Remove AIX support

There isn't a lot of user demand for AIX support, we have a bunch of
hacks to work around AIX-specific compiler bugs and idiosyncrasies,
and no one has stepped up to the plate to properly maintain it.
Remove support for AIX to get rid of that maintenance overhead. It's
still supported for stable versions.

The acute issue that triggered this decision was that after commit
8af2565248, the AIX buildfarm members have been hitting this
assertion:

    TRAP: failed Assert("(uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer)"), File: "md.c", Line: 472, PID: 2949728

Apperently the "pg_attribute_aligned(a)" attribute doesn't work on AIX
for values larger than PG_IO_ALIGN_SIZE, for a static const variable.
That could be worked around, but we decided to just drop the AIX support
instead.

Discussion: https://www.postgresql.org/message-id/20240224172345.32@rfd.leadboat.com
Reviewed-by: Andres Freund, Noah Misch, Thomas Munro

4 files changed, 16 insertions, 53 deletions

diff --git a/src/include/c.h b/src/include/c.h
index 2e3ea206e1c..cf37e02fe1f 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -105,8 +105,6 @@
  * GCC: https://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html
  * Clang: https://clang.llvm.org/docs/AttributeReference.html
  * Sunpro: https://docs.oracle.com/cd/E18659_01/html/821-1384/gjzke.html
- * XLC: https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.2/com.ibm.xlc131.aix.doc/language_ref/function_attributes.html
- * XLC: https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.2/com.ibm.xlc131.aix.doc/language_ref/type_attrib.html
  */
 
 /*
@@ -171,8 +169,8 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
-/* GCC and XLC support format attributes */
-#if defined(__GNUC__) || defined(__IBMC__)
+/* GCC supports format attributes */
+#if defined(__GNUC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
 #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
 #else
@@ -180,8 +178,8 @@
 #define pg_attribute_printf(f,a)
 #endif
 
-/* GCC, Sunpro and XLC support aligned, packed and noreturn */
-#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
+/* GCC and Sunpro support aligned, packed and noreturn */
+#if defined(__GNUC__) || defined(__SUNPRO_C)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #define pg_attribute_noreturn() __attribute__((noreturn))
 #define pg_attribute_packed() __attribute__((packed))
@@ -212,8 +210,8 @@
  * choose not to.  But, if possible, don't force inlining in unoptimized
  * debug builds.
  */
-#if (defined(__GNUC__) && __GNUC__ > 3 && defined(__OPTIMIZE__)) || defined(__SUNPRO_C) || defined(__IBMC__)
-/* GCC > 3, Sunpro and XLC support always_inline via __attribute__ */
+#if (defined(__GNUC__) && __GNUC__ > 3 && defined(__OPTIMIZE__)) || defined(__SUNPRO_C)
+/* GCC > 3 and Sunpro support always_inline via __attribute__ */
 #define pg_attribute_always_inline __attribute__((always_inline)) inline
 #elif defined(_MSC_VER)
 /* MSVC has a special keyword for this */
@@ -229,8 +227,8 @@
  * for proper cost attribution.  Note that unlike the pg_attribute_XXX macros
  * above, this should be placed before the function's return type and name.
  */
-/* GCC, Sunpro and XLC support noinline via __attribute__ */
-#if (defined(__GNUC__) && __GNUC__ > 2) || defined(__SUNPRO_C) || defined(__IBMC__)
+/* GCC and Sunpro support noinline via __attribute__ */
+#if (defined(__GNUC__) && __GNUC__ > 2) || defined(__SUNPRO_C)
 #define pg_noinline __attribute__((noinline))
 /* msvc via declspec */
 #elif defined(_MSC_VER)
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
deleted file mode 100644
index 5b1159c5785..00000000000
--- a/src/include/port/aix.h
+++ /dev/null
@@ -1,14 +0,0 @@
-/*
- * src/include/port/aix.h
- */
-#define CLASS_CONFLICT
-#define DISABLE_XOPEN_NLS
-
-/*
- * "IBM XL C/C++ for AIX, V12.1" miscompiles, for 32-bit, some inline
- * expansions of ginCompareItemPointers() "long long" arithmetic.  To take
- * advantage of inlining, build a 64-bit PostgreSQL.
- */
-#if defined(__ILP32__) && defined(__IBMC__)
-#define PG_FORCE_DISABLE_INLINE
-#endif
diff --git a/src/include/port/atomics.h b/src/include/port/atomics.h
index bf151037f72..504349080d4 100644
--- a/src/include/port/atomics.h
+++ b/src/include/port/atomics.h
@@ -84,11 +84,9 @@
  * using compiler intrinsics are a good idea.
  */
 /*
- * gcc or compatible, including clang and icc.  Exclude xlc.  The ppc64le "IBM
- * XL C/C++ for Linux, V13.1.2" emulates gcc, but __sync_lock_test_and_set()
- * of one-byte types elicits SIGSEGV.  That bug was gone by V13.1.5 (2016-12).
+ * gcc or compatible, including clang and icc.
  */
-#if (defined(__GNUC__) || defined(__INTEL_COMPILER)) && !(defined(__IBMC__) || defined(__IBMCPP__))
+#if defined(__GNUC__) || defined(__INTEL_COMPILER)
 #include "port/atomics/generic-gcc.h"
 #elif defined(_MSC_VER)
 #include "port/atomics/generic-msvc.h"
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 69582f4ae71..29ac6cdcd92 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -414,12 +414,6 @@ typedef unsigned int slock_t;
  * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
  * But if the spinlock is in ordinary memory, we can use lwsync instead for
  * better performance.
- *
- * Ordinarily, we'd code the branches here using GNU-style local symbols, that
- * is "1f" referencing "1:" and so on.  But some people run gcc on AIX with
- * IBM's assembler as backend, and IBM's assembler doesn't do local symbols.
- * So hand-code the branch offsets; fortunately, all PPC instructions are
- * exactly 4 bytes each, so it's not too hard to count.
  */
 static __inline__ int
 tas(volatile slock_t *lock)
@@ -430,15 +424,17 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     $+16		\n"		/* branch to li %1,1 */
+"	bne     1f			\n"
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     $+12		\n"		/* branch to lwsync */
+"	beq     2f			\n"
+"1: \n"
 "	li      %1,1		\n"
-"	b       $+12		\n"		/* branch to end of asm sequence */
+"	b       3f			\n"
+"2: \n"
 "	lwsync				\n"
 "	li      %1,0		\n"
-
+"3: \n"
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
@@ -666,21 +662,6 @@ tas(volatile slock_t *lock)
 
 #if !defined(HAS_TEST_AND_SET)	/* We didn't trigger above, let's try here */
 
-#if defined(_AIX)	/* AIX */
-/*
- * AIX (POWER)
- */
-#define HAS_TEST_AND_SET
-
-#include <sys/atomic_op.h>
-
-typedef int slock_t;
-
-#define TAS(lock)			_check_lock((slock_t *) (lock), 0, 1)
-#define S_UNLOCK(lock)		_clear_lock((slock_t *) (lock), 0)
-#endif	 /* _AIX */
-
-
 /* These are in sunstudio_(sparc|x86).s */
 
 #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))