powerpc: Add the lock elision using HTM

This patch adds support for lock elision using ISA 2.07 hardware
transactional memory instructions for pthread_mutex primitives.
Similar to s390 version, the for elision logic defined in
'force-elision.h' is only enabled if ENABLE_LOCK_ELISION is defined.

Also, the lock elision code should be able to be built even with
a compiler that does not provide HTM support with builtins.
However I have noted the performance is sub-optimal due scheduling
pressures.

sysdeps/unix/sysv/linux/powerpc/htm.h

@@ -0,0 +1,138 @@
+/* Shared HTM header.  Emulate transactional execution facility intrinsics for
+   compilers and assemblers that do not support the intrinsics and instructions
+   yet.
+
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _HTM_H
+#define _HTM_H 1
+
+#ifdef __ASSEMBLER__
+
+/* tbegin.  */
+.macro TBEGIN
+	.long 0x7c00051d
+.endm
+
+/* tend. 0  */
+.macro TEND
+	.long 0x7c00055d
+.endm
+
+/* tabort. code  */
+.macro TABORT code
+	.byte 0x7c
+	.byte \code
+	.byte 0x07
+	.byte 0x1d
+.endm
+
+/*"TEXASR - Transaction EXception And Summary Register"
+   mfspr %dst,130  */
+.macro TEXASR dst
+	mfspr \dst,130
+.endm
+
+#else
+
+#include <endian.h>
+
+/* Official HTM intrinsics interface matching GCC, but works
+   on older GCC compatible compilers and binutils.
+   We should somehow detect if the compiler supports it, because
+   it may be able to generate slightly better code.  */
+
+#define TBEGIN ".long 0x7c00051d"
+#define TEND   ".long 0x7c00055d"
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+# define TABORT ".byte 0x1d,0x07,%1,0x1d"
+#else
+# define TABORT ".byte 0x7c,%1,0x07,0x1d"
+#endif
+
+#define __force_inline        inline __attribute__((__always_inline__))
+
+#ifndef __HTM__
+
+#define _TEXASRU_EXTRACT_BITS(TEXASR,BITNUM,SIZE) \
+  (((TEXASR) >> (31-(BITNUM))) & ((1<<(SIZE))-1))
+#define _TEXASRU_FAILURE_PERSISTENT(TEXASRU) \
+  _TEXASRU_EXTRACT_BITS(TEXASRU, 7, 1)
+
+#define _tbegin()			\
+  ({ unsigned int __ret;		\
+     asm volatile (			\
+       TBEGIN "\t\n"			\
+       "mfcr   %0\t\n"			\
+       "rlwinm %0,%0,3,1\t\n"		\
+       "xori %0,%0,1\t\n"		\
+       : "=r" (__ret) :			\
+       : "cr0", "memory");		\
+     __ret;				\
+  })
+
+#define _tend()				\
+  ({ unsigned int __ret;		\
+     asm volatile (			\
+       TEND "\t\n"			\
+       "mfcr   %0\t\n"			\
+       "rlwinm %0,%0,3,1\t\n"		\
+       "xori %0,%0,1\t\n"		\
+       : "=r" (__ret) :			\
+       : "cr0", "memory");		\
+     __ret;				\
+  })
+
+#define _tabort(__code)			\
+  ({ unsigned int __ret;		\
+     asm volatile (			\
+       TABORT "\t\n"			\
+       "mfcr   %0\t\n"			\
+       "rlwinm %0,%0,3,1\t\n"		\
+       "xori %0,%0,1\t\n"		\
+       : "=r" (__ret) : "r" (__code)	\
+       : "cr0", "memory");		\
+     __ret;				\
+  })
+
+#define _texasru()			\
+  ({ unsigned long __ret;		\
+     asm volatile (			\
+       "mfspr %0,131\t\n"		\
+       : "=r" (__ret));			\
+     __ret;				\
+  })
+
+#define __builtin_tbegin(tdb)       _tbegin ()
+#define __builtin_tend(nested)      _tend ()
+#define __builtin_tabort(abortcode) _tabort (abortcode)
+#define __builtin_get_texasru()     _texasru ()
+
+#else
+# include <htmintrin.h>
+#endif /* __HTM__  */
+
+#endif /* __ASSEMBLER__ */
+
+/* Definitions used for TEXASR Failure code (bits 0:6), they need to be even
+   because tabort. always sets the first bit.  */
+#define _ABORT_LOCK_BUSY       0x3f   /* Lock already used.  */
+#define _ABORT_NESTED_TRYLOCK  0x3e   /* Write operation in trylock.  */
+#define _ABORT_SYSCALL         0x3d   /* Syscall issued.  */
+
+#endif