[llvm] r279125 - [SLP] Initialize VectorizedValue when gathering

Matthew Simpson via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 19 10:05:59 PDT 2016 

That's right. Can we just change this to a SaturatingAdd, then?

-- Matt

On Fri, Aug 19, 2016 at 12:58 PM, Michael Kuperstein via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> getTreeCost() can return INT_MAX, and tryToReduce() adds
> getReductionCost() to that.
> Looks like the UB has been there for a while, the new test just exposes it.
>
> On Fri, Aug 19, 2016 at 9:53 AM, Matthew Simpson via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Sorry about that, I’ll take a look!
>>
>>
>>
>> -- Matt
>>
>>
>>
>> *From:* Kostya Serebryany [mailto:kcc at google.com]
>> *Sent:* Friday, August 19, 2016 12:43 PM
>> *To:* Matthew Simpson <mssimpso at codeaurora.org>
>> *Cc:* LLVM Commits <llvm-commits at lists.llvm.org>
>> *Subject:* Re: [llvm] r279125 - [SLP] Initialize VectorizedValue when
>> gathering
>>
>>
>>
>> I think this is causing the ubsan bot failure. please fix:
>>
>> lib/Transforms/Vectorize/SLPVectorizer.cpp:4177:34: runtime error: signed integer overflow: 2147483647 + 11 cannot be represented in type 'int'
>>
>> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-
>> fast/builds/15655/steps/check-llvm%20ubsan/logs/stdio
>>
>>
>>
>> On Thu, Aug 18, 2016 at 12:50 PM, Matthew Simpson via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>> Author: mssimpso
>> Date: Thu Aug 18 14:50:32 2016
>> New Revision: 279125
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=279125&view=rev
>> Log:
>> [SLP] Initialize VectorizedValue when gathering
>>
>> We abort building vectorizable trees in some cases (e.g., if the maximum
>> recursion depth is reached, if the region size is too large, etc.). If
>> this
>> happens for a reduction, we can be left with a root entry that needs to be
>> gathered. For these cases, we need make sure we actually set
>> VectorizedValue to
>> the resulting vector.
>>
>> This patch ensures we properly set VectorizedValue, and it also ensures
>> the
>> insertelement sequence generated for the gathers is inserted at the
>> correct
>> location.
>>
>> Reference: https://llvm.org/bugs/show_bug.cgi?id=28330
>> Differential Revison: https://reviews.llvm.org/D23410
>>
>> Added:
>>     llvm/trunk/test/Transforms/SLPVectorizer/AArch64/gather-root.ll
>> Modified:
>>     llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transform
>> s/Vectorize/SLPVectorizer.cpp?rev=279125&r1=279124&r2=279125&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp Thu Aug 18
>> 14:50:32 2016
>> @@ -2153,11 +2153,61 @@ void BoUpSLP::reorderInputsAccordingToOp
>>  }
>>
>>  void BoUpSLP::setInsertPointAfterBundle(ArrayRef<Value *> VL) {
>> -  Instruction *VL0 = cast<Instruction>(VL[0]);
>> -  BasicBlock::iterator NextInst(VL0);
>> -  ++NextInst;
>> -  Builder.SetInsertPoint(VL0->getParent(), NextInst);
>> -  Builder.SetCurrentDebugLocation(VL0->getDebugLoc());
>> +
>> +  // Get the basic block this bundle is in. All instructions in the
>> bundle
>> +  // should be in this block.
>> +  auto *Front = cast<Instruction>(VL.front());
>> +  auto *BB = Front->getParent();
>> +  assert(all_of(make_range(VL.begin(), VL.end()), [&](Value *V) -> bool
>> {
>> +    return cast<Instruction>(V)->getParent() == BB;
>> +  }));
>> +
>> +  // The last instruction in the bundle in program order.
>> +  Instruction *LastInst = nullptr;
>> +
>> +  // Find the last instruction. The common case should be that BB has
>> been
>> +  // scheduled, and the last instruction is VL.back(). So we start with
>> +  // VL.back() and iterate over schedule data until we reach the end of
>> the
>> +  // bundle. The end of the bundle is marked by null ScheduleData.
