[llvm] 8d20f2c - Revert "[CodeGenPrepare] Fix isIVIncrement (PR49466)"

Philip Reames via llvm-commits llvm-commits at lists.llvm.org
Fri Mar 12 15:35:51 PST 2021


On 3/12/21 3:22 PM, Philip Reames via llvm-commits wrote:
>
>
> On 3/12/21 2:59 PM, Jordan Rupprecht wrote:
>>
>>
>> On Fri, Mar 12, 2021 at 4:29 PM Philip Reames 
>> <listmail at philipreames.com <mailto:listmail at philipreames.com>> wrote:
>>
>>     Jordan,
>>
>>     Please revert this change.
>>
>>     There's a couple of problems here:
>>
>>       * The change reverted looks obviously innocent. (e.g. it's
>>         bailing out of a transform slightly more often)
>>
>> I don't disagree that it "looks obviously innocent", but the proof is 
>> in the pudding: the reproducer I posted compiles ~instantly at one 
>> commit prior, and times out at the culprit commit. A change "looking" 
>> good should never be a basis for saying it must be correct and should 
>> not be reverted, especially when there is evidence it is a problem. 
>> At least, that's my personal opinion, but I should think that's a 
>> fairly basic and widely held belief.
>
> You're correct, but missing the point I was getting at. Admittedly, 
> poorly worded.
>
> While looking obviously innocent isn't reason not to revert itself, 
> it's definitely reason to take a slightly closer look and make sure 
> there's nothing else going on.  This is particularly relevant given 
> the other points in this discussion.
>
>>       * The change reverted was itself fixing a functional bug.  At a
>>         minimum, we'd need a larger revert to get ToT back to a sane
>>         state.
>>
>> The fix is introducing a different bug, and one which seems more 
>> widespread. At the very least, we haven't observed any of the crashes 
>> mentioned in PR49466, but we did notice a compile timeout in several 
>> different compilation units.
>
> Bug?  Discussion?  Response to original commit?
>
> Your observation may be true *for you*.  It is not necessarily true 
> for anyone else, and you bear the burden of making the case.  
> Particularly when reverting a functional fix.
>
> To be clear, I'm not saying you're wrong.  I'm saying you haven't 
> given anyone else enough information to tell if you are or not.
>
>>       * It is generally considered reasonable to provide a test case
>>         and wait a bit before reverting, at least once the patch is
>>         more than a few hours old.
>>
>> Sorry about that. I'll concede that I got a little trigger happy 
>> here, but I was hoping that would be waived by the fact that I gave a 
>> simple, concrete reproducer.
> Thanks for the acknowledgement.  To be fair, it would have been less 
> of an issue if the reproducer worked straight forwardly.
>>
>>       * Failure to provide an IR test case.
>>
>> (ditto, but see one below)
>>
>>       * Your test case does not reproduce.  Or at least, it doesn't
>>         reproduce when compiled with clang10 to IR and then run
>>         through (very recent, but without your change) ToT opt -O2. 
>>         If there's something specific about the interaction of clang
>>         and opt ToT, reducing this down to a IR test case becomes
>>         particularly important.
>>
>> This comment is going *way* off track -- the reproducer I posted 
>> *does* reproduce, at least for me, in the configuration I posted (a 
>> C++ source file, and just "clang -O2"). By saying it doesn't 
>> reproduce in a mixed configuration of an old version of clang to do 
>> the C++ -> IR combined with a ToT version of opt -O2 to do the IR -> 
>> object file is misleading -- it's true, but that's not at all what I 
>> was claiming, and I don't know where it's coming from.
>
> I actually don't think this is going off track at all.  Our default is 
> for IR test cases for IR problems.  Any reverting commit should 
> generally include a test case suitable for checkin (w/a bit of 
> cleanup) once the patch is fixed.  I'll admit, we're not strict about 
> this, but the expectation is definitely there.
>
> The discussion of the hybrid configuration is relevant *because* you 
> didn't provide a test case in a form I could easily use.  I don't work 
> on clang, don't build it regularly, and shouldn't have to investigate 
> a LLVM codegen regression.
