From: Segher Boessenkool <segher@kernel.crashing.org>
To: Sandipan Das <sandipan@linux.ibm.com>
Cc: mpe@ellerman.id.au, paulus@samba.org,
naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
anton@samba.org, ravi.bangoria@linux.ibm.com
Subject: Re: [PATCH 6/6] powerpc sstep: Add modsd, modud instruction emulation
Date: Tue, 4 Sep 2018 16:21:09 -0500 [thread overview]
Message-ID: <20180904212109.GP24439@gate.crashing.org> (raw)
In-Reply-To: <15e572f61bb5c74b01210b9245ce2750a31d6002.1535609090.git.sandipan@linux.ibm.com>
On Mon, Sep 03, 2018 at 08:49:38PM +0530, Sandipan Das wrote:
> +#ifdef __powerpc64__
> + case 265: /* modud */
> + if (!cpu_has_feature(CPU_FTR_ARCH_300))
> + return -1;
> + op->val = regs->gpr[ra] % regs->gpr[rb];
> + goto compute_done;
> +#endif
The mod instruction has special cases that aren't handled by this C code,
too (divide by 0, or signed division of the most negative number by -1).
For the mod intruction the behaviour is undefined in those cases, but you
probably should force some specific behaviour. You don't want the kernel
to execute a trap instruction, etc. :-)
Segher
next prev parent reply other threads:[~2018-09-04 21:22 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
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 [this message]
2018-09-05 11:53 ` Sandipan Das
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