>> +  if (BlocksSchedules.count(BB)) {
>> +    auto *Bundle = BlocksSchedules[BB]->getScheduleData(VL.back());
>> +    if (Bundle && Bundle->isPartOfBundle())
>> +      for (; Bundle; Bundle = Bundle->NextInBundle)
>> +        LastInst = Bundle->Inst;
>> +  }
>> +
>> +  // LastInst can still be null at this point if there's either not an
>> entry
>> +  // for BB in BlocksSchedules or there's no ScheduleData available for
>> +  // VL.back(). This can be the case if buildTree_rec aborts for various
>> +  // reasons (e.g., the maximum recursion depth is reached, the maximum
>> region
>> +  // size is reached, etc.). ScheduleData is initialized in the
>> scheduling
>> +  // "dry-run".
>> +  //
>> +  // If this happens, we can still find the last instruction by brute
>> force. We
>> +  // iterate forwards from Front (inclusive) until we either see all
>> +  // instructions in the bundle or reach the end of the block. If Front
>> is the
>> +  // last instruction in program order, LastInst will be set to Front,
>> and we
>> +  // will visit all the remaining instructions in the block.
>> +  //
>> +  // One of the reasons we exit early from buildTree_rec is to place an
>> upper
>> +  // bound on compile-time. Thus, taking an additional compile-time hit
>> here is
>> +  // not ideal. However, this should be exceedingly rare since it
>> requires that
>> +  // we both exit early from buildTree_rec and that the bundle be
>> out-of-order
>> +  // (causing us to iterate all the way to the end of the block).
>> +  if (!LastInst) {
>> +    SmallPtrSet<Value *, 16> Bundle(VL.begin(), VL.end());
>> +    for (auto &I : make_range(BasicBlock::iterator(Front), BB->end())) {
>> +      if (Bundle.erase(&I))
>> +        LastInst = &I;
>> +      if (Bundle.empty())
>> +        break;
>> +    }
>> +  }
>> +
>> +  // Set the insertion point after the last instruction in the bundle.
>> Set the
>> +  // debug location to Front.
>> +  Builder.SetInsertPoint(BB, next(BasicBlock::iterator(LastInst)));
>> +  Builder.SetCurrentDebugLocation(Front->getDebugLoc());
>>  }
>>
>>  Value *BoUpSLP::Gather(ArrayRef<Value *> VL, VectorType *Ty) {
>> @@ -2235,7 +2285,9 @@ Value *BoUpSLP::vectorizeTree(TreeEntry
>>
>>    if (E->NeedToGather) {
>>      setInsertPointAfterBundle(E->Scalars);
>> -    return Gather(E->Scalars, VecTy);
>> +    auto *V = Gather(E->Scalars, VecTy);
>> +    E->VectorizedValue = V;
>> +    return V;
>>    }
>>
>>    unsigned Opcode = getSameOpcode(E->Scalars);
>> @@ -2282,7 +2334,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry
>>          E->VectorizedValue = V;
>>          return V;
>>        }
>> -      return Gather(E->Scalars, VecTy);
>> +      setInsertPointAfterBundle(E->Scalars);
>> +      auto *V = Gather(E->Scalars, VecTy);
>> +      E->VectorizedValue = V;
>> +      return V;
>>      }
>>      case Instruction::ExtractValue: {
>>        if (canReuseExtract(E->Scalars, Instruction::ExtractValue)) {
>> @@ -2294,7 +2349,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry
>>          E->VectorizedValue = V;
>>          return propagateMetadata(V, E->Scalars);
>>        }
>> -      return Gather(E->Scalars, VecTy);
>> +      setInsertPointAfterBundle(E->Scalars);
>> +      auto *V = Gather(E->Scalars, VecTy);
