Removing handlers for the cases can't generate

Since I do not know the code that can be written to trigger these cases,
it is safer to not blindly optimize them (instead they will fall through
to the old case of all matching functions). It still matches all the
cases outlined in the regressions folder.

Author: thk123

regression/goto-analyzer/fp-removal17/main.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func()
+{
+  // There isn't an obvious reason to write this code, but perhaps some
+  // code can get transformed into this so we should still handle it.
+  (*(&f2))();
+}
+
+void main()
+{
+  func();
+}

regression/goto-analyzer/fp-removal17/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*f2();
+--
+^warning: ignoring

src/goto-programs/remove_function_pointers.cpp

@@ -698,17 +698,14 @@ void remove_function_pointerst::remove_function_pointer(
 
   const exprt &pointer=function.op0();
 
-  exprt precise_call;
   functionst functions;
   bool found_functions=false;
-  if(try_get_precise_call(pointer, precise_call))
-  {
-    to_code_function_call(target->code).function()=precise_call;
-    return;
-  }
 
   const c_qualifierst pointer_qualifers(pointer.type());
 
+  // This can happen for example with
+  // (*(&f2))();
+  // In this case we don't need constant check - implict
   found_functions=found_functions||try_get_from_address_of(pointer, functions);
 
   // If it is a symbol (except in the case where the symbol is the function
@@ -719,8 +716,6 @@ void remove_function_pointerst::remove_function_pointer(
       found_functions||try_get_call_from_symbol(pointer, functions);
   }
 
-  found_functions=found_functions||try_get_call_from_index(pointer, functions);
-
   if(functions.size()==1)
   {
     to_code_function_call(target->code).function()=functions.front();