[Bug c/87104] missed &, == optimization makes Emacs ~0.4% slower on x86-64

[eggert at cs dot ucla.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87104

--- Comment #1 from eggert at cs dot ucla.edu ---
Created attachment 44596
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44596&action=edit
output when compiling fg.c with "gcc -O2 -S" on x86-64