cmd/internal/obj: replace Addr.U struct {...} with Val interface{}

An interface{} is more in the spirit of the original union.
By my calculations, on 64-bit systems this reduces
Addr from 120 to 80 bytes, and Prog from 592 to 424 bytes.

Change-Id: I0d7b0981513c2a3c94c9ac76bb4f8816485b5a3c
Reviewed-on: https://go-review.googlesource.com/7744
Reviewed-by: Rob Pike <r@golang.org>

10 files changed, 59 insertions, 59 deletions

diff --git a/src/cmd/internal/obj/arm/asm5.go b/src/cmd/internal/obj/arm/asm5.go
index 96074c70f5..942fc70ff7 100644
--- a/src/cmd/internal/obj/arm/asm5.go
+++ b/src/cmd/internal/obj/arm/asm5.go
@@ -1116,10 +1116,10 @@ func aclass(ctxt *obj.Link, a *obj.Addr) int {
 		return C_GOK
 
 	case obj.TYPE_FCONST:
-		if chipzero5(ctxt, a.U.Dval) >= 0 {
+		if chipzero5(ctxt, a.Val.(float64)) >= 0 {
 			return C_ZFCON
 		}
-		if chipfloat5(ctxt, a.U.Dval) >= 0 {
+		if chipfloat5(ctxt, a.Val.(float64)) >= 0 {
 			return C_SFCON
 		}
 		return C_LFCON
@@ -2259,7 +2259,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 		}
 		o1 |= ((uint32(p.Scond) & C_SCOND) ^ C_SCOND_XOR) << 28
 		o1 |= (uint32(p.To.Reg) & 15) << 12
-		v := int32(chipfloat5(ctxt, p.From.U.Dval))
+		v := int32(chipfloat5(ctxt, p.From.Val.(float64)))
 		o1 |= (uint32(v) & 0xf) << 0
 		o1 |= (uint32(v) & 0xf0) << 12
 
diff --git a/src/cmd/internal/obj/arm/obj5.go b/src/cmd/internal/obj/arm/obj5.go
index 1f59c621c5..6b6e46b6a6 100644
--- a/src/cmd/internal/obj/arm/obj5.go
+++ b/src/cmd/internal/obj/arm/obj5.go
@@ -107,8 +107,8 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	// Rewrite float constants to values stored in memory.
 	switch p.As {
 	case AMOVF:
-		if p.From.Type == obj.TYPE_FCONST && chipfloat5(ctxt, p.From.U.Dval) < 0 && (chipzero5(ctxt, p.From.U.Dval) < 0 || p.Scond&C_SCOND != C_SCOND_NONE) {
-			f32 := float32(p.From.U.Dval)
+		if p.From.Type == obj.TYPE_FCONST && chipfloat5(ctxt, p.From.Val.(float64)) < 0 && (chipzero5(ctxt, p.From.Val.(float64)) < 0 || p.Scond&C_SCOND != C_SCOND_NONE) {
+			f32 := float32(p.From.Val.(float64))
 			i32 := math.Float32bits(f32)
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
@@ -125,8 +125,8 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 		}
 
 	case AMOVD:
-		if p.From.Type == obj.TYPE_FCONST && chipfloat5(ctxt, p.From.U.Dval) < 0 && (chipzero5(ctxt, p.From.U.Dval) < 0 || p.Scond&C_SCOND != C_SCOND_NONE) {
-			i64 := math.Float64bits(p.From.U.Dval)
+		if p.From.Type == obj.TYPE_FCONST && chipfloat5(ctxt, p.From.Val.(float64)) < 0 && (chipzero5(ctxt, p.From.Val.(float64)) < 0 || p.Scond&C_SCOND != C_SCOND_NONE) {
+			i64 := math.Float64bits(p.From.Val.(float64))
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
 			if s.Type == 0 {
@@ -201,7 +201,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 		autoffset = 0
 	}
 	cursym.Locals = autoffset
-	cursym.Args = p.To.U.Argsize
+	cursym.Args = p.To.Val.(int32)
 
