Tom Lane wrote:
>Manfred Spraul <manfred@colorfullife.com> writes:
>
>
>>After some massaging, I've succeeded in generating bad code using a
>>slightly modified MemSetAligned macro (parameters -O2
>>-fstrict-aliasing): gcc pipelined the x*x around the memset.
>>
>>
>
>As I already explained, we do not care about the MemSetAligned case.
>Is gcc 3.3 smart enough to optimize away the pointer alignment test
>in the full macro?
>
3.2 optimizes away the pointer alignment test, but then doesn't pipeline
the "x*x" calculation. It might be due to a known (and now fixed) bug in
gcc where is lost track of constants, and thus didn't succeed in
optimizing long calculations.
I don't have gcc 3.3 installed, but IMHO it would be insane to leave
strict alias analysis enabled - writing to *(int32*)addr violates the
alias rules, the bad code generated with MemSetAligned proved that.
Is someone around with 3.3 who could test MemSet?
--
Manfred