[Support/ELF] - Added DT_TLSDESC_PLT and DT_TLSDESC_GOT constants.

[grimar]

Summary

Added 2 constants:

DT_TLSDESC_PLT = 0x6FFFFEF6, Location of PLT entry for TLS descriptor resolver calls.
DT_TLSDESC_GOT = 0x6FFFFEF7, Location of GOT entry used by TLS descriptor resolver PLT entry.

Constants were taken from "Thread-Local Storage Descriptors for IA32 and AMD64/EM64T Version 0.9.5" http://www.fsfla.org/~lxoliva/writeups/TLS/RFC-TLSDESC-x86.txt
I need it for aarch64.

Not sure who is appropriate reviewer for it ?

[davide]

This one is a no-brainer. LGTM.

llvm/trunk/include/llvm/Support/ELF.h

enum {
   DT_PREINIT_ARRAYSZ = 33,    // Size of the DT_PREINIT_ARRAY array.
 
   DT_LOOS         = 0x60000000, // Start of environment specific tags.
   DT_HIOS         = 0x6FFFFFFF, // End of environment specific tags.
   DT_LOPROC       = 0x70000000, // Start of processor specific tags.
   DT_HIPROC       = 0x7FFFFFFF, // End of processor specific tags.
 
   DT_GNU_HASH     = 0x6FFFFEF5, // Reference to the GNU hash table.
+  DT_TLSDESC_PLT  = 0x6FFFFEF6, // Location of PLT entry for TLS descriptor resolver calls.
+  DT_TLSDESC_GOT  = 0x6FFFFEF7, // Location of GOT entry used by TLS descriptor resolver PLT entry.
   DT_RELACOUNT    = 0x6FFFFFF9, // ELF32_Rela count.
   DT_RELCOUNT     = 0x6FFFFFFA, // ELF32_Rel count.
 
   DT_FLAGS_1      = 0X6FFFFFFB, // Flags_1.
   DT_VERSYM       = 0x6FFFFFF0, // The address of .gnu.version section.
   DT_VERDEF       = 0X6FFFFFFC, // The address of the version definition table.
   DT_VERDEFNUM    = 0X6FFFFFFD, // The number of entries in DT_VERDEF.
   DT_VERNEED      = 0X6FFFFFFE, // The address of the version Dependency table.