Tom Lane wrote:
> Alan Stange <stange@rentec.com> writes:
>> - postgresql HEAD when using the Solaris compilers spro9 or newer will
>> only run on v9 based hardware using v8plus or v9 platform.
>> - postgresql HEAD when using gcc will run on anything as they generate
>> code for the v7 platform by default and the cas instruction isn't used
>> in any assembler code in postgresql.
>
> I gather from the contents of solaris_sparc.s that the Sun compilers can
> be expected to define __sparcv9 if compiling for v9 hardware. I'm
> inclined to #ifdef things so that we use cas if that symbol's defined and
> ldstub if not. I'm not sure if gcc can be expected to define the same
> symbol --- we might end up using ldstub always, even if we try to
> conditionalize the code for gcc.
This code isn't used by gcc, is it? Or are you thinking to use the same
assembler segment in the inline function used by gcc?
> Or we could just revert to ldstub. This seems like a lot of complexity
> for a so-far-entirely-hypothetical performance gain ...
I suspect that on machines like the UltraSparc T1 (the multi-core boxes)
this can have an impact (lots of additional memory writes). Even so,
that seems like a stretch.
Was there any reason given for the cas patch?
I might get around to doing the work for the Solaris compiler build to
support the inline keyword as well. I hacked on it a bit today but had
to get back to real work...
-- Alan
