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llvm-mirror/test/Analysis/BranchProbabilityInfo
Diego Novillo 62bfc25308 Fix information loss in branch probability computation.
Summary:
This addresses PR 22718. When branch weights are too large, they were
being clamped to the range [1, MaxWeightForBB]. But this clamping is
only applied to edges that go outside the range, so it distorts the
relative branch probabilities.

This patch changes the weight calculation to scale every branch so the
relative probabilities are preserved. The scaling is done differently
now. First, all the branch weights are added up, and if the sum exceeds
32 bits, it computes an integer scale to bring all the weights within
the range.

The patch fixes an existing test that had slightly wrong branch
probabilities due to the previous clamping. It now gets branch weights
scaled accordingly.

Reviewers: dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9442

llvm-svn: 236750
2015-05-07 17:22:06 +00:00
..
basic.ll Re-apply r234898 and fix tests. 2015-04-15 06:24:07 +00:00
loop.ll [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
noreturn.ll
pr18705.ll [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
pr22718.ll Fix information loss in branch probability computation. 2015-05-07 17:22:06 +00:00