[Sparc] Include __tls_get_addr in symbol table for TLS calls to it

Global Dynamic and Local Dynamic call relocations only implicitly
reference __tls_get_addr, but it still needs to be in the symbol table
to be bound at link time otherwise it fails to link. For details, see
https://sourceware.org/bugzilla/show_bug.cgi?id=22832.

Author: jrtc27

lib/Target/Sparc/MCTargetDesc/SparcMCExpr.cpp

@@ -193,14 +193,30 @@ static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) {
 void SparcMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const {
   switch(getKind()) {
   default: return;
+  case VK_Sparc_TLS_GD_CALL:
+  case VK_Sparc_TLS_LDM_CALL: {
+    // The corresponding relocations reference __tls_get_addr, as they call it,
+    // but this is only implicit; there is no connection in the ELF file
+    // between the relocation and the symbol, other than the specification for
+    // the semantics of the relocations. However, the symbol must be included
+    // in our symbol table despite the lack of references to it, since it needs
+    // to be bound during linking for these relocations. For details see
+    // https://sourceware.org/bugzilla/show_bug.cgi?id=22832.
+    MCSymbol *Symbol = Asm.getContext().getOrCreateSymbol("__tls_get_addr");
+    Asm.registerSymbol(*Symbol);
+    auto ELFSymbol = cast<MCSymbolELF>(Symbol);
+    if (!ELFSymbol->isBindingSet()) {
+      ELFSymbol->setBinding(ELF::STB_GLOBAL);
+      ELFSymbol->setExternal(true);
+    }
+    LLVM_FALLTHROUGH;
+  }
   case VK_Sparc_TLS_GD_HI22:
   case VK_Sparc_TLS_GD_LO10:
   case VK_Sparc_TLS_GD_ADD:
-  case VK_Sparc_TLS_GD_CALL:
   case VK_Sparc_TLS_LDM_HI22:
   case VK_Sparc_TLS_LDM_LO10:
   case VK_Sparc_TLS_LDM_ADD:
-  case VK_Sparc_TLS_LDM_CALL:
   case VK_Sparc_TLS_LDO_HIX22:
   case VK_Sparc_TLS_LDO_LOX10:
   case VK_Sparc_TLS_LDO_ADD:

test/CodeGen/SPARC/tls.ll

@@ -3,10 +3,10 @@
 ; RUN: llc <%s -march=sparc   -relocation-model=pic    | FileCheck %s --check-prefix=pic
 ; RUN: llc <%s -march=sparcv9 -relocation-model=pic    | FileCheck %s --check-prefix=pic
 
-; RUN: llc <%s -march=sparc   -relocation-model=static -filetype=obj | llvm-readobj -r | FileCheck %s --check-prefix=v8abs-obj
-; RUN: llc <%s -march=sparcv9 -relocation-model=static -filetype=obj | llvm-readobj -r | FileCheck %s --check-prefix=v9abs-obj
-; RUN: llc <%s -march=sparc   -relocation-model=pic    -filetype=obj | llvm-readobj -r | FileCheck %s --check-prefix=pic-obj
-; RUN: llc <%s -march=sparcv9 -relocation-model=pic    -filetype=obj | llvm-readobj -r | FileCheck %s --check-prefix=pic-obj
+; RUN: llc <%s -march=sparc   -relocation-model=static -filetype=obj | llvm-readobj -r -t | FileCheck %s --check-prefix=v8abs-obj
+; RUN: llc <%s -march=sparcv9 -relocation-model=static -filetype=obj | llvm-readobj -r -t | FileCheck %s --check-prefix=v9abs-obj
+; RUN: llc <%s -march=sparc   -relocation-model=pic    -filetype=obj | llvm-readobj -r -t | FileCheck %s --check-prefix=pic-obj
+; RUN: llc <%s -march=sparcv9 -relocation-model=pic    -filetype=obj | llvm-readobj -r -t | FileCheck %s --check-prefix=pic-obj
 
 @local_symbol = internal thread_local global i32 0
 @extern_symbol = external thread_local global i32
@@ -116,4 +116,15 @@ entry:
 ; pic-obj:    0x{{[0-9,A-F]+}} R_SPARC_TLS_GD_ADD extern_symbol 0x0
 ; pic-obj:    0x{{[0-9,A-F]+}} R_SPARC_TLS_GD_CALL extern_symbol 0x0
 ; pic-obj: ]
+; pic-obj:      Symbols [
+; pic-obj:        Symbol {
+; pic-obj:          Name: __tls_get_addr ({{[0-9]+}})
+; pic-obj-NEXT:     Value: 0x0
+; pic-obj-NEXT:     Size: 0
+; pic-obj-NEXT:     Binding: Global (0x1)
+; pic-obj-NEXT:     Type: None (0x0)
+; pic-obj-NEXT:     Other: 0
+; pic-obj-NEXT:     Section: Undefined (0x0)
+; pic-obj-NEXT:   }
+; pic-obj:      ]