[llvm-commits] [llvm] r162868 - /llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

[Alastair Murray]

Hi Andrew, Michael,

I believe this change (r162868) introduced an incorrect assert.

Please see the attached one line patch to remove it and associated test 
case (fails on svn trunk, passes with the assert removed).  I do not 
have commit access, so if the patch is okay then please commit it.

This assert trigger on 13 benchmarks in projects/test-suite when 
compiling with profiling data.

The test case was created by first letting bugpoint reduce a version of 
MultiSource/Applications/SPASS/SPASS which had branch weight metadata 
set by -profile-metadata-loader.  Then I further reduced it by hand 
(without a working simplifycfg bugpoint was limited).

I think the key to triggering the assert is to have partial weight 
metadata.  If the second branch in the test case is given metadata (even 
all 0 weights) then the assert does not trigger.  The metadata is 
missing due to an earlier pass not preserving it, but that is valid 
behaviour (though sub-optimal).

Regards,
Alastair.

On 29/08/12 17:46, Andrew Trick wrote:
> Author: atrick
> Date: Wed Aug 29 16:46:38 2012
> New Revision: 162868
>
> URL: http://llvm.org/viewvc/llvm-project?rev=162868&view=rev
> Log:
> Preserve branch profile metadata during switch formation.
>
> Patch by Michael Ilseman!
> This fixes SimplifyCFGOpt::FoldValueComparisonIntoPredecessors to preserve metata when folding conditional branches into switches.
 > *snip*

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