[llvm] r301196 - Compute safety information in a much finer granularity.
Xin Tong via llvm-commits
llvm-commits at lists.llvm.org
Mon May 1 08:56:45 PDT 2017
Yea, I am back to take a look at this today
On Mon, May 1, 2017 at 8:48 AM, Daniel Berlin <dberlin at dberlin.org> wrote:
> Thanks
> There are now more comments on the review anyway :)
>
>
> On Mon, Apr 24, 2017 at 11:38 AM, Xin Tong via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Thanks. I will take a look.
>> -Xin
>>
>> On Mon, Apr 24, 2017 at 11:38 AM, Evgenii Stepanov
>> <eugeni.stepanov at gmail.com> wrote:
>> > Verified and reverted.
>> >
>> > On Mon, Apr 24, 2017 at 11:34 AM, Evgenii Stepanov
>> > <eugeni.stepanov at gmail.com> wrote:
>> >> Hi,
>> >>
>> >> this must be yours. It it flakily crashing check-msan target on
>> >> Linux/x86_64. To reproduce, opt -O3 the attached IR file.
>> >>
>> >> ==50569==ERROR: AddressSanitizer: heap-use-after-free on address
>> >> 0x60e0000808f8 at pc 0x000000ccf4e2 bp 0x7ffe16d0e8c0 sp
>> >> 0x7ffe16d0e8b8
>> >> READ of size 8 at 0x60e0000808f8 thread T0
>> >> #0 0xccf4e1 in llvm::Instruction::getParent() const
>> >> /code/llvm/include/llvm/IR/Instruction.h:62:55
>> >> #1 0x30cbbb5 in llvm::DominatorTree::dominates(llvm::Instruction
>> >> const*, llvm::Instruction const*) const
>> >> /code/llvm/lib/IR/Dominators.cpp:90:35
>> >> #2 0x3cd60f2 in llvm::isGuaranteedToExecute(llvm::Instruction
>> >> const&, llvm::DominatorTree const*, llvm::Loop const*,
>> >> llvm::LoopSafetyInfo const*)
>> >> /code/llvm/lib/Transforms/Utils/LoopUtils.cpp:1050:14
>> >> #3 0x390bdd4 in (anonymous
>> >> namespace)::LoopUnswitch::processCurrentLoop()
>> >> /code/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:652:10
>> >> #4 0x390a555 in (anonymous
>> >> namespace)::LoopUnswitch::runOnLoop(llvm::Loop*, llvm::LPPassManager&)
>> >> /code/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:518:16
>> >> #5 0x265efc3 in
>> >> llvm::LPPassManager::runOnFunction(llvm::Function&)
>> >> /code/llvm/lib/Analysis/LoopPass.cpp:203:23
>> >> #6 0x3157d2b in
>> >> llvm::FPPassManager::runOnFunction(llvm::Function&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1513:27
>> >> #7 0x24efdb2 in (anonymous
>> >> namespace)::CGPassManager::RunPassOnSCC(llvm::Pass*,
>> >> llvm::CallGraphSCC&, llvm::CallGraph&, bool&, bool&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:149:25
>> >> #8 0x24ef78b in (anonymous
>> >> namespace)::CGPassManager::RunAllPassesOnSCC(llvm::CallGraphSCC&,
>> >> llvm::CallGraph&, bool&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:417:16
>> >> #9 0x24eee8b in (anonymous
>> >> namespace)::CGPassManager::runOnModule(llvm::Module&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:473:18
>> >> #10 0x31588cc in (anonymous
>> >> namespace)::MPPassManager::runOnModule(llvm::Module&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1590:27
>> >> #11 0x3158385 in llvm::legacy::PassManagerImpl::run(llvm::Module&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1693:44
>> >> #12 0xc69ebf in main /code/llvm/tools/opt/opt.cpp:738:10
>> >> #13 0x7f34fc5c0f44 in __libc_start_main
>> >> /build/eglibc-MjiXCM/eglibc-2.19/csu/libc-start.c:287
>> >> #14 0xb602c4 in _start (/code/build-llvm-asan/bin/opt+0xb602c4)
>> >>
>> >> 0x60e0000808f8 is located 120 bytes inside of 152-byte region
>> >> [0x60e000080880,0x60e000080918)
>> >> freed by thread T0 here:
>> >> #0 0xc2fcc2 in operator delete(void*)
>> >> /code/llvm/projects/compiler-rt/lib/asan/asan_new_delete.cc:126:3
