cmd/8g, cmd/internal/gc: clean up GO386 handling

This change cleans up some of the uglyness introduced in 8fc73a39
by moving the gc.Use_sse into the gc.Arch struct and adjusting its
zero value to be more useful.

Change-Id: I26ff5d9ac57b3f25e936519e443de6583cdafa56
Reviewed-on: https://go-review.googlesource.com/7994Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/8g/galign.go

@@ -54,6 +54,7 @@ func main() {
 	case "387":
 		gc.Thearch.FREGMIN = x86.REG_F0
 		gc.Thearch.FREGMAX = x86.REG_F7
+		gc.Thearch.Use387 = true
 	case "sse2":
 		gc.Thearch.FREGMIN = x86.REG_X0
 		gc.Thearch.FREGMAX = x86.REG_X7

src/cmd/8g/ggen.go

@@ -617,10 +617,10 @@ func cgen_float(n *gc.Node, res *gc.Node) {
 		return
 	}
 
-	if gc.Use_sse {
-		cgen_floatsse(n, res)
-	} else {
+	if gc.Thearch.Use387 {
 		cgen_float387(n, res)
+	} else {
+		cgen_floatsse(n, res)
 	}
 }
 
@@ -761,7 +761,7 @@ func bgen_float(n *gc.Node, true_ int, likely int, to *obj.Prog) {
 	var et int
 	var n2 gc.Node
 	var ax gc.Node
-	if gc.Use_sse {
+	if !gc.Thearch.Use387 {
 		if nl.Addable == 0 {
 			var n1 gc.Node
 			gc.Tempname(&n1, nl.Type)

src/cmd/8g/gsubr.go

@@ -402,7 +402,7 @@ func foptoas(op int, t *gc.Type, flg int) int {
 	a := obj.AXXX
 	et := int(gc.Simtype[t.Etype])
 
-	if gc.Use_sse {
+	if !gc.Thearch.Use387 {
 		switch uint32(op)<<16 | uint32(et) {
 		default:
 			gc.Fatal("foptoas-sse: no entry %v-%v", gc.Oconv(int(op), 0), gc.Tconv(t, 0))
@@ -1036,10 +1036,10 @@ func floatmove(f *gc.Node, t *gc.Node) {
 
 	switch uint32(ft)<<16 | uint32(tt) {
 	default:
-		if gc.Use_sse {
-			floatmove_sse(f, t)
-		} else {
+		if gc.Thearch.Use387 {
 			floatmove_387(f, t)
+		} else {
+			floatmove_sse(f, t)
 		}
 		return
 

src/cmd/internal/gc/go.go

@@ -632,8 +632,6 @@ var typesw *Node
 
 var nblank *Node
 
-var Use_sse bool // should we generate SSE2 instructions for 386 targets
-
 var hunk string
 
 var nhunk int32
@@ -832,6 +830,7 @@ type Arch struct {
 	Optoas       func(int, *Type) int
 	Doregbits    func(int) uint64
 	Regnames     func(*int) []string
+	Use387       bool // should 8g use 387 FP instructions instead of sse2.
 }
 
 var pcloc int32

src/cmd/internal/gc/gsubr.go

@@ -688,7 +688,7 @@ Switch:
 		Fatal("out of fixed registers")
 
 	case TFLOAT32, TFLOAT64:
-		if Thearch.Thechar == '8' && !Use_sse {
+		if Thearch.Use387 {
 			i = Thearch.FREGMIN // x86.REG_F0
 			break Switch
 		}

src/cmd/internal/gc/lex.go

@@ -277,17 +277,6 @@ func Main() {
 		Debug['l'] = 1 - Debug['l']
 	}
 
-	if Thearch.Thechar == '8' {
-		switch v := obj.Getgo386(); v {
-		case "387":
-			Use_sse = false
-		case "sse2":
-			Use_sse = true
-		default:
-			log.Fatalf("unsupported setting GO386=%s", v)
-		}
-	}
-
 	Thearch.Betypeinit()
 	if Widthptr == 0 {
 		Fatal("betypeinit failed")