From: Michael Ellerman <mpe@ellerman•id.au>
To: Anshuman Khandual <khandual@linux•vnet.ibm.com>, linuxppc-dev@ozlabs•org
Cc: mikey@neuling•org, sukadev@linux•vnet.ibm.com, dja@axtens•net
Subject: Re: [4/5] powerpc/perf: Change name & type of 'pred' in power_pmu_bhrb_read
Date: Wed, 29 Jul 2015 13:25:55 +1000 (AEST) [thread overview]
Message-ID: <20150729032555.CE6CB140E41@ozlabs.org> (raw)
In-Reply-To: <1435652431-22024-5-git-send-email-khandual@linux.vnet.ibm.com>
On Tue, 2015-30-06 at 08:20:30 UTC, Anshuman Khandual wrote:
> Branch record attributes 'mispred' and 'predicted' are single bit
> fields as defined in the perf ABI. Hence the data type of the field
> 'pred' used during BHRB processing should be changed from integer
> to bool. This patch also changes the name of the variable from 'pred'
> to 'mispred' making the logical inversion process more meaningful
> and readable.
This whole function is a mess.
There's no good reason why we're doing the assignment to pred/mispred in two
places to begin with, so if that was eliminated we wouldn't need a local for
mispred to begin with.
Then there's the type juggling, all of which probably works but is fishy and
horrible.
You take a u64, bitwise and it with a mask, assign that to a boolean, then take
the boolean, *bitwise* negate that and assign the result to a single bit
bitfield.
> + bool mispred;
> + mispred = val & BHRB_PREDICTION;
> + cpuhw->bhrb_entries[u_index].predicted = ~mispred;
cheers
next prev parent reply other threads:[~2015-07-29 3:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-30 8:20 [PATCH 0/5] BHRB fixes, improvements and cleanups Anshuman Khandual
2015-06-30 8:20 ` [PATCH 1/5] powerpc/perf: Drop the branch sample when 'from' cannot be fetched Anshuman Khandual
2015-07-27 4:19 ` [1/5] " Michael Ellerman
2015-07-28 3:08 ` Anshuman Khandual
2015-09-30 9:03 ` Anshuman Khandual
2015-09-30 10:46 ` Michael Ellerman
2015-06-30 8:20 ` [PATCH 2/5] powerpc/perf: Change type of the bhrb_users variable Anshuman Khandual
2015-08-03 1:35 ` [2/5] " Michael Ellerman
2015-06-30 8:20 ` [PATCH 3/5] powerpc/perf: Replace last usage of get_cpu_var with this_cpu_ptr Anshuman Khandual
2015-07-27 5:15 ` [3/5] " Michael Ellerman
2015-07-28 3:37 ` Anshuman Khandual
2015-06-30 8:20 ` [PATCH 4/5] powerpc/perf: Change name & type of 'pred' in power_pmu_bhrb_read Anshuman Khandual
2015-07-29 3:25 ` Michael Ellerman [this message]
2015-07-29 8:13 ` [4/5] " Anshuman Khandual
2015-06-30 8:20 ` [PATCH 5/5] powerpc/perf: Re organize PMU branch filter processing on POWER8 Anshuman Khandual
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