[clang] [llvm] [CIR][CUDA] Introduce cu.var_registration for shadow and attach device-side var metadata, internalize device side variables, and lower poison attribute (PR #190087)

[Akimasa Watanuki via cfe-commits]

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@@ -20,6 +20,25 @@
 using namespace clang;
 using namespace CIRGen;
 
+static std::unique_ptr<MangleContext> initDeviceMC(CIRGenModule &cgm) {
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Men-cotton wrote:

If we keep `deviceMC` in `CIRGenNVCUDARuntime` instead of the base class, the changes in `CIRGenCUDARuntime.cpp` seem unnecessary.

https://github.com/llvm/llvm-project/pull/190087