On Thursday, 31 July 2014 at 15:26:27 UTC, Artur Skawina via
Digitalmars-d wrote:
On 07/31/14 15:44, Daniel Gibson via Digitalmars-d wrote:
And don't forget this (rather old) case:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8537
(I really don't get why anyone would want such an
optimization: I want an optimizer to use clever inlining, use
SSE etc where it makes sense and stuff like that - but not to
remove code I wrote.)
That is actually not a bug, but a perfectly valid optimization.
The
compiler isn't clairvoyant and can not know that some data that
you
wrote, but never read back, matters.
The solution is to tell the compiler that you really need that
newly
(over-)written data. Eg
asm {"" : : "m"
(*cast(typeof(password[0])[9999999]*)password.ptr); }
(yes, stdizing compiler barriers would be a good idea)
artur
Any idea how dead store removal interacts with the modern C(++)
memory model? Another thread could hold a reference to the memory
being written to.
