GDC optimizations bug ?

[Iain Buclaw via D.gnu]

On 9 Nov 2014 08:40, "Maor via D.gnu" <d.gnu at puremagic.com> wrote:
>
> Hi,
>
> I'm trying to compile a program using inline asm with optimizations and I
got my inline asm functions thrown out by the optimizer although I declared
them as having side effects (by stating a memory clobber).
> I wrote the following toy program to demonstrate the problem:
>
> ----------------------------------------------
>
> import std.stdio;
> import gcc.attribute;
>
> @attribute("forceinline") ulong exchangeAndAdd(shared ulong *counter,
ulong addition) {
>       ulong retVal = void; // we don't want it initialized when dmd is
used
>       asm {
>         "
>           mov  %2, %0             ;
>           lock                    ;
>           xadd %0, (%1)           ;
>         ":
>         "=&r"(retVal) :
>         "r"(counter), "r"(addition) :

Maybe try:  "=m"(*counter)

The bug is likely in your input/output clobbers, gcc will always optimise
against you unless you get the input/output/clobbers precisely correct.

Iain.
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