[llvm] r303497 - [SCEV] Clarify behavior around max backedge taken count
Vitaly Buka via llvm-commits
llvm-commits at lists.llvm.org
Sun May 21 21:42:08 PDT 2017
Sorry, but it's not likely your patch.
I noticed that the error was there before.
On Sat, May 20, 2017 at 10:18 PM, Vitaly Buka <vitalybuka at google.com> wrote:
> Clang instrumented with msan (stage2) is building new clang (stage3).
>
> Easy but slow reproducer is to go to empty dir and run command below:
> BUILDBOT_REVISION=303497 BUILDBOT_CLOBBER=1 <path to llvm
> checkout>/projects/zorg/zorg/buildbot/builders/sanitizers/
> buildbot_bootstrap.sh
>
> On Sat, May 20, 2017 at 10:02 PM, Sanjoy Das <sanjoy at playingwithpointers.
> com> wrote:
>
>> Reverted in r303498
>>
>> On Sat, May 20, 2017 at 9:59 PM, Sanjoy Das
>> <sanjoy at playingwithpointers.com> wrote:
>> > Hi Vitaly,
>> >
>> > I'm about to revert this change, but I have a question -- what this
>> > failure seen when the ToT clang (built with a "known good" clang +
>> > msan) tried to build itself, or when a bootstrapped clang (i.e. a
>> > clang built with a ToT clang + msan) tried to bootstrap itself?
>> >
>> > Thanks
>> > -- Sanjoy
>> >
>> > On Sat, May 20, 2017 at 9:49 PM, Vitaly Buka <vitalybuka at google.com>
>> wrote:
>> >> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-
>> bootstrap/builds/1379/steps/check-llvm%20check-clang%
>> 20stage3%2Fmsan/logs/stdio
>> >>
>> >> FAILED: tools/llvm-xray/CMakeFiles/llvm-xray.dir/xray-color-helper.
>> cc.o
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm_build_msan/bin/clang++
>> >> -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_GLOBAL_ISEL -D_DEBUG -D_GNU_SOURCE
>> >> -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
>> >> -Itools/llvm-xray
>> >> -I/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstra
>> p/build/llvm/tools/llvm-xray
>> >> -Iinclude
>> >> -I/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstra
>> p/build/llvm/include
>> >> -fPIC -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -Wall -W
>> >> -Wno-unused-parameter -Wwrite-strings -Wcast-qual
>> >> -Wmissing-field-initializers -pedantic -Wno-long-long
>> >> -Wcovered-switch-default -Wnon-virtual-dtor -Wdelete-non-virtual-dtor
>> >> -Wstring-conversion -fcolor-diagnostics -ffunction-sections
>> -fdata-sections
>> >> -O3 -UNDEBUG -fno-exceptions -fno-rtti -MD -MT
>> >> tools/llvm-xray/CMakeFiles/llvm-xray.dir/xray-color-helper.cc.o -MF
>> >> tools/llvm-xray/CMakeFiles/llvm-xray.dir/xray-color-helper.cc.o.d -o
>> >> tools/llvm-xray/CMakeFiles/llvm-xray.dir/xray-color-helper.cc.o -c
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/llvm-xray/xray-color-helper.cc
>> >> ==969==WARNING: MemorySanitizer: use-of-uninitialized-value
>> >> #0 0x3533258 in
>> >> llvm::X86InstrInfo::AnalyzeBranchImpl(llvm::MachineBasicBlock&,
>> >> llvm::MachineBasicBlock*&, llvm::MachineBasicBlock*&,
>> >> llvm::SmallVectorImpl<llvm::MachineOperand>&,
>> >> llvm::SmallVectorImpl<llvm::MachineInstr*>&, bool) const
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/Target/X86/X86InstrInfo.cpp:6093:22
>> >> #1 0x353333d in
>> >> llvm::X86InstrInfo::analyzeBranch(llvm::MachineBasicBlock&,
>> >> llvm::MachineBasicBlock*&, llvm::MachineBasicBlock*&,
>> >> llvm::SmallVectorImpl<llvm::MachineOperand>&, bool) const
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/Target/X86/X86InstrInfo.cpp:6133:10
