[PATCH] Fix a bug in IfConverter with nested predicates

[Quentin Colombet]

Hi,

Here is a patch that fixes a bug in IfConverter with nested predicates.

The problem seems so obvious that I am wondering if I am missing something.
So although the patch is straightforward (one line change), please review carefully.
Note: I have tested it with -O3 -arch armv7 (apple iOS) against both SingleSource and Multisource tests.

** Context **
Prior to this patch, IfConverter may widen the cases where a sequence of instructions were executed because of the way it uses nested predicates. This result in incorrect execution.

For instance, Let A be a basic block that flows conditionally into B and B be a predicated block.
B can be predicated with A.BrToBPredicate into A iff B.Predicate is less "permissive" than A.BrToBPredicate, i.e., iff A.BrToBPredicate subsumes B.Predicate.

The IfConverter was checking the opposite: B.Predicate subsumes A.BrToBPredicate.

<rdar://problem/14379453>

** Solution **
Check the ‘subsumes’ property correctly.

Thanks for your review.

Cheers,

-Quentin
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