 	if ctxt.Debugzerostack != 0 {
 		if autoffset != 0 && p.From3.Offset&obj.NOSPLIT == 0 {
diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index ba56f82df0..d8f39fe405 100644
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -2625,7 +2625,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 
 		var rf int
 		if p.From.Type == obj.TYPE_CONST {
-			rf = chipfloat7(ctxt, p.From.U.Dval)
+			rf = chipfloat7(ctxt, p.From.Val.(float64))
 			if rf < 0 || true {
 				ctxt.Diag("invalid floating-point immediate\n%v", p)
 				rf = 0
diff --git a/src/cmd/internal/obj/arm64/obj7.go b/src/cmd/internal/obj/arm64/obj7.go
index 0b92cfcaf1..dfba86ccb9 100644
--- a/src/cmd/internal/obj/arm64/obj7.go
+++ b/src/cmd/internal/obj/arm64/obj7.go
@@ -240,7 +240,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	switch p.As {
 	case AFMOVS:
 		if p.From.Type == obj.TYPE_FCONST {
-			f32 := float32(p.From.U.Dval)
+			f32 := float32(p.From.Val.(float64))
 			i32 := math.Float32bits(f32)
 			literal := fmt.Sprintf("$f32.%08x", uint32(i32))
 			s := obj.Linklookup(ctxt, literal, 0)
@@ -253,7 +253,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 
 	case AFMOVD:
 		if p.From.Type == obj.TYPE_FCONST {
-			i64 := math.Float64bits(p.From.U.Dval)
+			i64 := math.Float64bits(p.From.Val.(float64))
 			literal := fmt.Sprintf("$f64.%016x", uint64(i64))
 			s := obj.Linklookup(ctxt, literal, 0)
 			s.Size = 8
@@ -480,7 +480,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	textstksiz := p.To.Offset
 	aoffset := int32(textstksiz)
 
-	cursym.Args = p.To.U.Argsize
+	cursym.Args = p.To.Val.(int32)
 	cursym.Locals = int32(textstksiz)
 
 	/*
diff --git a/src/cmd/internal/obj/data.go b/src/cmd/internal/obj/data.go
index 6321ca4f2a..ab3e2096d0 100644
--- a/src/cmd/internal/obj/data.go
+++ b/src/cmd/internal/obj/data.go
@@ -75,16 +75,16 @@ func savedata(ctxt *Link, s *LSym, p *Prog, pn string) {
 			ctxt.Diag("unexpected %d-byte floating point constant", siz)
 
 		case 4:
-			flt := math.Float32bits(float32(p.To.U.Dval))
+			flt := math.Float32bits(float32(p.To.Val.(float64)))
 			ctxt.Arch.ByteOrder.PutUint32(s.P[off:], flt)
 
 		case 8:
-			flt := math.Float64bits(p.To.U.Dval)
+			flt := math.Float64bits(p.To.Val.(float64))
 			ctxt.Arch.ByteOrder.PutUint64(s.P[off:], flt)
 		}
 
 	case TYPE_SCONST:
-		copy(s.P[off:off+siz], p.To.U.Sval)
+		copy(s.P[off:off+siz], p.To.Val.(string))
 
 	case TYPE_CONST, TYPE_ADDR:
 		if p.To.Sym != nil || int(p.To.Type) == TYPE_ADDR {
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 76dd72aa61..3b286af493 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -76,13 +76,13 @@ import "encoding/binary"
 //		Floating point constant value.
 //		Encoding:
 //			type = TYPE_FCONST
-//			u.dval = floating point value
+//			val = floating point value
 //
 //	$<string literal, up to 8 chars>
 //		String literal value (raw bytes used for DATA instruction).
 //		Encoding:
 //			type = TYPE_SCONST
-//			u.sval = string
+//			val = string
 //
 //	<register name>
 //		Any register: integer, floating point, control, segment, and so on.
@@ -94,7 +94,7 @@ import "encoding/binary"
 //	x(PC)
 //		Encoding:
 //			type = TYPE_BRANCH
-//			u.branch = Prog* reference OR ELSE offset = target pc (branch takes priority)
+//			val = Prog* reference OR ELSE offset = target pc (branch takes priority)
 //
 //	$±x-±y
 //		Final argument to TEXT, specifying local frame size x and argument size y.
@@ -106,7 +106,7 @@ import "encoding/binary"
 //		Encoding:
 //			type = TYPE_TEXTSIZE
 //			offset = x
-//			u.argsize = y
+//			val = int32(y)
 //
 //	reg<<shift, reg>>shift, reg->shift, reg@>shift
 //		Shifted register value, for ARM.
@@ -150,20 +150,21 @@ type Addr struct {
 	Index  int16
 	Scale  int16 // Sometimes holds a register.
 	Name   int8
-	Offset int64
-	Sym    *LSym
-	U      struct {
-		Sval    string
-		Dval    float64
-		Branch  *Prog
-		Argsize int32
-		Bits    uint64
-	}
-	Gotype *LSym
 	Class  int8
 	Etype  uint8
-	Node   interface{}
+	Offset int64
 	Width  int64
+	Sym    *LSym
+	Gotype *LSym
+
+	// argument value:
+	//	for TYPE_SCONST, a string
+	//	for TYPE_FCONST, a float64
+	//	for TYPE_BRANCH, a *Prog (optional)
+	//	for TYPE_TEXTSIZE, an int32 (optional)
+	Val interface{}
+
+	Node interface{} // for use by compiler
 }
 
