Re: solaris build problem with Sun compilers - Mailing list pgsql-ports

Tom Lane wrote:
> Alan Stange <stange@rentec.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".

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

  + If your life is a hard drive, Christ can be your backup. +
Index: src/backend/port/tas/solaris_sparc.s
===================================================================
RCS file: /cvsroot/pgsql/src/backend/port/tas/solaris_sparc.s,v
retrieving revision 1.6
diff -c -c -r1.6 solaris_sparc.s
*** src/backend/port/tas/solaris_sparc.s    17 May 2006 22:06:19 -0000    1.6
--- src/backend/port/tas/solaris_sparc.s    17 May 2006 23:42:40 -0000
***************
*** 16,21 ****
--- 16,38 ----
      .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.  If this fails on existing Solaris
+     ! systems, we need to use a !defined(__sparcv9) test
+     ! to fall back to the old "ldstub" call for sparcv8 compiles.
+     ! 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
+     !
+     ! This might work for sparc8:
+     ! ldstub [%o0],%o1    ! moves only a byte
+
      cas     [%o0],%o2,%o1
      mov     %o1,%o0
      retl
Index: src/include/storage/s_lock.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/storage/s_lock.h,v
retrieving revision 1.152
diff -c -c -r1.152 s_lock.h
*** src/include/storage/s_lock.h    29 Apr 2006 11:55:19 -0000    1.152
--- src/include/storage/s_lock.h    17 May 2006 23:43:03 -0000
***************
*** 311,316 ****
--- 311,320 ----
  {
      register slock_t _res;

+     /*
+      *    See comment in /pg/backend/port/tas/solaris_sparc.s for why this
+      *    uses "ldstub", and that file uses "cas".
+      */
      __asm__ __volatile__(
          "    ldstub    [%2], %0    \n"
  :        "=r"(_res), "+m"(*lock)