Pull in r353299 from upstream lld trunk (by George Rimar):

Recommit r353293 "[LLD][ELF] - Set DF_STATIC_TLS flag for i386 target."

  With the following changes:
  1) Compilation fix:
  std::atomic<bool> HasStaticTlsModel = false; ->
  std::atomic<bool> HasStaticTlsModel{false};

  2) Adjusted the comment in code.

  Initial commit message:

  DF_STATIC_TLS flag indicates that the shared object or executable
  contains code using a static thread-local storage scheme.

  Patch checks if IE/LE relocations were used to check if the code uses
  a static model. If so it sets the DF_STATIC_TLS flag.

  Differential revision: https://reviews.llvm.org/D57749

Pull in r353378 from upstream lld trunk (by George Rimar):

  [LLD][ELF] - Set DF_STATIC_TLS flag for X64 target

  This is the same as D57749, but for x64 target.

  "ELF Handling For Thread-Local Storage" p41 says
  (https://www.akkadia.org/drepper/tls.pdf):
  R_X86_64_GOTTPOFF relocation is used for IE TLS models.
  Hence if linker sees this relocation we should add DF_STATIC_TLS flag.

  Differential revision: https://reviews.llvm.org/D57821

This adds support to lld for the DF_STATIC_TLS flag in shared objects,
which signals to the dynamic linker that the shared object requires
static thread local storage.

See also:	https://reviews.freebsd.org/D19072
MFC after:	1 week

contrib/llvm/tools/lld/ELF/Arch/X86.cpp

@@ -70,6 +70,14 @@ static bool hasBaseReg(uint8_t ModRM) { return (ModRM & 0xc7) != 0x5; }
 
 RelExpr X86::getRelExpr(RelType Type, const Symbol &S,
                         const uint8_t *Loc) const {
+  // There are 4 different TLS variable models with varying degrees of
+  // flexibility and performance. LocalExec and InitialExec models are fast but
+  // less-flexible models. If they are in use, we set DF_STATIC_TLS flag in the
+  // dynamic section to let runtime know about that.
+  if (Type == R_386_TLS_LE || Type == R_386_TLS_LE_32 || Type == R_386_TLS_IE ||
+      Type == R_386_TLS_GOTIE)
+    Config->HasStaticTlsModel = true;
+
   switch (Type) {
   case R_386_8:
   case R_386_16:

contrib/llvm/tools/lld/ELF/Arch/X86_64.cpp

@@ -76,6 +76,9 @@ template <class ELFT> X86_64<ELFT>::X86_64() {
 template <class ELFT>
 RelExpr X86_64<ELFT>::getRelExpr(RelType Type, const Symbol &S,
                                  const uint8_t *Loc) const {
+  if (Type == R_X86_64_GOTTPOFF)
+    Config->HasStaticTlsModel = true;
+
   switch (Type) {
   case R_X86_64_8:
   case R_X86_64_16:

contrib/llvm/tools/lld/ELF/Config.h

@@ -18,6 +18,7 @@
 #include "llvm/Support/CachePruning.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Endian.h"
+#include <atomic>
 #include <vector>
 
 namespace lld {
@@ -81,6 +82,7 @@ struct VersionDefinition {
 // and such fields have the same name as the corresponding options.
 // Most fields are initialized by the driver.
 struct Configuration {
+  std::atomic<bool> HasStaticTlsModel{false};
   uint8_t OSABI = 0;
   llvm::CachePruningPolicy ThinLTOCachePolicy;
   llvm::StringMap<uint64_t> SectionStartMap;

contrib/llvm/tools/lld/ELF/SyntheticSections.cpp

@@ -1282,6 +1282,8 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
   }
   if (!Config->ZText)
     DtFlags |= DF_TEXTREL;
+  if (Config->HasStaticTlsModel)
+    DtFlags |= DF_STATIC_TLS;
 
   if (DtFlags)
     addInt(DT_FLAGS, DtFlags);