From: Michael Ellerman <mpe@ellerman.id.au>
To: "kernel test robot" <lkp@intel.com>, "Cédric Le Goater" <clg@kaod.org>
Cc: kbuild-all@lists.01.org, linux-kernel@vger.kernel.org
Subject: Re: arch/powerpc/kvm/powerpc.c:1141:7: warning: Redundant assignment of 'gpr' to itself. [selfAssignment]
Date: Sat, 26 Jun 2021 20:28:16 +1000 [thread overview]
Message-ID: <87mtrczzr3.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <202106252219.3RFYWdTc-lkp@intel.com>
kernel test robot <lkp@intel.com> writes:
> Hi Cédric,
>
> First bad commit (maybe != root cause):
>
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 44db63d1ad8d71c6932cbe007eb41f31c434d140
> commit: 9236f57a9e51c72ce426ccd2e53e123de7196a0f KVM: PPC: Make the VMX instruction emulation routines static
> date: 5 months ago
> compiler: powerpc64-linux-gcc (GCC) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
>
> cppcheck warnings: (new ones prefixed by >>)
>>> arch/powerpc/kvm/powerpc.c:1141:7: warning: Redundant assignment of 'gpr' to itself. [selfAssignment]
> gpr = sp_to_dp(gpr);
> ^
>>> arch/powerpc/kvm/powerpc.c:1341:7: warning: Redundant assignment of 'val' to itself. [selfAssignment]
> val = dp_to_sp(val);
Because of:
#ifdef CONFIG_PPC_FPU
static inline u64 sp_to_dp(u32 fprs)
{
u64 fprd;
preempt_disable();
enable_kernel_fp();
asm ("lfs%U1%X1 0,%1; stfd%U0%X0 0,%0" : "=m"UPD_CONSTR (fprd) : "m"UPD_CONSTR (fprs)
: "fr0");
preempt_enable();
return fprd;
}
static inline u32 dp_to_sp(u64 fprd)
{
u32 fprs;
preempt_disable();
enable_kernel_fp();
asm ("lfd%U1%X1 0,%1; stfs%U0%X0 0,%0" : "=m"UPD_CONSTR (fprs) : "m"UPD_CONSTR (fprd)
: "fr0");
preempt_enable();
return fprs;
}
#else
#define sp_to_dp(x) (x)
#define dp_to_sp(x) (x)
#endif /* CONFIG_PPC_FPU */
And you must be building the PPC_FPU=n case.
Surely the compiler is smart enough to generate no code for this. So
what's the harm? ie. why is this something we should be fixing?
cheers
prev parent reply other threads:[~2021-06-26 10:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-25 14:07 arch/powerpc/kvm/powerpc.c:1141:7: warning: Redundant assignment of 'gpr' to itself. [selfAssignment] kernel test robot
2021-06-26 10:28 ` Michael Ellerman [this message]
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