>
> (See also below.)
>
>>     Philip
>>
>>     p.s. To be clear, I'm happy to look at your original issue this
>>     afternoon if you've got something I can reproduce.
>>
>> Here's an IR reproducer with IR generated from ToT before my revert 
>> (at dfd27ebbd0eb137c9a439b7c537bb87ba903efd3):
>
> Ok, we have a problem here.  None of the following reproduce for me:
>
> $ ./llc -O2 jordan.ll
> $ ./llc -O2 jordan.ll
> $ ./llc -O2 jordan.ll --filetype=obj
> $ ./llc -O3 jordan.ll --filetype=obj
>
> LLC is ToT, just built with your change reverted locally.
>
>> $ bin/clang -c /tmp/repro.cc -O1 -S -emit-llvm -o /tmp/repro.ll
>> $ bin/clang -c /tmp/repro.ll -O2 -o /tmp/repro.o  # hangs
>
> Given the preceding, I am now asserting this is likely some clang 
> specific problem.  I've got a build of clang running now, will report 
> back in a bit.
>
With a newly build clang, I can reproduce what you're seeing. However, 
no attempt to mine to get IR out clang - I'm no expert here - has 
generated anything standalone reproducible in IR.

Looking at debug output does make it look the transform affected by the 
revert is involved in the infinite loop, but I *strongly* suspect the 
actual revert is just massaging the issue enough to avoid something lurking.

I will spend some time this afternoon investigating this.

I would strongly suggest you follow up with clang folks to figure out 
why clang and llc are not matching behavior.  That's a serious problem.

> The other option is that this is someway specific to your configuration.
>
>
>>
>> ; ModuleID = '/tmp/repro.cc'
>> source_filename = "/tmp/repro.cc"
>> target datalayout = 
>> "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
>> target triple = "x86_64-unknown-linux-gnu"
>>
>> %class.D = type { i64 }
>> %class.a = type { %class.g }
>> %class.g = type { i32*, i32* }
>>
>> $_ZNK1aIliEixEl = comdat any
>>
>> $_ZNK1aIliE1jEv = comdat any
>>
>> @o = dso_local local_unnamed_addr global i32 0, align 4
>> @p = dso_local local_unnamed_addr global i32 0, align 4
>> @.str = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
>>
>> ; Function Attrs: uwtable mustprogress
>> define dso_local void @_ZN1D1qERK1aIliE(%class.D* nocapture nonnull 
>> dereferenceable(8) %0, %class.a* nonnull align 8 dereferenceable(16) 
>> %1) local_unnamed_addr #0 align 2 {
>>   %3 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) 
>> %1, i64 0) #3
>>   %4 = icmp eq i64 %3, 0
>>   br i1 %4, label %26, label %5
>>
>> 5:                                                ; preds = %2
>>   %6 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %1)
>>   %7 = icmp eq i64 %6, 0
>>   br i1 %7, label %26, label %8
>>
>> 8:                                                ; preds = %5
>>   %9 = getelementptr inbounds %class.D, %class.D* %0, i64 0, i32 0
>>   br label %10
>>
>> 10:                                               ; preds = %8, %18
>>   %11 = phi i64 [ 0, %8 ], [ %23, %18 ]
>>   %12 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull 
>> dereferenceable(16) %1, i64 %11) #3
>>   %13 = icmp eq i64 %12, 0
>>   br i1 %13, label %18, label %14
>>
>> 14:                                               ; preds = %10, %14
>>   %15 = load i32, i32* @o, align 4, !tbaa !2
>>   %16 = call i32 @_Z3fn1IiiEiT_T0_PKc(i32 %15, i32 0, i8* 
>> getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0))
>>   %17 = icmp eq i32 %16, 0
>>   br i1 %17, label %18, label %14, !llvm.loop !6
>>
>> 18:                                               ; preds = %14, %10
>>   %19 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull 
>> dereferenceable(16) %1, i64 %11) #3
>>   %20 = load i32, i32* @p, align 4, !tbaa !2
>>   %21 = sext i32 %20 to i64
>>   %22 = sdiv i64 %19, %21
>>   store i64 %22, i64* %9, align 8, !tbaa !9
>>   %23 = add i64 %11, 1
>>   %24 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull 
>> dereferenceable(16) %1)
>>   %25 = icmp eq i64 %24, 0
>>   br i1 %25, label %26, label %10, !llvm.loop !12
>>
>> 26:                                               ; preds = %18, %5, %2
>>   ret void
>> }
>>
>> ; Function Attrs: nounwind uwtable willreturn mustprogress
>> define linkonce_odr dso_local i64 @_ZNK1aIliEixEl(%class.a* nonnull 
>> dereferenceable(16) %0, i64 %1) local_unnamed_addr #1 comdat align 2 {
>>   %3 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 0
>>   %4 = load i32*, i32** %3, align 8, !tbaa !13
>>   %5 = getelementptr inbounds i32, i32* %4, i64 %1
>>   %6 = load i32, i32* %5, align 4, !tbaa !2
>>   %7 = sext i32 %6 to i64
>>   ret i64 %7
>> }
>>
>> ; Function Attrs: nounwind uwtable willreturn mustprogress
>> define linkonce_odr dso_local i64 @_ZNK1aIliE1jEv(%class.a* nonnull 
>> dereferenceable(16) %0) local_unnamed_addr #1 comdat align 2 {
>>   %2 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 1
>>   %3 = load i32*, i32** %2, align 8, !tbaa !16
>>   %4 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 0
>>   %5 = load i32*, i32** %4, align 8, !tbaa !13
>>   %6 = ptrtoint i32* %3 to i64
>>   %7 = ptrtoint i32* %5 to i64
>>   %8 = sub i64 %6, %7
>>   %9 = ashr exact i64 %8, 2
>>   ret i64 %9
>> }
>>
>> declare dso_local i32 @_Z3fn1IiiEiT_T0_PKc(i32, i32, i8*) 
>> local_unnamed_addr #2
>>
>> attributes #0 = { uwtable mustprogress "frame-pointer"="none" 
>> "no-trapping-math"="true" "stack-protector-buffer-size"="8" 
>> "target-cpu"="x86-64" 
>> "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" 
>> "tune-cpu"="generic" }
>> attributes #1 = { nounwind uwtable willreturn mustprogress 
>> "frame-pointer"="none" "no-trapping-math"="true" 
>> "stack-protector-buffer-size"="8" "target-cpu"="x86-64" 
>> "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" 
>> "tune-cpu"="generic" }
>> attributes #2 = { "frame-pointer"="none" "no-trapping-math"="true" 
>> "stack-protector-buffer-size"="8" "target-cpu"="x86-64" 
>> "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" 
>> "tune-cpu"="generic" }
>> attributes #3 = { nounwind }
>>
>> !llvm.module.flags = !{!0}
>> !llvm.ident = !{!1}
>>
>> !0 = !{i32 1, !"wchar_size", i32 4}
>> !1 = !{!"clang version 13.0.0 
>> (https://github.com/llvm/llvm-project.git 
>> <https://github.com/llvm/llvm-project.git> 
>> dfd27ebbd0eb137c9a439b7c537bb87ba903efd3)"}
>> !2 = !{!3, !3, i64 0}
>> !3 = !{!"int", !4, i64 0}
>> !4 = !{!"omnipotent char", !5, i64 0}
>> !5 = !{!"Simple C++ TBAA"}
>> !6 = distinct !{!6, !7, !8}
>> !7 = !{!"llvm.loop.mustprogress"}
>> !8 = !{!"llvm.loop.unroll.disable"}
>> !9 = !{!10, !11, i64 0}
>> !10 = !{!"_ZTS1D", !11, i64 0}
>> !11 = !{!"long", !4, i64 0}
