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Date: Thu, 10 Mar 2005 17:31:00 -0000
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From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/20408] Unnecessary code generated for empty structs
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------- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-10 17:30 -------
(In reply to comment #10)
> I think we should produce an empty CONSTRUCTOR (which I am testing right now).
That did not fix it, we still get code generated for the "empty" struct:
;; D.1594 = {}
(nil)

;; foo (D.1594) [tail call]
(insn 10 8 11 (set (mem:QI (reg/f:SI 56 virtual-outgoing-args) [0 S1 A32])
        (reg:QI 58 [ D.1594 ])) -1 (nil)
    (nil))

(call_insn 11 10 0 (call (mem:QI (symbol_ref:SI ("_Z3foo1X") [flags 0x41] <function_decl 0x41e9ea6c 
foo>) [0 S1 A8])
        (const_int 4 [0x4])) -1 (nil)
    (nil)
    (nil))


But on PPC we get:
;; D.1588 = {}
(nil)

;; foo (D.1588) [tail call]
(insn 10 8 11 0 (set (reg:QI 3 r3)
        (reg:QI 118 [ D.1588 ])) -1 (nil)
    (nil))

(call_insn/j 11 10 12 0 (parallel [
            (call (mem:SI (symbol_ref:SI ("_Z3foo1X") [flags 0x41] <function_decl 0x41d9f984 foo>) [0 S4 
A8])
                (const_int 32 [0x20]))
            (use (const_int 0 [0x0]))
            (use (reg:SI 119))
            (return)
        ]) -1 (nil)
    (nil)
    (expr_list:REG_DEP_TRUE (use (reg:QI 3 r3))
        (nil)))


See the difference is that we pass on ppc via a register but on x86 we pass via the stack.  I don't know a 
way to fix this with a front-end change.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |middle-end


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20408