From 18ded03a82b187128679c2b8d87892903201c3a5 Mon Sep 17 00:00:00 2001
From: Ivan Maidanski <ivmai@mail.ru>
Date: Fri, 21 Oct 2011 12:23:03 +0400
Subject: [PATCH] Add FIXMEs to add AO_fetch_compare_and_swap primitives

---
 ChangeLog                                    |  1 +
 TODO                                         |  2 --
 doc/README.txt                               |  3 +++
 src/atomic_ops.c                             |  3 +++
 src/atomic_ops.h                             | 11 +++++++++--
 src/atomic_ops/generalize.h                  |  2 ++
 src/atomic_ops/sysdeps/ao_t_is_int.h         |  2 ++
 src/atomic_ops/sysdeps/armcc/arm_v6.h        |  2 ++
 src/atomic_ops/sysdeps/emul_cas.h            |  2 ++
 src/atomic_ops/sysdeps/gcc/alpha.h           |  2 ++
 src/atomic_ops/sysdeps/gcc/arm.h             |  2 ++
 src/atomic_ops/sysdeps/gcc/avr32.h           |  2 ++
 src/atomic_ops/sysdeps/gcc/hexagon.h         |  2 ++
 src/atomic_ops/sysdeps/gcc/ia64.h            |  2 ++
 src/atomic_ops/sysdeps/gcc/m68k.h            |  2 ++
 src/atomic_ops/sysdeps/gcc/mips.h            |  2 ++
 src/atomic_ops/sysdeps/gcc/powerpc.h         |  2 ++
 src/atomic_ops/sysdeps/gcc/s390.h            |  2 ++
 src/atomic_ops/sysdeps/gcc/sparc.h           |  2 ++
 src/atomic_ops/sysdeps/gcc/x86.h             |  2 ++
 src/atomic_ops/sysdeps/gcc/x86_64.h          |  2 ++
 src/atomic_ops/sysdeps/generic_pthread.h     |  2 ++
 src/atomic_ops/sysdeps/hpc/ia64.h            |  2 ++
 src/atomic_ops/sysdeps/ibmc/powerpc.h        |  4 ++--
 src/atomic_ops/sysdeps/icc/ia64.h            |  2 ++
 src/atomic_ops/sysdeps/msftc/common32_defs.h |  2 ++
 src/atomic_ops/sysdeps/msftc/x86_64.h        |  2 ++
 src/atomic_ops/sysdeps/sunc/x86.h            |  2 ++
 src/atomic_ops/sysdeps/sunc/x86_64.h         |  2 ++
 tests/list_atomic.template                   |  1 +
 tests/test_atomic_include.template           |  1 +
 31 files changed, 66 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 60d6ab2..770ae4e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,7 @@
 
 * Add '-no-undefined' to LDFLAGS in src/Makefile.am.
 * Add AO_and, AO_xor atomic operations.
+* Add AO_fetch_compare_and_swap primitives.
 * Add and fill in AUTHORS, TODO files.
 * Add atomic_ops.pc.in and atomic_ops-uninstalled.pc.in to pkgconfig folder.
 * Adjust AO_..._H macros in public headers.
diff --git a/TODO b/TODO
index 58114c5..d245225 100644
--- a/TODO
+++ b/TODO
@@ -1,8 +1,6 @@
 TODO tasks
 ==========
 
-Add equivalent of __sync_val_compare_and_swap. Add tests.
-
 Add C++0x ATM (atomic memory operations) layer.
 
