[libc] [llvm] [APFloat] Add exp function for APFloat::IEEESsingle using expf implementation from LLVM libc. (PR #143959)

[via llvm-commits]

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@@ -644,6 +644,17 @@ endif()
 
 set(LLVM_ENABLE_Z3_SOLVER_DEFAULT "${Z3_FOUND}")
 
+set(LLVM_INTEGRATE_LIBC "OFF" CACHE STRING "Use LLVM libc code directly if available.")
+
+if(LLVM_INTEGRATE_LIBC)
+  message(STATUS "LLVM_INTEGRATE_LIBC is ${LLVM_INTEGRATE_LIBC}")
+  include(FindLibcCommonUtils)
+  if(NOT TARGET llvm-libc-common-utilities)
+    message(STATUS "LLVM_INTEGRATE_LIBC is set but cannot find LLVM libc at ${libc_path}.")
+    set(LLVM_INTEGRATE_LIBC OFF)
+  endif()
+endif()
+
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lntue wrote:

It is actually much simpler if we make it required dependency and I'd be happy to update the PR if everyone is ok with that.  And if so, I think we could wait until after LLVM 21 cutoff, beginning of LLVM 22 for merging?  WDYT? @cor3ntin @nikic @jcranmer-intel 

https://github.com/llvm/llvm-project/pull/143959