Don't try to constant fold libm functions with non-finite arguments.

Usually we wouldn't do this anyway because llvm_fenv_testexcept would return an
exception, but we have seen some cases where neither errno nor fenv detect an
exception on arm-linux.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114893 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 96656a3..d3596d1 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -1094,6 +1094,13 @@
 
       if (!Ty->isFloatTy() && !Ty->isDoubleTy())
         return 0;
+
+      /// We only fold functions with finite arguments. Folding NaN and inf is
+      /// likely to be aborted with an exception anyway, and some host libms
+      /// have known errors raising exceptions.
+      if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity())
+        return 0;
+
       /// Currently APFloat versions of these functions do not exist, so we use
       /// the host native double versions.  Float versions are not called
       /// directly but for all these it is true (float)(f((double)arg)) ==