>> !12 = distinct !{!12, !7, !8}
>> !13 = !{!14, !15, i64 0}
>> !14 = !{!"_ZTS1g", !15, i64 0, !15, i64 8}
>> !15 = !{!"any pointer", !4, i64 0}
>> !16 = !{!14, !15, i64 8}
>>
>>     On 3/12/21 1:59 PM, Jordan Rupprecht via llvm-commits wrote:
>>>     Author: Jordan Rupprecht
>>>     Date: 2021-03-12T13:59:14-08:00
>>>     New Revision: 8d20f2c2c66eb486ff23cc3d55a53bd840b36971
>>>
>>>     URL:https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971  <https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971>
>>>     DIFF:https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971.diff  <https://github.com/llvm/llvm-project/commit/8d20f2c2c66eb486ff23cc3d55a53bd840b36971.diff>
>>>
>>>     LOG: Revert "[CodeGenPrepare] Fix isIVIncrement (PR49466)"
>>>
>>>     This reverts commit cf82700af8c658ae09b14c3d01bb1e73e48d3bd3 due to a compile timeout when building the following with `clang -O2`:
>>>
>>>     ```
>>>     template <class, class = int> class a;
>>>     struct b {
>>>        using d = int *;
>>>     };
>>>     struct e {
>>>        using f = b::d;
>>>     };
>>>     class g {
>>>     public:
>>>        e::f h;
>>>        e::f i;
>>>     };
>>>     template <class, class> class a : g {
>>>     public:
>>>        long j() const { return i - h; }
>>>        long operator[](long) const noexcept;
>>>     };
>>>     template <class c, class k> long a<c, k>::operator[](long l) const noexcept {
>>>        return h[l];
>>>     }
>>>     template <typename m, typename n> int fn1(m, n, const char *);
>>>     int o, p;
>>>     class D {
>>>        void q(const a<long> &);
>>>        long r;
>>>     };
>>>     void D::q(const a<long> &l) {
>>>        int s;
>>>        if (l[0])
>>>          for (; l.j(); ++s) {
>>>            if (l[s])
>>>              while (fn1(o, 0, ""))
>>>                ;
>>>            r = l[s] / p;
>>>          }
>>>     }
>>>     ```
>>>
>>>     Added:
>>>          
>>>
>>>     Modified:
>>>          llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>
>>>     Removed:
>>>          llvm/test/CodeGen/X86/pr49466.ll
>>>
>>>
>>>     ################################################################################
>>>     diff  --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>     index 0f698dd3b190..0b1156e2ace7 100644
>>>     --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>     +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
>>>     @@ -1332,7 +1332,7 @@ getIVIncrement(const PHINode *PN, const LoopInfo *LI) {
>>>       
>>>       static bool isIVIncrement(const BinaryOperator *BO, const LoopInfo *LI) {
>>>         auto *PN = dyn_cast<PHINode>(BO->getOperand(0));
>>>     -  if (!PN || LI->getLoopFor(BO->getParent()) != LI->getLoopFor(PN->getParent()))
>>>     +  if (!PN)
>>>           return false;
>>>         if (auto IVInc = getIVIncrement(PN, LI))
>>>           return IVInc->first == BO;
>>>     @@ -1347,7 +1347,6 @@ bool CodeGenPrepare::replaceMathCmpWithIntrinsic(BinaryOperator *BO,
>>>           if (!isIVIncrement(BO, LI))
>>>             return false;
>>>           const Loop *L = LI->getLoopFor(BO->getParent());
>>>     -    assert(L && "L should not be null after isIVIncrement()");
>>>           // Do not risk on moving increment into a child loop.
