[llvm] [llvm] Improve TLI for Darwin libsystem_m functions (PR #109479)

[Tex Riddell via llvm-commits]

================
@@ -0,0 +1,43 @@
+; RUN: opt -vector-library=Darwin_libsystem_m -passes=inject-tli-mappings,loop-vectorize -S < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
----------------
tex3d wrote:

@jroelofs 
I'm ready to update my PR with the atan2 additions from here, if that's what you'd prefer (I have them tested and ready to push).  It will introduce a conflict if one merges first from the change in `hasOptimizedCodeGen`, but it should be easy to resolve.

If you'd like me to do that, you can revert those changes from this PR, but I'm still curious about what tests the impact of the `hasOptimizedCodeGen` changes in this PR.

https://github.com/llvm/llvm-project/pull/109479