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

[Nikita Popov via llvm-commits]

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@@ -109,6 +109,18 @@ static constexpr float expf(float x) {
   return static_cast<float>(exp_hi * exp_mid * exp_lo);
 }
 
+// Directional rounding version of expf.
+LIBC_INLINE static float expf(float x, int rounding_mode) {
+  int current_rounding_mode = fputil::get_round();
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nikic wrote:

I'm kind of surprised that setting the rounding mode for a foo() implementation results in a foo() result with the correct rounding mode. Are the transcendental functions in libc specifically implemented in a way that satisfies that property?

Can you point me to where libc is testing these functions in different rounding modes?

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