[MC] Remove ELFRelocationEntry::OriginalAddend

For MIPS's o32 ABI (REL), https://reviews.llvm.org/D19718 introduced
`OriginalAddend` to find the matching R_MIPS_LO16 relocation for
R_MIPS_GOT16 when STT_SECTION conversion is applicable.

    lw $2, %lo(local1)
    lui $2, %got(local1)

However, we could just store the original `Addend` in
`ELFRelocationEntry` and remove `OriginalAddend`.

Note: The relocation ordering algorithm in
https://reviews.llvm.org/D19718 is inefficient (#104562), which will be
addressed by another patch.

Author: MaskRay

llvm/include/llvm/MC/MCELFObjectWriter.h

@@ -38,18 +38,15 @@ struct ELFRelocationEntry {
   unsigned Type;   // The type of the relocation.
   uint64_t Addend; // The addend to use.
   const MCSymbolELF *OriginalSymbol; // The original value of Symbol if we changed it.
-  uint64_t OriginalAddend; // The original value of addend.
 
   ELFRelocationEntry(uint64_t Offset, const MCSymbolELF *Symbol, unsigned Type,
-                     uint64_t Addend, const MCSymbolELF *OriginalSymbol,
-                     uint64_t OriginalAddend)
+                     uint64_t Addend, const MCSymbolELF *OriginalSymbol)
       : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend),
-        OriginalSymbol(OriginalSymbol), OriginalAddend(OriginalAddend) {}
+        OriginalSymbol(OriginalSymbol) {}
 
   void print(raw_ostream &Out) const {
     Out << "Off=" << Offset << ", Sym=" << Symbol << ", Type=" << Type
-        << ", Addend=" << Addend << ", OriginalSymbol=" << OriginalSymbol
-        << ", OriginalAddend=" << OriginalAddend;
+        << ", Addend=" << Addend << ", OriginalSymbol=" << OriginalSymbol;
   }
 
   LLVM_DUMP_METHOD void dump() const { print(errs()); }

llvm/lib/MC/ELFObjectWriter.cpp

@@ -1393,22 +1393,17 @@ void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
   bool RelocateWithSymbol =
       shouldRelocateWithSymbol(Asm, Target, SymA, C, Type) ||
       (Parent->getType() == ELF::SHT_LLVM_CALL_GRAPH_PROFILE);
-  uint64_t Addend = 0;
-
-  FixedValue = !RelocateWithSymbol && SymA && !SymA->isUndefined()
-                   ? C + Asm.getSymbolOffset(*SymA)
-                   : C;
-  if (usesRela(TO, FixupSection)) {
-    Addend = FixedValue;
-    FixedValue = 0;
-  }
+  uint64_t Addend = !RelocateWithSymbol && SymA && !SymA->isUndefined()
+                        ? C + Asm.getSymbolOffset(*SymA)
+                        : C;
+  FixedValue = usesRela(TO, FixupSection) ? 0 : Addend;
 
   if (!RelocateWithSymbol) {
     const auto *SectionSymbol =
         SecA ? cast<MCSymbolELF>(SecA->getBeginSymbol()) : nullptr;
     if (SectionSymbol)
       SectionSymbol->setUsedInReloc();
-    ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA, C);
+    ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA);
     Relocations[&FixupSection].push_back(Rec);
     return;
   }
@@ -1423,7 +1418,7 @@ void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
     else
       RenamedSymA->setUsedInReloc();
   }
-  ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA, C);
+  ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA);
   Relocations[&FixupSection].push_back(Rec);
 }
 

llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

@@ -166,10 +166,9 @@ static FindBestPredicateResult isMatchingReloc(const MipsRelocationEntry &X,
                                                const ELFRelocationEntry &R,
                                                unsigned MatchingType) {
   if (X.R.Type == MatchingType && X.R.OriginalSymbol == R.OriginalSymbol) {
-    if (!X.Matched &&
-        X.R.OriginalAddend == R.OriginalAddend)
+    if (!X.Matched && X.R.Addend == R.Addend)
       return FindBest_PerfectMatch;
-    else if (X.R.OriginalAddend >= R.OriginalAddend)
+    else if (X.R.Addend >= R.Addend)
       return FindBest_Match;
   }
   return FindBest_NoMatch;
@@ -183,8 +182,8 @@ static FindBestPredicateResult isMatchingReloc(const MipsRelocationEntry &X,
 /// - It is not already involved in a match.
 static bool compareMatchingRelocs(const MipsRelocationEntry &Candidate,
                                   const MipsRelocationEntry &PreviousBest) {
-  if (Candidate.R.OriginalAddend != PreviousBest.R.OriginalAddend)
-    return Candidate.R.OriginalAddend < PreviousBest.R.OriginalAddend;
+  if (Candidate.R.Addend != PreviousBest.R.Addend)
+    return Candidate.R.Addend < PreviousBest.R.Addend;
   return PreviousBest.Matched && !Candidate.Matched;
 }