 
diff --git a/doc/README.txt b/doc/README.txt
index 26a4f7f..348247d 100644
--- a/doc/README.txt
+++ b/doc/README.txt
@@ -100,6 +100,9 @@ int compare_and_swap(volatile AO_t * addr, AO_t old_val, AO_t new_val)
         Atomically compare *addr to old_val, and replace *addr by new_val
         if the first comparison succeeds.  Returns nonzero if the comparison
         succeeded and *addr was updated.
+AO_t fetch_compare_and_swap(volatile AO_t * addr, AO_t old_val, AO_t new_val)
+        Atomically compare *addr to old_val, and replace *addr by new_val
+        if the first comparison succeeds; returns the original value of *addr.
 AO_TS_VAL_t test_and_set(volatile AO_TS_t * addr)
         Atomically read the binary value at *addr, and set it.  AO_TS_VAL_t
         is an enumeration type which includes two values AO_TS_SET and
diff --git a/src/atomic_ops.c b/src/atomic_ops.c
index 3b86371..bd77bba 100644
--- a/src/atomic_ops.c
+++ b/src/atomic_ops.c
@@ -195,6 +195,7 @@ int AO_compare_and_swap_emulation(volatile AO_t *addr, AO_t old,
     sigset_t old_sigs;
     block_all_signals(&old_sigs);
 # endif
+
   lock(my_lock);
   if (*addr == old)
     {
@@ -210,6 +211,8 @@ int AO_compare_and_swap_emulation(volatile AO_t *addr, AO_t old,
   return result;
 }
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 int AO_compare_double_and_swap_double_emulation(volatile AO_double_t *addr,
                                                 AO_t old_val1, AO_t old_val2,
                                                 AO_t new_val1, AO_t new_val2)
diff --git a/src/atomic_ops.h b/src/atomic_ops.h
index 334dba0..ca3a21a 100644
--- a/src/atomic_ops.h
+++ b/src/atomic_ops.h
@@ -77,6 +77,7 @@
 /* AO_or                                                        */
 /* AO_xor                                                       */
 /* AO_compare_and_swap                                          */
+/* AO_fetch_compare_and_swap                                    */
 /*                                                              */
 /* Note that atomicity guarantees are valid only if both        */
 /* readers and writers use AO_ operations to access the         */
@@ -90,9 +91,14 @@
 /* or can only be read concurrently, then x can be accessed     */
 /* via ordinary references and assignments.                     */
 /*                                                              */
-/* Compare_and_exchange takes an address and an expected old    */
-/* value and a new value, and returns an int.  Nonzero          */
+/* AO_compare_and_swap takes an address and an expected old     */
+/* value and a new value, and returns an int.  Non-zero result  */
 /* indicates that it succeeded.                                 */
+/* AO_fetch_compare_and_swap takes an address and an expected   */
+/* old value and a new value, and returns the real old value.   */
+/* The operation succeeded if and only if the expected old      */
+/* value matches the old value returned.                        */
+/*                                                              */
 /* Test_and_set takes an address, atomically replaces it by     */
 /* AO_TS_SET, and returns the prior value.                      */
 /* An AO_TS_t location can be reset with the                    */
@@ -350,6 +356,7 @@
 # else
 #  error Cannot implement AO_compare_and_swap_full on this architecture.
 # endif
+/* FIXME: same for AO_fetch_compare_and_swap */
 #endif /* AO_REQUIRE_CAS && !AO_HAVE_compare_and_swap ... */
 
