Fix invalid cc_status after [const_][us]mulsi3_highpart

[Andreas Schwab]

On Jul 17 2018, Andreas Schwab <schwab@linux-m68k.org> wrote:

> The mulu.l insn sets the CC according to the 64-bit result, but we are
> only using the high part, so the Z flag cannot be used.  The other flags
> would still be valid, but we have no cc_status flag for that case.
>
> 	* config/m68k/m68k.md (umulsi3_highpart+1, const_umulsi3_highpart)
> 	(smulsi3_highpart+1, const_smulsi3_highpart): Add CC_STATUS_INIT.
>
> testsuite/:
> 	* gcc.target/m68k/mulsi_highpart.c: New test.

Backported to gcc-8 branch to fix PR target/86820.

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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