[ELF] Rename IsRela to HasAddend

`IsRela` is used by lld to differentiate REL and RELA static
relocations. The proposed CREL patch will reuse `IsRela` for CREL
(#91280). Rename `IsRela` to be more appropriate.

Pull Request: #96592

Author: MaskRay

lld/ELF/InputSection.cpp

@@ -411,7 +411,7 @@ void InputSection::copyRelocations(uint8_t *buf,
     auto *p = reinterpret_cast<typename ELFT::Rela *>(buf);
     buf += sizeof(RelTy);
 
-    if (RelTy::IsRela)
+    if (RelTy::HasAddend)
       p->r_addend = rel.addend;
 
     // Output section VA is zero for -r, so r_offset is an offset within the
@@ -452,7 +452,7 @@ void InputSection::copyRelocations(uint8_t *buf,
 
       int64_t addend = rel.addend;
       const uint8_t *bufLoc = sec->content().begin() + rel.offset;
-      if (!RelTy::IsRela)
+      if (!RelTy::HasAddend)
         addend = target.getImplicitAddend(bufLoc, type);
 
       if (config->emachine == EM_MIPS &&
@@ -471,7 +471,7 @@ void InputSection::copyRelocations(uint8_t *buf,
         addend += sec->getFile<ELFT>()->mipsGp0;
       }
 
-      if (RelTy::IsRela)
+      if (RelTy::HasAddend)
         p->r_addend = sym.getVA(addend) - section->getOutputSection()->addr;
       // For SHF_ALLOC sections relocated by REL, append a relocation to
       // sec->relocations so that relocateAlloc transitively called by
@@ -934,7 +934,7 @@ void InputSection::relocateNonAlloc(uint8_t *buf, ArrayRef<RelTy> rels) {
     const uint64_t offset = rel.r_offset;
     uint8_t *bufLoc = buf + offset;
     int64_t addend = getAddend<ELFT>(rel);
-    if (!RelTy::IsRela)
+    if (!RelTy::HasAddend)
       addend += target.getImplicitAddend(bufLoc, type);
 
     Symbol &sym = f->getRelocTargetSym(rel);
@@ -1007,10 +1007,11 @@ void InputSection::relocateNonAlloc(uint8_t *buf, ArrayRef<RelTy> rels) {
       }
     }
 
-    // For a relocatable link, content relocated by RELA remains unchanged and
-    // we can stop here, while content relocated by REL referencing STT_SECTION
-    // needs updating implicit addends.
-    if (config->relocatable && (RelTy::IsRela || sym.type != STT_SECTION))
+    // For a relocatable link, content relocated by relocation types with an
+    // explicit addend, such as RELA, remain unchanged and we can stop here.
+    // While content relocated by relocation types with an implicit addend, such
+    // as REL, needs the implicit addend updated.
+    if (config->relocatable && (RelTy::HasAddend || sym.type != STT_SECTION))
       continue;
 
     // R_ABS/R_DTPREL and some other relocations can be used from non-SHF_ALLOC

lld/ELF/Relocations.cpp

@@ -492,7 +492,8 @@ int64_t RelocationScanner::computeMipsAddend(const RelTy &rel, RelExpr expr,
 
   // The ABI says that the paired relocation is used only for REL.
   // See p. 4-17 at ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
-  if (RelTy::IsRela)
+  // This generalises to relocation types with implicit addends.
+  if (RelTy::HasAddend)
     return 0;
 
   RelType type = rel.getType(config->isMips64EL);
@@ -1448,7 +1449,7 @@ template <class ELFT, class RelTy> void RelocationScanner::scanOne(RelTy *&i) {
     return;
 
   RelExpr expr = target->getRelExpr(type, sym, sec->content().data() + offset);
-  int64_t addend = RelTy::IsRela
+  int64_t addend = RelTy::HasAddend
                        ? getAddend<ELFT>(rel)
                        : target->getImplicitAddend(
                              sec->content().data() + rel.r_offset, type);

llvm/include/llvm/Object/ELFTypes.h

@@ -384,7 +384,7 @@ struct Elf_Dyn_Impl : Elf_Dyn_Base<ELFT> {
 template <endianness Endianness>
 struct Elf_Rel_Impl<ELFType<Endianness, false>, false> {
   LLVM_ELF_IMPORT_TYPES(Endianness, false)
-  static const bool IsRela = false;
+  static const bool HasAddend = false;
   Elf_Addr r_offset; // Location (file byte offset, or program virtual addr)
   Elf_Word r_info;   // Symbol table index and type of relocation to apply
 
@@ -420,14 +420,14 @@ template <endianness Endianness>
 struct Elf_Rel_Impl<ELFType<Endianness, false>, true>
     : public Elf_Rel_Impl<ELFType<Endianness, false>, false> {
   LLVM_ELF_IMPORT_TYPES(Endianness, false)
-  static const bool IsRela = true;
+  static const bool HasAddend = true;
   Elf_Sword r_addend; // Compute value for relocatable field by adding this
 };
 
 template <endianness Endianness>
 struct Elf_Rel_Impl<ELFType<Endianness, true>, false> {
   LLVM_ELF_IMPORT_TYPES(Endianness, true)
-  static const bool IsRela = false;
+  static const bool HasAddend = false;
   Elf_Addr r_offset; // Location (file byte offset, or program virtual addr)
   Elf_Xword r_info;  // Symbol table index and type of relocation to apply
 
@@ -473,7 +473,7 @@ template <endianness Endianness>
 struct Elf_Rel_Impl<ELFType<Endianness, true>, true>
     : public Elf_Rel_Impl<ELFType<Endianness, true>, false> {
   LLVM_ELF_IMPORT_TYPES(Endianness, true)
-  static const bool IsRela = true;
+  static const bool HasAddend = true;
   Elf_Sxword r_addend; // Compute value for relocatable field by adding this.
 };