Should invalid __RTL testcase "startwith" passes emit a warning?

Matthew Malcomson
Tue Feb 19 14:29:00 GMT 2019

Hi there,

I'd like to make handling of the __RTL function testcases where the 
startwith pass name is either invalid, not used for that optimisation 
level, or non-existant more understandable.

Currently a problem with the pass name leaves around state that causes 
the compiler to ICE on other functions.
If the pass name is invalid or one not used for the current optimisation 
level then "dfinit" is run, but "dfinish" is not, which breaks an 
assertion in the `rest_of_handle_df_finish` function.
For any of the problems the "*clean_state" pass is not run, which causes 
an ICE on the first C function in the TU.

The ICE's I've seen can be avoided by always running the "*clean_state" 
pass (including if the startwith pass of the function is not specified) 
and by always running the "dfinish" pass if the "dfinit" pass is run and 
I am working on a patch to do this.

Since the function will not emit any code for any of these problems, I 
was wondering whether to emit a -Wunused-function warning pointing to 
the bad name (or to the area where a name should be), since it's 
unlikely to be intended.
The current behaviour (apart from causing an ICE on other functions) is 
to silently do nothing.

Example for "ICE after a bad name".

foo_a ()
   return 200;

int __RTL (startwith ("badname")) foo2 ()
(function "foo2"
     (block 2
       (edge-from entry (flags "FALLTHRU"))
       (cnote 3 [bb 2] NOTE_INSN_BASIC_BLOCK)
       (cinsn 101 (set (reg:DI x19) (reg:DI x0)))
       (cinsn 10 (use (reg/i:SI x19)))
       (edge-to exit (flags "FALLTHRU"))
     ) ;; block 2
   ) ;; insn-chain
) ;; function "foo2"


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