>> >> #2 0x42fddcc in llvm::TailDuplicator::tailDuplicate(bool,
>> >> llvm::MachineBasicBlock*, llvm::MachineBasicBlock*,
>> >> llvm::SmallVectorImpl<llvm::MachineBasicBlock*>&,
>> >> llvm::SmallVectorImpl<llvm::MachineInstr*>&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/TailDuplicator.cpp:837:10
>> >> #3 0x42fab3a in llvm::TailDuplicator::tailDuplicateAndUpdate(bool,
>> >> llvm::MachineBasicBlock*, llvm::MachineBasicBlock*,
>> >> llvm::SmallVectorImpl<llvm::MachineBasicBlock*>*,
>> llvm::function_ref<void
>> >> (llvm::MachineBasicBlock*)>*)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/TailDuplicator.cpp:148:8
>> >> #4 0x44e921b in (anonymous
>> >> namespace)::MachineBlockPlacement::maybeTailDuplicateBlock(
>> llvm::MachineBasicBlock*,
>> >> llvm::MachineBasicBlock*, (anonymous namespace)::BlockChain&,
>> >> llvm::SmallSetVector<llvm::MachineBasicBlock const*, 16u>*,
>> >> llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::
>> MachineBasicBlock,
>> >> true, false, void>, false, false>&, bool&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/MachineBlockPlacement.cpp:2620:11
>> >> #5 0x44cef5d in repeatedlyTailDuplicateBlock
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/MachineBlockPlacement.cpp:2501:13
>> >> #6 0x44cef5d in (anonymous
>> >> namespace)::MachineBlockPlacement::buildChain(llvm::MachineBasicBlock
>> >> const*, (anonymous namespace)::BlockChain&,
>> >> llvm::SmallSetVector<llvm::MachineBasicBlock const*, 16u>*)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/MachineBlockPlacement.cpp:1699
>> >> #7 0x44b6970 in (anonymous
>> >> namespace)::MachineBlockPlacement::buildCFGChains()
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/MachineBlockPlacement.cpp:2278:3
>> >> #8 0x44b14a9 in (anonymous
>> >> namespace)::MachineBlockPlacement::runOnMachineFunction(
>> llvm::MachineFunction&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/MachineBlockPlacement.cpp:2696:3
>> >> #9 0x3f6dcac in
>> >> llvm::MachineFunctionPass::runOnFunction(llvm::Function&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/CodeGen/MachineFunctionPass.cpp:62:13
>> >> #10 0x48e2bee in llvm::FPPassManager::runOnFunc
>> tion(llvm::Function&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/IR/LegacyPassManager.cpp:1519:27
>> >> #11 0x48e32b4 in llvm::FPPassManager::runOnModule(llvm::Module&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/IR/LegacyPassManager.cpp:1540:16
>> >> #12 0x48e45d3 in runOnModule
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/IR/LegacyPassManager.cpp:1596:27
>> >> #13 0x48e45d3 in llvm::legacy::PassManagerImpl::run(llvm::Module&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/lib/IR/LegacyPassManager.cpp:1699
>> >> #14 0x5d3e27e in EmitAssembly
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/CodeGen/BackendUtil.cpp:792:19
>> >> #15 0x5d3e27e in clang::EmitBackendOutput(clang
>> ::DiagnosticsEngine&,
>> >> clang::HeaderSearchOptions const&, clang::CodeGenOptions const&,
>> >> clang::TargetOptions const&, clang::LangOptions const&,
>> llvm::DataLayout
>> >> const&, llvm::Module*, clang::BackendAction,
>> >> std::__1::unique_ptr<llvm::raw_pwrite_stream,
>> >> std::__1::default_delete<llvm::raw_pwrite_stream> >)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/CodeGen/BackendUtil.cpp:1101
>> >> #16 0x74dfefe in
>> >> clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/CodeGen/CodeGenAction.cpp:258:7
