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From: Prakhar Bahuguna <prakhar.bahuguna@arm.com>
To: <richard.sandiford@linaro.org>
Cc: <gcc-patches@gcc.gnu.org>, <nd@arm.com>
Subject: Re: [PATCH, GCC/ARM/gcc-7-branch] Backport PR71607
Date: Wed, 31 May 2017 15:40:00 -0000	[thread overview]
Message-ID: <20170531153845.b23jxwtbrovcxje7@e107464-lin.cambridge.arm.com> (raw)
In-Reply-To: <87fuflmar4.fsf@linaro.org>

On 31/05/2017 14:11:43, Richard Sandiford wrote:
> Prakhar Bahuguna <prakhar.bahuguna@arm.com> writes:
> > On 31/05/2017 09:19:40, Richard Sandiford wrote:
> >> const_ints are supposed to be stored in sign-extended form, so a 32-bit
> >> integer with the MSB set should be 0xffffffff80000000|x instead of
> >> 0x80000000|x.  It's a bug if you have one where that isn't true.
> >> 
> >> In the patch it looks like this could come from:
> >> ...these two splits, where the GEN_INTs should probably be:
> >> 
> >>   gen_int_mode (..., SImode);
> >> 
> >> instead.
> >
> > Hi Richard, thanks for the tip. Is there a test case that could produce an
> > incorrect result? I've attempted to create one using negative doubles and
> > floats but haven't succeeded.
> 
> Just to check, are you testing with --enable-checking=yes,rtl?
> 
> When the values you tried were split, did you get the sign-extended form
> or the zero-extended form?
> 
> Thanks,
> Richard

I've now rebuilt with --enable-checking=yes,rtl and it appears that the split
values are being correctly sign-extended in the rtl and appear correctly in the
assembly.

However, if you believe it is safer to use gen_int_mode(), I'll respin the
patch accordingly.

-- 

Prakhar Bahuguna

  reply	other threads:[~2017-05-31 15:38 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-25 14:02 Prakhar Bahuguna
2017-05-31  8:25 ` Richard Sandiford
2017-05-31 13:11   ` Prakhar Bahuguna
2017-05-31 13:20     ` Richard Sandiford
2017-05-31 15:40       ` Prakhar Bahuguna [this message]
2017-06-01  6:16         ` Richard Sandiford
2017-06-01 10:21           ` Prakhar Bahuguna

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