>> >> #1 0x107cff9 in
>> >> llvm::iplist_impl<llvm::simple_ilist<llvm::Instruction>,
>> >> llvm::SymbolTableListTraits<llvm::Instruction>
>>
>> >>> >>>::erase(llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction,
>> >> true, false, void>, false, false>)
>> >> /code/llvm/include/llvm/ADT/ilist.h:281:5
>> >> #2 0x2fa5a7c in
>> >> llvm::iplist_impl<llvm::simple_ilist<llvm::Instruction>,
>> >> llvm::SymbolTableListTraits<llvm::Instruction>
>>
>> >>> >>>::erase(llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction,
>> >> true, false, void>, false, false>,
>> >>
>> >> llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction,
>> >> true, false, void>, false, false>)
>> >> /code/llvm/include/llvm/ADT/ilist.h:318:15
>> >> #3 0x2fa17f7 in llvm::BasicBlock::~BasicBlock()
>> >> /code/llvm/lib/IR/BasicBlock.cpp:85:12
>> >> #4 0x2fa1a0d in llvm::BasicBlock::~BasicBlock()
>> >> /code/llvm/lib/IR/BasicBlock.cpp:64:27
>> >> #5 0x2fa4a59 in
>> >> llvm::iplist_impl<llvm::simple_ilist<llvm::BasicBlock>,
>> >> llvm::SymbolTableListTraits<llvm::BasicBlock>
>>
>> >>> >>>::erase(llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::BasicBlock,
>> >> true, false, void>, false, false>)
>> >> /code/llvm/include/llvm/ADT/ilist.h:281:5
>> >> #6 0x3ca62a2 in llvm::removeUnreachableBlocks(llvm::Function&,
>> >> llvm::LazyValueInfo*)
>> >> /code/llvm/lib/Transforms/Utils/Local.cpp:1725:33
>> >> #7 0x3a2a34c in simplifyFunctionCFG(llvm::Function&,
>> >> llvm::TargetTransformInfo const&, llvm::AssumptionCache*, int, bool)
>> >> /code/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp:162:22
>> >> #8 0x3157d2b in
>> >> llvm::FPPassManager::runOnFunction(llvm::Function&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1513:27
>> >> #9 0x24efdb2 in (anonymous
>> >> namespace)::CGPassManager::RunPassOnSCC(llvm::Pass*,
>> >> llvm::CallGraphSCC&, llvm::CallGraph&, bool&, bool&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:149:25
>> >> #10 0x24ef78b in (anonymous
>> >> namespace)::CGPassManager::RunAllPassesOnSCC(llvm::CallGraphSCC&,
>> >> llvm::CallGraph&, bool&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:417:16
>> >> #11 0x24eee8b in (anonymous
>> >> namespace)::CGPassManager::runOnModule(llvm::Module&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:473:18
>> >> #12 0x31588cc in (anonymous
>> >> namespace)::MPPassManager::runOnModule(llvm::Module&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1590:27
>> >> #13 0x3158385 in llvm::legacy::PassManagerImpl::run(llvm::Module&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1693:44
>> >> #14 0xc69ebf in main /code/llvm/tools/opt/opt.cpp:738:10
>> >> #15 0x7f34fc5c0f44 in __libc_start_main
>> >> /build/eglibc-MjiXCM/eglibc-2.19/csu/libc-start.c:287
>> >>
>> >> previously allocated by thread T0 here:
>> >> #0 0xc2f0c2 in operator new(unsigned long)
>> >> /code/llvm/projects/compiler-rt/lib/asan/asan_new_delete.cc:82:35
>> >> #1 0x3202025 in llvm::User::allocateFixedOperandUser(unsigned
>> >> long, unsigned int, unsigned int) /code/llvm/lib/IR/User.cpp:128:7
>> >> #2 0x3202025 in llvm::User::operator new(unsigned long, unsigned
>> >> int) /code/llvm/lib/IR/User.cpp:146
>> >> #3 0x3122ce8 in llvm::CallInst::cloneImpl() const
>> >> /code/llvm/lib/IR/Instructions.cpp:3955:11
>> >> #4 0x310ab55 in llvm::Instruction::clone() const
>> >> /code/llvm/include/llvm/IR/Instruction.def:186:1
>> >> #5 0x3c345bf in llvm::CloneBasicBlock(llvm::BasicBlock const*,
