Extended Description

It is common in C++ code to end up with an invoke whose unwind destination just does the C++ equivalent of an unwind. This should be turned into a call, saving on code size and speeding up unwinding. For example, here is a testcase:

#include
int f() {
std::string s("hola");
return s.length();
}

This compiles to:

...
invoke void @​_ZNSsC1EPKcRKSaIcE(...)
to label %bb69 unwind label %lpad
...
%tmp116 = invoke i32 @​_ZN9__gnu_cxx18__exchange_and_addEPVii( i32*
%tmp114, i32 -1 )
to label %invcont115 unwind label %lpad148
...
pad: ; preds = %entry
%eh_ptr = call i8* @​llvm.eh.exception( ) ; <i8*> [#uses=2]
%eh_select147 = call i32 (i8*, i8*, ...)* @​llvm.eh.selector.i32( i8*
%eh_ptr, i8* bitcast (i32 (...)* @​__gxx_personality_v0 to i8*), i8* null )
br label %Unwind

lpad148: ; preds = %bb111
%eh_ptr149 = call i8* @​llvm.eh.exception( ) ; <i8*> [#uses=2]
%eh_select151 = call i32 (i8*, i8*, ...)* @​llvm.eh.selector.i32( i8*
%eh_ptr149, i8* bitcast (i32 (...)* @​__gxx_personality_v0 to i8*), i8* null )
br label %Unwind

Unwind: ; preds = %lpad148, %lpad
%eh_exception.0 = phi i8* [ %eh_ptr, %lpad ], [ %eh_ptr149, %lpad148 ]
call i32 (...)* @​_Unwind_Resume_or_Rethrow( i8* %eh_exception.0 )
unreachable

Both of these invokes can be turned into (throwing) call instructions, saving code size and reducing compile time.

-Chris