[llvm] r301196 - Compute safety information in a much finer granularity.
Evgenii Stepanov via llvm-commits
llvm-commits at lists.llvm.org
Mon Apr 24 11:38:14 PDT 2017
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.
>>
>>
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