>> >> #17 0x848e176 in clang::ParseAST(clang::Sema&, bool, bool)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/Parse/ParseAST.cpp:159:13
>> >> #18 0x69f82ba in clang::FrontendAction::Execute()
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/Frontend/FrontendAction.cpp:837:8
>> >> #19 0x693a02c in
>> >> clang::CompilerInstance::ExecuteAction(clang::FrontendAction&)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/Frontend/CompilerInstance.cpp:970:11
>> >> #20 0x6bc3705 in
>> >> clang::ExecuteCompilerInvocation(clang::CompilerInstance*)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/lib/FrontendTool/ExecuteCompilerIn
>> vocation.cpp:249:25
>> >> #21 0x976e25 in cc1_main(llvm::ArrayRef<char const*>, char const*,
>> >> void*)
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/tools/driver/cc1_main.cpp:221:13
>> >> #22 0x970ce7 in ExecuteCC1Tool
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/tools/driver/driver.cpp:299:12
>> >> #23 0x970ce7 in main
>> >> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/
>> build/llvm/tools/clang/tools/driver/driver.cpp:380
>> >> #24 0x7f561ec5c82f in __libc_start_main
>> >> (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
>> >> #25 0x8f0d38 in _start
>> >> (/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap
>> /build/llvm_build_msan/bin/clang-5.0+0x8f0d38)
>> >>
>> >>
>> >> On Sat, May 20, 2017 at 6:47 PM, Sanjoy Das via llvm-commits
>> >> <llvm-commits at lists.llvm.org> wrote:
>> >>>
>> >>> Author: sanjoy
>> >>> Date: Sat May 20 20:47:50 2017
>> >>> New Revision: 303497
>> >>>
>> >>> URL: http://llvm.org/viewvc/llvm-project?rev=303497&view=rev
>> >>> Log:
>> >>> [SCEV] Clarify behavior around max backedge taken count
>> >>>
>> >>> This change makes the split between the "exact" backedge taken count
>> >>> and the "maximum" backedge taken count a bit more obvious. Both of
>> >>> these are upper bounds on the number of times the loop header
>> >>> executes (since SCEV does not account for most kinds of abnormal
>> >>> control flow), but the latter is guaranteed to be a constant.
>> >>>
>> >>> There were a few places where the max backedge taken count *was* a
>> >>> non-constant; I've changed those to compute constants instead.
>> >>>
>> >>> At this point, I'm not sure if the constant max backedge count can be
>> >>> computed by calling `getUnsignedRange(Exact).getUnsignedMax()`
>> without
>> >>> losing precision. If it can, we can simplify even further by making
>> >>> `getMaxBackedgeTakenCount` a thin wrapper around
>> >>> `getBackedgeTakenCount` and `getUnsignedRange`.
>> >>>
>> >>> Modified:
>> >>> llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
>> >>> llvm/trunk/lib/Analysis/ScalarEvolution.cpp
>> >>> llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll
>> >>> llvm/trunk/test/Analysis/ScalarEvolution/trip-count-pow2.ll
>> >>>
>> >>> Modified: llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/
>> Analysis/ScalarEvolution.h?rev=303497&r1=303496&r2=303497&view=diff
>> >>>
>> >>> ============================================================
>> ==================
>> >>> --- llvm/trunk/include/llvm/Analysis/ScalarEvolution.h (original)
>> >>> +++ llvm/trunk/include/llvm/Analysis/ScalarEvolution.h Sat May 20
>> 20:47:50
>> >>> 2017
>> >>> @@ -656,10 +656,12 @@ private:
>> >>> /// Test whether this BackedgeTakenInfo contains complete
>> >>> information.