 /* The most common way to clear a test-and-set location         */
diff --git a/src/atomic_ops/generalize.h b/src/atomic_ops/generalize.h
index 91a96fe..2131685 100644
--- a/src/atomic_ops/generalize.h
+++ b/src/atomic_ops/generalize.h
@@ -1053,6 +1053,8 @@
 # endif
 #endif /* AO_HAVE_compare_and_swap_full */
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #if !defined(AO_HAVE_compare_and_swap) \
     && defined(AO_HAVE_compare_and_swap_release)
 # define AO_compare_and_swap(addr,old,new_val) \
diff --git a/src/atomic_ops/sysdeps/ao_t_is_int.h b/src/atomic_ops/sysdeps/ao_t_is_int.h
index 3b6f165..33d3e4d 100644
--- a/src/atomic_ops/sysdeps/ao_t_is_int.h
+++ b/src/atomic_ops/sysdeps/ao_t_is_int.h
@@ -72,6 +72,8 @@
 # define AO_HAVE_int_compare_and_swap
 #endif
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* AO_load */
 #if defined(AO_HAVE_load_acquire) \
     && !defined(AO_HAVE_int_load_acquire)
diff --git a/src/atomic_ops/sysdeps/armcc/arm_v6.h b/src/atomic_ops/sysdeps/armcc/arm_v6.h
index 7b43151..16e7f1a 100644
--- a/src/atomic_ops/sysdeps/armcc/arm_v6.h
+++ b/src/atomic_ops/sysdeps/armcc/arm_v6.h
@@ -198,6 +198,8 @@ __asm__ {
 }
 #define AO_HAVE_compare_and_swap
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* helper functions for the Realview compiler: LDREXD is not usable
  * with inline assembler, so use the "embedded" assembler as
  * suggested by ARM Dev. support (June 2008). */
diff --git a/src/atomic_ops/sysdeps/emul_cas.h b/src/atomic_ops/sysdeps/emul_cas.h
index 1aa34d9..fa93141 100644
--- a/src/atomic_ops/sysdeps/emul_cas.h
+++ b/src/atomic_ops/sysdeps/emul_cas.h
@@ -64,6 +64,8 @@ void AO_store_full_emulation(volatile AO_t *addr, AO_t val);
 # define AO_HAVE_compare_double_and_swap_double_full
 #endif
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #undef AO_store
 #undef AO_HAVE_store
 #undef AO_store_write
diff --git a/src/atomic_ops/sysdeps/gcc/alpha.h b/src/atomic_ops/sysdeps/gcc/alpha.h
index 61d0433..016e4d1 100644
--- a/src/atomic_ops/sysdeps/gcc/alpha.h
+++ b/src/atomic_ops/sysdeps/gcc/alpha.h
@@ -61,3 +61,5 @@ AO_compare_and_swap(volatile AO_t *addr,
   return (int)was_equal;
 }
 #define AO_HAVE_compare_and_swap
+
+/* FIXME: implement AO_fetch_compare_and_swap */
diff --git a/src/atomic_ops/sysdeps/gcc/arm.h b/src/atomic_ops/sysdeps/gcc/arm.h
index 3e5fd02..5a53d4e 100644
--- a/src/atomic_ops/sysdeps/gcc/arm.h
+++ b/src/atomic_ops/sysdeps/gcc/arm.h
@@ -265,6 +265,8 @@ AO_compare_and_swap(volatile AO_t *addr, AO_t old_val, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #if !defined(__ARM_ARCH_6__) && !defined(__ARM_ARCH_6J__) \
     && !defined(__ARM_ARCH_6T2__) && !defined(__ARM_ARCH_6Z__) \
     && !defined(__ARM_ARCH_6ZT2__) && (!defined(__thumb__) \
diff --git a/src/atomic_ops/sysdeps/gcc/avr32.h b/src/atomic_ops/sysdeps/gcc/avr32.h
index 7a2fbed..c1bf56c 100644
--- a/src/atomic_ops/sysdeps/gcc/avr32.h
+++ b/src/atomic_ops/sysdeps/gcc/avr32.h
@@ -63,3 +63,5 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val)
        return (int)ret;
 }
 #define AO_HAVE_compare_and_swap_full
+
+/* FIXME: implement AO_fetch_compare_and_swap */
diff --git a/src/atomic_ops/sysdeps/gcc/hexagon.h b/src/atomic_ops/sysdeps/gcc/hexagon.h
index fdc9e56..9dff708 100644
--- a/src/atomic_ops/sysdeps/gcc/hexagon.h
+++ b/src/atomic_ops/sysdeps/gcc/hexagon.h
@@ -92,4 +92,6 @@ AO_compare_and_swap(volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #include "../ao_t_is_int.h"
diff --git a/src/atomic_ops/sysdeps/gcc/ia64.h b/src/atomic_ops/sysdeps/gcc/ia64.h
index 60c7a7e..086f314 100644
--- a/src/atomic_ops/sysdeps/gcc/ia64.h
+++ b/src/atomic_ops/sysdeps/gcc/ia64.h
@@ -189,6 +189,8 @@ AO_compare_and_swap_release(volatile AO_t *addr,
 }
 #define AO_HAVE_compare_and_swap_release
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 AO_INLINE int
 AO_char_compare_and_swap_acquire(volatile unsigned char *addr,
                                  unsigned char old, unsigned char new_val)
diff --git a/src/atomic_ops/sysdeps/gcc/m68k.h b/src/atomic_ops/sysdeps/gcc/m68k.h
index c898082..a00afe7 100644
--- a/src/atomic_ops/sysdeps/gcc/m68k.h
+++ b/src/atomic_ops/sysdeps/gcc/m68k.h
@@ -63,4 +63,6 @@ AO_compare_and_swap_full(volatile AO_t *addr,
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #include "../ao_t_is_int.h"
diff --git a/src/atomic_ops/sysdeps/gcc/mips.h b/src/atomic_ops/sysdeps/gcc/mips.h
index 527a347..a91426c 100644
--- a/src/atomic_ops/sysdeps/gcc/mips.h
+++ b/src/atomic_ops/sysdeps/gcc/mips.h
@@ -94,6 +94,8 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val) {
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /*
  * FIXME: We should also implement fetch_and_add and or primitives
  * directly.
diff --git a/src/atomic_ops/sysdeps/gcc/powerpc.h b/src/atomic_ops/sysdeps/gcc/powerpc.h
index 69ec05b..5312a8e 100644
--- a/src/atomic_ops/sysdeps/gcc/powerpc.h
+++ b/src/atomic_ops/sysdeps/gcc/powerpc.h
@@ -225,6 +225,8 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val) {
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 AO_INLINE AO_t
 AO_fetch_and_add(volatile AO_t *addr, AO_t incr) {
   AO_t oldval;
diff --git a/src/atomic_ops/sysdeps/gcc/s390.h b/src/atomic_ops/sysdeps/gcc/s390.h
index c05dc85..fadf944 100644
--- a/src/atomic_ops/sysdeps/gcc/s390.h
+++ b/src/atomic_ops/sysdeps/gcc/s390.h
@@ -59,4 +59,6 @@ AO_INLINE int AO_compare_and_swap_full(volatile AO_t *addr,
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* FIXME: Add double-wide compare-and-swap for 32-bit executables.      */
diff --git a/src/atomic_ops/sysdeps/gcc/sparc.h b/src/atomic_ops/sysdeps/gcc/sparc.h
index 41bc2f5..7647893 100644
--- a/src/atomic_ops/sysdeps/gcc/sparc.h
+++ b/src/atomic_ops/sysdeps/gcc/sparc.h
@@ -63,6 +63,8 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val) {
 #define AO_HAVE_compare_and_swap_full
 #endif /* !AO_NO_SPARC_V9 */
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* FIXME: This needs to be extended for SPARC v8 and v9.        */
 /* SPARC V8 also has swap.  V9 has CAS.                         */
 /* There are barriers like membar #LoadStore.                   */
diff --git a/src/atomic_ops/sysdeps/gcc/x86.h b/src/atomic_ops/sysdeps/gcc/x86.h
index b304dd0..c408dbc 100644
--- a/src/atomic_ops/sysdeps/gcc/x86.h
+++ b/src/atomic_ops/sysdeps/gcc/x86.h
@@ -149,6 +149,8 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* Returns nonzero if the comparison succeeded. */
 /* Really requires at least a Pentium.          */
 AO_INLINE int
diff --git a/src/atomic_ops/sysdeps/gcc/x86_64.h b/src/atomic_ops/sysdeps/gcc/x86_64.h
index 9225270..de68c0f 100644
--- a/src/atomic_ops/sysdeps/gcc/x86_64.h
+++ b/src/atomic_ops/sysdeps/gcc/x86_64.h
@@ -143,6 +143,8 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #ifdef AO_CMPXCHG16B_AVAILABLE
 