 const (
@@ -198,13 +199,8 @@ const (
 // TODO(rsc): Describe TEXT/GLOBL flag in from3, DATA width in from3.
 type Prog struct {
 	Ctxt     *Link
-	Pc       int64
-	Lineno   int32
 	Link     *Prog
-	As       int16
-	Scond    uint8
 	From     Addr
-	Reg      int16
 	From3    Addr
 	To       Addr
 	To2      Addr
@@ -213,9 +209,14 @@ type Prog struct {
 	Pcond    *Prog
 	Comefrom *Prog
 	Pcrel    *Prog
+	Pc       int64
+	Lineno   int32
 	Spadj    int32
+	As       int16
+	Reg      int16
 	Mark     uint16
 	Optab    uint16
+	Scond    uint8
 	Back     uint8
 	Ft       uint8
 	F3t      uint8
diff --git a/src/cmd/internal/obj/pass.go b/src/cmd/internal/obj/pass.go
index 50d21e9e00..50dda94c8c 100644
--- a/src/cmd/internal/obj/pass.go
+++ b/src/cmd/internal/obj/pass.go
@@ -90,7 +90,7 @@ func checkaddr(ctxt *Link, p *Prog, a *Addr) {
 			return
 		}
 
-		if a.Reg != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.U.Bits != 0 {
+		if a.Reg != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.Val != nil {
 			break
 		}
 		return
@@ -111,7 +111,7 @@ func checkaddr(ctxt *Link, p *Prog, a *Addr) {
 		return
 
 	case TYPE_ADDR:
-		if a.U.Bits != 0 {
+		if a.Val != nil {
 			break
 		}
 		if a.Reg == 0 && a.Index == 0 && a.Scale == 0 && a.Name == 0 && a.Sym == nil {
@@ -120,13 +120,13 @@ func checkaddr(ctxt *Link, p *Prog, a *Addr) {
 		return
 
 	case TYPE_SHIFT:
-		if a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.U.Bits != 0 {
+		if a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.Val != nil {
 			break
 		}
 		return
 
 	case TYPE_REGREG:
-		if a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.U.Bits != 0 {
+		if a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.Val != nil {
 			break
 		}
 		return
@@ -140,7 +140,7 @@ func checkaddr(ctxt *Link, p *Prog, a *Addr) {
 	// Expect sym and name to be set, nothing else.
 	// Technically more is allowed, but this is only used for *name(SB).
 	case TYPE_INDIR:
-		if a.Reg != 0 || a.Index != 0 || a.Scale != 0 || a.Name == 0 || a.Offset != 0 || a.Sym == nil || a.U.Bits != 0 {
+		if a.Reg != 0 || a.Index != 0 || a.Scale != 0 || a.Name == 0 || a.Offset != 0 || a.Sym == nil || a.Val != nil {
 			break
 		}
 		return
@@ -167,10 +167,9 @@ func linkpatch(ctxt *Link, sym *LSym) {
 		if p.To.Type != TYPE_BRANCH {
 			continue
 		}
-		if p.To.U.Branch != nil {
-			// TODO: Remove to.u.branch in favor of p->pcond.
-			p.Pcond = p.To.U.Branch
-
+		if p.To.Val != nil {
+			// TODO: Remove To.Val.(*Prog) in favor of p->pcond.
+			p.Pcond = p.To.Val.(*Prog)
 			continue
 		}
 
@@ -198,7 +197,7 @@ func linkpatch(ctxt *Link, sym *LSym) {
 			p.To.Type = TYPE_NONE
 		}
 
-		p.To.U.Branch = q
+		p.To.Val = q
 		p.Pcond = q
 	}
 
diff --git a/src/cmd/internal/obj/ppc64/obj9.go b/src/cmd/internal/obj/ppc64/obj9.go
index f47d81d77e..90fa725239 100644
--- a/src/cmd/internal/obj/ppc64/obj9.go
+++ b/src/cmd/internal/obj/ppc64/obj9.go
@@ -56,7 +56,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	switch p.As {
 	case AFMOVS:
 		if p.From.Type == obj.TYPE_FCONST {
-			f32 := float32(p.From.U.Dval)
+			f32 := float32(p.From.Val.(float64))
 			i32 := math.Float32bits(f32)
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
@@ -69,7 +69,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 
 	case AFMOVD:
 		if p.From.Type == obj.TYPE_FCONST {
-			i64 := math.Float64bits(p.From.U.Dval)
+			i64 := math.Float64bits(p.From.Val.(float64))
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
 			s.Size = 8
@@ -130,7 +130,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	p := cursym.Text
 	textstksiz := p.To.Offset
 