>> >> llvm::ValueMap<llvm::Value const*, llvm::WeakVH,
>> >> llvm::ValueMapConfig<llvm::Value const*, llvm::sys::SmartMutex<false>
>> >>> >&, llvm::Twine const&, llvm::Function*, llvm::ClonedCodeInfo*)
>> >> /code/llvm/lib/Transforms/Utils/CloneFunction.cpp:52:32
>> >> #6 0x39129f7 in (anonymous
>> >> namespace)::LoopUnswitch::UnswitchNontrivialCondition(llvm::Value*,
>> >> llvm::Constant*, llvm::Loop*, llvm::TerminatorInst*)
>> >> /code/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:1148:25
>> >> #7 0x390ddf7 in (anonymous
>> >> namespace)::LoopUnswitch::UnswitchIfProfitable(llvm::Value*,
>> >> llvm::Constant*, llvm::TerminatorInst*)
>> >> /code/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:826:3
>> >> #8 0x390c004 in (anonymous
>> >> namespace)::LoopUnswitch::processCurrentLoop()
>> >> /code/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:670:13
>> >> #9 0x390a555 in (anonymous
>> >> namespace)::LoopUnswitch::runOnLoop(llvm::Loop*, llvm::LPPassManager&)
>> >> /code/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:518:16
>> >> #10 0x265efc3 in
>> >> llvm::LPPassManager::runOnFunction(llvm::Function&)
>> >> /code/llvm/lib/Analysis/LoopPass.cpp:203:23
>> >> #11 0x3157d2b in
>> >> llvm::FPPassManager::runOnFunction(llvm::Function&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1513:27
>> >> #12 0x24efdb2 in (anonymous
>> >> namespace)::CGPassManager::RunPassOnSCC(llvm::Pass*,
>> >> llvm::CallGraphSCC&, llvm::CallGraph&, bool&, bool&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:149:25
>> >> #13 0x24ef78b in (anonymous
>> >> namespace)::CGPassManager::RunAllPassesOnSCC(llvm::CallGraphSCC&,
>> >> llvm::CallGraph&, bool&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:417:16
>> >> #14 0x24eee8b in (anonymous
>> >> namespace)::CGPassManager::runOnModule(llvm::Module&)
>> >> /code/llvm/lib/Analysis/CallGraphSCCPass.cpp:473:18
>> >> #15 0x31588cc in (anonymous
>> >> namespace)::MPPassManager::runOnModule(llvm::Module&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1590:27
>> >> #16 0x3158385 in llvm::legacy::PassManagerImpl::run(llvm::Module&)
>> >> /code/llvm/lib/IR/LegacyPassManager.cpp:1693:44
>> >> #17 0xc69ebf in main /code/llvm/tools/opt/opt.cpp:738:10
>> >> #18 0x7f34fc5c0f44 in __libc_start_main
>> >> /build/eglibc-MjiXCM/eglibc-2.19/csu/libc-start.c:287
>> >>
>> >> SUMMARY: AddressSanitizer: heap-use-after-free
>> >> /code/llvm/include/llvm/IR/Instruction.h:62:55 in
>> >> llvm::Instruction::getParent() const
>> >> Shadow bytes around the buggy address:
>> >> 0x0c1c800080c0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fa
>> >> 0x0c1c800080d0: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
>> >> 0x0c1c800080e0: fd fd fd fd fd fd fd fd fd fd fd fd fa fa fa fa
>> >> 0x0c1c800080f0: fa fa fa fa fd fd fd fd fd fd fd fd fd fd fd fd
>> >> 0x0c1c80008100: fd fd fd fd fd fd fd fd fa fa fa fa fa fa fa fa
>> >> =>0x0c1c80008110: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd[fd]
>> >> 0x0c1c80008120: fd fd fd fa fa fa fa fa fa fa fa fa fd fd fd fd
>> >> 0x0c1c80008130: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
>> >> 0x0c1c80008140: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
>> >> 0x0c1c80008150: fd fd fd fd fd fd fd fd fd fd fd fd fa fa fa fa
>> >> 0x0c1c80008160: fa fa fa fa fd fd fd fd fd fd fd fd fd fd fd fd
>> >> Shadow byte legend (one shadow byte represents 8 application bytes):
>> >> Addressable: 00
>> >> Partially addressable: 01 02 03 04 05 06 07
>> >> Heap left redzone: fa
