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Date: Mon, 19 Oct 2020 16:20:37 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Henri Cloetens <henri.cloetens@blueice.be>
Cc: gcc-help@gcc.gnu.org
Subject: Re: Issue during combine.
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On Mon, Oct 19, 2020 at 09:56:04PM +0200, Henri Cloetens wrote:
> - However, during the "checking", the combiner calls "simplify_subreg" 
> in simplify-rtx.c.
> - There, it crashes on "/gcc_assert(innermode != VOIDmode)/.

Because that is invalid RTL.

> /(insn 2354 2352 1743 175 (set (reg/v:SI 197 [ dig ])//
> //        (if_then_else (eq (subreg:QI (reg:SI 632) 1)//
> //                (const_int 1 [0x1]))//
> //            (reg:SI 708)//
> //            (reg/v:SI 197 [ dig ]))) 

This is incorrect already (should be if_then_else:SI).  It could have
crashed earlier...  You can configure with "--enable-checking=yes,rtl"
to find many such problems (default is just "yes", see the manual for
other things you can ask to be checked ("tree" is useful; some others
are very very slow)).

HtH,


Segher