Dwarf Exception Handling question

[Walter Bright via Digitalmars-d]

I'm struggling to understand dwarf EH, and figure it's a good idea to try and 
make it binary compatible with what gdc does, or at least not gratuitously 
different. If I use gdc to compile this:

void foo1() {
         abc();
         try {
                 def();
         }
         catch(DD t) {
                 ghi(t);
         }
         catch(CC t) {
                 ghi(t);
         }
         catch {
                 mno();
         }
         jkl();
}

the code generated looks like this:

_D3eh54foo1FZv:
                 push    RBP
                 mov     RBP,RSP
                 sub     RSP,010h
                 call      abc
                 call      def
L12:            call      jkl
                 jmp short       L86
                 cmp     RDX,2
                 je      L59
                 cmp     RDX,3
                 je      L7F
                 cmp     RDX,1
                 je      L33
                 mov     RDI,RAX
                 call    _Unwind_Resume
L33:            sub     RAX,8
                 mov     RAX,[RAX]
                 mov     ESI,offset _D3eh52DD7__ClassZ
                 mov     RDI,RAX
                 call    _d_dynamic_cast
                 mov     -8[RBP],RAX
                 mov     RAX,-8[RBP]
                 mov     RDI,RAX
                 call      ghi
                 jmp short       L12
L59:            sub     RAX,8
                 mov     RAX,[RAX]
                 mov     ESI,offset _D3eh52CC7__ClassZ
                 mov     RDI,RAX
                 call    _d_dynamic_cast
                 mov     -010h[RBP],RAX
                 mov     RAX,-010h[RBP]
                 mov     RDI,RAX
                 call      ghi
                 jmp short       L12
L7F:            call      mno
                 jmp short       L12
L86:            leave
                 ret

The calls to _d_dynamic cast appear to be redundant - shouldn't the value in RDX 
be sufficient? And why is there a 'default' call to _Unwind_Resume if RDX isn't 
an expected value? Shouldn't the personality routine simply not jump to the 
landing pad if none of the catch types are satisfied?