>> >>> bool hasFullInfo() const { return isComplete(); }
>> >>>
>> >>> - /// Return an expression indicating the exact backedge-taken
>> count of
>> >>> the
>> >>> - /// loop if it is known or SCEVCouldNotCompute otherwise. This
>> is the
>> >>> - /// number of times the loop header can be guaranteed to execute,
>> >>> minus
>> >>> - /// one.
>> >>> + /// Return an expression indicating the exact *backedge-taken*
>> >>> + /// count of the loop if it is known or SCEVCouldNotCompute
>> >>> + /// otherwise. If execution makes it to the backedge on every
>> >>> + /// iteration (i.e. there are no abnormal exists like exception
>> >>> + /// throws and thread exits) then this is the number of times the
>> >>> + /// loop header will execute minus one.
>> >>> ///
>> >>> /// If the SCEV predicate associated with the answer can be
>> different
>> >>> /// from AlwaysTrue, we must add a (non null) Predicates
>> argument.
>> >>> @@ -1398,11 +1400,11 @@ public:
>> >>> const SCEV *getExitCount(const Loop *L, BasicBlock *ExitingBlock);
>> >>>
>> >>> /// If the specified loop has a predictable backedge-taken count,
>> >>> return it,
>> >>> - /// otherwise return a SCEVCouldNotCompute object. The
>> backedge-taken
>> >>> count
>> >>> - /// is the number of times the loop header will be branched to from
>> >>> within
>> >>> - /// the loop. This is one less than the trip count of the loop,
>> since
>> >>> it
>> >>> - /// doesn't count the first iteration, when the header is branched
>> to
>> >>> from
>> >>> - /// outside the loop.
>> >>> + /// otherwise return a SCEVCouldNotCompute object. The
>> backedge-taken
>> >>> count is
>> >>> + /// the number of times the loop header will be branched to from
>> within
>> >>> the
>> >>> + /// loop, assuming there are no abnormal exists like exception
>> throws.
>> >>> This is
>> >>> + /// one less than the trip count of the loop, since it doesn't
>> count
>> >>> the first
>> >>> + /// iteration, when the header is branched to from outside the
>> loop.
>> >>> ///
>> >>> /// Note that it is not valid to call this method on a loop
>> without a
>> >>> /// loop-invariant backedge-taken count (see
>> >>> @@ -1417,8 +1419,10 @@ public:
>> >>> const SCEV *getPredicatedBackedgeTakenCount(const Loop *L,
>> >>> SCEVUnionPredicate
>> >>> &Predicates);
>> >>>
>> >>> - /// Similar to getBackedgeTakenCount, except return the least SCEV
>> >>> value
>> >>> - /// that is known never to be less than the actual backedge taken
>> >>> count.
>> >>> + /// When successful, this returns a SCEVConstant that is greater
>> than
>> >>> or equal
>> >>> + /// to (i.e. a "conservative over-approximation") of the value
>> returend
>> >>> by
>> >>> + /// getBackedgeTakenCount. If such a value cannot be computed, it
>> >>> returns the
>> >>> + /// SCEVCouldNotCompute object.