>>>           if (LI->getLoopFor(Cmp->getParent()) != L)
>>>             return false;
>>>
>>>     diff  --git a/llvm/test/CodeGen/X86/pr49466.ll b/llvm/test/CodeGen/X86/pr49466.ll
>>>     deleted file mode 100644
>>>     index 4f6574d9bbf2..000000000000
>>>     --- a/llvm/test/CodeGen/X86/pr49466.ll
>>>     +++ /dev/null
>>>     @@ -1,122 +0,0 @@
>>>     -; RUN: opt < %s -O2 -codegenprepare -S | FileCheck %s
>>>     -
>>>     -target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
>>>     -target triple = "x86_64-unknown-linux-gnu"
>>>     -
>>>     - at b = dso_local local_unnamed_addr global i64 0, align 8
>>>     - at c = dso_local local_unnamed_addr global i64 0, align 8
>>>     - at d = dso_local local_unnamed_addr global i64 0, align 8
>>>     - at e = dso_local local_unnamed_addr global i64 0, align 8
>>>     - at f = dso_local local_unnamed_addr global i64 0, align 8
>>>     - at g = dso_local local_unnamed_addr global i64 0, align 8
>>>     -
>>>     -; CHECK-LABEL: @m(
>>>     -
>>>     -define dso_local i32 @m() local_unnamed_addr {
>>>     -entry:
>>>     -  %0 = load i64, i64* @f, align 8
>>>     -  %1 = inttoptr i64 %0 to i32*
>>>     -  %2 = load i64, i64* @c, align 8
>>>     -  %conv18 = trunc i64 %2 to i32
>>>     -  %cmp = icmp slt i32 %conv18, 3
>>>     -  %3 = load i64, i64* @d, align 8
>>>     -  %conv43 = trunc i64 %3 to i8
>>>     -  %tobool40.not = icmp eq i8 %conv43, 0
>>>     -  br label %for.cond
>>>     -
>>>     -for.cond:                                         ; preds = %for.cond39.preheader, %entry
>>>     -  %j.0 = phi i32 [ undef, %entry ], [ %j.1.lcssa, %for.cond39.preheader ]
>>>     -  %p.0 = phi i64 [ undef, %entry ], [ %p.1.lcssa, %for.cond39.preheader ]
>>>     -  %i.0 = phi i32 [ undef, %entry ], [ %i.1.lcssa, %for.cond39.preheader ]
>>>     -  %cmp73 = icmp slt i32 %i.0, 3
>>>     -  br i1 %cmp73, label %for.body.preheader, label %for.cond39.preheader
>>>     -
>>>     -for.body.preheader:                               ; preds = %for.cond
>>>     -  br label %for.body
>>>     -
>>>     -for.cond1.loopexit:                               ; preds = %for.inc34.preheader, %for.end12
>>>     -  br i1 %cmp, label %for.body, label %for.cond39.preheader.loopexit
>>>     -
>>>     -for.cond39.preheader.loopexit:                    ; preds = %for.cond1.loopexit
>>>     -  br label %for.cond39.preheader
>>>     -
>>>     -for.cond39.preheader:                             ; preds = %for.cond39.preheader.loopexit, %for.cond
>>>     -  %j.1.lcssa = phi i32 [ %j.0, %for.cond ], [ %conv18, %for.cond39.preheader.loopexit ]
>>>     -  %p.1.lcssa = phi i64 [ %p.0, %for.cond ], [ 0, %for.cond39.preheader.loopexit ]
>>>     -  %i.1.lcssa = phi i32 [ %i.0, %for.cond ], [ %conv18, %for.cond39.preheader.loopexit ]
>>>     -  br i1 %tobool40.not, label %for.cond, label %for.inc42.preheader
>>>     -
>>>     -for.inc42.preheader:                              ; preds = %for.cond39.preheader
>>>     -  br label %for.inc42
>>>     -
>>>     -for.body:                                         ; preds = %for.body.preheader, %for.cond1.loopexit
>>>     -  %l.176 = phi i8 [ %sub, %for.cond1.loopexit ], [ 0, %for.body.preheader ]
>>>     -  %p.175 = phi i64 [ 0, %for.cond1.loopexit ], [ %p.0, %for.body.preheader ]
>>>     -  %j.174 = phi i32 [ %conv18, %for.cond1.loopexit ], [ %j.0, %for.body.preheader ]
>>>     -  %tobool.not = icmp eq i32 %j.174, 0
>>>     -  br i1 %tobool.not, label %cleanup45, label %for.cond2.preheader
>>>     -
