test LGDR

before g = 42
before f = 0x1.f0f0f0f0f0f0fp-783
copy f to g
after  g = 0f0f0f0f0f0f0f0f
after  f = 0x1.f0f0f0f0f0f0fp-783

test LDGR

before g = 0f0f0f0f0f0f0f0f
before f = 0x1.91eb851eb851fp+1
copy g to f
after  g = 0f0f0f0f0f0f0f0f
after  f = 0x1.f0f0f0f0f0f0fp-783