[SimplifyLibCalls] Don't depend on a called function having a name, it might be an indirect call.

Fixes the crasher in PR25651 and related crashers using the same pattern.

llvm-svn: 254145
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 8e0481d..da85252 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1112,14 +1112,12 @@
       B.SetFastMathFlags(FMF);
 
       LibFunc::Func Func;
-      Function *Callee = OpC->getCalledFunction();
-      StringRef FuncName = Callee->getName();
-
-      if (TLI->getLibFunc(FuncName, Func) && TLI->has(Func) &&
-          (Func == LibFunc::exp || Func == LibFunc::exp2))
+      Function *OpCCallee = OpC->getCalledFunction();
+      if (OpCCallee && TLI->getLibFunc(OpCCallee->getName(), Func) &&
+          TLI->has(Func) && (Func == LibFunc::exp || Func == LibFunc::exp2))
         return EmitUnaryFloatFnCall(
-            B.CreateFMul(OpC->getArgOperand(0), Op2, "mul"), FuncName, B,
-            Callee->getAttributes());
+            B.CreateFMul(OpC->getArgOperand(0), Op2, "mul"),
+            OpCCallee->getName(), B, OpCCallee->getAttributes());
     }
   }
 
@@ -1382,8 +1380,7 @@
   // tanl(atanl(x)) -> x
   LibFunc::Func Func;
   Function *F = OpC->getCalledFunction();
-  StringRef FuncName = F->getName();
-  if (TLI->getLibFunc(FuncName, Func) && TLI->has(Func) &&
+  if (F && TLI->getLibFunc(F->getName(), Func) && TLI->has(Func) &&
       ((Func == LibFunc::atan && Callee->getName() == "tan") ||
        (Func == LibFunc::atanf && Callee->getName() == "tanf") ||
        (Func == LibFunc::atanl && Callee->getName() == "tanl")))
@@ -1458,9 +1455,9 @@
     return;
 
   Function *Callee = CI->getCalledFunction();
-  StringRef FuncName = Callee->getName();
   LibFunc::Func Func;
-  if (!TLI->getLibFunc(FuncName, Func) || !TLI->has(Func) || !isTrigLibCall(CI))
+  if (Callee && (!TLI->getLibFunc(Callee->getName(), Func) || !TLI->has(Func) ||
+                 !isTrigLibCall(CI)))
     return;
 
   if (IsFloat) {