[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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@@ -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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arsenm wrote:

We're not compiling LLVM with strictfp (which also barely works, on one target). Can we instead just call a fixed rounding mode implementation in libc? 

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