 /* NEC LE-IT: older AMD Opterons are missing this instruction.
diff --git a/src/atomic_ops/sysdeps/generic_pthread.h b/src/atomic_ops/sysdeps/generic_pthread.h
index 8c8a91a..f051fc9 100644
--- a/src/atomic_ops/sysdeps/generic_pthread.h
+++ b/src/atomic_ops/sysdeps/generic_pthread.h
@@ -233,6 +233,8 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* Unlike real architectures, we define both double-width CAS variants. */
 
 typedef struct {
diff --git a/src/atomic_ops/sysdeps/hpc/ia64.h b/src/atomic_ops/sysdeps/hpc/ia64.h
index b793fcb..68e78cd 100644
--- a/src/atomic_ops/sysdeps/hpc/ia64.h
+++ b/src/atomic_ops/sysdeps/hpc/ia64.h
@@ -107,6 +107,8 @@ AO_compare_and_swap_release(volatile AO_t *addr,
 }
 #define AO_HAVE_compare_and_swap_release
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 AO_INLINE int
 AO_char_compare_and_swap_acquire(volatile unsigned char *addr,
                                  unsigned char old, unsigned char new_val)
diff --git a/src/atomic_ops/sysdeps/ibmc/powerpc.h b/src/atomic_ops/sysdeps/ibmc/powerpc.h
index 4378dca..a51c3d5 100644
--- a/src/atomic_ops/sysdeps/ibmc/powerpc.h
+++ b/src/atomic_ops/sysdeps/ibmc/powerpc.h
@@ -120,5 +120,5 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap_full
 
