cmd/internal/obj/mips: materialize float constant 0 from zero register

Materialize float constant 0 from integer zero register, instead
of loading from constant pool.

Change-Id: Ie4728895b9d617bec2a29d15729c0efaa10eedbb
Reviewed-on: https://go-review.googlesource.com/32109
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/internal/obj/mips/obj0.go

@@ -58,6 +58,12 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 		if p.From.Type == obj.TYPE_FCONST {
 			f32 := float32(p.From.Val.(float64))
 			i32 := math.Float32bits(f32)
+			if i32 == 0 {
+				p.As = AMOVV
+				p.From.Type = obj.TYPE_REG
+				p.From.Reg = REGZERO
+				break
+			}
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
 			s.Size = 4
@@ -70,6 +76,12 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 	case AMOVD:
 		if p.From.Type == obj.TYPE_FCONST {
 			i64 := math.Float64bits(p.From.Val.(float64))
+			if i64 == 0 {
+				p.As = AMOVV
+				p.From.Type = obj.TYPE_REG
+				p.From.Reg = REGZERO
+				break
+			}
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
 			s.Size = 8