[SCEV] See through op.with.overflow intrinsics (re-apply)

Description

[SCEV] See through op.with.overflow intrinsics (re-apply)

Summary:
This change teaches SCEV to see reduce `(extractvalue
0 (op.with.overflow X Y)) into op X Y` (with a no-wrap tag if
possible).

This was first checked in at r265912 but reverted in r265950 because it
exposed some issues around how SCEV handled post-inc add recurrences.
Those issues have now been fixed.

Reviewers: atrick, regehr

Subscribers: mcrosier, mzolotukhin, llvm-commits

Differential Revision: http://reviews.llvm.org/D18684

Details

Committed
sanjoyMay 28 2016, 5:34 PM
Differential Revision
D18684: [SCEV] See through op.with.overflow intrinsics
Parents
rL271151: [SCEV] Don't always add no-wrap flags to post-inc add recs
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