libitm/config/x86/target.h

   1 /* Copyright (C) 2008-2024 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU Transactional Memory Library (libitm).
   5
   6    Libitm is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    Libitm is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14    more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 // We'll be using some of the cpu builtins, and their associated types.
  26 #include <x86intrin.h>
  27 #include <cpuid.h>
  28
  29 namespace GTM HIDDEN {
  30
  31 /* ??? This doesn't work for Win64.  */
  32 typedef struct gtm_jmpbuf
  33 {
  34   void *cfa;
  35 #ifdef __x86_64__
  36   unsigned long long rbx;
  37   unsigned long long rbp;
  38   unsigned long long r12;
  39   unsigned long long r13;
  40   unsigned long long r14;
  41   unsigned long long r15;
  42   unsigned long long ssp;
  43   unsigned long long rip;
  44 #else
  45   unsigned long ebx;
  46   unsigned long esi;
  47   unsigned long edi;
  48   unsigned long ebp;
  49   unsigned long ssp;
  50   unsigned long eip;
  51 #endif
  52 } gtm_jmpbuf;
  53
  54 /* x86 doesn't require strict alignment for the basic types.  */
  55 #define STRICT_ALIGNMENT 0
  56
  57 /* The size of one line in hardware caches (in bytes). */
  58 #define HW_CACHELINE_SIZE 64
  59
  60
  61 static inline void
  62 cpu_relax (void)
  63 {
  64   __builtin_ia32_pause ();
  65 }
  66
  67 // Use Intel RTM if supported by the assembler.
  68 // See gtm_thread::begin_transaction for how these functions are used.
  69 #ifdef HAVE_AS_RTM
  70 #define USE_HTM_FASTPATH
  71 #ifdef __x86_64__
  72 // Use the custom fastpath in ITM_beginTransaction.
  73 #define HTM_CUSTOM_FASTPATH
  74 #endif
  75
  76 static inline bool
  77 htm_available ()
  78 {
  79   const unsigned cpuid_rtm = bit_RTM;
  80   unsigned vendor;
  81
  82   if (__get_cpuid_max (0, &vendor) >= 7)
  83     {
  84       unsigned a, b, c, d;
  85       unsigned family;
  86
  87       __cpuid (1, a, b, c, d);
  88       family = (a >> 8) & 0x0f;
  89       /* TSX is broken on some processors.  TSX can be disabled by microcode,
  90          but we cannot reliably detect whether the microcode has been
  91          updated.  Therefore, do not report availability of TSX on these
  92          processors.  We use the same approach here as in glibc (see
  93          https://sourceware.org/ml/libc-alpha/2016-12/msg00470.html).  */
  94       if (vendor == signature_INTEL_ebx && family == 0x06)
  95         {
  96           unsigned model = ((a >> 4) & 0x0f) + ((a >> 12) & 0xf0);
  97           unsigned stepping = a & 0x0f;
  98           if (model == 0x3c
  99               /* Xeon E7 v3 has correct TSX if stepping >= 4.  */
 100               || (model == 0x3f && stepping < 4)
 101               || model == 0x45
 102               || model == 0x46)
 103             return false;
 104         }
 105
 106       __cpuid_count (7, 0, a, b, c, d);
 107       if (b & cpuid_rtm)
 108         return true;
 109     }
 110   return false;
 111 }
 112
 113 static inline uint32_t
 114 htm_init ()
 115 {
 116   // Maximum number of times we try to execute a transaction as a HW
 117   // transaction.
 118   // ??? Why 2?  Any offline or runtime tuning necessary?
 119   return htm_available () ? 2 : 0;
 120 }
 121
 122 static inline uint32_t
 123 htm_begin ()
 124 {
 125   return _xbegin();
 126 }
 127
 128 static inline bool
 129 htm_begin_success (uint32_t begin_ret)
 130 {
 131   return begin_ret == _XBEGIN_STARTED;
 132 }
 133
 134 static inline void
 135 htm_commit ()
 136 {
 137   _xend();
 138 }
 139
 140 static inline void
 141 htm_abort ()
 142 {
 143   // ??? According to a yet unpublished ABI rule, 0xff is reserved and
 144   // supposed to signal a busy lock.  Source: andi.kleen@intel.com
 145   _xabort(0xff);
 146 }
 147
 148 static inline bool
 149 htm_abort_should_retry (uint32_t begin_ret)
 150 {
 151   return begin_ret & _XABORT_RETRY;
 152 }
 153
 154 /* Returns true iff a hardware transaction is currently being executed.  */
 155 static inline bool
 156 htm_transaction_active ()
 157 {
 158   return _xtest() != 0;
 159 }
 160 #endif
 161
 162
 163 } // namespace GTM