tree 7f77d9b76f00ed4d91b06eea60953f7a624e5feb
parent ca7b5ab5ef0e8943fda34c6347a2f10136bd7fcf
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> 1573204860 +0100
committer Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> 1574345699 +0100

Force some compilers to respect volatile reads

Inspection of the generated assembly showed that before this commit, armcc 5
was optimizing away the successive reads to the volatile local variable that's
used for double-checks. Inspection also reveals that inserting a call to an
external function is enough to prevent it from doing that.

The tested versions of ARM-GCC, Clang and Armcc 6 (aka armclang) all keep the
double read, with our without a call to an external function in the middle.

The inserted function can also be changed to insert a random delay if
desired in the future, as it is appropriately places between the reads.