As a general "advanced assembly", what is the memory model of llvm IR？

Question

Recently, I hope to write GC for llvm. After reading about GC in llvm IR in a fragmented way, I want to know what is behind llvm IR. If you want to write a garbage collector for llvm, you should be familiar with the memory allocation of llvm. As a general "advanced assembly", what is the memory model of llvm IR and how to combine your understanding of it when writing a garbage collector, The alloca instruction, the @ malloc function and the new operator in C + + have their mapping to llvm IR with the help of clang, but I don't know the details of their memory application, so it's difficult to realize garbage collection similar to mark and tidy