[llvm] r257279 - [JumpThreading] Don't forget to report that the IR changed

[Hans Wennborg via llvm-commits]

r257279 and r257280 both landed before the branch (r257626), so I
think we're good here already.

Thanks,
Hans

On Wed, Feb 17, 2016 at 10:39 AM, Dimitry Andric <dimitry at andric.com> wrote:
> Hi David(s),
>
> Can we get r257279 and its followup approved for the 3.8 branch?  Hans, is
> there still time for RC3? :)
>
> -Dimitry
>
> On 11 Jan 2016, at 06:42, David Majnemer via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>
> Yes, I added one yesterday (r257280).
>
> On Sunday, January 10, 2016, David Blaikie <dblaikie at gmail.com> wrote:
>>
>> any way to test this?
>>
>> On Sat, Jan 9, 2016 at 11:13 PM, David Majnemer via llvm-commits
>> <llvm-commits at lists.llvm.org> wrote:
>>>
>>> Author: majnemer
>>> Date: Sun Jan 10 01:13:04 2016
>>> New Revision: 257279
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=257279&view=rev
>>> Log:
>>> [JumpThreading] Don't forget to report that the IR changed
>>>
>>> JumpThreading's runOnFunction is supposed to return true if it made any
>>> changes.  JumpThreading has a call to removeUnreachableBlocks which may
>>> result in changes to the IR but runOnFunction didn't appropriate account
>>> for this possibility, leading to badness.
>>>
>>> While we are here, make sure to call LazyValueInfo::eraseBlock in
>>> removeUnreachableBlocks;  JumpThreading preserves LVI.
>>>
>>> This fixes PR26096.
>>>
>>> Modified:
>>>     llvm/trunk/include/llvm/Transforms/Utils/Local.h
>>>     llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
>>>     llvm/trunk/lib/Transforms/Utils/Local.cpp
>>>
>>> Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=257279&r1=257278&r2=257279&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
>>> +++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Sun Jan 10 01:13:04
>>> 2016
>>> @@ -42,6 +42,7 @@ class TargetLibraryInfo;
>>>  class TargetTransformInfo;
>>>  class DIBuilder;
>>>  class DominatorTree;
>>> +class LazyValueInfo;
>>>
>>>  template<typename T> class SmallVectorImpl;
>>>
>>> @@ -303,7 +304,7 @@ void removeUnwindEdge(BasicBlock *BB);
>>>  /// \brief Remove all blocks that can not be reached from the function's
>>> entry.
>>>  ///
>>>  /// Returns true if any basic block was removed.
>>> -bool removeUnreachableBlocks(Function &F);
>>> +bool removeUnreachableBlocks(Function &F, LazyValueInfo *LVI = nullptr);
>>>
>>>  /// \brief Combine the metadata of two instructions so that K can
>>> replace J
>>>  ///
>>>
>>> Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=257279&r1=257278&r2=257279&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Sun Jan 10
>>> 01:13:04 2016
>>> @@ -211,11 +211,12 @@ bool JumpThreading::runOnFunction(Functi
>>>    // we will loop forever. We take care of this issue by not jump
>>> threading for
>>>    // back edges. This works for normal cases but not for unreachable
>>> blocks as
>>>    // they may have cycle with no back edge.
>>> -  removeUnreachableBlocks(F);
>>> +  bool EverChanged = false;
>>> +  EverChanged |= removeUnreachableBlocks(F, LVI);
>>>
>>>    FindLoopHeaders(F);
>>>
>>> -  bool Changed, EverChanged = false;
>>> +  bool Changed;
>>>    do {
>>>      Changed = false;
>>>      for (Function::iterator I = F.begin(), E = F.end(); I != E;) {
>>>
>>> Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=257279&r1=257278&r2=257279&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Utils/Local.cpp Sun Jan 10 01:13:04 2016
>>> @@ -23,6 +23,7 @@
>>>  #include "llvm/Analysis/EHPersonalities.h"
>>>  #include "llvm/Analysis/InstructionSimplify.h"
>>>  #include "llvm/Analysis/MemoryBuiltins.h"
>>> +#include "llvm/Analysis/LazyValueInfo.h"
>>>  #include "llvm/Analysis/ValueTracking.h"
>>>  #include "llvm/IR/CFG.h"
>>>  #include "llvm/IR/Constants.h"
>>> @@ -1407,7 +1408,7 @@ void llvm::removeUnwindEdge(BasicBlock *
>>>  /// removeUnreachableBlocksFromFn - Remove blocks that are not
>>> reachable, even
>>>  /// if they are in a dead cycle.  Return true if a change was made,
>>> false
>>>  /// otherwise.
>>> -bool llvm::removeUnreachableBlocks(Function &F) {
>>> +bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI) {
>>>    SmallPtrSet<BasicBlock*, 128> Reachable;
>>>    bool Changed = markAliveBlocks(F, Reachable);
>>>
>>> @@ -1428,6 +1429,8 @@ bool llvm::removeUnreachableBlocks(Funct
>>>           ++SI)
>>>        if (Reachable.count(*SI))
>>>          (*SI)->removePredecessor(&*BB);
>>> +    if (LVI)
>>> +      LVI->eraseBlock(&*BB);
>>>      BB->dropAllReferences();
>>>    }
>>>
>>>
>>>
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>>
>>
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