[ELF][MIPS] Don't emit dynamic relocations for PIE non-preemptible TLS

[jrtc27]

Summary

Whilst not wrong (unless using static PIE where the relocations are
likely not implemented by the runtime), this is inefficient, as the TLS
module indices and offsets are independent of the executable's load
address.

[jrtc27]

Use the more conventional .pie rather than -pie.exe for the tests

[MaskRay]

LGTM.

[atanasyan]

LGTM

lld/ELF/SyntheticSections.cpp

for (std::pair<Symbol *, size_t> &p : got.tls) {
       uint64_t offset = p.second * config->wordsize;
       if (s->isPreemptible)
         mainPart->relaDyn->addReloc(target->tlsGotRel, this, offset, s);
     }
     for (std::pair<Symbol *, size_t> &p : got.dynTlsSymbols) {
       Symbol *s = p.first;
       uint64_t offset = p.second * config->wordsize;
       if (s == nullptr) {
-        if (!config->isPic)
+        if (!config->shared)
           continue;
         mainPart->relaDyn->addReloc(target->tlsModuleIndexRel, this, offset, s);
       } else {
         // When building a shared library we still need a dynamic relocation
         // for the module index. Therefore only checking for
         // S->isPreemptible is not sufficient (this happens e.g. for
         // thread-locals that have been marked as local through a linker script)
-        if (!s->isPreemptible && !config->isPic)
+        if (!s->isPreemptible && !config->shared)
           continue;
         mainPart->relaDyn->addReloc(target->tlsModuleIndexRel, this, offset, s);
         // However, we can skip writing the TLS offset reloc for non-preemptible
         // symbols since it is known even in shared libraries
         if (!s->isPreemptible)
           continue;
         offset += config->wordsize;
         mainPart->relaDyn->addReloc(target->tlsOffsetRel, this, offset, s);
for (const FileGot &g : gots) {
     if (&g == &gots.front())
       for (const std::pair<Symbol *, size_t> &p : g.global)
         write(p.second, p.first, 0);
     for (const std::pair<Symbol *, size_t> &p : g.relocs)
       write(p.second, p.first, 0);
     for (const std::pair<Symbol *, size_t> &p : g.tls)
       write(p.second, p.first, p.first->isPreemptible ? 0 : -0x7000);
     for (const std::pair<Symbol *, size_t> &p : g.dynTlsSymbols) {
-      if (p.first == nullptr && !config->isPic)
+      if (p.first == nullptr && !config->shared)
         write(p.second, nullptr, 1);
       else if (p.first && !p.first->isPreemptible) {
-        // If we are emitting PIC code with relocations we mustn't write
+        // If we are emitting a shared libary with relocations we mustn't write
         // anything to the GOT here. When using Elf_Rel relocations the value
         // one will be treated as an addend and will cause crashes at runtime
-        if (!config->isPic)
+        if (!config->shared)
           write(p.second, nullptr, 1);
         write(p.second + 1, p.first, -0x8000);
       }
     }
   }
 }
 
 // On PowerPC the .plt section is used to hold the table of function addresses

lld/test/ELF/mips-tls-64.s

 # RUN:         . = 0x30000; .got  : { *(.got)  } \
 # RUN:       }" > %t.script
 
 # RUN: ld.lld %t.o %t.so -script %t.script -o %t.exe
 # RUN: llvm-objdump -d -s -t --no-show-raw-insn %t.exe \
 # RUN:   | FileCheck -check-prefix=DIS %s
 # RUN: llvm-readobj -r -A %t.exe | FileCheck %s
 
+# RUN: ld.lld -pie %t.o %t.so -script %t.script -o %t.pie
+# RUN: llvm-objdump -d -s -t --no-show-raw-insn %t.pie \
+# RUN:   | FileCheck -check-prefix=DIS %s
+# RUN: llvm-readobj -r -A %t.pie | FileCheck %s
+
 # RUN: ld.lld -shared %t.o %t.so -script %t.script -o %t-out.so
 # RUN: llvm-objdump -d -s -t --no-show-raw-insn %t-out.so \
 # RUN:   | FileCheck -check-prefix=DIS-SO %s
 # RUN: llvm-readobj -r -A %t-out.so | FileCheck -check-prefix=SO %s
 
 # DIS: 0000000000000000 l       .tdata  0000000000000000 loc
 # DIS: 0000000000000000         *UND*   0000000000000000 foo
 # DIS: 0000000000000004 g       .tdata  0000000000000000 bar

lld/test/ELF/mips-tls.s

 # RUN:         . = 0x30000; .got  : { *(.got)  } \
 # RUN:       }" > %t.script
 
 # RUN: ld.lld %t.o %t.so -script %t.script -o %t.exe
 # RUN: llvm-objdump -d -s -t --no-show-raw-insn %t.exe \
 # RUN:   | FileCheck -check-prefix=DIS %s
 # RUN: llvm-readobj -r -A %t.exe | FileCheck %s
 
+# RUN: ld.lld -pie %t.o %t.so -script %t.script -o %t.pie
+# RUN: llvm-objdump -d -s -t --no-show-raw-insn %t.pie \
+# RUN:   | FileCheck -check-prefix=DIS %s
+# RUN: llvm-readobj -r -A %t.pie | FileCheck %s
+
 # RUN: ld.lld -shared %t.o %t.so -script %t.script -o %t-out.so
 # RUN: llvm-objdump -d -s -t --no-show-raw-insn %t-out.so \
 # RUN:   | FileCheck -check-prefix=DIS-SO %s
 # RUN: llvm-readobj -r -A %t-out.so | FileCheck -check-prefix=SO %s
 
 # DIS: 00000000 l      .tdata          00000000 loc
 # DIS: 00000000        *UND*           00000000 foo
 # DIS: 00000004 g      .tdata          00000000 bar