[Bug c/66348] Simple loop has only lower half of the 64-bit counter initialized correctly

[sebastiano.vigna at unimi dot it]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66348

--- Comment #2 from Sebastiano Vigna <sebastiano.vigna at unimi dot it> ---
Er... it's perfectly possible. My knowledge of x64 assembly is rudimentary, but
I wanted to try a diagnosis.

What is definitely true is that at -O0 we enter and exit the loop as it should
happen, and at -O1 we never exit the loop. For the time being we are
#pragma'ing the function to remove optimizations.