If a module has many values that need to be resolved by
ResolvedUndefsIn, compilation takes quadratic time overall. Solve should
do a small amount of work, since not much is added to the worklists each
time markOverdefined is called. But ResolvedUndefsIn is linear over the
length of the function/module, so resolving one undef at a time is
quadratic in general.
To solve this, make ResolvedUndefsIn resolve every undef value at once,
instead of resolving them one at a time. This loses a little
optimization power, but can be a lot faster.
We still need a loop around ResolvedUndefsIn because markOverdefined
could change the set of blocks that are live. That should be uncommon,
hopefully. We could optimize it by tracking which blocks transition from
dead to live, instead of iterating over the whole module to find them.
But I'll leave that for later. (The whole function will become a lot
simpler once we start pruning branches on undef.)
The regression test changes seem minor. The specific cases in question
could probably be optimized with a bit more work, but they seem like
edge cases that don't really matter.
Fixes an "infinite" compile issue my team found on an internal workoad.
Differential Revision: https://reviews.llvm.org/D89080
Reapply with DTU update moved after CFG update, which is a
requirement of the API.
-----
Non-feasible control-flow edges are currently removed by replacing
the branch condition with a constant and then calling
ConstantFoldTerminator. This happens in a rather roundabout manner,
by inspecting the users (effectively: predecessors) of unreachable
blocks, and further complicated by the need to explicitly materialize
the condition for "forced" edges. I would like to extend SCCP to
discard switch conditions that are non-feasible based on range
information, but this is incompatible with the current approach
(as there is no single constant we could use.)
Instead, this patch explicitly removes non-feasible edges. It
currently only needs to handle the case where there is a single
feasible edge. The llvm_unreachable() branch will need to be
implemented for the aforementioned switch improvement.
Differential Revision: https://reviews.llvm.org/D84264
It breaks stage-2 build. Clang crashed when compiling
llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp
llvm/Support/GenericDomTree.h eraseNode: Node is not a leaf node
Non-feasible control-flow edges are currently removed by replacing
the branch condition with a constant and then calling
ConstantFoldTerminator. This happens in a rather roundabout manner,
by inspecting the users (effectively: predecessors) of unreachable
blocks, and further complicated by the need to explicitly materialize
the condition for "forced" edges. I would like to extend SCCP to
discard switch conditions that are non-feasible based on range
information, but this is incompatible with the current approach
(as there is no single constant we could use.)
Instead, this patch explicitly removes non-feasible edges. It
currently only needs to handle the case where there is a single
feasible edge. The llvm_unreachable() branch will need to be
implemented for the aforementioned switch improvement.
Differential Revision: https://reviews.llvm.org/D84264
Currently SCCP does not widen PHIs, stores or along call edges
(arguments/return values), but on operations that directly extend ranges
(like binary operators).
This means PHIs, stores and call edges are not pessimized by widening
currently, while binary operators are. The main reason for widening
operators initially was that opting-out for certain operations was
more straight-forward in the initial implementation (and it did not
matter too much, as range support initially was only implemented for a
very limited set of operations.
During the discussion in D78391, it was suggested to consider flipping
widening to PHIs, stores and along call edges. After adding support for
tracking the number of range extensions in ValueLattice, limiting the
number of range extensions per value is straight forward.
This patch introduces a MaxWidenSteps option to the MergeOptions,
limiting the number of range extensions per value. For PHIs, it seems
natural allow an extension for each (active) incoming value plus 1. For
the other cases, a arbitrary limit of 10 has been chosen initially. It would
potentially make sense to set it depending on the users of a
function/global, but that still needs investigating. This potentially
leads to more state-changes and longer compile-times.
The results look quite promising (MultiSource, SPEC):
Same hash: 179 (filtered out)
Remaining: 58
Metric: sccp.IPNumInstRemoved
Program base widen-phi diff
test-suite...ks/Prolangs-C/agrep/agrep.test 58.00 82.00 41.4%
test-suite...marks/SciMark2-C/scimark2.test 32.00 43.00 34.4%
test-suite...rks/FreeBench/mason/mason.test 6.00 8.00 33.3%
test-suite...langs-C/football/football.test 104.00 128.00 23.1%
test-suite...cations/hexxagon/hexxagon.test 36.00 42.00 16.7%
test-suite...CFP2000/177.mesa/177.mesa.test 214.00 249.00 16.4%
test-suite...ngs-C/assembler/assembler.test 14.00 16.00 14.3%
test-suite...arks/VersaBench/dbms/dbms.test 10.00 11.00 10.0%
test-suite...oxyApps-C++/miniFE/miniFE.test 43.00 47.00 9.3%
test-suite...ications/JM/ldecod/ldecod.test 179.00 195.00 8.9%
test-suite...CFP2006/433.milc/433.milc.test 249.00 265.00 6.4%
test-suite.../CINT2000/175.vpr/175.vpr.test 98.00 104.00 6.1%
test-suite...peg2/mpeg2dec/mpeg2decode.test 70.00 74.00 5.7%
test-suite...CFP2000/188.ammp/188.ammp.test 71.00 75.00 5.6%
test-suite...ce/Benchmarks/PAQ8p/paq8p.test 111.00 117.00 5.4%
test-suite...ce/Applications/Burg/burg.test 41.00 43.00 4.9%
test-suite...000/197.parser/197.parser.test 66.00 69.00 4.5%
test-suite...tions/lambda-0.1.3/lambda.test 23.00 24.00 4.3%
test-suite...urce/Applications/lua/lua.test 301.00 313.00 4.0%
test-suite...TimberWolfMC/timberwolfmc.test 76.00 79.00 3.9%
test-suite...lications/ClamAV/clamscan.test 991.00 1030.00 3.9%
test-suite...plications/d/make_dparser.test 53.00 55.00 3.8%
test-suite...fice-ispell/office-ispell.test 83.00 86.00 3.6%
test-suite...lications/obsequi/Obsequi.test 28.00 29.00 3.6%
test-suite.../Prolangs-C/bison/mybison.test 56.00 58.00 3.6%
test-suite.../CINT2000/254.gap/254.gap.test 170.00 176.00 3.5%
test-suite.../Applications/lemon/lemon.test 30.00 31.00 3.3%
test-suite.../CINT2000/176.gcc/176.gcc.test 1202.00 1240.00 3.2%
test-suite...pplications/treecc/treecc.test 79.00 81.00 2.5%
test-suite...chmarks/MallocBench/gs/gs.test 357.00 366.00 2.5%
test-suite...eeBench/analyzer/analyzer.test 103.00 105.00 1.9%
test-suite...T2006/445.gobmk/445.gobmk.test 1697.00 1724.00 1.6%
test-suite...006/453.povray/453.povray.test 1812.00 1839.00 1.5%
test-suite.../Benchmarks/Bullet/bullet.test 337.00 342.00 1.5%
test-suite.../CINT2000/252.eon/252.eon.test 426.00 432.00 1.4%
test-suite...T2000/300.twolf/300.twolf.test 214.00 217.00 1.4%
test-suite...pplications/oggenc/oggenc.test 244.00 247.00 1.2%
test-suite.../CINT2006/403.gcc/403.gcc.test 4008.00 4055.00 1.2%
test-suite...T2006/456.hmmer/456.hmmer.test 175.00 177.00 1.1%
test-suite...nal/skidmarks10/skidmarks.test 430.00 434.00 0.9%
test-suite.../Applications/sgefa/sgefa.test 115.00 116.00 0.9%
test-suite...006/447.dealII/447.dealII.test 1082.00 1091.00 0.8%
test-suite...6/482.sphinx3/482.sphinx3.test 141.00 142.00 0.7%
test-suite...ocBench/espresso/espresso.test 152.00 153.00 0.7%
test-suite...3.xalancbmk/483.xalancbmk.test 4003.00 4025.00 0.5%
test-suite...lications/sqlite3/sqlite3.test 548.00 551.00 0.5%
test-suite...marks/7zip/7zip-benchmark.test 5522.00 5551.00 0.5%
test-suite...nsumer-lame/consumer-lame.test 208.00 209.00 0.5%
test-suite...:: External/Povray/povray.test 1556.00 1563.00 0.4%
test-suite...000/186.crafty/186.crafty.test 298.00 299.00 0.3%
test-suite.../Applications/SPASS/SPASS.test 2019.00 2025.00 0.3%
test-suite...ications/JM/lencod/lencod.test 8427.00 8449.00 0.3%
test-suite...6/464.h264ref/464.h264ref.test 6797.00 6813.00 0.2%
test-suite...6/471.omnetpp/471.omnetpp.test 431.00 430.00 -0.2%
test-suite...006/450.soplex/450.soplex.test 446.00 447.00 0.2%
test-suite...0.perlbench/400.perlbench.test 1729.00 1727.00 -0.1%
test-suite...000/255.vortex/255.vortex.test 3815.00 3819.00 0.1%
Reviewers: efriedma, nikic, davide
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D79036
This patch switches SCCP to use ValueLatticeElement for lattice values,
instead of the local LatticeVal, as first step to enable integer range support.
This patch does not make use of constant ranges for additional operations
and the only difference for now is that integer constants are represented by
single element ranges. To preserve the existing behavior, the following helpers
are used
* isConstant(LV): returns true when LV is either a constant or a constant range with a single element. This should return true in the same cases where LV.isConstant() returned true previously.
* getConstant(LV): returns a constant if LV is either a constant or a constant range with a single element. This should return a constant in the same cases as LV.getConstant() previously.
* getConstantInt(LV): same as getConstant, but additionally casted to ConstantInt.
Reviewers: davide, efriedma, mssimpso
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D60582
This includes a fix for cases where things get marked as overdefined in
ResolvedUndefsIn, but we later discover a constant. To avoid crashing,
we consistently bail out on overdefined values in the visitors. This is
similar to the previous behavior with forcedconstant.
This reverts the revert commit 02b72f564c8be0b4f4337d5c4a3fcf7e8018a818.
This version includes a fix for a set of crashes caused by marking
values depending on a yet unknown & tracked call as overdefined.
In some cases, we would later discover that the call has a constant
result and try to mark a user of it as constant, although it was already
marked as overdefined. Most instruction handlers bail out early if the
instruction is already overdefined. But that is not necessary for
CastInsts for example. By skipping values that depend on skipped
calls, we resolve the crashes and also improve the precision in some
cases (see resolvedundefsin-tracked-fn.ll).
Note that we may not skip PHI nodes that may depend on a skipped call,
but they can be safely marked as overdefined, as we bail out early if
the PHI node is overdefined.
This reverts the revert commit
a74b31a3e9cd844c7ce2087978568e3f5ec8519.
