[llvm] Overhaul the TargetMachine and LLVMTargetMachine Classes (PR #111234)

[Matin Raayai via llvm-commits]

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@@ -256,7 +256,7 @@ struct LandingPadInfo {
 
 class LLVM_ABI MachineFunction {
   Function &F;
-  const LLVMTargetMachine &Target;
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matinraayai wrote:

I don't think there's a need anymore. I'm hoping `CodeGenCommonTMImpl` is treated as just a set of function implementation, and there won't be any hard requirement on subclassing it if you want to use the target independent code generator (CodeGen) library.

In other words, a Target can just ignore everything in `CodeGenCommonTMImpl` and start from scratch, but still use the CodeGen library.

https://github.com/llvm/llvm-project/pull/111234