cmd/internal/obj: eliminate Ctxt.Mode

Replace Ctxt.Mode with a method, Ctxt.RegWidth,
which is calculated directly off the arch info.

I believe that Prog.Mode can also be removed; future CL.

This is a step towards obj.Link immutability.

Passes toolstash-check -all.

Updates #15756

Change-Id: Ifd7f8f6ed0a2fdc032d1dd306fcd695a14aa5bc5
Reviewed-on: https://go-review.googlesource.com/38446
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

3 files changed, 24 insertions, 32 deletions

diff --git a/src/cmd/internal/obj/mips/a.out.go b/src/cmd/internal/obj/mips/a.out.go
index f732ed5235..0d838a75f8 100644
--- a/src/cmd/internal/obj/mips/a.out.go
+++ b/src/cmd/internal/obj/mips/a.out.go
@@ -29,7 +29,10 @@
 
 package mips
 
-import "cmd/internal/obj"
+import (
+	"cmd/internal/obj"
+	"cmd/internal/sys"
+)
 
 //go:generate go run ../stringer.go -i $GOFILE -o anames.go -p mips
 
@@ -218,8 +221,8 @@ const (
 )
 
 const (
-	Mips32 = 32
-	Mips64 = 64
+	Mips32 = sys.MIPS
+	Mips64 = sys.MIPS64
 )
 
 const (
diff --git a/src/cmd/internal/obj/mips/asm0.go b/src/cmd/internal/obj/mips/asm0.go
index 897073e95e..139b82726f 100644
--- a/src/cmd/internal/obj/mips/asm0.go
+++ b/src/cmd/internal/obj/mips/asm0.go
@@ -31,6 +31,7 @@ package mips
 
 import (
 	"cmd/internal/obj"
+	"cmd/internal/sys"
 	"fmt"
 	"log"
 	"sort"
@@ -47,14 +48,14 @@ const (
 )
 
 type Optab struct {
-	as    obj.As
-	a1    uint8
-	a2    uint8
-	a3    uint8
-	type_ int8
-	size  int8
-	param int16
-	mode  int
+	as     obj.As
+	a1     uint8
+	a2     uint8
+	a3     uint8
+	type_  int8
+	size   int8
+	param  int16
+	family sys.ArchFamily // 0 means both Mips32 and Mips64
 }
 
 var optab = []Optab{
@@ -465,7 +466,7 @@ func span0(ctxt *obj.Link, cursym *obj.LSym) {
 
 		cursym.Size = c
 	}
-	if ctxt.Mode&Mips64 != 0 {
+	if ctxt.Arch.Family == sys.MIPS64 {
 		c += -c & (mips64FuncAlign - 1)
 	}
 	cursym.Size = c
@@ -702,7 +703,7 @@ func oplook(ctxt *obj.Link, p *obj.Prog) *Optab {
 	c3 := &xcmp[a3]
 	for i := range ops {
 		op := &ops[i]
-		if int(op.a2) == a2 && c1[op.a1] && c3[op.a3] && (ctxt.Mode&op.mode == op.mode) {
+		if int(op.a2) == a2 && c1[op.a1] && c3[op.a3] && (op.family == 0 || ctxt.Arch.Family == op.family) {
 			p.Optab = uint16(cap(optab) - cap(ops) + i + 1)
 			return op
 		}
@@ -1068,7 +1069,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 
 	add := AADDU
 
-	if ctxt.Mode&Mips64 != 0 {
+	if ctxt.Arch.Family == sys.MIPS64 {
 		add = AADDVU
 	}
 	switch o.type_ {
@@ -1081,7 +1082,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 
 	case 1: /* mov r1,r2 ==> OR r1,r0,r2 */
 		a := AOR
-		if p.As == AMOVW && ctxt.Mode&Mips64 != 0 {
+		if p.As == AMOVW && ctxt.Arch.Family == sys.MIPS64 {
 			a = AADDU // sign-extended to high 32 bits
 		}
 		o1 = OP_RRR(oprrr(ctxt, a), uint32(REGZERO), uint32(p.From.Reg), uint32(p.To.Reg))
diff --git a/src/cmd/internal/obj/mips/obj0.go b/src/cmd/internal/obj/mips/obj0.go
index fe1ce9c027..11434751e2 100644
--- a/src/cmd/internal/obj/mips/obj0.go
+++ b/src/cmd/internal/obj/mips/obj0.go
@@ -38,18 +38,6 @@ import (
 )
 
 func progedit(ctxt *obj.Link, p *obj.Prog) {
-	// Maintain information about code generation mode.
-	if ctxt.Mode == 0 {
-		switch ctxt.Arch.Family {
-		default:
-			ctxt.Diag("unsupported arch family")
-		case sys.MIPS:
-			ctxt.Mode = Mips32
-		case sys.MIPS64:
-			ctxt.Mode = Mips64
-		}
-	}
-
 	p.From.Class = 0
 	p.To.Class = 0
 
@@ -89,7 +77,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	case AMOVD:
 		if p.From.Type == obj.TYPE_FCONST {
 			i64 := math.Float64bits(p.From.Val.(float64))
-			if i64 == 0 && ctxt.Mode&Mips64 != 0 {
+			if i64 == 0 && ctxt.Arch.Family == sys.MIPS64 {
 				p.As = AMOVV
 				p.From.Type = obj.TYPE_REG
 				p.From.Reg = REGZERO
@@ -285,7 +273,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	}
 
 	var mov, add obj.As
-	if ctxt.Mode&Mips64 != 0 {
+	if ctxt.Arch.Family == sys.MIPS64 {
 		add = AADDV
 		mov = AMOVV
 	} else {
@@ -303,7 +291,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 			autosize = int32(textstksiz + ctxt.FixedFrameSize())
 			if (p.Mark&LEAF != 0) && autosize <= int32(ctxt.FixedFrameSize()) {
 				autosize = 0
-			} else if autosize&4 != 0 && ctxt.Mode&Mips64 != 0 {
+			} else if autosize&4 != 0 && ctxt.Arch.Family == sys.MIPS64 {
 				autosize += 4
 			}
 
@@ -534,7 +522,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 		}
 	}
 
-	if ctxt.Mode&Mips32 != 0 {
+	if ctxt.Arch.Family == sys.MIPS {
 		// rewrite MOVD into two MOVF in 32-bit mode to avoid unaligned memory access
 		for p = cursym.Text; p != nil; p = p1 {
 			p1 = p.Link
@@ -633,7 +621,7 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
 
 	var mov, add, sub obj.As
 
-	if ctxt.Mode&Mips64 != 0 {
+	if ctxt.Arch.Family == sys.MIPS64 {
 		add = AADDV
 		mov = AMOVV
 		sub = ASUBVU