 0 {
+		p.From3 = new(obj.Addr)
 		p.From3.Type = obj.TYPE_REG
 		p.From3.Reg = p.From.Index
 		p.From.Index = 0
@@ -2954,16 +2955,18 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
 	// Change encoding generated by assemblers and compilers (if any) and remove.
 	switch p.As {
 	case AIMUL3Q, APEXTRW, APINSRW, APINSRD, APINSRQ, APSHUFHW, APSHUFL, APSHUFW, ASHUFPD, ASHUFPS, AAESKEYGENASSIST, APSHUFD, APCLMULQDQ:
-		if p.From3.Type == obj.TYPE_NONE {
-			p.From3 = p.From
+		if p.From3Type() == obj.TYPE_NONE {
+			p.From3 = new(obj.Addr)
+			*p.From3 = p.From
 			p.From = obj.Addr{}
 			p.From.Type = obj.TYPE_CONST
 			p.From.Offset = p.To.Offset
 			p.To.Offset = 0
 		}
 	case ACMPSD, ACMPSS, ACMPPS, ACMPPD:
-		if p.From3.Type == obj.TYPE_NONE {
-			p.From3 = p.To
+		if p.From3Type() == obj.TYPE_NONE {
+			p.From3 = new(obj.Addr)
+			*p.From3 = p.To
 			p.To = obj.Addr{}
 			p.To.Type = obj.TYPE_CONST
 			p.To.Offset = p.From3.Offset
@@ -2979,7 +2982,10 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
 	}
 
 	ft := int(p.Ft) * Ymax
-	f3t := oclass(ctxt, p, &p.From3) * Ymax
+	f3t := Ynone * Ymax
+	if p.From3 != nil {
+		f3t = oclass(ctxt, p, p.From3) * Ymax
+	}
 	tt := int(p.Tt) * Ymax
 
 	xo := obj.Bool2int(o.op[0] == 0x0f)
@@ -3153,7 +3159,7 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
 
 			case Zm_r_i_xm:
 				mediaop(ctxt, o, op, int(yt.zoffset), z)
-				asmand(ctxt, p, &p.From, &p.From3)
+				asmand(ctxt, p, &p.From, p.From3)
 				ctxt.Andptr[0] = byte(p.To.Offset)
 				ctxt.Andptr = ctxt.Andptr[1:]
 
@@ -3177,7 +3183,7 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
 					ctxt.Andptr[0] = byte(op)
 					ctxt.Andptr = ctxt.Andptr[1:]
 				}
-				asmand(ctxt, p, &p.From3, &p.To)
+				asmand(ctxt, p, p.From3, &p.To)
 				ctxt.Andptr[0] = byte(p.From.Offset)
 				ctxt.Andptr = ctxt.Andptr[1:]
 

src/cmd/internal/obj/x86/obj6.go

@@ -209,7 +209,9 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	}
 
 	if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
-		nacladdr(ctxt, p, &p.From3)
+		if p.From3 != nil {
+			nacladdr(ctxt, p, p.From3)
+		}
 		nacladdr(ctxt, p, &p.From)
 		nacladdr(ctxt, p, &p.To)
 	}
@@ -347,7 +349,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 				p.From.Offset = 0
 			}
 		}
-		if p.From3.Name == obj.NAME_EXTERN {
+		if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
 			ctxt.Diag("don't know how to handle %v with -dynlink", p)
 		}
 		var source *obj.Addr
@@ -715,12 +717,14 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 		if a == obj.NAME_PARAM {
 			p.From.Offset += int64(deltasp) + int64(pcsize)
 		}
-		a = int(p.From3.Name)
-		if a == obj.NAME_AUTO {
-			p.From3.Offset += int64(deltasp) - int64(bpsize)
-		}
-		if a == obj.NAME_PARAM {
-			p.From3.Offset += int64(deltasp) + int64(pcsize)
+		if p.From3 != nil {
+			a = int(p.From3.Name)
+			if a == obj.NAME_AUTO {
+				p.From3.Offset += int64(deltasp) - int64(bpsize)
+			}
+			if a == obj.NAME_PARAM {
+				p.From3.Offset += int64(deltasp) + int64(pcsize)
+			}
 		}
 		a = int(p.To.Name)
 		if a == obj.NAME_AUTO {

