llvm-project

47d74ca1 - [FuncAttrs][LTO] Relax norecurse attribute inference during postlink LTO (#158608)

[FuncAttrs][LTO] Relax norecurse attribute inference during postlink LTO (#158608) This PR, which supersedes https://github.com/llvm/llvm-project/pull/139943, extends the scenarios where the 'norecurse' attribute can be inferred. Currently, the 'norecurse' attribute is only inferred if all called functions also have this attribute. This change introduces a new pass in the LTO pipeline, run after Whole Program Devirtualization, to broaden the inference criteria. The new pass inspects all functions in the module and sets a flag if any functions are external or have their addresses taken (while ignoring those already marked norecurse). This flag is then used with the existing conditions to enable inference in more cases. This enhancement allows 'norecurse' to be applied in situations where a function calls a recursive function, but is not part of the same recursion chain. For example, foo can now be marked 'norecurse' in the following scenarios: `foo -> callee1 -> callee2 -> callee2` In this case, foo and callee1 can both be marked 'norecurse' because they're not part of the callee2 recursion. Similarly, foo can be marked 'norecurse' here: `foo -> callee1 -> callee2 -> callee1` Here, foo is not part of the callee1 -> callee2 -> callee1 recursion chain, so it can be marked 'norecurse'.