>> +      E->VectorizedValue = V;
>> +      return V;
>>      }
>>      case Instruction::ZExt:
>>      case Instruction::SExt:
>>
>> Added: llvm/trunk/test/Transforms/SLPVectorizer/AArch64/gather-root.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transfor
>> ms/SLPVectorizer/AArch64/gather-root.ll?rev=279125&view=auto
>> ============================================================
>> ==================
>> --- llvm/trunk/test/Transforms/SLPVectorizer/AArch64/gather-root.ll
>> (added)
>> +++ llvm/trunk/test/Transforms/SLPVectorizer/AArch64/gather-root.ll Thu
>> Aug 18 14:50:32 2016
>> @@ -0,0 +1,95 @@
>> +; RUN: opt < %s -slp-vectorizer -S | FileCheck %s --check-prefix=DEFAULT
>> +; RUN: opt < %s -slp-recursion-max-depth=0 -slp-vectorizer -S |
>> FileCheck %s --check-prefix=GATHER
>> +
>> +target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:6
>> 4-i128:128-n32:64-S128"
>> +target triple = "aarch64--linux-gnu"
>> +
>> + at a = common global [80 x i8] zeroinitializer, align 16
>> +
>> +; DEFAULT-LABEL: @PR28330(
>> +; DEFAULT: %tmp17 = phi i32 [ %tmp34, %for.body ], [ 0, %entry ]
>> +; DEFAULT: %tmp18 = phi i32 [ %tmp35, %for.body ], [ %n, %entry ]
>> +; DEFAULT: %[[S0:.+]] = select <8 x i1> %1, <8 x i32> <i32 -720, i32
>> -720, i32 -720, i32 -720, i32 -720, i32 -720, i32 -720, i32 -720>, <8 x
>> i32> <i32 -80, i32 -80, i32 -80, i32 -80, i32 -80, i32 -80, i32 -80, i32
>> -80>
>> +; DEFAULT: %[[R0:.+]] = shufflevector <8 x i32> %[[S0]], <8 x i32>
>> undef, <8 x i32> <i32 4, i32 5, i32 6, i32 7, i32 undef, i32 undef, i32
>> undef, i32 undef>
>> +; DEFAULT: %[[R1:.+]] = add <8 x i32> %[[S0]], %[[R0]]
>> +; DEFAULT: %[[R2:.+]] = shufflevector <8 x i32> %[[R1]], <8 x i32>
>> undef, <8 x i32> <i32 2, i32 3, i32 undef, i32 undef, i32 undef, i32 undef,
>> i32 undef, i32 undef>
>> +; DEFAULT: %[[R3:.+]] = add <8 x i32> %[[R1]], %[[R2]]
>> +; DEFAULT: %[[R4:.+]] = shufflevector <8 x i32> %[[R3]], <8 x i32>
>> undef, <8 x i32> <i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32
>> undef, i32 undef, i32 undef>
>> +; DEFAULT: %[[R5:.+]] = add <8 x i32> %[[R3]], %[[R4]]
>> +; DEFAULT: %[[R6:.+]] = extractelement <8 x i32> %[[R5]], i32 0
>> +; DEFAULT: %tmp34 = add i32 %[[R6]], %tmp17
>> +;
>> +; GATHER-LABEL: @PR28330(
>> +; GATHER: %tmp17 = phi i32 [ %tmp34, %for.body ], [ 0, %entry ]
>> +; GATHER: %tmp18 = phi i32 [ %tmp35, %for.body ], [ %n, %entry ]
>> +; GATHER: %tmp19 = select i1 %tmp1, i32 -720, i32 -80
>> +; GATHER: %tmp21 = select i1 %tmp3, i32 -720, i32 -80
>> +; GATHER: %tmp23 = select i1 %tmp5, i32 -720, i32 -80
>> +; GATHER: %tmp25 = select i1 %tmp7, i32 -720, i32 -80
>> +; GATHER: %tmp27 = select i1 %tmp9, i32 -720, i32 -80
>> +; GATHER: %tmp29 = select i1 %tmp11, i32 -720, i32 -80
>> +; GATHER: %tmp31 = select i1 %tmp13, i32 -720, i32 -80
>> +; GATHER: %tmp33 = select i1 %tmp15, i32 -720, i32 -80
>> +; GATHER: %[[I0:.+]] = insertelement <8 x i32> undef, i32 %tmp19, i32 0
>> +; GATHER: %[[I1:.+]] = insertelement <8 x i32> %[[I0]], i32 %tmp21, i32 1
>> +; GATHER: %[[I2:.+]] = insertelement <8 x i32> %[[I1]], i32 %tmp23, i32 2
>> +; GATHER: %[[I3:.+]] = insertelement <8 x i32> %[[I2]], i32 %tmp25, i32 3
>> +; GATHER: %[[I4:.+]] = insertelement <8 x i32> %[[I3]], i32 %tmp27, i32 4
