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

[Corentin Jabot via llvm-commits]

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@@ -5601,6 +5606,35 @@ float APFloat::convertToFloat() const {
   return Temp.getIEEE().convertToFloat();
 }
 
+#ifdef LLVM_INTEGRATE_LIBC
+APFloat exp(const APFloat &X, RoundingMode rounding_mode) {
+  assert((&X.getSemantics() == (const llvm::fltSemantics *)&semIEEEsingle) &&
+         "Float semantics is not IEEEsingle");
+  if (&X.getSemantics() == (const llvm::fltSemantics *)&semIEEEsingle) {
+    int current_rounding_mode = fegetround();
+    switch (rounding_mode) {
+    case APFloat::rmNearestTiesToEven:
+      fesetround(FE_TONEAREST);
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cor3ntin wrote:

I think the suggestion is to do `LIBC_NAMESPACE::shared::expf(X.convertToFloat(), rounding_mode)` and not mess with global state. It would be _much_ cleaner if that were possible

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