-	cursym.Args = p.To.U.Argsize
+	cursym.Args = p.To.Val.(int32)
 	cursym.Locals = int32(textstksiz)
 
 	/*
diff --git a/src/cmd/internal/obj/util.go b/src/cmd/internal/obj/util.go
index a2f3c1f8f1..b0d10b5fd5 100644
--- a/src/cmd/internal/obj/util.go
+++ b/src/cmd/internal/obj/util.go
@@ -389,8 +389,8 @@ func Dconv(p *Prog, a *Addr) string {
 			str = fmt.Sprintf("%s(SB)", a.Sym.Name)
 		} else if p != nil && p.Pcond != nil {
 			str = fmt.Sprintf("%d", p.Pcond.Pc)
-		} else if a.U.Branch != nil {
-			str = fmt.Sprintf("%d", a.U.Branch.Pc)
+		} else if a.Val != nil {
+			str = fmt.Sprintf("%d", a.Val.(*Prog).Pc)
 		} else {
 			str = fmt.Sprintf("%d(PC)", a.Offset)
 		}
@@ -412,14 +412,14 @@ func Dconv(p *Prog, a *Addr) string {
 		}
 
 	case TYPE_TEXTSIZE:
-		if a.U.Argsize == ArgsSizeUnknown {
+		if a.Val.(int32) == ArgsSizeUnknown {
 			str = fmt.Sprintf("$%d", a.Offset)
 		} else {
-			str = fmt.Sprintf("$%d-%d", a.Offset, a.U.Argsize)
+			str = fmt.Sprintf("$%d-%d", a.Offset, a.Val.(int32))
 		}
 
 	case TYPE_FCONST:
-		str = fmt.Sprintf("%.17g", a.U.Dval)
+		str = fmt.Sprintf("%.17g", a.Val.(float64))
 		// Make sure 1 prints as 1.0
 		if !strings.ContainsAny(str, ".e") {
 			str += ".0"
@@ -427,7 +427,7 @@ func Dconv(p *Prog, a *Addr) string {
 		str = fmt.Sprintf("$(%s)", str)
 
 	case TYPE_SCONST:
-		str = fmt.Sprintf("$%q", a.U.Sval)
+		str = fmt.Sprintf("$%q", a.Val.(string))
 
 	case TYPE_ADDR:
 		str = fmt.Sprintf("$%s", Mconv(a))
diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index cf226d8672..6a0baa66a3 100644
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -201,7 +201,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	// Convert AMOVSS $(0), Xx to AXORPS Xx, Xx
 	case AMOVSS:
 		if p.From.Type == obj.TYPE_FCONST {
-			if p.From.U.Dval == 0 {
+			if p.From.Val.(float64) == 0 {
 				if p.To.Type == obj.TYPE_REG && REG_X0 <= p.To.Reg && p.To.Reg <= REG_X15 {
 					p.As = AXORPS
 					p.From = p.To
@@ -227,7 +227,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 		ACOMISS,
 		AUCOMISS:
 		if p.From.Type == obj.TYPE_FCONST {
-			f32 := float32(p.From.U.Dval)
+			f32 := float32(p.From.Val.(float64))
 			i32 := math.Float32bits(f32)
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
@@ -246,7 +246,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	case AMOVSD:
 		// Convert AMOVSD $(0), Xx to AXORPS Xx, Xx
 		if p.From.Type == obj.TYPE_FCONST {
-			if p.From.U.Dval == 0 {
+			if p.From.Val.(float64) == 0 {
 				if p.To.Type == obj.TYPE_REG && REG_X0 <= p.To.Reg && p.To.Reg <= REG_X15 {
 					p.As = AXORPS
 					p.From = p.To
@@ -272,7 +272,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 		ACOMISD,
 		AUCOMISD:
 		if p.From.Type == obj.TYPE_FCONST {
-			i64 := math.Float64bits(p.From.U.Dval)
+			i64 := math.Float64bits(p.From.Val.(float64))
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
 			if s.Type == 0 {
@@ -361,7 +361,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 		bpsize = 0
 	}
 
-	textarg := int64(p.To.U.Argsize)
+	textarg := int64(p.To.Val.(int32))
 	cursym.Args = int32(textarg)
 	cursym.Locals = int32(p.To.Offset)