>>>     -for.cond2.preheader:                              ; preds = %for.body
>>>     -  %tobool3.not69 = icmp eq i64 %p.175, 0
>>>     -  %.pr.pre = load i64, i64* @e, align 8
>>>     -  br i1 %tobool3.not69, label %for.end12, label %for.body4.preheader
>>>     -
>>>     -for.body4.preheader:                              ; preds = %for.cond2.preheader
>>>     -  %4 = sub i64 0, %p.175
>>>     -  %xtraiter = and i64 %4, 7
>>>     -  %lcmp.mod.not = icmp eq i64 %xtraiter, 0
>>>     -  br i1 %lcmp.mod.not, label %for.body4.prol.loopexit, label %for.body4.prol.preheader
>>>     -
>>>     -for.body4.prol.preheader:                         ; preds = %for.body4.preheader
>>>     -  %5 = mul nsw i64 %xtraiter, -1
>>>     -  br label %for.body4.prol
>>>     -
>>>     -for.body4.prol:                                   ; preds = %for.body4.prol.preheader, %for.body4.prol
>>>     -  %lsr.iv = phi i64 [ 0, %for.body4.prol.preheader ], [ %lsr.iv.next, %for.body4.prol ]
>>>     -  %lsr.iv.next = add nsw i64 %lsr.iv, -1
>>>     -  %prol.iter.cmp.not = icmp eq i64 %5, %lsr.iv.next
>>>     -  br i1 %prol.iter.cmp.not, label %for.body4.prol.loopexit.loopexit, label %for.body4.prol
>>>     -
>>>     -for.body4.prol.loopexit.loopexit:                 ; preds = %for.body4.prol
>>>     -  %6 = sub i64 %p.175, %lsr.iv.next
>>>     -  br label %for.body4.prol.loopexit
>>>     -
>>>     -for.body4.prol.loopexit:                          ; preds = %for.body4.prol.loopexit.loopexit, %for.body4.preheader
>>>     -  %p.270.unr = phi i64 [ %p.175, %for.body4.preheader ], [ %6, %for.body4.prol.loopexit.loopexit ]
>>>     -  %7 = icmp ugt i64 %p.175, -8
>>>     -  br i1 %7, label %for.end12, label %for.body4.preheader89
>>>     -
>>>     -for.body4.preheader89:                            ; preds = %for.body4.prol.loopexit
>>>     -  br label %for.body4
>>>     -
>>>     -for.body4:                                        ; preds = %for.body4.preheader89, %for.body4
>>>     -  %p.270 = phi i64 [ %inc11.7, %for.body4 ], [ %p.270.unr, %for.body4.preheader89 ]
>>>     -  %inc11.7 = add i64 %p.270, 8
>>>     -  %tobool3.not.7 = icmp eq i64 %inc11.7, 0
>>>     -  br i1 %tobool3.not.7, label %for.end12.loopexit, label %for.body4
>>>     -
>>>     -for.end12.loopexit:                               ; preds = %for.body4
>>>     -  br label %for.end12
>>>     -
>>>     -for.end12:                                        ; preds = %for.end12.loopexit, %for.body4.prol.loopexit, %for.cond2.preheader
>>>     -  %8 = load i32, i32* %1, align 4
>>>     -  %conv23 = zext i32 %8 to i64
>>>     -  %9 = load i64, i64* @b, align 8
>>>     -  %div24 = udiv i64 %9, %conv23
>>>     -  store i64 %div24, i64* @b, align 8
>>>     -  %sub = add i8 %l.176, -1
>>>     -  %tobool32.not72 = icmp eq i64 %.pr.pre, 0
>>>     -  br i1 %tobool32.not72, label %for.cond1.loopexit, label %for.inc34.preheader
>>>     -
>>>     -for.inc34.preheader:                              ; preds = %for.end12
>>>     -  store i64 0, i64* @e, align 8
>>>     -  br label %for.cond1.loopexit
>>>     -
>>>     -for.inc42:                                        ; preds = %for.inc42.preheader, %for.inc42
>>>     -  br label %for.inc42
>>>     -
>>>     -cleanup45:                                        ; preds = %for.body
>>>     -  %cmp13 = icmp ne i8 %l.176, 0
>>>     -  %conv16 = zext i1 %cmp13 to i32
>>>     -  ret i32 %conv16
>>>     -}
>>>
>>>
>>>              
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>>
>
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