>> >>> const SCEV *getMaxBackedgeTakenCount(const Loop *L);
>> >>>
>> >>> /// Return true if the backedge taken count is either the value
>> >>> returned by
>> >>>
>> >>> Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/
>> ScalarEvolution.cpp?rev=303497&r1=303496&r2=303497&view=diff
>> >>>
>> >>> ============================================================
>> ==================
>> >>> --- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
>> >>> +++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Sat May 20 20:47:50
>> 2017
>> >>> @@ -5947,6 +5947,8 @@ ScalarEvolution::BackedgeTakenInfo::getM
>> >>> if (any_of(ExitNotTaken, PredicateNotAlwaysTrue) || !getMax())
>> >>> return SE->getCouldNotCompute();
>> >>>
>> >>> + assert((isa<SCEVCouldNotCompute>(getMax()) ||
>> >>> isa<SCEVConstant>(getMax())) &&
>> >>> + "No point in having a non-constant max backedge taken
>> count!");
>> >>> return getMax();
>> >>> }
>> >>>
>> >>> @@ -5972,7 +5974,11 @@ bool ScalarEvolution::BackedgeTakenInfo:
>> >>> }
>> >>>
>> >>> ScalarEvolution::ExitLimit::ExitLimit(const SCEV *E)
>> >>> - : ExactNotTaken(E), MaxNotTaken(E), MaxOrZero(false) {}
>> >>> + : ExactNotTaken(E), MaxNotTaken(E), MaxOrZero(false) {
>> >>> + assert((isa<SCEVCouldNotCompute>(MaxNotTaken) ||
>> >>> + isa<SCEVConstant>(MaxNotTaken)) &&
>> >>> + "No point in having a non-constant max backedge taken
>> count!");
>> >>> +}
>> >>>
>> >>> ScalarEvolution::ExitLimit::ExitLimit(
>> >>> const SCEV *E, const SCEV *M, bool MaxOrZero,
>> >>> @@ -5981,6 +5987,9 @@ ScalarEvolution::ExitLimit::ExitLimit(
>> >>> assert((isa<SCEVCouldNotCompute>(ExactNotTaken) ||
>> >>> !isa<SCEVCouldNotCompute>(MaxNotTaken)) &&
>> >>> "Exact is not allowed to be less precise than Max");
>> >>> + assert((isa<SCEVCouldNotCompute>(MaxNotTaken) ||
>> >>> + isa<SCEVConstant>(MaxNotTaken)) &&
>> >>> + "No point in having a non-constant max backedge taken
>> count!");
>> >>> for (auto *PredSet : PredSetList)
>> >>> for (auto *P : *PredSet)
>> >>> addPredicate(P);
>> >>> @@ -5989,11 +5998,19 @@ ScalarEvolution::ExitLimit::ExitLimit(
>> >>> ScalarEvolution::ExitLimit::ExitLimit(
>> >>> const SCEV *E, const SCEV *M, bool MaxOrZero,
>> >>> const SmallPtrSetImpl<const SCEVPredicate *> &PredSet)
>> >>> - : ExitLimit(E, M, MaxOrZero, {&PredSet}) {}
>> >>> + : ExitLimit(E, M, MaxOrZero, {&PredSet}) {
>> >>> + assert((isa<SCEVCouldNotCompute>(MaxNotTaken) ||
>> >>> + isa<SCEVConstant>(MaxNotTaken)) &&
>> >>> + "No point in having a non-constant max backedge taken
>> count!");
>> >>> +}
>> >>>
>> >>> ScalarEvolution::ExitLimit::ExitLimit(const SCEV *E, const SCEV *M,
>> >>> bool MaxOrZero)
>> >>> - : ExitLimit(E, M, MaxOrZero, None) {}
>> >>> + : ExitLimit(E, M, MaxOrZero, None) {
>> >>> + assert((isa<SCEVCouldNotCompute>(MaxNotTaken) ||
>> >>> + isa<SCEVConstant>(MaxNotTaken)) &&
>> >>> + "No point in having a non-constant max backedge taken
>> count!");
>> >>> +}
>> >>>
>> >>> /// Allocate memory for BackedgeTakenInfo and copy the not-taken
>> count of
>> >>> each
>> >>> /// computable exit into a persistent ExitNotTakenInfo array.
>> >>> @@ -6018,6 +6035,8 @@ ScalarEvolution::BackedgeTakenInfo::Back
>> >>>
>> >>> return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken,
>> >>> std::move(Predicate));
>> >>> });
>> >>> + assert((isa<SCEVCouldNotCompute>(MaxCount) ||
>> >>> isa<SCEVConstant>(MaxCount)) &&
>> >>> + "No point in having a non-constant max backedge taken
>> count!");
>> >>> }
>> >>>
>> >>> /// Invalidate this result and free the ExitNotTakenInfo array.