>> >> Freed heap region: fd
>> >> Stack left redzone: f1
>> >> Stack mid redzone: f2
>> >> Stack right redzone: f3
>> >> Stack after return: f5
>> >> Stack use after scope: f8
>> >> Global redzone: f9
>> >> Global init order: f6
>> >> Poisoned by user: f7
>> >> Container overflow: fc
>> >> Array cookie: ac
>> >> Intra object redzone: bb
>> >> ASan internal: fe
>> >> Left alloca redzone: ca
>> >> Right alloca redzone: cb
>> >>
>> >>
>> >>
>> >>
>> >> On Mon, Apr 24, 2017 at 10:12 AM, Xin Tong via llvm-commits
>> >> <llvm-commits at lists.llvm.org> wrote:
>> >>> Author: trentxintong
>> >>> Date: Mon Apr 24 12:12:22 2017
>> >>> New Revision: 301196
>> >>>
>> >>> URL: http://llvm.org/viewvc/llvm-project?rev=301196&view=rev
>> >>> Log:
>> >>> Compute safety information in a much finer granularity.
>> >>>
>> >>> Summary:
>> >>> Instead of keeping a variable indicating whether there are early exits
>> >>> in the loop. We keep all the early exits. This improves LICM's
>> >>> ability to
>> >>> move instructions out of the loop based on is-guaranteed-to-execute.
>> >>>
>> >>> I am going to update compilation time as well soon.
>> >>>
>> >>> Reviewers: hfinkel, sanjoy, efriedma, mkuper
>> >>>
>> >>> Reviewed By: hfinkel
>> >>>
>> >>> Subscribers: llvm-commits, mzolotukhin
>> >>>
>> >>> Differential Revision: https://reviews.llvm.org/D32433
>> >>>
>> >>> Added:
>> >>> llvm/trunk/test/Transforms/LICM/loop-early-exits.ll
>> >>> Modified:
>> >>> llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
>> >>> llvm/trunk/lib/Transforms/Scalar/LICM.cpp
>> >>> llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
>> >>> llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
>> >>> llvm/trunk/test/Transforms/LICM/preheader-safe.ll
>> >>>
>> >>> Modified: llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h?rev=301196&r1=301195&r2=301196&view=diff
>> >>>
>> >>> ==============================================================================
>> >>> --- llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h (original)
>> >>> +++ llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h Mon Apr 24
>> >>> 12:12:22 2017
>> >>> @@ -46,9 +46,9 @@ class TargetLibraryInfo;
>> >>> /// \brief Captures loop safety information.
>> >>> /// It keep information for loop & its header may throw exception.
>> >>> struct LoopSafetyInfo {
>> >>> - bool MayThrow = false; // The current loop contains an
>> >>> instruction which
>> >>> - // may throw.
>> >>> - bool HeaderMayThrow = false; // Same as previous, but specific to
>> >>> loop header
>> >>> + // The early exits in the loop, excluding loop exits.
>> >>> + // These are calls that might throw, infinite loop, etc.
>> >>> + SmallVector<Instruction *, 4> EarlyExits;
>> >>> // Used to update funclet bundle operands.
>> >>> DenseMap<BasicBlock *, ColorVector> BlockColors;
>> >>>
>> >>>
>> >>> Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=301196&r1=301195&r2=301196&view=diff
>> >>>
>> >>> ==============================================================================
>> >>> --- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
>> >>> +++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Mon Apr 24 12:12:22 2017
>> >>> @@ -478,27 +478,17 @@ bool llvm::hoistRegion(DomTreeNode *N, A
>> >>> ///
>> >>> void llvm::computeLoopSafetyInfo(LoopSafetyInfo *SafetyInfo, Loop
>> >>> *CurLoop) {
>> >>> assert(CurLoop != nullptr && "CurLoop cant be null");
>> >>> - BasicBlock *Header = CurLoop->getHeader();
>> >>> - // Setting default safety values.
