Re: solaris build problem with Sun compilers

[Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>]

Bruce Momjian wrote:
> Tom Lane wrote:
> > Alan Stange <stange(at)rentec(dot)com> writes:
> > > I believe the trick here is that Solaris 10 will only run on v9 hardware 
> > > (or the sun4u systems), which all have the instruction.   But the v8 ABI 
> > > "model" doesn't have it.   So, in some sense the ABI doesn't "allow" 
> > > this instruction, but the hardware does, so they can just slam it in 
> > > knowing that it'll work.
> > 
> > Well, that might be OK for Sun's compiler since they know what a given
> > version of Solaris will run on.  But I don't think we can adopt the same
> > attitude for our gcc code path; that has to work on Sparc-based Linuxen
> > and BSDen.  I don't think it's appropriate to kiss off support for v8
> > chips when we haven't seen any proof at all of a performance boost in
> > return.
> > 
> > Maybe the right answer is to leave the code as-is, ie, deliberately not
> > the same for Sun and gcc compilers.
> 
> OK, I have applied the following patch which documents that the Solaris
> CC TAS ASM only works for sparc9.  Hopefully either sparc8 is not needed
> (unlikely) or someone will fix it.  I have CC'ed the original
> contributor who added "cas".

Oh, I just found this email that has a simplified sparc8 asm:

	http://archives.postgresql.org/pgsql-ports/2006-05/msg00025.php

Attached is the new solaris_sparc.s file with the #ifdef sparc8 test;
applied.

-- 
  Bruce Momjian   http://candle.pha.pa.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

!=======================================================================
! solaris_sparc.s -- compare and swap for solaris_sparc
!=======================================================================

! Fortunately the Sun compiler can process cpp conditionals with -P

! '/' is the comment for x86, while '!' is the comment for Sparc

#if defined(__sparcv9) || defined(__sparc)

	.section        ".text"
	.align  8
	.skip   24
	.align  4

	.global pg_atomic_cas
pg_atomic_cas:
	
	! "cas" only works on sparcv9 chips, and requies a compiler
	! that is targeting sparcv9.  It will fail on a compiler
	! targeting sparcv8, and of course will not be understood
	! by a sparcv8 CPU.  gcc continues to use "ldstub" because
	! there is no indication which sparc version it is targeting.
	!
	! There actually is a trick for embedding "cas" for a compiler
	! that is targeting sparcv8:
	!
	!   http://cvs.opensolaris.org/source/xref/on/usr/src/lib/libc/sparc/threads/sparc.il

#ifdef __sparcv9
	cas     [%o0],%o2,%o1
#else
	ldstub [%o0],%o1
#endif
	mov     %o1,%o0
	retl
	nop
	.type   pg_atomic_cas,2
	.size   pg_atomic_cas,(.-pg_atomic_cas)
#endif