[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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@@ -8356,4 +8356,23 @@ TEST(APFloatTest, hasSignBitInMSB) {
   EXPECT_FALSE(APFloat::hasSignBitInMSB(APFloat::Float8E8M0FNU()));
 }
 
+#ifdef LLVM_INTEGRATE_LIBC
+TEST(APFloatTest, expf) {
+  EXPECT_EQ(
+      1.0f,
+      llvm::exp(APFloat(0.0f), APFloat::rmNearestTiesToEven).convertToFloat());
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arsenm wrote:

Compare bit-equal? Can you also test the edge case values, nan, inf, denormals, -0 

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