virtual-incoming-args meaning

[Henri-Pierre CHARLES <Henri-Pierre dot Charles at prism dot uvsq dot fr>]

Hello,
In the process to port gcc, we have a problem. We have write a first version 
of the md file, build gcc and cc1, try it. Gcc crash just after the rtl  
generation when we want to compile this small function vide.c:

void add ()
{
}

with gcc -da we only get the vide.c.00.rtl :
;; Function add
(note 2 0 3 NOTE_INSN_DELETED 0)
(insn 3 2 4 (set (reg:SI 133)
        (reg/f:SI 128 virtual-incoming-args)) -1 (nil)
    (nil))
(note 4 3 6 NOTE_INSN_FUNCTION_BEG 0)
(note 6 4 8 NOTE_INSN_FUNCTION_END 0)
(code_label 8 6 0 2 "" "" [0 uses])

We certainly have a problem in the md file. 
What is the meaning of virtual-incoming-args ?

Thank

H-P

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