llvm-project

35b38863 - [win/arm64] Enable tail call with inreg arguments when possible (#134671)

[win/arm64] Enable tail call with inreg arguments when possible (#134671) Tail calls were disabled from callers with inreg parameters in 5dc8aeb with a fixme to check if the callee also takes an inreg parameter. The issue is that inreg parameters (which are passed in x0 or x1 for free and member functions respectively) are supposed to be returned (in x0) at the end of the function. In case of a tail call, that means the callee needs to return the same value as the caller would. We can check for that case, and it's not as niche as it sounds, as that's how Clang will lower one function with an sret return value calling another, such as: ``` struct T { int x; }; struct S { T foo(); T bar(); }; T S::foo() { return bar(); } // foo's sret argument will get passed directly to bar ``` Fixes #133098