[PPC64] Allow R_PPC64_DTPREL* to preemptable local-dynamic symbols

[MaskRay]

.

[ruiu]

LGTM

[MaskRay]

ELF/Relocations.cpp

251

relaxTlsLdToLe is redefined by PPC64 X86 X86_64 (no MIPS). So PPC64 is the last user.

test/ELF/ppc64-tls-ld-preemptable.s

10

The disassembled instructions are consistent with ld.bfd and gold

R_DTPREL can just use return Sym.getVA(A);

[MaskRay]

Simplify test

ELF/Arch/PPC64.cpp

RelExpr PPC64::getRelExpr(RelType Type, const Symbol &S,
   case R_PPC64_DTPREL16_HI:
   case R_PPC64_DTPREL16_HIGHER:
   case R_PPC64_DTPREL16_HIGHERA:
   case R_PPC64_DTPREL16_HIGHEST:
   case R_PPC64_DTPREL16_HIGHESTA:
   case R_PPC64_DTPREL16_LO:
   case R_PPC64_DTPREL16_LO_DS:
   case R_PPC64_DTPREL64:
-    return R_ABS;
+    return R_DTPREL;
   case R_PPC64_TLSGD:
     return R_TLSDESC_CALL;
   case R_PPC64_TLSLD:
     return R_TLSLD_HINT;
   case R_PPC64_TLS:
     return R_TLSIE_HINT;
   default:
     return R_ABS;

ELF/InputSection.cpp

default:
     llvm_unreachable("unhandled Config->EMachine");
   }
 }
 
 static uint64_t getRelocTargetVA(const InputFile *File, RelType Type, int64_t A,
                                  uint64_t P, const Symbol &Sym, RelExpr Expr) {
   switch (Expr) {
   case R_ABS:
+  case R_DTPREL:
   case R_RELAX_TLS_LD_TO_LE_ABS:
   case R_RELAX_GOT_PC_NOPIC:
     return Sym.getVA(A);
-  case R_DTPREL:
-    return Sym.getVA(A);
   case R_ADDEND:
     return A;
   case R_ARM_SBREL:
     return Sym.getVA(A) - getARMStaticBase(Sym);
   case R_GOT:
   case R_RELAX_TLS_GD_TO_IE_ABS:
     return Sym.getGotVA() + A;
   case R_GOTONLY_PC:

ELF/Relocations.cpp

if (oneof<R_TLSLD_GOT, R_TLSLD_GOTPLT, R_TLSLD_PC, R_TLSLD_HINT>(
     if (In.Got->addTlsIndex())
       In.RelaDyn->addReloc(Target->TlsModuleIndexRel, In.Got,
                            In.Got->getTlsIndexOff(), nullptr);
     C.Relocations.push_back({Expr, Type, Offset, Addend, &Sym});
     return 1;
   }
 
   // Local-Dynamic relocs can be relaxed to Local-Exec.
-  // TODO Delete R_ABS after all R_*_DTPREL_* relocations migrate to R_DTPREL.
-  if ((Expr == R_ABS || Expr == R_DTPREL) && !Config->Shared) {
+  if (Expr == R_DTPREL && !Config->Shared) {
     C.Relocations.push_back(
         {Target->adjustRelaxExpr(Type, nullptr, R_RELAX_TLS_LD_TO_LE), Type,
          Offset, Addend, &Sym});
     return 1;
   }
 
   // Local-Dynamic sequence where offset of tls variable relative to dynamic
   // thread pointer is stored in the got.

test/ELF/ppc64-tls-ld-preemptable.s

+# REQUIRES: ppc
+# RUN: llvm-mc -filetype=obj -triple=ppc64le %s -o %t.o
+# RUN: ld.lld %t.o -shared -o %t.so
+# RUN: llvm-objdump -d --no-show-raw-insn %t.so | FileCheck %s
+# RUN: llvm-nm %t.so | FileCheck --check-prefix=NM %s
+# RUN: llvm-readelf -x .rodata %t.so | FileCheck --check-prefix=RODATA %s
+
+# 42 - 0x8000 = -32726
+# CHECK:      addis 4, 3, 0
+# CHECK-NEXT: addi 4, 3, -32726
+# CHECK-NEXT: lwz 0, 0(4)
+# CHECK-NEXT: lis 5, 0
+# CHECK-NEXT: ori 5, 5, 0
+
+# NM: 000000000000002a B i
+# RODATA: 2a000000 00000000
+
+# We used to error on R_PPC64_DTPREL* to preemptable symbols.
+# i is STB_GLOBAL and preemptable.
+.globl foo
+foo:
+  addis 4, 3, i@dtprel@ha # R_PPC64_DTPREL16_HA
+  addi 4, 4, i@dtprel@l   # R_PPC64_DTPREL16_LO
+
+  lis 5, i@dtprel@highesta # R_PPC64_DTPREL16_HIGHESTA
+  ori 5, 5, i@dtprel@highera # R_PPC64_DTPREL16_HIGHERA
+
+.section .rodata,"a",@progbits
+.quad i@dtprel+32768
+
+.section .tbss,"awT",@nobits
+  .space 42
+.globl i
+i:
+  .long 0
+  .size i, 4