[Bug target/79058] [7 Regression] ARM: internal compiler error: in extract_constrain_insn, at recog.c:2213

["krebbel at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79058

--- Comment #12 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
(In reply to Dominik Vogt from comment #11)
> gccint:
> > A operand which is read by the instruction can be tied to an earlyclobber
> > operand if its only use as an input occurs before the early result is written.
> 
> Mabe it's allowed here because of the forced split?
> 
>     operands[3] = gen_lowpart (SImode, operands[0]); 
>     operands[5] = gen_highpart (SImode, operands[0]); 
>  
>     operands[4] = simplify_gen_binary (AND, SImode, 
>                                            gen_lowpart (SImode,
> operands[1]), 
>                                            gen_lowpart (SImode,
> operands[2])); 
>     operands[6] = simplify_gen_binary (AND, SImode, 
>                                            gen_highpart (SImode,
> operands[1]), 
>                                            gen_highpart_mode (SImode,
> DImode, o\
> perands[2]));

The splitter probably is the reason why the early clobber has been added.
Handling the SImode part separately requires that the source reg does not match
the target reg. Alternative 4 does not appear to be correct to me. It uses an
early clobber and a matching constraint between source and target. Reload
cannot meet both requirements. Since the alternative 4 just seems to be a
subset of alternative 5 I'm wondering if it could not just be removed?!