>> >>> @@ -6279,7 +6298,7 @@ ScalarEvolution::ExitLimit ScalarEvoluti
>> >>> // to not.
>> >>> if (isa<SCEVCouldNotCompute>(MaxBECount) &&
>> >>> !isa<SCEVCouldNotCompute>(BECount))
>> >>> - MaxBECount = BECount;
>> >>> + MaxBECount =
>> >>> getConstant(getUnsignedRange(BECount).getUnsignedMax());
>> >>>
>> >>> return ExitLimit(BECount, MaxBECount, false,
>> >>> {&EL0.Predicates, &EL1.Predicates});
>> >>> @@ -7583,13 +7602,20 @@ ScalarEvolution::howFarToZero(const SCEV
>> >>> loopHasNoAbnormalExits(AddRec->getLoop())) {
>> >>> const SCEV *Exact =
>> >>> getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) :
>> Step);
>> >>> - return ExitLimit(Exact, Exact, false, Predicates);
>> >>> + const SCEV *Max =
>> >>> + Exact == getCouldNotCompute()
>> >>> + ? Exact
>> >>> + : getConstant(getUnsignedRange(Exact).getUnsignedMax());
>> >>> + return ExitLimit(Exact, Max, false, Predicates);
>> >>> }
>> >>>
>> >>> // Solve the general equation.
>> >>> - const SCEV *E = SolveLinEquationWithOverflow(
>> >>> - StepC->getAPInt(), getNegativeSCEV(Start), *this);
>> >>> - return ExitLimit(E, E, false, Predicates);
>> >>> + const SCEV *E = SolveLinEquationWithOverflow(StepC->getAPInt(),
>> >>> +
>> getNegativeSCEV(Start),
>> >>> *this);
>> >>> + const SCEV *M = E == getCouldNotCompute()
>> >>> + ? E
>> >>> + :
>> >>> getConstant(getUnsignedRange(E).getUnsignedMax());
>> >>> + return ExitLimit(E, M, false, Predicates);
>> >>> }
>> >>>
>> >>> ScalarEvolution::ExitLimit
>> >>> @@ -9218,8 +9244,9 @@ ScalarEvolution::howManyLessThans(const
>> >>> getConstant(StrideForMaxBECount),
>> false);
>> >>> }
>> >>>
>> >>> - if (isa<SCEVCouldNotCompute>(MaxBECount))
>> >>> - MaxBECount = BECount;
>> >>> + if (isa<SCEVCouldNotCompute>(MaxBECount) &&
>> >>> + !isa<SCEVCouldNotCompute>(BECount))
>> >>> + MaxBECount = getConstant(getUnsignedRange(B
>> ECount).getUnsignedMax());
>> >>>
>> >>> return ExitLimit(BECount, MaxBECount, MaxOrZero, Predicates);
>> >>> }
>> >>>
>> >>> Modified: llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis
>> /ScalarEvolution/nsw.ll?rev=303497&r1=303496&r2=303497&view=diff
>> >>>
>> >>> ============================================================
>> ==================
>> >>> --- llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll (original)
>> >>> +++ llvm/trunk/test/Analysis/ScalarEvolution/nsw.ll Sat May 20
>> 20:47:50
>> >>> 2017
>> >>> @@ -102,7 +102,7 @@ for.body.i.i:
>> >>> %cmp.i.i = icmp eq i32* %ptrincdec.i.i, %end
>> >>> br i1 %cmp.i.i, label %_ZSt4fillIPiiEvT_S1_RKT0_.exit, label
>> >>> %for.body.i.i
>> >>> ; CHECK: Loop %for.body.i.i: backedge-taken count is ((-4 + (-1 *
>> %begin)
>> >>> + %end) /u 4)
>> >>> -; CHECK: Loop %for.body.i.i: max backedge-taken count is ((-4 + (-1 *
>> >>> %begin) + %end) /u 4)
