[llvm] [NewPM][CodeGen] add TargetPassConfig like API (PR #70906)

[Arthur Eubanks via llvm-commits]

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@@ -17,6 +17,51 @@
 
 using namespace llvm;
 
+namespace {
+
+/// RAII class to replace addMachinePrePasses/addMachinePostPasses
+/// If we need more complex logics, consider add class like
+/// CodeGenInstrumentation
+// TODO: skip FreeMachineFunctionPass and AsmPrinter
+class PrePostPasses {
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aeubanks wrote:

shouldn't this something that goes into `PIC`, rather than a separate RAII class? a random
```
PrePostPasses Hook(...);
```
in the code below goes against the entire purpose of pass instrumentation

https://github.com/llvm/llvm-project/pull/70906