>> +; GATHER: %[[I5:.+]] = insertelement <8 x i32> %[[I4]], i32 %tmp29, i32 5
>> +; GATHER: %[[I6:.+]] = insertelement <8 x i32> %[[I5]], i32 %tmp31, i32 6
>> +; GATHER: %[[I7:.+]] = insertelement <8 x i32> %[[I6]], i32 %tmp33, i32 7
>> +; GATHER: %[[R0:.+]] = shufflevector <8 x i32> %[[I7]], <8 x i32> undef,
>> <8 x i32> <i32 4, i32 5, i32 6, i32 7, i32 undef, i32 undef, i32 undef, i32
>> undef>
>> +; GATHER: %[[R1:.+]] = add <8 x i32> %[[I7]], %[[R0]]
>> +; GATHER: %[[R2:.+]] = shufflevector <8 x i32> %[[R1]], <8 x i32> undef,
>> <8 x i32> <i32 2, i32 3, i32 undef, i32 undef, i32 undef, i32 undef, i32
>> undef, i32 undef>
>> +; GATHER: %[[R3:.+]] = add <8 x i32> %[[R1]], %[[R2]]
>> +; GATHER: %[[R4:.+]] = shufflevector <8 x i32> %[[R3]], <8 x i32> undef,
>> <8 x i32> <i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef,
>> i32 undef, i32 undef>
>> +; GATHER: %[[R5:.+]] = add <8 x i32> %[[R3]], %[[R4]]
>> +; GATHER: %[[R6:.+]] = extractelement <8 x i32> %[[R5]], i32 0
>> +; GATHER: %tmp34 = add i32 %[[R6]], %tmp17
>> +
>> +define void @PR28330(i32 %n) {
>> +entry:
>> +  %tmp0 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]* @a,
>> i64 0, i64 1), align 1
>> +  %tmp1 = icmp eq i8 %tmp0, 0
>> +  %tmp2 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]* @a,
>> i64 0, i64 2), align 2
>> +  %tmp3 = icmp eq i8 %tmp2, 0
>> +  %tmp4 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]* @a,
>> i64 0, i64 3), align 1
>> +  %tmp5 = icmp eq i8 %tmp4, 0
>> +  %tmp6 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]* @a,
>> i64 0, i64 4), align 4
>> +  %tmp7 = icmp eq i8 %tmp6, 0
>> +  %tmp8 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]* @a,
>> i64 0, i64 5), align 1
>> +  %tmp9 = icmp eq i8 %tmp8, 0
>> +  %tmp10 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]*
>> @a, i64 0, i64 6), align 2
>> +  %tmp11 = icmp eq i8 %tmp10, 0
>> +  %tmp12 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]*
>> @a, i64 0, i64 7), align 1
>> +  %tmp13 = icmp eq i8 %tmp12, 0
>> +  %tmp14 = load i8, i8* getelementptr inbounds ([80 x i8], [80 x i8]*
>> @a, i64 0, i64 8), align 8
>> +  %tmp15 = icmp eq i8 %tmp14, 0
>> +  br label %for.body
>> +
>> +for.body:
>> +  %tmp17 = phi i32 [ %tmp34, %for.body ], [ 0, %entry ]
>> +  %tmp18 = phi i32 [ %tmp35, %for.body ], [ %n, %entry ]
>> +  %tmp19 = select i1 %tmp1, i32 -720, i32 -80
>> +  %tmp20 = add i32 %tmp17, %tmp19
>> +  %tmp21 = select i1 %tmp3, i32 -720, i32 -80
>> +  %tmp22 = add i32 %tmp20, %tmp21
>> +  %tmp23 = select i1 %tmp5, i32 -720, i32 -80
>> +  %tmp24 = add i32 %tmp22, %tmp23
>> +  %tmp25 = select i1 %tmp7, i32 -720, i32 -80
>> +  %tmp26 = add i32 %tmp24, %tmp25
>> +  %tmp27 = select i1 %tmp9, i32 -720, i32 -80
>> +  %tmp28 = add i32 %tmp26, %tmp27
>> +  %tmp29 = select i1 %tmp11, i32 -720, i32 -80
>> +  %tmp30 = add i32 %tmp28, %tmp29
>> +  %tmp31 = select i1 %tmp13, i32 -720, i32 -80
>> +  %tmp32 = add i32 %tmp30, %tmp31
>> +  %tmp33 = select i1 %tmp15, i32 -720, i32 -80
>> +  %tmp34 = add i32 %tmp32, %tmp33
>> +  %tmp35 = add nsw i32 %tmp18, -1
>> +  %tmp36 = icmp eq i32 %tmp35, 0
>> +  br i1 %tmp36, label %for.end, label %for.body
>> +
>> +for.end:
>> +  ret void
>> +}
>>
>>
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