[Qemu-devel] Re: [PATCH 16/28] migration: use global variable directly

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/24/2011 08:09 AM, Markus Armbruster wrote:
> For completeness: a local variable may be necessary to convince the
> optimizer that the value doesn't change.  Cases where this matters
> exist, but they're rare.

In particular, for non-pointers they're nonexistent if the variable is 
static and you never use &current_migration, i.e. if the variable 
doesn't escape.

If the above conditions are satisfied and you have a loop that never 
"leaves" the C file, you could even see the compiler keep the variable 
in a register for the whole duration of the loop and store the modified 
change after the loop.

Paolo