MCValue: reduce getSymB uses

The MCValue::SymB MCSymbolRefExpr member might be replaced with a
MCSymbol in the future. Reduce direct access.

Author: MaskRay

llvm/lib/MC/MCAssembler.cpp

@@ -201,11 +201,9 @@ bool MCAssembler::evaluateFixup(const MCFixup &Fixup, const MCFragment *DF,
     if (Sym.isDefined())
       Value += getSymbolOffset(Sym);
   }
-  if (const MCSymbolRefExpr *B = Target.getSymB()) {
-    const MCSymbol &Sym = B->getSymbol();
-    if (Sym.isDefined())
-      Value -= getSymbolOffset(Sym);
-  }
+  if (const MCSymbol *Sub = Target.getSubSym())
+    if (Sub->isDefined())
+      Value -= getSymbolOffset(*Sub);
 
   bool ShouldAlignPC = FixupFlags & MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
   assert((ShouldAlignPC ? IsPCRel : true) &&

llvm/lib/MC/MCValue.cpp

@@ -9,6 +9,7 @@
 #include "llvm/MC/MCValue.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
@@ -28,9 +29,9 @@ void MCValue::print(raw_ostream &OS) const {
 
   OS << *getSymA();
 
-  if (getSymB()) {
+  if (auto *B = getSubSym()) {
     OS << " - ";
-    OS << *getSymB();
+    B->print(OS, nullptr);
   }
 
   if (getConstant())

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp

@@ -498,7 +498,8 @@ bool LoongArchAsmBackend::handleAddSubRelocations(const MCAssembler &Asm,
     llvm_unreachable("unsupported fixup size");
   }
   MCValue A = MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
-  MCValue B = MCValue::get(Target.getSymB());
+  MCValue B = MCValue::get(
+      MCSymbolRefExpr::create(Target.getSubSym(), Asm.getContext()));
   auto FA = MCFixup::create(Fixup.getOffset(), nullptr, std::get<0>(FK));
   auto FB = MCFixup::create(Fixup.getOffset(), nullptr, std::get<1>(FK));
   auto &Assembler = const_cast<MCAssembler &>(Asm);

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -2806,7 +2806,7 @@ bool RISCVAsmParser::isSymbolDiff(const MCExpr *Expr) {
   MCValue Res;
   if (Expr->evaluateAsRelocatable(Res, nullptr)) {
     return Res.getRefKind() == RISCVMCExpr::VK_None && Res.getSymA() &&
-           Res.getSymB();
+           Res.getSubSym();
   }
   return false;
 }

llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp

@@ -657,7 +657,8 @@ bool RISCVAsmBackend::handleAddSubRelocations(const MCAssembler &Asm,
     llvm_unreachable("unsupported fixup size");
   }
   MCValue A = MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
-  MCValue B = MCValue::get(Target.getSymB());
+  MCValue B = MCValue::get(
+      MCSymbolRefExpr::create(Target.getSubSym(), Asm.getContext()));
   auto FA = MCFixup::create(
       Fixup.getOffset(), nullptr,
       static_cast<MCFixupKind>(FirstLiteralRelocationKind + TA));