From: Paul Mackerras <paulus@ozlabs.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Sandipan Das <sandipan@linux.ibm.com>,
mpe@ellerman.id.au, naveen.n.rao@linux.vnet.ibm.com,
linuxppc-dev@lists.ozlabs.org, anton@samba.org,
ravi.bangoria@linux.ibm.com
Subject: Re: [PATCH 3/6] powerpc sstep: Add cnttzw, cnttzd instruction emulation
Date: Wed, 5 Sep 2018 16:36:33 +1000 [thread overview]
Message-ID: <20180905063633.GA10965@fergus> (raw)
In-Reply-To: <20180904211207.GO24439@gate.crashing.org>
On Tue, Sep 04, 2018 at 04:12:07PM -0500, Segher Boessenkool wrote:
> On Mon, Sep 03, 2018 at 08:49:35PM +0530, Sandipan Das wrote:
> > + case 538: /* cnttzw */
> > + if (!cpu_has_feature(CPU_FTR_ARCH_300))
> > + return -1;
> > + val = (unsigned int) regs->gpr[rd];
> > + op->val = ( val ? __builtin_ctz(val) : 32 );
> > + goto logical_done;
> > +#ifdef __powerpc64__
> > + case 570: /* cnttzd */
> > + if (!cpu_has_feature(CPU_FTR_ARCH_300))
> > + return -1;
> > + val = regs->gpr[rd];
> > + op->val = ( val ? __builtin_ctzl(val) : 64 );
> > + goto logical_done;
>
> __builtin_ctz(val) is undefined for val == 0.
Which would be why he only calls it when val != 0, presumably, and
uses 64 when val == 0. Apart from idiosyncratic whitespace his code
looks correct to me.
Are you saying there is a bug in his code, or that his patch
description is incomplete, or what?
Paul.
next prev parent reply other threads:[~2018-09-05 6:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-03 15:19 [PATCH 0/6] powerpc sstep: Extend instruction emulation support Sandipan Das
2018-09-03 15:19 ` [PATCH 1/6] powerpc sstep: Add maddhd, maddhdu, maddld instruction emulation Sandipan Das
2018-09-04 22:12 ` Segher Boessenkool
2018-09-05 11:30 ` Sandipan Das
2019-02-20 0:51 ` Michael Ellerman
2018-09-03 15:19 ` [PATCH 2/6] powerpc sstep: Add darn " Sandipan Das
2019-02-20 0:50 ` Michael Ellerman
2019-02-20 9:49 ` Sandipan Das
2018-09-03 15:19 ` [PATCH 3/6] powerpc sstep: Add cnttzw, cnttzd " Sandipan Das
2018-09-04 21:12 ` Segher Boessenkool
2018-09-05 6:36 ` Paul Mackerras [this message]
2018-09-03 15:19 ` [PATCH 4/6] powerpc sstep: Add extswsli " Sandipan Das
2018-09-03 15:19 ` [PATCH 5/6] powerpc sstep: Add modsw, moduw " Sandipan Das
2018-09-03 15:19 ` [PATCH 6/6] powerpc sstep: Add modsd, modud " Sandipan Das
2018-09-04 21:21 ` Segher Boessenkool
2018-09-05 11:53 ` Sandipan Das
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