[Bug target/84710] [8 Regression] ICE: RTL check: expected code 'reg', have 'subreg' in rhs_regno, at rtl.h:1896 with -O -fno-forward-propagate

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84710

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #8)
> Ah right, I had checking disabled.  Need more coffee I guess.

You don't really need to build the checking compiler for this though, it is
enough to put a breakpoint on that REGNO (x) line and debug_rtx (x) first.

> The insns I see are different:
> 
> Trying 19, 20 -> 21:
>    19: r106:SI#0=0
>    20: r108:SI=zero_extend(r106:SI#0)
>    21: r109:SI=r108:SI 0>>0x8
>       REG_DEAD r108:SI
> 
> (see insn 20); maybe the i3 in #c1 is already modified?

Likely, yes.  I've just done up and debug_rtx on the 3 insns passed to
try_combine.

> The #c5 patch is okay for trunk, thanks!

Thanks.