[TLI] Handle cabs without parameters gracefully

Check that the function has at least one parameter before trying
to access its type.

Fixes llvm#148770.

Author: nikic

llvm/lib/Analysis/TargetLibraryInfo.cpp

@@ -1122,7 +1122,7 @@ bool TargetLibraryInfoImpl::isValidProtoForLibFunc(const FunctionType &FTy,
   case LibFunc_cabsf:
   case LibFunc_cabsl: {
     Type *RetTy = FTy.getReturnType();
-    if (!RetTy->isFloatingPointTy())
+    if (!RetTy->isFloatingPointTy() || NumParams == 0)
       return false;
 
     Type *ParamTy = FTy.getParamType(0);

llvm/test/Transforms/InferFunctionAttrs/no-proto.ll

@@ -977,3 +977,6 @@ declare void @vsscanf(...)
 
 ; CHECK: declare void @write(...)
 declare void @write(...)
+
+; CHECK: declare double @cabs(...)
+declare double @cabs(...)