return x.Add(x, n) // make sure result > 1<<(size-1)
}

func runGCD(b *testing.B, aSize, bSize uint) {
	if isRaceBuilder && (aSize > 1000 || bSize > 1000) {
		b.Skip("skipping on race builder")
	}
	b.Run("WithoutXY", func(b *testing.B) {
		runGCDExt(b, aSize, bSize, false)
	})
	b.Run("WithXY", func(b *testing.B) {
		runGCDExt(b, aSize, bSize, true)
	})
}

func runGCDExt(b *testing.B, aSize, bSize uint, calcXY bool) {