[PATCH] D78376: [SCCP] Use range imposed by condition as upper bound for widening.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: efriedma, mssimpso, davide.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

In some cases we can do better than going to overdefined when widening.
The range imposed by a condition for example provides an upper bound on
the range of a value. Instead of widening to overdefined we can widen to
that range.

We have to ensure that the upper bound contains the merge result,
otherwise the merge step would not be monotone any longer.

This improves the number of instructions removed for some programs

Tests: 237
Same hash: 219 (filtered out)
Remaining: 18
Metric: sccp.IPNumInstRemoved

Program                                        base    p1      diff
 test-suite...ks/Prolangs-C/agrep/agrep.test    40.00   57.00  42.5%
 test-suite...cations/hexxagon/hexxagon.test    30.00   36.00  20.0%
 test-suite...langs-C/football/football.test    85.00   96.00  12.9%
 test-suite...rks/FreeBench/pifft/pifft.test    26.00   28.00   7.7%
 test-suite...CFP2000/188.ammp/188.ammp.test    67.00   71.00   6.0%
 test-suite...000/197.parser/197.parser.test    59.00   61.00   3.4%
 test-suite.../CINT2000/254.gap/254.gap.test   158.00  162.00   2.5%
 test-suite...pplications/treecc/treecc.test    66.00   67.00   1.5%
 test-suite...TimberWolfMC/timberwolfmc.test    67.00   68.00   1.5%
 test-suite...CFP2000/177.mesa/177.mesa.test   202.00  204.00   1.0%
 test-suite...lications/ClamAV/clamscan.test   902.00  910.00   0.9%
 test-suite...6/482.sphinx3/482.sphinx3.test   137.00  138.00   0.7%
 test-suite.../CINT2000/176.gcc/176.gcc.test   1118.00 1123.00  0.4%
 test-suite.../CINT2006/403.gcc/403.gcc.test   3831.00 3847.00  0.4%
 test-suite.../Benchmarks/Bullet/bullet.test   320.00  321.00   0.3%
 test-suite...000/255.vortex/255.vortex.test   3805.00 3809.00  0.1%
 test-suite...:: External/Povray/povray.test   1537.00 1538.00  0.1%
 test-suite...006/453.povray/453.povray.test   1772.00 1773.00  0.1%


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78376

Files:
  llvm/include/llvm/Analysis/ValueLattice.h
  llvm/lib/Transforms/Scalar/SCCP.cpp
  llvm/test/Transforms/SCCP/widening.ll

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