[llvm] MC: Store MCRelaxableFragment MCInst out-of-line (PR #147229)

[Fangrui Song via llvm-commits]

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@@ -431,16 +428,38 @@ class MCDataFragment : public MCEncodedFragment {
 ///
 class MCRelaxableFragment : public MCEncodedFragment {
   /// The instruction this is a fragment for.
-  MCInst Inst;
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MaskRay wrote:

MCInst::setFlags is only called by X86 (mostly disassembly, the MCInstLower uses don't use MCRelaxableFragment) and SPIRV (not using MCRelaxableFragment). Added an assert (Inst.getFlags()==0).

https://github.com/llvm/llvm-project/pull/147229