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Subject: [Bug target/54602] [SH] Register pop insn not put in rts delay slot
Date: Tue, 09 Oct 2012 22:52:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54602

Oleg Endo <olegendo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-10-09
     Ever Confirmed|0                           |1

--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-10-09 22:52:19 UTC ---
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 ....