>> >>> +; CHECK: Loop %for.body.i.i: max backedge-taken count is
>> >>> 4611686018427387903
>> >>> _ZSt4fillIPiiEvT_S1_RKT0_.exit: ; preds =
>> >>> %for.body.i.i, %entry
>> >>> ret void
>> >>> }
>> >>>
>> >>> Modified: llvm/trunk/test/Analysis/ScalarEvolution/trip-count-pow2.ll
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis
>> /ScalarEvolution/trip-count-pow2.ll?rev=303497&r1=303496&
>> r2=303497&view=diff
>> >>>
>> >>> ============================================================
>> ==================
>> >>> --- llvm/trunk/test/Analysis/ScalarEvolution/trip-count-pow2.ll
>> (original)
>> >>> +++ llvm/trunk/test/Analysis/ScalarEvolution/trip-count-pow2.ll Sat
>> May 20
>> >>> 20:47:50 2017
>> >>> @@ -14,7 +14,7 @@ exit:
>> >>>
>> >>> ; CHECK-LABEL: @test1
>> >>> ; CHECK: Loop %loop: backedge-taken count is ((-32 + (96 * %n)) /u
>> 32)
>> >>> -; CHECK: Loop %loop: max backedge-taken count is ((-32 + (96 * %n))
>> /u
>> >>> 32)
>> >>> +; CHECK: Loop %loop: max backedge-taken count is 134217727
>> >>> }
>> >>>
>> >>> ; PR19183
>> >>> @@ -32,7 +32,7 @@ exit:
>> >>>
>> >>> ; CHECK-LABEL: @test2
>> >>> ; CHECK: Loop %loop: backedge-taken count is ((-32 + (32 * (%n /u
>> 32)))
>> >>> /u 32)
>> >>> -; CHECK: Loop %loop: max backedge-taken count is ((-32 + (32 * (%n /u
>> >>> 32))) /u 32)
>> >>> +; CHECK: Loop %loop: max backedge-taken count is 134217727
>> >>> }
>> >>>
>> >>> define void @test3(i32 %n) {
>> >>> @@ -49,7 +49,7 @@ exit:
>> >>>
>> >>> ; CHECK-LABEL: @test3
>> >>> ; CHECK: Loop %loop: backedge-taken count is ((-32 + (32 * %n)) /u
>> 32)
>> >>> -; CHECK: Loop %loop: max backedge-taken count is ((-32 + (32 * %n))
>> /u
>> >>> 32)
>> >>> +; CHECK: Loop %loop: max backedge-taken count is 134217727
>> >>> }
>> >>>
>> >>> define void @test4(i32 %n) {
>> >>> @@ -66,7 +66,7 @@ exit:
>> >>>
>> >>> ; CHECK-LABEL: @test4
>> >>> ; CHECK: Loop %loop: backedge-taken count is ((-4 + (-1431655764 *
>> %n))
>> >>> /u 4)
>> >>> -; CHECK: Loop %loop: max backedge-taken count is ((-4 + (-1431655764
>> *
>> >>> %n)) /u 4)
>> >>> +; CHECK: Loop %loop: max backedge-taken count is 1073741823
>> >>> }
>> >>>
>> >>> define void @test5(i32 %n) {
>> >>> @@ -83,5 +83,5 @@ exit:
>> >>>
>> >>> ; CHECK-LABEL: @test5
>> >>> ; CHECK: Loop %loop: backedge-taken count is ((-4 + (4 * %n)) /u 4)
>> >>> -; CHECK: Loop %loop: max backedge-taken count is ((-4 + (4 * %n)) /u
>> 4)
>> >>> +; CHECK: Loop %loop: max backedge-taken count is 1073741823
>> >>> }
>> >>>
>> >>>
>> >>> _______________________________________________
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>> >>> llvm-commits at lists.llvm.org
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>> >>
>> >>
>>
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