[PATCH] Allow blocks to be merged when one has an undef input to a phi.

[Evan Cheng]

Hi Mark,

The revised patch seems fine to me. Have you test against the LLVM test suite and / or a clang self-hosting build?

Thanks,

Evan

On Jun 17, 2013, at 10:41 AM, Mark Lacey <mark.lacey at apple.com> wrote:

> Hi All,
> 
> This is a relatively small patch I re-submitted last week which seems to have gotten lost in the shuffle. 
> 
> Can someone take a look and commit if everything looks good?
> 
> Thanks,
> 
> Mark
> 
> 
> TryToSimplifyUncondBranchFromEmptyBlock was checking that any common
> predecessors of the two blocks it is attempting to merge supply the
> same incoming values to any phi in the successor block. This change
> allows merging in the case where there is one or more incoming values
> that are undef. The undef values are rewritten to match the non-undef
> value that flows from the other edge.
> 
> Merged the tests from
> - test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll
> into
> - test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll
> and also added tests to this file for the situation addressed by this
> patch.
> 
> <rdar://problem/12801861>
> ---
> lib/Transforms/Utils/Local.cpp                     |  76 ++++++-
> .../SimplifyCFG/2008-05-16-PHIBlockMerge.ll        | 131 -----------
> .../SimplifyCFG/EqualPHIEdgeBlockMerge.ll          | 240 ++++++++++++++++++++-
> 3 files changed, 307 insertions(+), 140 deletions(-)
> delete mode 100644 test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll
> 
> <0001-Allow-blocks-to-be-merged-when-one-has-an-undef-inpu.patch>_______________________________________________
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