src/cmd/old5a/a.y

@@ -221,12 +221,16 @@ inst:
 	{
 		asm.Settext($2.Sym);
 		outcode($1, Always, &$2, 0, &$5);
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}
 	}
 |	LTYPEB name ',' con ',' '$' textsize
 	{
 		asm.Settext($2.Sym);
 		outcode($1, Always, &$2, 0, &$7);
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST;
 			lastpc.From3.Offset = int64($4)
 		}
@@ -238,12 +242,16 @@ inst:
 	{
 		asm.Settext($2.Sym)
 		outcode($1, Always, &$2, 0, &$4)
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}
 	}
 |	LGLOBL name ',' con ',' imm
 	{
 		asm.Settext($2.Sym)
 		outcode($1, Always, &$2, 0, &$6)
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = int64($4)
 		}
@@ -256,6 +264,7 @@ inst:
 	{
 		outcode($1, Always, &$2, 0, &$6)
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = int64($4)
 		}

src/cmd/old6a/a.y

@@ -196,6 +196,7 @@ spec1:	/* DATA */
 		a.to = $6
 		outcode(obj.ADATA, &a)
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -206,12 +207,16 @@ spec2:	/* TEXT */
 	{
 		asm.Settext($2.Sym);
 		outcode(obj.ATEXT, &Addr2{from: $2, to: $5})
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}	
 	}
 |	LTYPET mem ',' con ',' '$' textsize
 	{
 		asm.Settext($2.Sym);
 		outcode(obj.ATEXT, &Addr2{from: $2, to: $7})
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -222,12 +227,16 @@ spec11:	/* GLOBL */
 	{
 		asm.Settext($2.Sym)
 		outcode(obj.AGLOBL, &Addr2{from: $2, to: $4})
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}	
 	}
 |	LTYPEG mem ',' con ',' imm
 	{
 		asm.Settext($2.Sym)
 		outcode(obj.AGLOBL, &Addr2{from: $2, to: $6})
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}

src/cmd/old6a/lex.go

@@ -960,7 +960,10 @@ func outcode(a int, g2 *Addr2) {
 	p.As = int16(a)
 	p.Lineno = stmtline
 	p.From = g2.from
-	p.From3 = g2.from3
+	if g2.from3.Type != 0 {
+		p.From3 = new(obj.Addr)
+		*p.From3 = g2.from3
+	}
 	p.To = g2.to
 	p.Pc = int64(asm.PC)
 

src/cmd/old8a/a.y

@@ -194,6 +194,7 @@ spec1:	/* DATA */
 	{
 		outcode(obj.ADATA, &Addr2{$2, $6})
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -204,12 +205,16 @@ spec2:	/* TEXT */
 	{
 		asm.Settext($2.Sym);
 		outcode(obj.ATEXT, &Addr2{$2, $5})
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}
 	}
 |	LTYPET mem ',' con ',' '$' textsize
 	{
 		asm.Settext($2.Sym);
 		outcode(obj.ATEXT, &Addr2{$2, $7})
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -220,12 +225,16 @@ spec8:	/* GLOBL */
 	{
 		asm.Settext($2.Sym);
 		outcode(obj.AGLOBL, &Addr2{$2, $4})
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}
 	}
 |	LTYPEG mem ',' con ',' imm
 	{
 		asm.Settext($2.Sym);
 		outcode(obj.AGLOBL, &Addr2{$2, $6})
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}

src/cmd/old9a/a.y

@@ -630,12 +630,16 @@ inst:
 	{
 		asm.Settext($2.Sym);
 		outcode(int($1), &$2, 0, &$5);
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}
 	}
 |	LTEXT name ',' con ',' '$' textsize
 	{
 		asm.Settext($2.Sym);
 		outcode(int($1), &$2, int($4), &$7);
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -647,12 +651,16 @@ inst:
 	{
 		asm.Settext($2.Sym)
 		outcode(int($1), &$2, 0, &$4)
+		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
+		}
 	}
 |	LGLOBL name ',' con ',' imm
 	{
 		asm.Settext($2.Sym)
 		outcode(int($1), &$2, 0, &$6)
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -665,6 +673,7 @@ inst:
 	{
 		outcode(int($1), &$2, 0, &$6);
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -673,6 +682,7 @@ inst:
 	{
 		outcode(int($1), &$2, 0, &$6);
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}
@@ -681,6 +691,7 @@ inst:
 	{
 		outcode(int($1), &$2, 0, &$6);
 		if asm.Pass > 1 {
+			lastpc.From3 = new(obj.Addr)
 			lastpc.From3.Type = obj.TYPE_CONST
 			lastpc.From3.Offset = $4
 		}

src/cmd/old9a/lex.go

@@ -536,7 +536,10 @@ func outgcode(a int, g1 *obj.Addr, reg int, g2, g3 *obj.Addr) {
 	}
 	p.From = *g1
 	p.Reg = int16(reg)
-	p.From3 = *g2
+	if g2.Type != 0 {
+		p.From3 = new(obj.Addr)
+		*p.From3 = *g2
+	}
 	p.To = *g3
 	p.Pc = int64(asm.PC)