We can perform CSE on recipes that do not directly map to Instruction
opcodes. One example is VPVectorPointerRecipe. Currently this is handled
by supporting them in ::canHandle, but currently that means that we
return std::nullopt from getOpcodeOrIntrinsicID() for it. This currently
only works, because the only case we return std::nullopt and perform CSE
is VPVectorPointerRecipe. But that does not work if we support more such
recipes, like VPPredInstPHIRecipe
(https://github.com/llvm/llvm-project/pull/162110).
To fix this, return a custom opcode from getOpcodeOrIntrinsicID for
recipes like VPVectorPointerRecipe, using the VPDefID after all regular
instruction opcodes.
PR: https://github.com/llvm/llvm-project/pull/162267
9bb0eedb59