[llvm] [Instrumentor] Add comparison instrumentation opportunity (PR #204069)

[Kevin Sala Penades via llvm-commits]

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@@ -903,6 +905,42 @@ static void readValuePack(const Range &R, Value &Pack,
   }
 }
 
+template <unsigned... Opcodes>
+Value *InstructionIO<Opcodes...>::getOpcode(Value &V, Type &Ty,
+                                            InstrumentationConfig &IConf,
+                                            InstrumentorIRBuilderTy &IIRB) {
+  auto &I = cast<Instruction>(V);
+  return getCI(&Ty, I.getOpcode());
+}
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kevinsala wrote:

I just remembered `InstructionIO` is a template class, so having the template definitions in the source file will be highly problematic and will end up with undefined references. I still think it's good to have these functions within the "common" class. Two possible solutions for that:
1. Move the definition also to the header file.
2. If the previous is not possible for some reason, we can have a `InstructionBaseIO` class (non-template) and have the functions there. So the inheritance chain is: _InstrumentationOpportunity_ <- _InstructionBaseIO_ (non-template) <- _InstructionIO_ (template) <- _CompareIO_.

Makes sense?

https://github.com/llvm/llvm-project/pull/204069