[MC] Check RelaxFixupKind instead of hard coding RISC-V/LoongArch

Author: MaskRay

llvm/include/llvm/MC/MCAsmBackend.h

@@ -50,8 +50,10 @@ class MCAsmBackend {
 
   const llvm::endianness Endian;
 
-  /// Fixup kind used for linker relaxation. Currently only used by RISC-V.
+  /// Fixup kind used for linker relaxation. Currently only used by RISC-V
+  /// and LoongArch.
   const unsigned RelaxFixupKind;
+  bool allowLinkerRelaxation() const { return RelaxFixupKind != MaxFixupKind; }
 
   /// Return true if this target might automatically pad instructions and thus
   /// need to emit padding enable/disable directives around sensative code.

llvm/lib/MC/MCExpr.cpp

@@ -627,8 +627,7 @@ static void AttemptToFoldSymbolOffsetDifference(
   // .size/.fill), disable the fast path.
   bool Layout = Asm->hasLayout();
   if (Layout && (InSet || !SecA.hasInstructions() ||
-                 !(Asm->getContext().getTargetTriple().isRISCV() ||
-                   Asm->getContext().getTargetTriple().isLoongArch()))) {
+                 !Asm->getBackend().allowLinkerRelaxation())) {
     // If both symbols are in the same fragment, return the difference of their
     // offsets. canGetFragmentOffset(FA) may be false.
     if (FA == FB && !SA.isVariable() && !SB.isVariable()) {