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Subject: [Bug target/54602] [SH] Register pop insn not put in rts delay slot
Date: Tue, 09 Oct 2012 22:58:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54602

--- Comment #2 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-10-09 22:57:40 UTC ---
(In reply to comment #1)
> The problem is the "*movsi_pop" insn.  It prevents delay-slot stuffing of pop
> insns on everything < SH3.  This was probably added to avoid pop insns in
> interrupt handler functions, which return with 'rte' instead of 'rts', see PR
> 53689.
> Adding "&& current_function_interrupt" to the condition of the "*movsi_pop"
> insn fixes the problem, while maintaining correct code for interrupt handler
> functions.
> 
> There is also the following in sh.md:
> 
> (define_delay
>   (eq_attr "type" "return")
>   [(and (eq_attr "in_delay_slot" "yes")
>     (ior (and (eq_attr "interrupt_function" "no")
>           (eq_attr "type" "!pload,prset"))
>          (and (eq_attr "interrupt_function" "yes")
>           (ior
>            (not (match_test "TARGET_SH3"))
>            (eq_attr "hit_stack" "no")
>            (eq_attr "banked" "no"))))) (nil) (nil)])
> 
> which should actually prevent normal movsi pop insn from slipping into the
> delay slot.  I've tapped the "hit_stack" test and it is not invoked for
> interrupt functions for some reason ....

... because this define_delay applies for return insns, not for mem loads. 
D'uh. :T