sysdeps/sparc/sysdep.h

   1 /* Copyright (C) 2011-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #define _SYSDEPS_SYSDEP_H 1
  19 #include <bits/hwcap.h>
  20
  21 #ifdef  __ASSEMBLER__
  22
  23 #define SPARC_PIC_THUNK(reg)                                            \
  24         .ifndef __sparc_get_pc_thunk.reg;                               \
  25         .section .text.__sparc_get_pc_thunk.reg,"axG",@progbits,__sparc_get_pc_thunk.reg,comdat; \
  26         .align   32;                                                    \
  27         .weak    __sparc_get_pc_thunk.reg;                              \
  28         .hidden  __sparc_get_pc_thunk.reg;                              \
  29         .type    __sparc_get_pc_thunk.reg, #function;                   \
  30 __sparc_get_pc_thunk.reg:                                               \
  31         jmp     %o7 + 8;                                                \
  32          add    %o7, %reg, %##reg;                                      \
  33         .previous;                                                      \
  34         .endif;
  35
  36 /* The "-4" and "+4" offsets against _GLOBAL_OFFSET_TABLE_ are
  37    critical since they represent the offset from the thunk call to the
  38    instruction containing the _GLOBAL_OFFSET_TABLE_ reference.
  39    Therefore these instructions cannot be moved around without
  40    appropriate adjustments to those offsets.
  41
  42    Furthermore, these expressions are special in another regard.  When
  43    the assembler sees a reference to _GLOBAL_OFFSET_TABLE_ inside of
  44    a %hi() or %lo(), it emits a PC-relative relocation.  This causes
  45    R_SPARC_HI22 to turn into R_SPARC_PC22, and R_SPARC_LO10 to turn into
  46    R_SPARC_PC10, respectively.
  47
  48    Even when v9 we use a call sequence instead of using "rd %pc" because
  49    RDPC is extremely expensive and incurs a full pipeline flush.  */
  50
  51 #define SPARC_PIC_THUNK_CALL(reg)                                       \
  52         sethi   %hi(_GLOBAL_OFFSET_TABLE_-4), %##reg;                   \
  53         call    __sparc_get_pc_thunk.reg;                               \
  54          or     %##reg, %lo(_GLOBAL_OFFSET_TABLE_+4), %##reg;
  55
  56 #define SETUP_PIC_REG(reg)                                              \
  57         SPARC_PIC_THUNK(reg)                                            \
  58         SPARC_PIC_THUNK_CALL(reg)
  59
  60 #define SETUP_PIC_REG_LEAF(reg, tmp)                                    \
  61         SPARC_PIC_THUNK(reg)                                            \
  62         mov     %o7, %##tmp;                                            \
  63         SPARC_PIC_THUNK_CALL(reg);                                      \
  64         mov     %##tmp, %o7;
  65
  66 #undef ENTRY
  67 #define ENTRY(name)                     \
  68         .align  4;                      \
  69         .global C_SYMBOL_NAME(name);    \
  70         .type   name, @function;        \
  71 C_LABEL(name)                           \
  72         cfi_startproc;
  73
  74 #undef END
  75 #define END(name)                       \
  76         cfi_endproc;                    \
  77         .size name, . - name
  78
  79 #define ENTRY_NOCFI(name)                       \
  80         .align  4;                      \
  81         .global C_SYMBOL_NAME(name);    \
  82         .type   name, @function;        \
  83 C_LABEL(name)
  84
  85 #define END_NOCFI(name)                 \
  86         .size name, . - name
  87
  88 #undef LOC
  89 #define LOC(name)  .L##name
  90
  91 #endif  /* __ASSEMBLER__ */