-/* FIXME: We should also implement fetch_and_add and or primitives      */
-/* directly.                                                            */
+/* FIXME: We should also implement AO_fetch_compare_and_swap,           */
+/* AO_fetch_and_add, AO_and/or/xor primitives directly.                 */
diff --git a/src/atomic_ops/sysdeps/icc/ia64.h b/src/atomic_ops/sysdeps/icc/ia64.h
index cfa2073..9562265 100644
--- a/src/atomic_ops/sysdeps/icc/ia64.h
+++ b/src/atomic_ops/sysdeps/icc/ia64.h
@@ -152,6 +152,8 @@ AO_compare_and_swap_release(volatile AO_t *addr,
 }
 #define AO_HAVE_compare_and_swap_release
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 AO_INLINE int
 AO_char_compare_and_swap_acquire(volatile unsigned char *addr,
                                  unsigned char old, unsigned char new_val)
diff --git a/src/atomic_ops/sysdeps/msftc/common32_defs.h b/src/atomic_ops/sysdeps/msftc/common32_defs.h
index 5d519f0..3b5c782 100644
--- a/src/atomic_ops/sysdeps/msftc/common32_defs.h
+++ b/src/atomic_ops/sysdeps/msftc/common32_defs.h
@@ -115,4 +115,6 @@ AO_compare_and_swap_full(volatile AO_t *addr, AO_t old, AO_t new_val)
 # endif
 }
 # define AO_HAVE_compare_and_swap_full
+
+/* FIXME: implement AO_fetch_compare_and_swap */
 #endif /* AO_ASSUME_WINDOWS98 */
diff --git a/src/atomic_ops/sysdeps/msftc/x86_64.h b/src/atomic_ops/sysdeps/msftc/x86_64.h
index 135a053..3b10543 100644
--- a/src/atomic_ops/sysdeps/msftc/x86_64.h
+++ b/src/atomic_ops/sysdeps/msftc/x86_64.h
@@ -85,6 +85,8 @@ AO_compare_and_swap_full(volatile AO_t *addr,
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 /* As far as we can tell, the lfence and sfence instructions are not    */
 /* currently needed or useful for cached memory accesses.               */
 
diff --git a/src/atomic_ops/sysdeps/sunc/x86.h b/src/atomic_ops/sysdeps/sunc/x86.h
index 9abd8a0..8db5851 100644
--- a/src/atomic_ops/sysdeps/sunc/x86.h
+++ b/src/atomic_ops/sysdeps/sunc/x86.h
@@ -142,6 +142,8 @@ AO_compare_and_swap_full (volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #if 0
 /* FIXME: not tested (and probably wrong). Besides,     */
 /* it tickles a bug in Sun C 5.10 (when optimizing).    */
diff --git a/src/atomic_ops/sysdeps/sunc/x86_64.h b/src/atomic_ops/sysdeps/sunc/x86_64.h
index 5be6d9a..d888a5d 100644
--- a/src/atomic_ops/sysdeps/sunc/x86_64.h
+++ b/src/atomic_ops/sysdeps/sunc/x86_64.h
@@ -142,6 +142,8 @@ AO_compare_and_swap_full (volatile AO_t *addr, AO_t old, AO_t new_val)
 }
 #define AO_HAVE_compare_and_swap_full
 
+/* FIXME: implement AO_fetch_compare_and_swap */
+
 #ifdef AO_CMPXCHG16B_AVAILABLE
 /* NEC LE-IT: older AMD Opterons are missing this instruction.
  * On these machines SIGILL will be thrown.
diff --git a/tests/list_atomic.template b/tests/list_atomic.template
index 7fdef11..1c1d632 100644
--- a/tests/list_atomic.template
+++ b/tests/list_atomic.template
@@ -65,4 +65,5 @@ void list_atomicXX(void)
 # else
     "No AO_compare_and_swapXX";
 # endif
+/* FIXME: test AO_fetch_compare_and_swap */
 }
diff --git a/tests/test_atomic_include.template b/tests/test_atomic_include.template
index 9fec3f9..ea1f14c 100644
--- a/tests/test_atomic_include.template
+++ b/tests/test_atomic_include.template
@@ -170,6 +170,7 @@ void test_atomicXX(void)
     MISSING(AO_compare_and_swap);
     if (x == 13) x = 42;
 # endif
+/* FIXME: test AO_fetch_compare_and_swap */
 # if defined(AO_HAVE_orXX)
     AO_orXX(&x, 66);
     TA_assert(x == 106);
-- 
2.7.4