On Wed, 23 Jan 2019, Warren D Smith wrote: > x = x^x; > > The purpose of the above is to load "x" with zero. > For very wide types, say 256 bits wide, explicitly loading 0 > is deprecated by Intel since taking too much memory. > XORing x with itself always yields 0 and is allegedly > a better thing to do.
There is widespread support in WG14 for C semantics being uninitialized values being unstable, so that there is no need for the two reads of x to return the same value and x^x is also an unspecified value. See e.g. <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2221.htm>. -- Joseph S. Myers jos...@codesourcery.com
