[clang][SPIR][SPIRV] Materialize non-generic null pointers via addrspacecast#161773

wenju-he merged 3 commits intollvm:mainllvm/llvm-project:mainfrom

wenju-he:CommonSPIRTargetCodeGenInfo-getNullPointerwenju-he/llvm-project:CommonSPIRTargetCodeGenInfo-getNullPointerCopy head branch name to clipboard