>> >>> - SafetyInfo->MayThrow = false;
>> >>> - SafetyInfo->HeaderMayThrow = false;
>> >>> - // Iterate over header and compute safety info.
>> >>> - for (BasicBlock::iterator I = Header->begin(), E = Header->end();
>> >>> - (I != E) && !SafetyInfo->HeaderMayThrow; ++I)
>> >>> - SafetyInfo->HeaderMayThrow |=
>> >>> - !isGuaranteedToTransferExecutionToSuccessor(&*I);
>> >>> -
>> >>> - SafetyInfo->MayThrow = SafetyInfo->HeaderMayThrow;
>> >>> - // Iterate over loop instructions and compute safety info.
>> >>> - // Skip header as it has been computed and stored in
>> >>> HeaderMayThrow.
>> >>> - // The first block in loopinfo.Blocks is guaranteed to be the
>> >>> header.
>> >>> - assert(Header == *CurLoop->getBlocks().begin() && "First block must
>> >>> be header");
>> >>> - for (Loop::block_iterator BB = std::next(CurLoop->block_begin()),
>> >>> + // Iterate over loop instructions and compute early exit points.
>> >>> + for (Loop::block_iterator BB = CurLoop->block_begin(),
>> >>> BBE = CurLoop->block_end();
>> >>> - (BB != BBE) && !SafetyInfo->MayThrow; ++BB)
>> >>> - for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end();
>> >>> - (I != E) && !SafetyInfo->MayThrow; ++I)
>> >>> - SafetyInfo->MayThrow |=
>> >>> !isGuaranteedToTransferExecutionToSuccessor(&*I);
>> >>> + BB != BBE; ++BB) {
>> >>> + for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end(); I
>> >>> != E;
>> >>> + ++I) {
>> >>> + if (isGuaranteedToTransferExecutionToSuccessor(&*I))
>> >>> + continue;
>> >>> + SafetyInfo->EarlyExits.push_back(&*I);
>> >>> + }
>> >>> + }
>> >>>
>> >>> // Compute funclet colors if we might sink/hoist in a function with
>> >>> a funclet
>> >>> // personality routine.
>> >>> @@ -1094,7 +1084,7 @@ bool llvm::promoteLoopAccessesToScalars(
>> >>>
>> >>> // Do we know this object does not escape ?
>> >>> bool IsKnownNonEscapingObject = false;
>> >>> - if (SafetyInfo->MayThrow) {
>> >>> + if (!SafetyInfo->EarlyExits.empty()) {
>> >>> // If a loop can throw, we have to insert a store along each
>> >>> unwind edge.
>> >>> // That said, we can't actually make the unwind edge explicit.
>> >>> Therefore,
>> >>> // we have to prove that the store is dead along the unwind edge.
>> >>>
>> >>> Modified: llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp?rev=301196&r1=301195&r2=301196&view=diff
>> >>>
>> >>> ==============================================================================
>> >>> --- llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp (original)
>> >>> +++ llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp Mon Apr 24
>> >>> 12:12:22 2017
>> >>> @@ -272,7 +272,7 @@ bool LoopIdiomRecognize::runOnCountableL
>> >>> // Give up if the loop has instructions may throw.
>> >>> LoopSafetyInfo SafetyInfo;
>> >>> computeLoopSafetyInfo(&SafetyInfo, CurLoop);
>> >>> - if (SafetyInfo.MayThrow)
>> >>> + if (!SafetyInfo.EarlyExits.empty())
>> >>> return MadeChange;
>> >>>
>> >>> // Scan all the blocks in the loop that are not in subloops.
