[polly] r255503 - Revert "Always treat scalar writes as MUST_WRITEs"

[Johannes Doerfert via llvm-commits]

On 12/14, Tobias Grosser via llvm-commits wrote:
> Author: grosser
> Date: Mon Dec 14 09:05:37 2015
> New Revision: 255503
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=255503&view=rev
> Log:
> Revert "Always treat scalar writes as MUST_WRITEs"
> 
> This reverts commit r255471.
> 
> Johannes raised in the post-commit review of r255471 the concern that PHI
> writes in non-affine regions with two exiting blocks are not really MUST_WRITE,
> but we just know that at least one out of the set of all possible PHI writes
> will be executed. Modeling all PHI nodes as MUST_WRITEs is probably save, but
> adding the needed documentation for such a special case is probably not worth
> the effort. Michael will be proposing a new patch that ensures only a single
> PHI_WRITE is created for non-affine regions, which - besides other benefits -
> should also allow us to use a single well-defined MUST_WRITE for such PHI
> writes.
I remember my concerns but I do not recall anything about a "single
PHI_WRITE". Did I miss some emails again?
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