[llvm-commits] [llvm] r167942 - /llvm/trunk/lib/Transforms/Vectorize/BBVectorize.cpp

[Chandler Carruth]

On Wed, Nov 14, 2012 at 1:29 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> ----- Original Message -----
>> From: "Chandler Carruth" <chandlerc at google.com>
>> To: "Hal Finkel" <hfinkel at anl.gov>
>> Cc: "Commit Messages and Patches for LLVM" <llvm-commits at cs.uiuc.edu>
>> Sent: Wednesday, November 14, 2012 3:20:21 PM
>> Subject: Re: [llvm-commits] [llvm] r167942 - /llvm/trunk/lib/Transforms/Vectorize/BBVectorize.cpp
>>
>> On Wed, Nov 14, 2012 at 10:38 AM, Hal Finkel <hfinkel at anl.gov> wrote:
>> > Author: hfinkel
>> > Date: Wed Nov 14 12:38:11 2012
>> > New Revision: 167942
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=167942&view=rev
>> > Log:
>> > Fix the largest offender of determinism in BBVectorize
>> >
>> > Iterating over the children of each node in the potential
>> > vectorization
>> > plan must happen in a deterministic order (because it affects which
>> > children
>> > are erased when two children conflict). There was no need for this
>> > data
>> > structure to be a map in the first place, so replacing it with a
>> > vector
>> > is a small change.
>> >
>> > I believe that this was the last remaining instance if iterating
>> > over the
>> > elements of a Dense* container where the iteration order could
>> > matter.
>> > There are some remaining iterations over std::*map containers where
>> > the order
>> > might matter, but so long as the Value* for instructions in a block
>> > increase
>> > with the order of the instructions in the block (or decrease)
>> > monotonically,
>> > then this will appear to be deterministic.
>>
>> Pointers should not be assumed to be deterministically ordered. Any
>> ordering which is based on the numerical sort of addresses is a
>> non-determinism bug.
>
> Agreed. As I said to Sean just a few minutes ago:

Sorry, wasn't aware that replaced the Value* ordering issue. =] Sorry
for the noise!