>> >>>
>> >>> Modified: llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp?rev=301196&r1=301195&r2=301196&view=diff
>> >>>
>> >>> ==============================================================================
>> >>> --- llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp (original)
>> >>> +++ llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp Mon Apr 24 12:12:22
>> >>> 2017
>> >>> @@ -1044,21 +1044,11 @@ bool llvm::isGuaranteedToExecute(const I
>> >>> const DominatorTree *DT, const Loop
>> >>> *CurLoop,
>> >>> const LoopSafetyInfo *SafetyInfo) {
>> >>> // We have to check to make sure that the instruction dominates all
>> >>> - // of the exit blocks. If it doesn't, then there is a path out of
>> >>> the loop
>> >>> - // which does not execute this instruction, so we can't hoist it.
>> >>> -
>> >>> - // If the instruction is in the header block for the loop (which is
>> >>> very
>> >>> - // common), it is always guaranteed to dominate the exit blocks.
>> >>> Since this
>> >>> - // is a common case, and can save some work, check it now.
>> >>> - if (Inst.getParent() == CurLoop->getHeader())
>> >>> - // If there's a throw in the header block, we can't guarantee
>> >>> we'll reach
>> >>> - // Inst.
>> >>> - return !SafetyInfo->HeaderMayThrow;
>> >>> -
>> >>> - // Somewhere in this loop there is an instruction which may throw
>> >>> and make us
>> >>> - // exit the loop.
>> >>> - if (SafetyInfo->MayThrow)
>> >>> - return false;
>> >>> + // of the exit points. If it doesn't, then there is a path out of
>> >>> the loop
>> >>> + // which does not execute this instruction and its not guaranteed
>> >>> to execute.
>> >>> + for (Instruction *ExitInst : SafetyInfo->EarlyExits)
>> >>> + if (!DT->dominates(&Inst, ExitInst))
>> >>> + return false;
>> >>>
>> >>> // Get the exit blocks for the current loop.
>> >>> SmallVector<BasicBlock *, 8> ExitBlocks;
>> >>> @@ -1071,7 +1061,9 @@ bool llvm::isGuaranteedToExecute(const I
>> >>>
>> >>> // As a degenerate case, if the loop is statically infinite then we
>> >>> haven't
>> >>> // proven anything since there are no exit blocks.
>> >>> - if (ExitBlocks.empty())
>> >>> + // However, we also special case instruction from the header as the
>> >>> header
>> >>> + // is always guaranteed to execute.
>> >>> + if (ExitBlocks.empty() && Inst.getParent() != CurLoop->getHeader())
>> >>> return false;
>> >>>
>> >>> // FIXME: In general, we have to prove that the loop isn't an
>> >>> infinite loop.
>> >>>
>> >>> Added: llvm/trunk/test/Transforms/LICM/loop-early-exits.ll
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/loop-early-exits.ll?rev=301196&view=auto
>> >>>
>> >>> ==============================================================================
>> >>> --- llvm/trunk/test/Transforms/LICM/loop-early-exits.ll (added)
>> >>> +++ llvm/trunk/test/Transforms/LICM/loop-early-exits.ll Mon Apr 24
>> >>> 12:12:22 2017
>> >>> @@ -0,0 +1,82 @@
>> >>> +; RUN: opt -S -licm < %s | FileCheck %s
>> >>> +
>> >>> +declare void @use(i64 %a)
>> >>> +declare void @use_nothrow(i64 %a) nounwind
>> >>> +declare void @use_nothing()
>> >>> +
>> >>> +; We can move this udiv out of the loop as it comes before
>> >>> +; the call instruction that may throw.
>> >>> +define void @throw_header1(i64 %x, i64 %y, i1* %cond) {
>> >>> +; CHECK-LABEL: throw_header1
>> >>> +; CHECK: %div = udiv i64 %x, %y
>> >>> +; CHECK-LABEL: loop
>> >>> +; CHECK: call void @use(i64 %div)
>> >>> +entry:
>> >>> + br label %loop
>> >>> +
>> >>> +loop: ; preds = %entry,
>> >>> %for.inc
>> >>> + %div = udiv i64 %x, %y
>> >>> + call void @use(i64 %div)
>> >>> + br label %loop
>> >>> +}
>> >>> +
>> >>> +; We can not move this udiv out of the loop as it comes after
>> >>> +; the call instruction that may throw.
