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

[Matt Arsenault via llvm-commits]

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@@ -379,3 +379,9 @@ if(LLVM_WITH_Z3)
     ${Z3_INCLUDE_DIR}
     )
 endif()
+
+if(LLVM_INTEGRATE_LIBC)
+  set_property(TARGET LLVMSupport PROPERTY CXX_STANDARD 17)
+  target_include_directories(LLVMSupport PRIVATE "${LLVM_INCLUDE_DIR}/../../libc")
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arsenm wrote:

It's ugly but maybe we can have these return std::optional and just fail out if the support wasn't built? 

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