[dev.regabi] cmd/compile: remove workarounds for go/constant issues

These were fixed in CLs 273086 and 273126, which have been merged back
into dev.regabi already.

Passes toolstash -cmp.

Change-Id: I011e9ed7062bc034496a279e21cc163267bf83fd
Reviewed-on: https://go-review.googlesource.com/c/go/+/280643
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>

src/cmd/compile/internal/typecheck/const.go

@@ -564,20 +564,11 @@ func EvalConst(n ir.Node) ir.Node {
 	return n
 }
 
-func makeInt(i *big.Int) constant.Value {
-	if i.IsInt64() {
-		return constant.Make(i.Int64()) // workaround #42640 (Int64Val(Make(big.NewInt(10))) returns (10, false), not (10, true))
-	}
-	return constant.Make(i)
-}
-
 func makeFloat64(f float64) constant.Value {
 	if math.IsInf(f, 0) {
 		base.Fatalf("infinity is not a valid constant")
 	}
-	v := constant.MakeFloat64(f)
-	v = constant.ToFloat(v) // workaround #42641 (MakeFloat64(0).Kind() returns Int, not Float)
-	return v
+	return constant.MakeFloat64(f)
 }
 
 func makeComplex(real, imag constant.Value) constant.Value {

src/cmd/compile/internal/typecheck/iexport.go

@@ -936,7 +936,7 @@ func (w *exportWriter) mpfloat(v constant.Value, typ *types.Type) {
 	if acc != big.Exact {
 		base.Fatalf("mantissa scaling failed for %f (%s)", f, acc)
 	}
-	w.mpint(makeInt(manti), typ)
+	w.mpint(constant.Make(manti), typ)
 	if manti.Sign() != 0 {
 		w.int64(exp)
 	}

src/cmd/compile/internal/typecheck/iimport.go

@@ -372,7 +372,7 @@ func (p *importReader) value(typ *types.Type) constant.Value {
 	case constant.Int:
 		var i big.Int
 		p.mpint(&i, typ)
-		return makeInt(&i)
+		return constant.Make(&i)
 	case constant.Float:
 		return p.float(typ)
 	case constant.Complex: