forked from OSchip/llvm-project
[Passes] Run peeling as part of simple/full loop unrolling.
Loop peeling removes conditions from loop bodies that become invariant
after a small number of iterations. When triggered, this leads to fewer
compares and possibly PHIs in loop bodies, enabling further
optimizations. The current cost-model of loop peeling should be quite
conservative/safe, i.e. only peel if a condition in the loop becomes
known after peeling.
For example, see PR47671, where loop peeling enables vectorization by
removing a PHI the vectorizer does not understand. Granted, the
loop-vectorizer could also be taught about constant PHIs, but loop
peeling is likely to enable other optimizations as well.
This has an impact on quite a few benchmarks from
MultiSource/SPEC2000/SPEC2006 on X86 with -O3 -flto, for example
Same hash: 186 (filtered out)
Remaining: 51
Metric: loop-vectorize.LoopsVectorized
Program base patch diff
test-suite...ve-susan/automotive-susan.test 8.00 9.00 12.5%
test-suite...nal/skidmarks10/skidmarks.test 35.00 31.00 -11.4%
test-suite...lications/sqlite3/sqlite3.test 41.00 43.00 4.9%
test-suite...s/ASC_Sequoia/AMGmk/AMGmk.test 25.00 26.00 4.0%
test-suite...006/450.soplex/450.soplex.test 88.00 89.00 1.1%
test-suite...TimberWolfMC/timberwolfmc.test 120.00 119.00 -0.8%
test-suite.../CINT2006/403.gcc/403.gcc.test 215.00 216.00 0.5%
test-suite...006/447.dealII/447.dealII.test 957.00 958.00 0.1%
test-suite...ternal/HMMER/hmmcalibrate.test 75.00 75.00 0.0%
Same hash: 186 (filtered out)
Remaining: 51
Metric: loop-vectorize.LoopsAnalyzed
Program base patch diff
test-suite...ks/Prolangs-C/agrep/agrep.test 440.00 434.00 -1.4%
test-suite...nal/skidmarks10/skidmarks.test 312.00 308.00 -1.3%
test-suite...marks/7zip/7zip-benchmark.test 6399.00 6323.00 -1.2%
test-suite...lications/minisat/minisat.test 134.00 135.00 0.7%
test-suite...rks/FreeBench/pifft/pifft.test 295.00 297.00 0.7%
test-suite...TimberWolfMC/timberwolfmc.test 1879.00 1869.00 -0.5%
test-suite...pplications/treecc/treecc.test 689.00 691.00 0.3%
test-suite...T2000/300.twolf/300.twolf.test 1593.00 1597.00 0.3%
test-suite.../Benchmarks/Bullet/bullet.test 1394.00 1392.00 -0.1%
test-suite...ications/JM/ldecod/ldecod.test 1431.00 1429.00 -0.1%
test-suite...6/464.h264ref/464.h264ref.test 2229.00 2230.00 0.0%
test-suite...lications/sqlite3/sqlite3.test 2590.00 2589.00 -0.0%
test-suite...ications/JM/lencod/lencod.test 2732.00 2733.00 0.0%
test-suite...006/453.povray/453.povray.test 3395.00 3394.00 -0.0%
Note the -11% regression in number of loops vectorized for skidmarks. I
suspect this corresponds to the fact that those loops are gone now (see
the reduction in number of loops analyzed by LV).
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D88471
This commit is contained in:
Florian Hahn
parent
4dc110a4b8
commit
35b3989a30
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@ -190,7 +190,8 @@ Pass *createLoopUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false,
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int Count = -1, int AllowPartial = -1,
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int Runtime = -1, int UpperBound = -1,
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int AllowPeeling = -1);
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// Create an unrolling pass for full unrolling that uses exact trip count only.
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// Create an unrolling pass for full unrolling that uses exact trip count only
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// and also does peeling.
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Pass *createSimpleLoopUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false,
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bool ForgetAllSCEV = false);
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@ -22,7 +22,7 @@ class Function;
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class Loop;
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class LPMUpdater;
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/// Loop unroll pass that only does full loop unrolling.
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/// Loop unroll pass that only does full loop unrolling and peeling.
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class LoopFullUnrollPass : public PassInfoMixin<LoopFullUnrollPass> {
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const int OptLevel;
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@ -458,7 +458,7 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
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if (EnableLoopInterchange)
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MPM.add(createLoopInterchangePass()); // Interchange loops
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// Unroll small loops
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// Unroll small loops and perform peeling.
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MPM.add(createSimpleLoopUnrollPass(OptLevel, DisableUnrollLoops,
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ForgetAllSCEVInLoopUnroll));
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addExtensionsToPM(EP_LoopOptimizerEnd, MPM);
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@ -1072,7 +1072,7 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
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if (EnableConstraintElimination)
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PM.add(createConstraintEliminationPass());
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// Unroll small loops
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// Unroll small loops and perform peeling.
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PM.add(createSimpleLoopUnrollPass(OptLevel, DisableUnrollLoops,
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ForgetAllSCEVInLoopUnroll));
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PM.add(createLoopDistributePass());
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@ -1301,7 +1301,7 @@ Pass *llvm::createLoopUnrollPass(int OptLevel, bool OnlyWhenForced,
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Pass *llvm::createSimpleLoopUnrollPass(int OptLevel, bool OnlyWhenForced,
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bool ForgetAllSCEV) {
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return createLoopUnrollPass(OptLevel, OnlyWhenForced, ForgetAllSCEV, -1, -1,
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0, 0, 0, 0);
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0, 0, 0, 1);
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}
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PreservedAnalyses LoopFullUnrollPass::run(Loop &L, LoopAnalysisManager &AM,
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@ -1329,7 +1329,7 @@ PreservedAnalyses LoopFullUnrollPass::run(Loop &L, LoopAnalysisManager &AM,
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OnlyWhenForced, ForgetSCEV, /*Count*/ None,
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/*Threshold*/ None, /*AllowPartial*/ false,
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/*Runtime*/ false, /*UpperBound*/ false,
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/*AllowPeeling*/ false,
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/*AllowPeeling*/ true,
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/*AllowProfileBasedPeeling*/ false,
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/*FullUnrollMaxCount*/ None) !=
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LoopUnrollResult::Unmodified;
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@ -11,7 +11,9 @@ target triple = "x86_64-apple-macosx"
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define i32 @test(i32* readonly %p, i32* readnone %q) {
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; CHECK-LABEL: define i32 @test(
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; CHECK-NOT: vector.body
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; CHECK: vector.body:
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; CHECK: %index.next = add i64 %index, 8
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; CHECK: middle.block:
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;
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entry:
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%cmp.not7 = icmp eq i32* %p, %q
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