>> >>> +define void @throw_header2(i64 %x, i64 %y, i1* %cond) {
>> >>> +; CHECK-LABEL: throw_header2
>> >>> +; CHECK-LABEL: loop
>> >>> +; CHECK: call void @use_nothing()
>> >>> +; CHECK: %div = udiv i64 %x, %y
>> >>> +entry:
>> >>> + br label %loop
>> >>> +
>> >>> +loop: ; preds = %entry,
>> >>> %for.inc
>> >>> + call void @use_nothing()
>> >>> + %div = udiv i64 %x, %y
>> >>> + call void @use_nothrow(i64 %div)
>> >>> + br label %loop
>> >>> +}
>> >>> +
>> >>> +; We can move this udiv out of the loop as it comes before
>> >>> +; the call instruction that may throw.
>> >>> +define void @throw_body1(i64 %x, i64 %y, i1* %cond) {
>> >>> +; CHECK-LABEL: throw_body1
>> >>> +; CHECK: %div = udiv i64 %x, %y
>> >>> +; CHECK-LABEL: loop
>> >>> +entry:
>> >>> + br label %loop
>> >>> +
>> >>> +loop: ; preds = %entry,
>> >>> %for.inc
>> >>> + br label %body
>> >>> +
>> >>> +body:
>> >>> + %div = udiv i64 %x, %y
>> >>> + call void @use(i64 %div)
>> >>> + br i1 undef, label %loop, label %exit
>> >>> +
>> >>> +exit:
>> >>> + ret void
>> >>> +}
>> >>> +
>> >>> +; We can not move this udiv out of the loop as it comes after
>> >>> +; the call instruction that may throw.
>> >>> +define void @throw_body2(i64 %x, i64 %y, i1* %cond) {
>> >>> +; CHECK-LABEL: throw_body2
>> >>> +; CHECK-LABEL: loop
>> >>> +; CHECK: call void @use_nothing()
>> >>> +; CHECK: %div = udiv i64 %x, %y
>> >>> +entry:
>> >>> + br label %loop
>> >>> +
>> >>> +loop: ; preds = %entry,
>> >>> %for.inc
>> >>> + br label %body
>> >>> +
>> >>> +body:
>> >>> + call void @use_nothing()
>> >>> + %div = udiv i64 %x, %y
>> >>> + call void @use_nothrow(i64 %div)
>> >>> + br i1 undef, label %loop, label %exit
>> >>> +
>> >>> +exit:
>> >>> + ret void
>> >>> +}
>> >>>
>> >>> Modified: llvm/trunk/test/Transforms/LICM/preheader-safe.ll
>> >>> URL:
>> >>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/preheader-safe.ll?rev=301196&r1=301195&r2=301196&view=diff
>> >>>
>> >>> ==============================================================================
>> >>> --- llvm/trunk/test/Transforms/LICM/preheader-safe.ll (original)
>> >>> +++ llvm/trunk/test/Transforms/LICM/preheader-safe.ll Mon Apr 24
>> >>> 12:12:22 2017
>> >>> @@ -21,20 +21,6 @@ loop2:
>> >>> call void @use_nothrow(i64 %div)
>> >>> br label %loop
>> >>> }
>> >>> -; Negative test
>> >>> -define void @throw_header(i64 %x, i64 %y, i1* %cond) {
>> >>> -; CHECK-LABEL: throw_header
>> >>> -; CHECK-LABEL: loop
>> >>> -; CHECK: %div = udiv i64 %x, %y
>> >>> -; CHECK: call void @use(i64 %div)
>> >>> -entry:
>> >>> - br label %loop
>> >>> -
>> >>> -loop: ; preds = %entry,
>> >>> %for.inc
>> >>> - %div = udiv i64 %x, %y
>> >>> - call void @use(i64 %div)
>> >>> - br label %loop
>> >>> -}
>> >>>
>> >>> ; The header is known no throw, but the loop is not. We can
>> >>> ; still lift out of the header.
>> >>>
>> >>>
>> >>> _______________________________________________
>> >>> llvm-commits mailing list
>> >>> llvm-commits at lists.llvm.org
>> >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>>
>>
>> --
>> Software Engineer
>> Employee of Facebook Inc.
>> _______________________________________________
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>
>
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